pikeng-insight

Introduction

Electricity travels fast, cannot be stored easily or cheaply and cannot be switched from one route to another. These three principles are basic to the operation of an electric power system. Electricity is almost instantaneous. When a light is turned on, electricity must be readily available. Since it is not stored anywhere on the power grid, electricity must somehow be dispatched immediately. A generator is not simply started up to provide this power. Electric power must be managed so that electricity is always available for all the lights, appliances and other uses that are required at any particular moment. Electricity travelling from one point to another follows the path of least resistance rather than the shortest distance. With long distances of interconnected wires, electricity may travel miles out of any direct path to get where it is needed. As a result of these three principles, designing and operating an electrical system is complex and requires constant management.

Energy is used in diverse ways and the most commonly utilized form of energy is heat. Energy may be obtained either directly or indirectly from energy sources; electrical energy or electricity, for instance, is always invariably produced indirectly from a myriad of primary energy sources. Electricity is one of the key types of energy; it is made up basically of the flow of tiny particles of matter called electrons. Practically everything on this earth, including humans, have some electrons and therefore can be described as partly electrical, that is why we received shock from electricity. 

Defining and Measuring

Electricity is simply the flow or exchange of electrons between atoms, as it was generally known that an Atom is electrically neutral i.e. the aggregated of positive charge {Proton} is exactly equal to aggregate of negative charge {Electron}. The atoms of some metals, such as copper and aluminum, have electrons that move easily. That makes these metals good electrical conductors. Electricity is created when a coil of metal wire is turned near a magnet. Thus, an electric generator is simply a coil of wire spinning around a magnet. This phenomenon enables us to build generators that produce electricity in power plants.

The push, or pressure, forcing electricity from a generator is expressed as volts. The flow of electricity is called current. Current is measured in amperes (amps). Watts are a measure of the amount of work done by electricity. Watts are calculated by multiplying amps by volts. Electrical appliances, light bulbs and motors have certain wattage requirements, which depend on the task they are expected to perform. One kilowatt (1,000 watts) equals 1.34 horsepower likewise One-horsepower equal 746 watt. The watt (W) represents the unit of measure of electric power or rate of doing work. Large amounts of electric power are denoted as follows:

1. Kilowatt (kW): equal to 1,000 W

2. Megawatt (MW): equal to 1,000,000 W or 1,000 kW

3. Gigawatt (GW): equal to 1,000,000,000 W; 1,000,000 kW or 1,000 MW

4. Terawatt (TW): equal to 1,000,000,000,000 W; 1,000,000,000 kW; 1,000,000 MW or 1,000 GW. 

Typical example; A 60-W incandescent bulb will, require 60 watts of electric power to operate or light up. On the other hand, A 3-kW electric kettle will need 3,000 watts of electric power to operate or boil water. The kilowatt-hour (kWh) is the basic unit of measure of the amount or quantity of electricity (electric energy) used. A kilowatt-hour is equal to one kilowatt of electric power supplied to or taken from an electrical power system for one hour. It represents the amount of work done by one kilowatt in one hour. Other representations of electric energy utilized are the following:

1. KiloWatt-hour (Wh): equal to 1000 of Wattage  or 1kW of energy  used for 1hr 

2. Megawatt-hour (MWh): equal to 1,000,000 Wattage  or 1,000kW of energy  used for 1hr

3. Gigawatt-hour (GWh): equal to 1,000,000,000 Wattage  or 1,000,000 kW or 1,ooo MW of energy  used for 1hr

4. Terawatt-hour (TWh): equal to 1,000,000,000,000 Wattage  or 1,000,000,000 kW, 1,000,000 MW, 1,000 GW of energy  used for 1hr.

The kilowatt-hour (kWh) is also known as one unit of electricity i.e. if a 100-W bulb work continuously for 10 hours, then 1 unit or 1 kilowatt-hour of electricity has been used. This is described in mathematical form as:

100-W x 10 hours = 1000 Wh = 1 kWh = 1 unit of electricity. It means a bulb of 100w capacity will use 1 KW of electricity for 10 hours continuously or interuptedly.

Most electric plants generate kilowatts (kW) or megawatts (MW) of electric power while the energy production could be in billions of units or kilowatt-hours (kWh). The average electricity usage in Nigeria varies due to categories of consumer from 24KWh to 220MWh monthly, with large differences between industrial users and residential users as well as between urban users and rural users. The world average for electricity consumption is from 242 kWh per person. In high income countries, average consumption is more than 667 kWh per person. Electricity is generated and usually transmitted as alternating current (AC). The direction of current flow is reversed 50 times per second, called 50 hertz (Hz). Because of the interconnection within the power grids, the frequency is the same throughout the grid.

Operators strive to maintain this frequency at 50 Hz. Higher voltages in many instances can be transmitted more easily by direct current (DC). High voltage direct current (HVDC) lines are used to move electricity long distances.

DEMAND: It is load requirement {either in KW or KVA} average over a suitable and specified interval of time of short duration

AVERAGE DEMAND: It is average power requirement during some specified period of time of considerable duration such as day, month or year, which give us daily, monthly or annual average power respectively.

NOTE: Average Power Demand for a specific period can be obtain by dividing the Energy consumption in Kilo-Watt hour {KWh} by the number of hours in the period {i.e. Average Power = KWh consumed in the period/ hours in the period}. 

MAXIMUM DEMAND: It is the greatest of all the DEMANDS, which have occurred during a given period. It is measured according to specification, over a prescribe time interval during a certain period such as day, month or year. 

DEMAND FACTOR: It is a factor used for estimating the proportion of the total connected load, which will come on the power plant at one-time i.e. the ratio of actual MAXIMUM DEMAND made by the load to the rating of the connected load.

                     Demand Factor= Maximum Demand/ connected load.

DIVERSITY FACTOR: It is a factor of the sum of the individual maximum demands of the different elements of a load during a specified period to the coincident demand of all these elements of load during same period.

                      Diversity Factor = Maximum Demand/ Connected Load

Load Factor: It is the ratio of average power to the maximum demand, and the Load factor fall into three categories:

Annual Load Factor = No. of Units Consumed per Year/ Maximum Demand * 8760

Monthly Load Factor=No. of Units Consumed per Month/ Maximum Demand * 720

Daily Load Factor = No. of Units Consumed per Day/ Maximum Demand * 24 

NOTE: Due to non-availability of PHCN supply for 24 hours per day, your Load factor will depend on the numbers of hours PHCN supply was available.

CONNECTED LOAD FACTOR: It is the ratio of the average power input to the connected load.

CALCULATION INVOLVE IN KNOWING TARIFF

 Maximum Demand {KW}     = Kilo-Volt Amperes {KVA} * Power factor {P.F}

Average Power                       = KWh Consumed in the Period/ Hours in the Period   

     ‘            ‘                   OR    = Maximum Demand * Load Factor

Energy Consumed per Year, Month or Day = Average Power * No. of Hours

Maximum Demand Charge   = Amount charge per KVA * Consumed KVA

Energy Charge           = Amount per KWh * Energy Consumed during the period

Total Charges            = Maximum Demand charge + Energy Charge

Note: This is global acceptable calculation in knowing tariffs worldwide, but due to different categories of consumers in Nigeria, the Maximum Demand charge is not applicable to consumers that fall within the Residential R1 to Commercial C2, which we fall into Residential R4, due to the fact that we adopt bulk metering practice in our estate, see below the latest Tariff code details from Nigerian Electricity Regulatory Commission and moreso you in order country can check with your regulatory body on tariff to determine what your cost will be at the end of the month, so do not allow anybody to cheat you do it yourself, if you have doubt about your bill, we can help you analyst it out.

Published by:

PIKARB Dey-ola

+2348028981751

There are many challenges affecting the availability of electricity supply {power} in this country, from generation to transmission and from distribution to utilization of the generated and transmitted electricity supply.

 The stakeholders and general public were all lamenting that generation is the problem because we  generate less then 4,000MGW to the approximately 6,000MGW of our present power generation capacity and the government has committed themself to increase the nation power generation capacity to 40,000MGW by year 2020, which some expert are saying it may not be realistic by then.  After indepth energy-audit from consuming end down to the generating end, they found out that some losses occured, which they attribute it to transmission  and distribution losses, which most of these losses are non-technical and trying to integrate SCADA system between generating line down to the main distribution station, neglecting the sub-stations {33 & 11kv} and the utilizer {consumer}, if truly we want to end the problem of power outage and shortage in our country, the better way forward to achieve this as a nation {Nigeria} is “DISTRIBUTION AUTOMATION”, because the conventional method in place can not guarantee efficient and quality electricity supply.

 INTRODUCTION

 The power supply industry may seem to lack competition all over the World, this come to conclusion because Power Company operates in a sectional region not serve by other companies. Favourable electric rates are a compelling factor in the sector or type of industry, although this factor is much less important in times when costs are rising rapidly and rates charged for power are uncertain than in period of stable economy condition. Electricity rates are compelling factors by National Electricity Regulatory Commission {NERC} however, this place constant pressure on companies to achieve maximum economy and earn a reasonable profit in the face of advancing cost of their production.

Power shortage and outage in Nigeria is endemic, despite government huge and continuous investment in the power sector and additional power generation every year, this appear to be no chance of shortage or outage syndrome rising-up in the near future. Barring two or three generating station with hydro potent and with two or more other potent source of generating electricity, this perpetual power deficit still exists. It seem there is no respite from these crippling deficit as seen from figures they published from time to time but, no improvement on the power outage and shortage.

 In Nigeria power sector, it has almost become a ritual insistently screeching for more power generation, this school of thought is predominant to everybody. My belief is that, it is only needed concept of load management, which emphasize continuous and copious supply of energy to all sectors of consumers at all times. This ideal proposition could be achieved, only if we have unlimited resources at our command.

 But in present practice by PHCN, these resources are not only limited but not in existence or scarce. These scarce resources are to be distributed throughout the country uniformly and called for immediate attention. A Demand Based Energy Management, that is in existence would therefore only result in outage and shortage syndrome repeating itself endlessly, since the ever grow “DEMAND” could never be met fully and satisfactory. A better approach should replace or upgrade the “Demand Based Energy Management” {DBEM} to “Need Based Energy Management” {NBEM}.

NEED BASED ENERGY MANAGEMENT

In Power sector, there is a distinct difference between ‘DEMAND’ and ‘NEED’. Consumers of electricity supply can be classified into five broad categories: Industrial, Agricultural, Commercial, Domestic and Essential services. Industrial can be sub-divided into shift based industries and continuous process industries, while Agricultural can be sub-divided also into irrigation tube-wells and rural industries, but presently PHCN categories them to Industrial, Domestic and Commercial.

Out of these several groups and sub-groups only three, the continuous process industries, domestic consumer and essentials services need power round the clock, other may DEMAND power for 24 hours, but they don’t NEED it round the clock.

 With a ‘NEED BASED ENERGY MANAGEMENT’ we can:

-         Identify the needs of various consumers

-         Forecast the generation requirement based on need

-         Plan Power generation efficiently as per forecast

-         Lay-down a suitable transmission and distribution network

-         Regulate distribution as per need

-         Monitoring matching of need with supply.

 The greatest or only bugbear of NBEM is distribution network, if this can be perfected there is no other problem with the method. Consumers can not be supplied power as per their need, since the present distribution network is full of constraints and it is clumsy to the core and the hindrance of the system are many like poor reliability, high line loss, low/high voltage profile, overloading of the transformer, poor maintenance, absence of conservation method, harmonics presence, inadequate clearance, stealing/selling of power, haphazard layout, whimsical load connection e.t.c. With a single feeder connected to all types of consumers, there is no-load discipline and the distribution network is exposed to several mal-practices and distortion, so if power problem is to be solved and over in Nigeria “Distribution hold the key not generation as we are all clamouring.

 ADVANTAGES OF NBEM

-           It ensures high resilience of supply to consumers, meeting the specific demand effectively for periods of actual requirement.

-           The system losses can be substantially reduced since line and equipments does not get overloaded at any point of time.

-           The voltage profile at all level is improved thus safeguarding the customer’s equipment from losing their efficiency and performance at low/high voltage.

-           The scheme facilitates the adoption of energy conservation method and audit policy.

-           Power outages are reduced and quality of power improves leading to better health, industrial and agricultural productivity.

 CONVENTIONAL DISTRIBUTION NETWORK

At present, the power supply network in Nigeria which is general concerns of the common man on the street, is the distribution network of 11kv HT{High Tension} lines or Feeders downstream of the 33kv substation. Each 11kv feeder, which emanates from 33kv substation, branch into several subsidiary 11kv feeders to carry power supply close to the load points, where it is further step-down to 415/230v {i.e. three phase four-wire and single phase two-wire network} through the means of 11kv/415v transformer at the sub-station or at times 33kv/415v {for industrial purpose}, from this substation, the LT{Low Tension} line carry power supply close to the consumer point of connection with three phase four wire[415v], where connection for single phase two-wire[220/230v] purpose is also possible.

 The structure of the distribution feeders in Nigeria today does not support quick fault detection, isolation of faulty region and restoration of supply to the maximum outage area that is healthy. With the absence of switches at different points in the distribution network, it is hardly possible to isolate loads for load shedding as and when required. The option available in the present distribution network of PHCN is the circuit breaker, one at each every main 11kv feeder at the 33kv substation is provided and also going round to remove link fuses from transformer or opening the feeder link. However the circuit breaker is actually provided as a means of protection to completely isolate the downstream network in the event of a fault, carrying-out repair or general maintenance, while going round to remove the link-fuse is done manually by PHCN personnel. Using this as a tool for load management is not desirable as it disconnects the power supply to a very large segment of consumers and highly risk which can result to fatal injury, redundancy and other factors to personnel and equipments. Clearly, there is a need to put in place a network/system that can achieve a finer resolution in load management.

 For example, till date in the event of a fault on any feeder section downstream, the circuit breaker at the 33kv substation trips [open] and as a result of this, there is power outage over a large section on the distribution network. If the faulty segment could be precisely/quickly identified or the G&P link fuse-out in such substation, it would be possible to restore power supply back to the black-out area, but if not they will usually go round to look for affected section and isolate the link to the affected area, through sectionalizing switches place at the strategic location in various feeder segment and it may be after several hours or days, before they can identify, rectify or isolate the faulty section, in order to restore power supply back to unaffected or healthy feeder segment.

 The lack of information at the base station (33kv substation), of the loading and healthy status of every consumer substation and associated feeders is primary causes of poor power problem in Nigeria, and also the absence of monitoring overload occurrences which typically result to low voltage at the customer end, which increase the risk of frequent breakdown of transformers and feeders. 

AUTOMATED DISTRIBUTION NETWORK

 The inefficient operation of the conventional distribution system can be mainly attributed to frequent occurrences of faults and the uncertainty in detecting them early. To enhance the power supply distribution resilience, sectionalizing switches are to be provided along the way of primary feeders. Thus by adding faults detecting relay to the sectionalizing switches along with the circuit breaker and protective relay at consumer substation (11kv/415v substation). The system will be capable of determine fault section.

To reduce the service disruption area in case of power failure, the normally open (NO) of sectionalize switch called “Route Tie” switch are use to supply restoration process. The operation of these switches is control from the control center through the “REMOTE TERMINAL UNIT {RTU} at the consumer {11kv/415v} substation.

 In automated distribution system or network, the various quantities e.g. voltage, current, frequency, switch status, temperature, oil level e.t.c. are recorded in the field at the consumer substation and feeders, using a data acquisition device called Remote Terminal Unit. These quantities are transmitted on-line to the base station through a communication media. The acquired data will be processed at the base station for display at the multiple computers through a graphic user interface {GUI}. In the event of a system quantity crossing a pre-defined threshold, an alarm is generated for operator intervention. Any control action, for opening or closing of the switch or circuit breaker is initiated by the operator and transmitted from 33kv base station through communication channel to the Remote Terminal Units {RTU’s} associated with the corresponding switch or CB. The desired switching takes place and the action is acknowledged back to operator.

 All the above mentioned function of data collection, data transmission, data monitoring, data processing, man-machine interface, e.t.c. are realize using an integrated distribution called SCADA {Supervisory Control And Data Acquisition} system.

 The implementation of this SCADA system in the electricity utilization will involves the installation of following units:

-         Sectionalizing Switches

-         Remote Terminal Unit

-         Data Acquisition System

-         Communication Interface

-         Control Computer

DISTRIBUTION AUTOMATION

 Distribution Automation functions provides a means to more effectively manage minute by minute continuous operation of a distribution system. Distribution Automation provides a tool to achieve a maximum utilization of the utility physical plant and to provide the highest quality of service to consumer. Obviously, both the utility and its consumers are beneficiaries of successful Distribution Automation. Distribution Automation system are modular, hence they may be implemented in stages, commencing from a modest degree of capability and complexity and growing as necessary to achieve tangible and intangible economic benefits; for instant a utility may start with a limited capability SCADA system for substation monitoring and control, extend this to the feeders and finally implement a complete integration of automation functions. System implemented in this fashion must be designed to accommodate future expansion.

 Distribution Automation system offers an integrated “Distribution Management System” {DMS}. As in any other SCADA system, Distribution SCADA involves collecting and analyzing information to take decisions, implementing the appropriate decisions and then verifying that the desire result are achieved. Operation management supports the analysis of distribution network, it models the load profile to present state of the network. Load flow calculation estimate voltage levels and power flows at each feeder. Job management makes switching order handling easier work protection tagging ensures the safety of repair crew on duty. Outage management and service restoration facilitates to reduce outage time, thereby increasing the reliability of the supply. Remote metering provides for the appropriate selection of energy registers where time-of-use rates are in effect, thus improving energy metering service to be more accurate and more frequent.

 LOAD MANAGEMENT IN DMS

 This involves controlling system loads by remote control of individual customer loads. Control includes suppressing or biasing automatic control of cyclic loads, as well as load switching. Load Management can also be effected by inducing customers to suppress loads during utility selected daily periods by means of time-of-day rate incentives. Distribution Automation provides the control and monitoring ability required for both the load management scenarios-viz-direct control of customers’ loads and monitoring necessary to verify that programmed levels are achieved. Execution of load management provides several possible benefits to the utility and its customer. Maximum utilization of the existing distribution system can lead to deferrals of capital expenditure. This is achieved by

-           Shaping the daily, monthly or annual} load characteristic by suppressing loads at peak times and encourage energy consumption at off-peak times.

-           Minimizing the requirement for more costly generation or power purchased by suppressing loads.

-           Relieving the consequences of significant loss of generation or similar emergency situation by suppressing load.

-           Reducing cold load pick-up during re-energized of circuits using devices with cold load pick-up features.

 The effectiveness of direct control of customer loads is obviously enhanced by selecting the larger and more significant customer loads. These include electric space and water heater, air-conditioning, washing machines, dryers and other of comparable magnitude.

 More sophisticated customer’s activated load management strategies are under research, taking advantage of the capabilities of Distribution Automation and of customers installed load control PC, with such arrangement the utility could vary rates throughout the day, reflecting actual generation costs and any system supply capability constrains and broadcast to a customer selected cost bias, this is sometimes called as “SPOT-PRICING”.

 AUTOMATED DISTRIBUTION SYSTEM

 In the conventional distribution system the abnormal condition are detected manually which costs lots of time and money to both consumer and power industry. In order to maintain high service quality and reliability and also minimize loss in revenues, automation is required. Automation need to be applied to the sub-stations distribution system so that problems on distribution network may be detected and operated upon, so as to minimize the outage time.

 The equipments either fixed or/and programmable, which are used for distribution automation include;

-           Data collection equipment

-           Data transmission {tele-metering} equipment

-           Data monitoring equipment

-           Data processing equipment

-           Man-machine interface.

 All the above equipments are integrated through distribution SCADA system. Distribution SCADA involves collecting and analyzing information to take decisions and then implement them and finally verifying whether desire results are achieved. The implementation of SCADA system in the electric utility involves the installation of following units.

 A}        DATA ACQUISITION UNIT

 The basic variables {data} required for control, monitoring and protection include current, voltage, frequency, time, power-factor, reactive power and real or active power. The data may be tapped in analog or digital format as required. For data collection purpose CT’s i.e. current transformer and PT’s i.e. potential or voltage transformer are used. Transducers may be needed to convert the data into electrical form to enable easy measurement and transmission, the data is amplified in signal amplifier and conditioned in data signal conditioner and later transmitted from the process location to the transmission room, in the control room data processing and data logging are performed which includes input scanning at required interval, recording, programming and display by microprocessor, PLC PC e.t.c.

 B}        REMOTE TERMINAL UNIT [RTU]

 RTU is used to record and check signals, measure values and meter readings before transmitting them to control station and in the opposite direction to transmit commands, set-point values and other signal to the switch-gear and actuator.

 C}        COMMUNICATION UNIT

 A good data communication system to transmit the control command and data between distribution control centre and large number of remotely located devices is a prerequisite for a good performance of DA system. Wide ranges of communication technologies are available to perform the task of DA system, which include Public Telephone Communication [either leased or dedicated line], Power Line Carrier Communication [PLCC], Ultra High Frequency Multi-Address Radio System [UHF MARS] and Very High Frequency Radio [VHFR].

 DISTRIBUTION AUTOMATION

 Distribution Automation can be broadly classified as:-

-           Substation Automation

-           Feeder Automation

-           Consumer side Automation

 1}         SUBSTATION AUTOMATION

 Substation Automation is the cutting edge technology in electrical engineering, it means having an intelligent and interactive power distribution network which result to:-

-           Increase in performance and resilience of electrical protection

-           Advance disturbance and event recording capability, aiding in details electrical fault analysis.

-           Display of real-time substation information in a control center.

-           Remote switching and advanced supervisory control.

-           Increase integrity and safety of the electrical power network including advanced interlocking functions.

-           Advanced automation functions like intelligent load-shedding.

 REQUIREMENTS FOR SUBSTATION AUTOMATION

 The general requirements for selecting an automation system while designing new or upgrading substation are:

-           The system should be adaptable to any vendor’s hardware

-           It should incorporate distributed architecture to minimize wiring

-           It should be flexible and easily setup by the user.

-           The substation unit should include a computer or control-module to store data and pre-process information.

 FUNCTION OF SUBSTATION AUTOMATION 

Bus-voltages and frequencies, line-loading, transformer-loading, power-factor, real-time and reactive power flow, temperature, etc. are the basic variables related with substation control and instrumentation. The various supervision, control and protection are performed in the substation control-room, these panels along with PC aids in automatic operation of various circuit-breakers, tap-changers, auto-reclosers, sectionalizing-switches and other devices during faults and abnormal conditions. Thus primary control in substation is of two categories:

-           Normal routine operation by operators command with the aid of analog and digital control system.

-           Automatic operation by action of protective relays, control system and PC.

 The automated substation functioning can be treated as integration of two sub-systems, as discussed below:

A}        CONTROL SYSTEM

The task of control system in a substation includes data collection, scanning, event reporting and recording, voltage control, power control, frequency control, other automatic and semi-automatic controls etc. The various switching action like auto-re-closing of line, circuit-breakers, operation of sectionalizing switches, on-load tap-changers are performed by remote command from control room. The other sequential operations like load transfer from one bus to another load shedding etc. are also taken care by control center.

B}        PROTECTIVE SYSTEM

The task of protective system includes sensing abnormal condition, annunciation of abnormal condition, alarm, automatic tripping, back-up protection, protective signaling.

 The above two system work in close co-operation with each other, most of the above functions i.e. automatic switching sequences, sequential event recording, compiling of energy and other reports etc. are integrated in software in the substation computer or programmed in control-module. This software or programming is of modular design, which facilitates addition of new functions, the communication between circuit breakers, auto-reclosers and sectionalizing switches in the primary and secondary distribution circuits located in the field and the PC in distribution substation control room may be through Radio Tele-control and Fibre-optic channel or Power-line carrier channel as is feasible.  

 2}         FEEDER AUTOMATION

 Automating the fault diagnosis and supply restoration process significantly reduces the duration of service interruption. The key objective behind automating the service restoration process is to restore supply to maximum loads in out-of-service zones. This is achieved by reconfiguring the network such that the constraints of the system are not violated. Providing timely restoration of supply to outage areas of the feeder, these enhance the value of service to customers and retain the revenue for the power industry.

 The system data consisting of the status signals and electrical analog quantities are obtained using a suitable Data Acquisition System and processed by the control computer for typical functions of fault detection, isolation and network reconfiguration for supply restoration. The equipments normally required in Feeder Automation are discussed below:

A}        DISTRIBUTION EQUIPMENTS

This includes transformers, breakers, load-break switches and motor operators, power re-closures, voltage regulators, capacitor banks etc.

B}        INTERFACE EQUIPMENTS

Interface equipment is required for the purpose of data acquisition and control. Potential transformer, current transformer with VAR meter and voltage transducer, relay is some example.

C}        AUTOMATION EQUIPMENTS

Automation equipments include a DAS, communication equipment, substation remote terminal unit {RTU} and distribution feeder RTU, current-to-voltage converter etc.

 3}         CONSUMER-SIDE AUTOMATION

 Consumer side automation is very important for a distribution company as almost 70% of all the losses are taking place on distribution side alone. It is needed to evaluate the performance of a specific area in the distribution system and judge the overall losses.

 ENERGY AUDITING

 Energy audit has a very wide range of application in the electrical systems. It means overall accounting of energy generated, transmitted and distributed. As far as distribution side is concerned energy audit would mean overall accounting of energy supplied to and utilized by the consumers. It can also be used for rethinking about billing strategy, usefulness of an individual subscriber, loading of a given feeder etc.

 Remote metering suppose to be use in energy auditing in which the energy used by a consumer is billed from a remote [distant] location without actually going to the place. In remote metering, the concept of TOD [Time-of-Day] metering can be introduced somewhere in the electronic meters at consumers service entrance point and programmed to read the following meter readings on monthly basis

I}         KW hrs consumed during calendar month by the consumer during low tariff and high tariff hours.

II}        KVA maximum demand by the consumer during the calendar month {i.e. based on maximum demand lasting for 30 minutes duration}.

III}      Low tariff off-peak hour consumption.

 These readings are telemeter to the control room for the purpose of monthly billing and cash collection through the various mode of communication available [viz- telephonic and wireless communication] depending on the load condition of the consumer. Tampering of energy-meter [if done] is also telemeter for taking action /penalty and disconnection of service.

 Thus energy audit, though a very cumbersome and tedious job, can make a non-profitable business of distribution into highly profitable one.

 ADVANTAGES OF DISTRIBUTION AUTOMATION

 More and more electric utilities are looking to distribution automation as an answer to the three major economic challenges facing the industry.

-           The rising cost of adding generating capacity

-           Increased saturation of existing distribution network and

-           Greater sensitivity to customer service, as well as in areas related to operational cost saving as given below:

A}        REDUCE LINE LOSS

The distribution substation is the electrical hub for the distribution network. A close co-ordination between the substation equipments, distribution feeders and associated equipment is necessary to increase system reliability. Volt/VAr control is addressed through expert algorithms which monitors and controls substation voltage devices in co-ordination with downtime voltage devices to reduce line loss and increase line through-out.

B}        POWER LINE QUALITY

Mitigation equipment is essential to maintain power quality over distribution feeders. The substation RTU in conjunction with power monitoring equipment on the feeders monitors, detects and control power related problems before they occur, providing a greater level of customer satisfaction.

C}        DEFERRED CAPITAL EXPENSES

A preventive maintenance algorithm may be integrated into the system. The resulting ability to schedule maintenance reduces labour cost, optimizes equipment use and extends equipment life-span.

D}        ENERGY COST REDUCTION

Real-time monitoring of power usage through-out the distribution feeder, provide data allowing the end user to track his energy consumption patterns, allocate usage and assign accountability to first line supervisors and daily operating personnel to reduce overall cost.

E}        OPTIMAL ENERGY USE

Real-time control, as part of a fully-integrated automated power management system, provides the ability to perform calculation to reduce demand changes. It also offers a load-shedding/preservation algorithm to optimize utility and multiple power sources, integrating cost of power into the algorithm.

F}        ECONOMIC BENEFITS

Investment related benefits of distribution automation come from a more effective use of the system. Utilities are able to operate close to the edge to the physical limits of their systems, distribution automation makes this possible by providing increased availability of better data for planning, engineering and maintenance. Investment related benefits can be achieved by deferring addition of generation capacity, releasing transmission capacity and deferring the additional, replacement of distribution substation equipment. Features such as Voltage/VAr control, data monitoring and logging and load-management contribute to capital deferred benefits.

 Distribution automation can provide a balance of both quantitative and qualitative benefits in the areas of interruption and customer service by automatically locating feeder faults, decreasing the time required to restore service to un-faulted feeder sections and reducing cost associated with customer complaints.

G}        IMPROVED RELIABILITY {RESILIENCE}

On the qualitative side, resilience adds perceived value for customer and reduces the number of complaints. Distribution automation features that provide interruption and customer service related benefits includes load-shedding and other automatic control functions.

 Lower operating costs are other major benefits of distribution automation. Operating cost reduction are achieved through improved voltage profiles control VAr flow, repairs and maintenance savings, generation fuel savings from reduced substation transformer load losses, reduced feeder primary and distribution transformer losses, load-management and reduced spinning reserve requirements. In addition, data acquisition and processing and remote metering functions play a large role in reducing operating cost and should be considered an integral part of any distribution automation system.

 Through real-time operation, the control computer can locate the fault much faster and control the switches and re-closures to quickly re-route power and minimize the total time-out, thus increasing the system reliability.

H}        COMPABILITY

Distribution Automation spans many functional and product area including computer system, application software, RTU’s communication system and meter products. No single vendor provides all the pieces, therefore in order to be able to supply utility with a complete and integrated system, it is important for the supplier to have alliances and agreements with other vendors.

 Conclusion

Effective distribution automation systems combine complementary function and capabilities and require an architecture that is flexible or “OPEN” so that it can accommodate product from different vendors. In addition a distribution automation system often requires interfaces with existing system in order to allow migration and integration and also to monitor security network, efficiency e.t.c.

Watch-out for the full publication online and other means of media publication.

PIKARB Dey-ola

A Generator sets are set of mechanical devices that converts mechanical energy to electrical energy.  Generator comprises of engine system, air-intake system, cooling system, electrical system, lubricating system, fuel system and battery system.

Engine System: It is the major and central part where other systems are connected to for proper operation and efficiency of the generator, it comprises of front, rear, exhaust-side and fuel-side connection point

Front View Connection Point: We have exhaust air inlet, drive belt, vibration damper, fan pulley, water pump, charging alternator, fuel pump drive cover, coolant filter, turbor charger inlet and outlet.

Rear View  Connection Point: We have pilot bearing bore, flexplate mounting holes, turbocharger exhaust outlet, crankcase breather vent tube, flywheel and flywheel housing.

Exhaust Side View Connection Point: it consists of fifteen connection point like water-outlet, lubricating oil filter, temperature thermostart and sensor, lubricating oil pressure before and after filter, lubricating oil cooler, coolant inlet, 1/2” NPTF i.e. coolant, turbocharger oil drain, exhaust outlet, wastagate actuator and air outlet, provision cab heater and finally provision for coolant heater.

Fuel Pump Side View Connection Point: We have rearlifting bracket, M22 x 1.50 {air}, fuel/water seperator or filter, fuel transfer pump, 3/4 x 16″ UNF tap for magnetic pickup, provision for oil pan sump heater, lubricating oil drainage plug, front engine mounting bracket, fuel injection pump, front engine mounting bracket, distributor valve, high pressure line and 1/4″ NPTF {air}.

To be continued

Articulated and Edited by

PIKARB Dey-ola

Introduction

Protection in electrical/electronic installation and equipments need to be take as priority in existences and usefulness to both human life and to the property, the motives behind this is for good efficiency i.e. it will guide against loss or huge mis-fortune { safety and running cost {maintenance} and repair cost reduction}.

A good protection provided for elect/elect. installation and equipments will give self reliance and confidence that if eventually anything go wrong live and property will be guide against and it would not result to huge down cost and time.

Necessary protective device put in place serve as resilience against undue inteferrence that can happen on the circuitry network, either by means of excessive current, mechanical damages or leakages of current to exposed path of the property, which all these can cause fire-outbreak or injury to peoples or livestocks, so we discussed briefly below on necessary protection to guide against or put in place.

What Is Protection

Protection is no difference from what we know in literary word i.e. whether to protect against personal or financial loss by means of insurance and from injury or discomfort by the use of the correct protective clothing and also protection of propery by putting security measures in place such as locks, alarm/buglar system. Electrical engineers share these concept too, which make them emphasis that electrical system should be:

Protected against mechanical damages

Protected against electric shock/electrocution of persons/livestock or damage to equipments and installation

Protected against excessive current

Mechanical Protection

Protection against mechanical damages has not to do only with compression or bruise by solid objetcs or physical impact, it includes protection against corrosion, thermal effects, external influences, liquid, name it. Even it includes some unseen occurrence like serious electrical over-current left unattended to for too long and the likes, which can result to degradation of insulation, distortion of cables, flashing, fire-outbreak e.t.c.

Excessive Current Protection

Excessive current is a current that is greater than the normal rated current in a circuit and it is as a result of an overloading, short-circuit or fault current, in a circuit. These occurrences need to be protected or guide against in order to avoid damage to installation conductors and equipments by means of circuit-breakers, fuses and so on.

Overloading current: Usually happen in a healthy circuit, due to faulty equipments, surge that arise when starting motors {i.e. instatenous current rise due to the principle of operation or windings in machinery}, or by adding to much loads { i.e. appliances, gadgets, devices e.t.c. to a circuits} over specified rated capacity of a circuits or installations or equipments, and it is one of the reason you have burnt around your socket-outlet [fixed or extension] or any other places you may see or notice burnt in your installation or equipments.

Short-circuits  current: Are currents that occur or flow when  there is a ‘dead or short’ between live  conductors i.e. phase and neutral for single phase and phase to phase for three phase installation. Short circuit current is the same but the way is usually used to signify the value of short circuit current at fuse or circuit breaker position. Short circuit current is of great importance that can rupture or open fuses and breakers if exist in an installation.

Electric-shock/Electrocution: Either to personnels or livestock can occur when the current flowing through the installation or equipments find it way either through lapses in any aforementioned protection to the exposed metal path of the installation or due to the high resistivity of the soil area or what the earthing materials {i.e. earthing rod/electrode, down conductor, check article on earthing for further insight} offer to a flow of current, which make the currents or voltages flowing across the current carrying conductor not to balanced or neutralize in the installation with its prospective potential {i.e. the Zero/O voltage} of the general mass of earth, which in-turn will want to find prospective potential by all means and with  Zero/O voltage potential of metal part and the ground which any living being touched and stand on make the currents or voltages to find the Zero voltage, because all the living being have low resistivity to flow of current {i.e. we are good conducting materials due to flow of blood in our system}, that is one of the reason we are advice to protect our selves by putting on protective cloth, hand-gloves, safety shoes and so on, when intend to touch electrical installation.

Conclusion

We believe you can see now how protection is very paramount in our electrical/electronic installation and equipments and it is not for you alone but for your entire household.

So, that is the reason you and your entire household we receive shock or get electrocute, if proper protection is not put in place and this has resulted to wasteful of  many lifes and properties and also make most peoples loose their loved one and properties to fire-outbreak.

Our question now is what are you waiting for to get protected from the monster called electricity, so act now in order not to regrets later.

For comments and comprehensive analysis  and practical compliance just contact us through mail pikengconsult@yahoo.com or by dialing +2348028981751 from your cell-phone.

PIKARB DEY-OLA             {For PIKENG INSIGHT}

WHAT IS EARTHING?  

“Earthing” is described as a system of electrical connections to the general mass of earth, the primary characteristic that determining the effectiveness of an earth electrode is the resistance, which it provides between the earthing system and the general mass of earth.  

Earthing is the essential part of your installation or any power network both at high, medium or low voltage set-up, it provide some resistivity to the flow of current in an installation through the earth electrode {earth-rod} buried or embeded to the general mass of earth.The purpose of Earthing  is to provide:

Protection of buildings and installations against lightning. 

Safety of human and animal life by limiting touch and step voltages to safe values. 

An installation or building without good earthing system is at great risk to equipments, life and other valuable things within and outside the environment, it is to this affirmation that make different bodies  with groups of engineers to recommend good earthing method like, TN-S, TN-C e.t.c. 

Good earthing system required low soil resistivity, while the soil resistivity (specific resistance of the soil) is usually measured in Ohm metres, one Ohm metre being the resistivity the soil has when it has a resistance of one Ohm between the opposite faces of a cube of soil having one metre sides. Soil resistivity varies greatly from one location to another. For example, soil around the banks of a river have a resistivity in the order of 1.5 Ohm metres. In the other extreme, dry sand in elevated areas an have values as high as 10,000 Ohm metres.

The resistance of the earth path is determined, (1) by the resistivity of the soil surrounding the earth rod, (2) by its contact resistance between the earth rod and the surrounding soil and, (3) by the resistance of the earth rod and connecting conductors. When an electrical current passes into the soil from a buried earth rod, it passes from a low resistance metal into an immediate area of high resistance soil.

 There are some basic defination relating to earthing they are:-

Earthing or earthing system

It is the total of all means and measure of an electrical circut, accessible conductive parts of electrical equipment (exposed conductive parts) or conductive parts in the vicinity of an electrical installation (extraneous conductive parts) are connected to earth.  It is a metal conductor or any metal part that conduct in the same manner, which is embedded or buried in the ground and electrically connected to it, or  in the concrete, which is in contact with the earth over a large area.

Earthing conductor

It is a conductor which connected a part of an electrical installation to the exposed condusive parts or extraneous conductive parts to an earth electrode or which interconnects earth electrodes. The earthing conductor is laid above the soil or, if it is buried in the soil, is insulated from it.

Reference earth

Earth electrode

It is the part of the ground, particularly on the surface, located outside the region influence of the considered earth electrode, i.e. between two random points at which there is no perceptible voltages resulting from the earthing current flow through this electrode. The potential of reference earth is always assumed to be zero.

Earthing voltage (earthing potential)

Ve is the voltage occurring between the earthing system and reference earth at a given value of the earth current flowing through this earthing system.

Earth resistivity (specific earth resistance)

It is the resistance, measured between two opposite faces, of a one-metre cube of earth. The earth resistivity is expressed in ohm-meter.

Earthing resistance and earth surface potential distribution are the main parameters characterising electrical properties of the earthing system.

Electrical parameters of the earthing system depend on both soil properties and earth electrode geometry.

Soil properties are characterised by earth resistivity, which changes over a wide range from a few Wm up to few thousand Wm, depending on the type of ground and its structure, as well as its humidity. As a result, it is difficult to calculate an exact value of earthing resistance. All relationships describing earthing resistanceare derived with the assumption that the ground has a homogenous structure and constant resistivity. Ideally, the earth surface potential should be flat in the area around the earth electrode, this is important for protection against electric shock, and is characterised by touch and step voltages. Rod electrodes have a most unfavourable surface potential distribution, while meshed electrodes have a much flatter distribution.

The behaviour of the earthing system for high transient currents should be considered. Very high current values diminish earthing resistance due to the strong electric field between the earth electrode and the soil, while fast current changes increase earthing impedance due to earth electrode inductance. The earthing impedance is, in this case, a superposition of both these events.

Conclusion

There are more to earthing these is just a bit insight about it and be very aware that poor earthing method in your building are liable to collapsing or fracture during lightning i.e. thunder strike, surge or any atmospheric dischage which can also result to damage some of your sensitive equipment.

Also, your electrical earthing installation should have good sound of electrical and mechanical properties in order to avoid disturbance can lead to fire out-break or arcing on any of the installation contacts

For comprehensive details on earthing system, methodology, resistivity and many more, feel free to contact us and we do justice to it for you, especially students of electrical/electronics engineering, fresh graduate, apprentices and reseacher, captain of industries or anybody that might show interest.

Edited and Articulated By

PIKARB DEY-OLA

For PIKENG INSIGHT

 Frequently Asked Question

Q.      Is there any different between Common bulbs and Energy saver?

Ans.    Yes there is much difference between the 2-types of bulbs, energy saver save more electricity supply either on PHCN or Generator supply, higher efficiency, longer-lifespan e.t.c., while common bulbs consumed much, low-efficiency and short lifespan .

Q.      What is the efficiency different between the 2 types of bulbs?

Ans.    Energy saver has 80% efficiency over common bulbs.

Q.       What is the life-span of the 2 types of bulbs?

Ans.    The minimum life-span for energy saving bulbs is 6,000 hours {18-months}, some have up to 15,000 hours {45-months}, while the maximum hours of common-bulbs is 1,000 hours {3-months}, check the bulb carton for verification.

Q.       What do I stand to gain if I swap from Common bulbs to Energy saving lamp?

Ans.     Longer-life, Low- PHCN bill, Low running cost, low generated heat e.t.c.

Q.        How does a lower rating Energy saver be more efficient than higher rating Common bulb?

Ans.    Its efficiency comes from differences between their rating as the energy saver with its low rating has similar or more luminous intensity {LUMEN} on working plane with common bulb.

Q.       What about its longer-life span?

Ans.    Its long existence is due to methodology used to power the lamp by rectifying the 220v AC supply to 12v DC supply.

Q.        What is different between AC supply and DC supply?

Ans.    Alternating current it is a circuit that its voltage or current has both directional and magnitude waves, which make the current or voltage more sinusodial, while Direct current it is a circuit that its voltage or current  has only directional waves and its voltage or current are not sinusodial in nature.

Q.       What makes bulbs, lamps or light more brighter than each other?

Ans.    Its only their lumen rating {i.e. luminous intensity of  the types of  gas coated inside the bulb that fall on a working plane} that make them brighter.

Q.      What about their capacity rating?

Ans.    Their capacity rating does not really make them brighter,  it only make them consumed more electricity supply and generated heat.

Q.      Why?

Ans.    Due to principle of operation of illumination each gas has its luminous intensity {lumen}i.e. an illumination use an ultra-violet gas to emitted from a source.

Q.      Can I get some helpful hints or tips on cost implication?

Ans.   Yes, read the below article for brief explanation and if you need further or more details on it, send us message through our facebook page or an e-mail through pikengconsult@yahoo.com

70%  REDUCTION ON YOUR PHCN BILL CONSUMPTION

Have you read the previous articles posted on illumination and understand or see the differences between Energy Saving Lamp and Common Bulbs we used in our differents homes and offices,.

Now its time to know the cost implication of both types,  most of us belief will do save money in buying things  by considering the initially cost and without proper running cost analysis, researched revealed that some people belief that buying common bulbs of 40w/60w is cheaper than buy an energy saving lamp, though its somehow true when considering the initially cost of the common bulbs to energy saving lamp price which energy saver bulbs, but in real practical world i.e the running cost, the common bulbs has over 40o% cost implication than energy saver, we mean in terms of running cost a typical example is a 40w, 400 lumen incandescent bulb was switched ON for 12 hours[6:30pm-6:30am} for 30-days , likewise a 8w, 420 lumen energy saver bulb was switched ON for the same period, the incandescent bulb cost #50.00, while the energy saver bulb cost #150.00, now lets do the comparison on the running cost

Let assumed our homes billed as Residential 2, with tarrif per kilowatt-hour of #4.4o.

A kilowatt-hour means 1000w/1kw is being used for an hour

 Total running hours of the bulbs in 30 days is 12 x 30 = 360 hours

The running cost of 40w common bulb 1s 40 x  360 divide by 1000=14.4 x 4.4 = # 63.36.

While the running cost of 8w energy saver is 8 x360 divide by 1000=2.88 x 4.4 = #12.67.

There is assurance that the energy saver will last for minimum of one-year in existence and the common bulb will last for maximum of 4-month and with the differences, you will buy the common bulbs at least 3-times within one-year.

Recommendation/ advise for long-last existence of your bulbs and PHCN bill reduction

1    Switch-off your light during day-lights

2    Switch-off your bulbs when PHCN supply fails or fluctuate

3    Ensure that the bulbs is fasten properly with the lampholder

4   Ensure/ Check for proper tighten of the cables/wires at the lampholder cable/wire terminals

5    Replace all your common bulbs to energy saving bulbs

6    Observe your PHCN bill every-month  after necessary adjustment

NB: If you can put all these in place, you are going to see the differences in your PHCN bill and payless that what you pay before, provided the PHCN staff have access to record your meter reading.

Illumination it is simply lighting in literary word and this exist in our various homes and offices, one way or the other by different method and types of lighting we put in place.

Lighting is very essential for our daily activities, most especially during the hours of darkness or places but the approach we give to it in most of our homes and offices make it much consumable than other equipments using electricity supply in our environments, although it have limited ratings to some equipments in our homes and offices but if we can observed very well, we will discover that our light was  switched-ON for long duration than pressing-iron and high wattages appliances, for example let assumed we have 5nos of 60w bulb in homes and pressing-iron of 1000w and we used our iron once in a week for 1-hour and we put-ON our light bulb for 12 hours a day [ 6.30pm-6.30am], the result at the end of the month for each of the appliances is that the pressing-iron consumed 4-units of energy [electricity] supply, while the light bulb consumed 108-units of energy [electricity] supply, the we pay for each of the appliances is as follows for a residential homes categorised as  RESIDENTIAL 2 by Nigerian Electricity Regulatory Commission [NERC] is #4.40k  and the amout charge for the comsumption units of each appliance, for pressing-iron is #17.60k, while #475.20k will be charge for the consumption of the light-bulb. Note you can see how to know your energy consumption on our article ” FACTORS INFLUENCING COSTS AND TARRIFS OF ELECTRICITY SUPPLY posted on the discussion tab our Fan and Group page at http//www.facebook.com/pikarb engineering cconsult

The differences in their consumption is not akin at all and also in some homes they have up 2o nos of 40w bulbs with their chandeliar-fittings alone, while in some homes they swithed their light-ON for 24hours, due to interior decoration like curtains, window blind and other stuff which make place a bit dark.

It is not a problem to have light switched-ON for 24 hours in our homes because it has beautiful effect on it, but if we want to do that we can use energy saving light like, energy saver bulbs 0r flouresent fittings indoor/outdoor instead of common 60w, 100w, 200w, 250w, 400w, 500w 0r 1000w bulbs, halogen or flood-light and they will still the brighting effects.

So, watch-out for insight on big differences between energy saving lamp and other types of lamps like incandescent bulbs e.t.c., we hope you will find this insight helpful, likewise we welcome your views, comments and enquiries

Happy reading

PIKARB DEY-OLA { for PIKENG INSIGHT}

 Editorial Notes

 Our second publication in the month of July 2010, will focused on ILLUMINATION. Illumination it is simply lighting in literary word and this exist in our various homes and offices, one way or the other by different method and types of lighting we put in place.

Many homes and offices dont know that, there lighting consumption  alone   constitute 70% of their NEPA/PHCN monthly bill, compare to other equipments.

Lighting is very essential, especially during the hours of darkness for proper visualization of humans, objects and things aroud us. With this concept we put in place differents method and types of light which consumed or contribute  70% of our energy consumption range from incandescent bulb, mercury bulb, halogen bulb, flourescent, flood-light e.t.c., so we hope this publication will help you out on how you can choose the method and type of light that will reduce your energy consumption and costs.

Our main focused on Illumination will be the differences, advantages/dis-advantages, costs implication between Incandescent light {Bulb}, High pressure mercury lamp and  Energy saving lamp with examples, illustrations and references, anybody that wish to make enquiries or details articles about other types of  lighting should mail us through pikengconsult@yahoo.com.

Watch-out through our blog on 26th July 2010

Yes its time for us to unleashed our first issue on our feature PIKENG INSIGHT, here we go:

RESILIENCE ON YOUR EQUIPMENTS AND INSTALLATION

Resilience as the name implies and after searching carefully for the meaning in different dictionaries {Chambers, Oxford, Longman, Therasus name it} in literary word apart from technology meaning which we familiar with, the meaning still reflect the same inline with technological term.

Resilience is the availabilty methodology of your equipments or installation to do real-work without or less interruption and it is the key parameters in determining the quality of either your equipments or installations, this terms has its require or expected values in this western world as 99.98% is expected for domestic usage, while 99.996% is required of commercial/industrial usage, such high levels of resilient can not happen naturally or by chance: they are the result of excellent design and good maintenance practice and procedure and attention to detail.

As it is observed globally, availablity potentially reduces at every connection, protection device, cable, etc throughout the installation so that it is highest at the point of common coupling (PCC) and lowest at the equipment terminals, availability at the PCC is estimated around 99.98% because the supply network is highly redundant.

High reliability and redundancy is a good concept of resilient in an equipments or installation, if there is high reliability alone without a redundancy feature on your equipments or installation, it will be only monitor failure rate which is the concept of high reliability as there are various type of failures and the basic requirement of high reliability of individual units is discussed in the next section and redundancy in this aspect is not worthless, we mean idleness,readiness i.e. it can be call to operartion anytime it necessity arise.

Reliability

Reliability is the probability that a system or components will performed a required function under stated condition for a specified period of time and it is measured in terms of the Mean Time To Failure (MTTF). The MTTF is quoted in hours and is the average time taken for each individual member of a large population of standard production parts to fail. Reliability is difficult and time consuming to measure; it is a statistical number derived from a combination of historic experience with similar components and relatively short-term tests on large numbers of the components in question. As products mature, longer-term data accumulates and confidence in the MTTF figure increases. But it is not a guarantee.

Failure may occur as we have it, as catastrophic failure i.e. complete and sudden failure, like a light bulb failing, or as degradation failure i.e. gradual or partial failure, like an electronic device/television set moving outside its specification. Also in the case of an electrical supply, a complete loss of power would be a catastrophic failure, while voltage or frequency deviation would be regarded as degradation failure. A failure is primary if it is not caused by failure in another part of the system, and secondary if it is the result of the failure of another part of the system. As an example, the normal failure of a light bulb would be a primary failure, but failure following a severe overvoltage would be a secondary failure because it is the result of a failure elsewhere. Reliability data can only give information about primary failures that is one of the reason it should not only compliment Resilient. Some failures may be obvious, such as the blowing of a light bulb, but in other cases, it may be much harder to determine that a failure has occurred. For example, a complex electronic circuit that must meet a detailed specification has failed if any parameter has moved outside the specified limits although this may not be apparent to the user. An electronic interface circuit may be required to have a certain immunity to noise voltage; failure to maintain this immunity would not be noticed under noise free conditions, but the symptoms would be apparent under more extreme conditions. In such cases failures and errors may appear to be random and it is likely to be difficult to localise the cause and effect a repair rapidly.

Failure is has three differrent distinct periods on bath-tube curved namely;

Early life or Early failure or burn-in period
Useful life or normal operating period or constant
Wear-out or old age

Early life or Burn-in

This is the period, when failure-rate(t) is decreasing as weak or substandard components fail. It is known as the early life, early failure, infant mortality or burn-in period. The reasons for the first three terms should be obvious. Burn-in is a process sometimes used in the final stages of manufacture of components in order to weed out early failures. It involves the components being run under normal conditions (or controlled conditions somewhat more severe than normal to accelerate the process) for sufficiently long to survive the early life period. See the stage on attached fig. on bath-tub curve

Useful life or Normal operating period or Constant Failure period

This is a period of effectively constant, relatively low failure-rate(t), known as the useful life or normal operating period. During this time, the failure rate is independent of the time for which the component has been run. In other words, the probability of failure of a component is the same throughout this period. See the stage on attached fig. on bath-tub curve.

Wear-out or old age

This is the period, when the failure rate increases steeply with time, known as the wear-out or old age period. The bathtub curve describes the behaviour that might well be expected for many types of component, or even for complex systems such as a UPS. Taking the familiar example of light bulbs, failures during early life might be due to filaments that have been badly attached to their supports, that have been locally drawn too thin or that have nicks in them. Another cause of early failure could be leaky glass envelopes, leading to filament oxidisation. During useful life the filaments gradually evaporate and become thinner until they break, usually under the thermal stress induced by current surges at switching-ON. If all bulbs were identical and were operated under identical conditions, they would all fail at the same time. However, since no manufacturing process will produce identical components, some will have serious faults leading to failure during early life, and the failure rate decreases as the weaker components are weeded out. Similarly, it is reasonable to expect a range of failure times during the wear-out period. In the case of light bulbs, filament composition, thickness, length and shape will vary slightly from bulb to bulb, thus leading to a spread in the time at which they finally break. As the bulbs get older, their probability of failure increases, giving a steep rise on the right-hand side of the bathtub curve. It is perhaps harder to see why there should be any failures at all during the normal operating period, once early failures have been weeded out and there has not yet been any significant wear. A detailed analysis of the numerous ways in which a light bulb could fail would be extremely complex because of the variety of mechanical, thermal and chemical processes that can take place. The wide range of possibilities, each with its own time dependence, averages out to produce a failure probability that is effectively independent of time. The process is referred to as ‘memory-less’, because the probability of failure is assumed to be independent of previous history. These failures are also sometimes called catastrophic because they are unexpected. In fact, in many cases, the wear-out processes are already taking place at a very low level so the process is not truly ‘memory-less’. The manufacture of components and assemblies often involves a burn-in process so that those subject to early life failure can be removed from the supply chain. In many cases, electronic components do not reach their wear-out period during operational life, they may have useful lives that are much longer than the operational life of the system in which they are used. Routine maintenance procedures should be designed to ensure that components that can wear out like rechargeable batteries, for example are replaced well before the onset of wear-out. Because of this, it is usually possible to assume that components are run only during their period of useful life and that they have a constant failure rate. See the stage on attached fig. on bath-tub curve.

Mean time to failure (MTTF)

The mean time to failure is a term that is applied to non-repairable parts such as light bulbs and is a measurement of the average time to failure of a large number of similar parts which operate under specified conditions. The conditions of test are important, for example an increase in the operating temperature or voltage of most components will reduce the MTTF.

In practice, the MTTF is often calculated from data taken over a period of time in which not all the components fail. In this case MTTF = Total operating time for all components /No of failures at that time.

Mean time between failures (MTBF)

In the case of components or system elements that can be repaired, failure rates are often expressed in terms of the mean time between failures (MTBF) rather than mean time to failure (MTTF). This is a measure of the average time that a piece of equipment performs its function without requiring repair (although it may require routine scheduled maintenance). Because MTTF and MTBF are statistical quantities, a large number of failures must be recorded in order to establish confidence in the result. Testing one piece of equipment for a very long time is impracticable so it is usual to test a large number of samples simultaneously for a shorter period, and to determine the total number of faults in the total operating time for all of the samples. This method assumes that burn-in and wear-out failure modes are not involved.

Availability and mean time to repair (MTTR)

System users are now more concerned with availability rather than reliability. The availability of a system or of a component is the proportion of time for which it is operating correctly and available for use. It is the ratio of operational time to total time, which is the sum of the operational and repair times. The average time needed for repairs is called the mean time to repair (MTTR).
Availability = MTBF/[MTBF + MTTR]

MTTR times are specified by manufacturers under ideal conditions, assuming, for example, that the site of the failure is obvious, that the required skill level to identify it is available, that suitable spares and repair procedures are on hand and that, once repaired, the system can be tested and recommissioned. In real life failures occur at the worst possible time. A quoted MTTR of twenty minutes is of little advantage if an
engineer has to travel to site to identify the problem and then procure parts from a depot or, worse, a distributor. Following repair, the system must be tested and recommissioned before real work can begin again. Each of these steps may take many times longer than the repair itself. Some delays can be avoided, critical spares can be held locally, in-house staff can be trained to provide the necessary technical skills but these steps have to be implemented well in advance and are not without their own cost implications. Taking the simple example of a television repair that takes, say 30 minutes to replace a circuit board, the manufacturer would quote a MTTR of 0.5 hours. But the user sees things differently. The set breaks down while the repair shop is closed. It has to be collected, the fault identified, and the replacement parts identified. After an estimate is prepared and approved, the part is procured, and – now the 30 minutes start fitted and tested. The next day the set is returned to the user, who has experienced a MTTR of perhaps one week. If the MTBF were long enough the user may be quite content, but if the MTBF is short the user may well want to have a redundant television set available! Often, the repair will take the form of replacement by a new or previously repaired component or subsystem. When a repaired sub-system is fitted it must be remembered that only a few of the components are new while the rest of the components are already aged. The MTTF must be less than that of a new unit.
To be completely fair, the MTTR should also include the downtime required for normal in-service preventative maintenance, such as servicing of a generator engine, replacement of the batteries or cleaning the ventilation fan filters of a UPS, etc. Fortunately, downtime to allow for preventative maintenance can be planned so that disruption is minimised but, often, cannot be eliminated.
Maximising the proportion of time a system is available involves trade-offs between component reliability and repair time. For instance, plug-in components are usually much less reliable than hard-wired ones, because of the relatively high failure rates of connections. On the other hand, the repair times of plug-in components will be much shorter than those for hard wired ones because they can simply be replaced by
relatively less skilled operators. The optimum balance depends on the absolute values of MTBF and the true MTTR, taking full account of the facilities and expertise available on-site. System availability is simply the MTBF divided by MTBF plus the true MTTR – including the extra items just discussed. Bald availability figures often look very impressive but must be used with care. An apparently excellent availability of 0.9999 translates to an unavailability of about one hour per year – a completely unacceptable level for many operations. Achieving better than this in practice – simply by increasing reliability – is quite difficult; MTBF figures, being statistical, cannot be relied upon in any particular instance and MTTR figures are usually optimistic, being based on the assumptions made in the calm atmosphere of a working system. Furthermore, the complexity of modern systems, such as commercial computer networks and factory process control, means that a large number of sub-systems have to work perfectly together to keep the operation running. Achieving higher availability requires a different design approach, one that focuses on tolerating and surviving the inevitable failures rather than trying to reduce them in other words, resilient design.

Resilience

A resilient system once again is one that can withstand a number of sub-system and components failures while continuing to operate normally. This can be achieved by installing additional equipment – redundancy together with careful design – eliminating single points of failure – and well planned maintenance.
A balanced approach is essential. Adding redundant equipment is straightforward but it is expensive and so must be done after proper consideration of the costs and benefits. Introducing proper maintenance procedures is relatively cheap, but ensuring that they are properly observed is never easy! A careful balance of technical and managerial or procedural solutions will give the best cost/benefit ratio.

The essential elements of a resilient installation are:

redundancy

elimination of single points of failure

good maintenance procedures i.e. high reliability

Redundancy

Redundancy is a useful method of increasing availability and optimising the balance between operation effectiveness and expenditure. Alternative circuits, equipment or components are installed so that, in the event of one or a few failures, functionality is preserved. The level and type of redundancy provided determines the level of functionality retained and the number and types of faults permitted.

Standby redundancy

Standby redundancy means that an alternative means of performing the function is provided but is inoperative until needed. It is switched on upon failure of the primary means of performing the function. An IT department might keep several spare monitors and use them to replace those that fail in service, this is an example of standby redundancy.

The disadvantage of standby redundancy is that there is an inevitable period of disruption between the failure occurring and the redundant unit being brought into use. Such schemes are rarely satisfactory for critical systems in modern commercial and industrial situations.

Active or parallel redundancy

In active or parallel redundancy all redundant units are operating simultaneously rather than being switched on when needed. The most obvious approach is to use two components, each capable of carrying the full load so that, if one should fail, the other will take over this is referred to as 1+1 redundancy. An alternative approach is to split the load among a number of units, each capable of carrying only a fraction of the load, and provide just one additional redundant unit this is referred to as N+1 redundancy. For very critical loads, more than one fully rated redundant unit may be provided. For
example, a 1+2 redundancy scheme would have three fully rated units supporting the load and would require all three units to fail before the system fails. Because there is no interruption, active redundancy is suitable for computer installations. The use of mirrored disks in a server computer is an example of 1+1 redundancy.

N+1 redundancy

A lower cost alternative is to use a larger number of lower rated units to support the load and to provide one extra redundant unit. For example, a 800 kVA load could be connected to five 200 kVA UPS units, any four of which would be sufficient to support the load. This would be referred to as 4+1 redundancy because four units are required and one is redundant. N+1 redundancy can be cheaper to implement than 1+1, and is more flexible; if the load grows it is simple to add another unit so that a 2+1 system becomes a 3+1 system. On the other hand, extremes should be avoided; every additional unit is another potential failure so there is a balance to be struck between the additional system resilience versus additional cost and increased unit (not system) failure potential. A RAID 5 disk system in a server computer is an example of N+1 redundancy. Additional error correction data is added to the original data and then logically dispersed over a number of disks. If one disk fails, all the data can be recovered in real time from the remaining disks and the failed disk contents reconstructed.
It is worth noting that the provision of a UPS in the first place is an acceptance of the need for a redundant power supply and adding redundancy to the UPS itself is a logical extension of that concept. see attach fig. on redundancy

Eliminating single points of failure

Adding redundancy is costly so how much and what to provide must be carefully considered. A risk assessment must be carried out, in which the risk of a particular failure occurring and the effect of that failure on the system is judged. Priority should be given to those failures where the combination of probability and system effect is highest possibly including a very rare event of catastrophic effect and a frequent event that causes minor disruption. This study should identify all single points of failure, those simple single failures that can bring down a whole operation. The study should be exhaustive and pedantic, looking not only at major pieces of equipment but also the control boxes and signal wiring that connects them. If the control system or its interconnections are the cause of the failure, the expensive standby equipment will not help!

A resilient power supply system must be design two has independent supplies from separate grid points backed up by two independent standby generators. Power from either input rail can be routed to either or both output rails directly or via either of two UPS units. Static transfer switches (STS) are used to connect and isolate equipment and paths as required. This example is symmetrical and assumes that the loads on each output are equally critical; in other circumstances, one output may be used to supply highly critical loads while the other supplies normal loads. In normal service power from one supply would be routed to both outputs via a UPS. In the event of a supply failure, connection would be made to the alternative supply with the UPS providing power during the short changeover period. If the alternative supply were unavailable, then a standby generator would be started and once up to speed, connected to the system; again a UPS would provide power during the start-up delay. If both supplies and both generators should fail, or be out of service for maintenance, then the UPS units would be used to supply the output rails independently. Load shedding would then be applied to extend the life of the supply. This is an extreme example. It would be rather expensive to implement but may be justifiable in situations where loss of life or serious financial loss may result from failure. It is used here to illustrate what can be achieved but in most circumstances a subset of this system would be appropriate based on a critical examination of the risks involved and the cost of protection.

Maintaining a resilient system

Maintenance procedures are the key to preserving the resilience of a system and these procedures must be taken into account during the risk appraisal. If, for example, one of four UPS units has failed, and the remaining three are carrying the load, how is this situation recognised so that a repair can be effected? What is the risk of a second failure occurring while the remaining units are operating at the higher load? Could the load have grown after commissioning beyond the capacity of only three units without the maintenance staff being aware? Detailed procedures must be developed to cover these and many other situations during the risk analysis phase so that they can be rigorously tested. The fact that an installation has been designed to be resilient can encourage lax maintenance standards. After all, it doesn’t matter if a particular unit fails – the site can survive without it. This attitude is a recipe for disaster. Firstly, there are more than enough reasons why a failure should occur and there is no need to
multiply the possibilities. Secondly, if a unit breaks down due to lack of maintenance, it is likely that its

counterparts are in a similar state and are likely to fail as well when faced with additional load.

Testing the system is also important. Maintenance staff need to be confident that the system will cope with failures and must test regularly by simulating the loss of individual items of equipment. This is a brave step, best first taken early in the commissioning of the site. Having established that the site is resilient, regular testing can be undertaken with high confidence of success. Naturally, testing should always be undertaken when the consequences of failure are at a minimum, but must also represent real site conditions. see attached fig. on resilient design

Conclusion

Availability is the primary concern of installation designers and maintainers. High availability cannot be practically achieved by high reliability alone and a good resilient design and proper maintenance procedures are:-

1 Having a UPS back-up for your electronics equipment for not less than 3minutes when supply fail either on PHCN or GEN.

2 Proper shut-down of both electrical and electronics equipments.

3 Having a stabilized or regulated voltage for your equipments to meet its specification by means of pure-sine wave stabilizer/AVR or gadgets.

4 Having a proper or normal rating and sensitve protecting device for your equipments and installation and residual current circuit breaker and good earthing system TN-S is recommend.

5 Daily/weekly routine maintenance and quarterly/di-annual/annual preventive maintenance on your machineries and equipments and so on

Designing and implementing a resilient system is a good step in a long journey and it save you 60% cost implication if you implement it and follow the necessary procedure to keep it in place and best to give you assurrance if something go wrong, so check it-out and digest it worth a while the figs is attahced with the link below.
Figs on resilient of your equipments and installation

Edited and Articulated By:

PIKARB DEY-OLA{ for PIKENG INSIGHT}
+2348028981751