Planning and Operation of Electricity Distribution Networks - - PowerPoint PPT Presentation
Planning and Operation of Electricity Distribution Networks Speaker: Engr. Ezonfade, Percy Speaker: Engr. Ezonfade, Percy Project M anager, Lilleker Bros. Nig. Ltd At the NEF2017 Annual Conference/ Exhibition Table of Contents 1.0
1.0 Introduction and General Overview of an Interconnected Power System as it Applies to Nigeria 2.0 Features of Planned Power Distribution System 3.0 Basic Problems and Challenges in a Typical Overhead Line Distribution system 4.0 Recommendations for Improved Distribution Practice 5.0 Conclusion/ Remarks
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1.1 The power system in Nigeria that is of a distributed generation system interconnected in a National Grid 1.2 The generating stations generate at 11kv or 33kV 50Hz or any other similar generator specs as the case maybe, depending on the unit size of the generator and the Genco busbar specs 1.3 The generating stations connect to Transmission or the National grid at 330kV or 132kV 1.4 Transmission connects Distribution at 33kV as standard in Nigeria 1.5 Distribution connects consumers at 33kV (for some industrial consumers), 11kV (for many commercial off-takers with dedicated transformer greater that 500kVA). 1.6 Residential or other type consumers with substation capacities less than 500kVA are presently connected at 415/ 240volts 50Hz in a system largely described as overhead Low Voltage Distribution System. Some distributions concerns are now upgrading to M V distribution system at 11kV to reduce tech losses. These systems have much smaller substation unit capacities typically at 50kVA to 100kVA max. 1.7 Our National grid code specified 11kV or 33kV 50Hz at generation, 132/ 330kV 50Hz at transmission and 11kV / 415/ 240volts 50Hz at distribution/ consumer level. 1.8 The unbundled power sector in Nigeria comprises the Generation Companies (Gencos), the Transmission Company (TCN) and the Distribution Companies (Discos)
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Typically Coal, gas or hydro turbine stations are available in Nigeria. Several
National Grid System
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2.1 Distribution in an unbundled power system is the technical and commercial activities of the business entity saddled with the responsibility of receiving power from the grid, connecting consumers and billing. 2.2 Distribution must work or carry out this task in the most efficient manner that reduces losses (commercial and technical) to the barest minimum such that a planned distribution system is a designed distribution system. 2.3 Distribution sells the power generated by the Gencos that they would have received via Transmission and pays everyone through the market operator. 2.4 Effective planning of distribution system is required at the onset for the business thereof to be profitable and mutually beneficial to the power off-takers/ consumers as well the Discos. 2.5 A planned distribution system is system where the consumers are metered with operative vending system for the prepaid consumers. 2.6 A planned distribution system should deliver on the grid code, i.e. deliver the authorized and specified supply voltage to consumer meter board. Anything less is a technical gamble. A distribution system that does not achieve this singular objective is a failed system that would also have impact on its overall profitability. 2.7 A planed distribution system should therefore afford the Disco the opportunity to carry out tech and commercial evaluation of any off-taker’s request for connection before deciding on how best to connect them.
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2.8 In the planning or design of overhead distribution systems like we have in Nigeria, it is necessary to tropicalize and derate the aluminum conductors in use due to heavy sagging
factor is typical for most practical purposes. Some Nigerian wires and cables may already be tropicalized. 2.9 Distribution planning engineers should therefore consult data sheets of the cables and wires they are given to use on them projects. 2.10 M ost of the low voltage problems experienced at the distribution outlets are traceable to
adjustments at the power transformers to compensate for any significant drops in voltage. 2.11 A properly planned distribution system should also then be efficiently supervised and manned and provided with sufficient logistics support to respond to emergencies especially in our overhead line system.
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3.1 A major drawback of overhead distribution system is the attendant low reliability index. 3.2 In an unbundled system there are clear cut responsibilities amongst the major players in the sector namely the Discos, Gencos and Transmission. 3.3 Due this split in management responsibilities, a Disco may be called upon to receive power for their districts and they would say no as they are not bound to take your power either, and in most cases without giving any reasons. The reality however is that they don’t have the capacity to evacuate or distribute the power due to the general decay in distribution infrastructure. 3.4 Unbundled power sector has led to less integration in the system. The unbundled management style places more emphasis on the services they offer and getting paid for those services in the end and at a price they agree with. 3.5 Exorbitant Tariffs. Discos have been having running battles with the sector regulators
charging higher tariff structures, I believe that the Discos are not earning enough money due to their inability to expand or maintain their facilities; occasioned by low revenue base on account of reduced quality of services.
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3.6 Lack of sound maintenance. M ain distribution facilities such as transformers are not being replaced as and when due or when they fail. The only visible maintenance efforts you probably see is fault tracing and restoration of supplies. So if your transformer fails you will have to replace it by yourself is a common thing in the industry. 3.7 There is a general decay in electricity distribution infrastructure in the country that need urgent attention and the federal and state governments who are still major stake holders should be prepared to address this problem for the sector to survive the times. This is because Investors didn’t inherit much in the first place, though equipment failures have gone worse under their watch. 3.8 Today distribution is being funded by a few consumers who can afford the high tariffs compared to buying diesel for their generating sets; and through estimated bills, the rest is paid by the general public, though they may have no idea how much electricity they consumed during the month. 3.9 Lack of meters. M etering is below 50% with most Discos and this gap needs to be reduced and eventually erased. 3.10 There is pervasive unemployment in the sector with the Discos retrenching most of the staff they inherited at the onset. Some say the wage bill is too high and so they want down sizing to shed weight and survive or they just employ less experienced staff which cost them much
unacceptable and portends danger for the sector which shows that it is not a healthy sector. 3.11 Another good performance indicator is the thriving diesel genset sales and maintenance business in the country. An equally thriving power sector can erase this extremely high cost
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4.1 The unit of electricity that consumers pay for is a product of the power consumed in kilowatts over the time that the power supply was kept ON (that’s why it is called kilowatts-hour i.e. kWh). S
supply ON for as long as the consumer needs it (ie long time of several hours during the billing period) multiplied by the load in Kilowatts gives the units in kWh. Distribution practice that does not keep the power supply ON but keeps switching OFF does not earn much money in commercial electricity terms. Equally, the big gigawatts of power we hear the Gencos are generating does not convert to revenue unless the Discos are able to connect consumers and put the power to commercial use. Just as govt gives support to the Gencos and the Transmission company to
their activities because privatization is not complete in the power sector until the discos are positioned to provide quality services to be able to function with transmission and generation as an integrated system. 4.2 Some urban city councils have to see the need to de-emphasize the aesthetics trees give to the environments over our collective need for power supply since our system is still an overhead
4.3 Overhead distribution is cheap and cost effective and is something we should continue to manage in our developing power sector. 4.4 Discos need to do more on equipment replacement and breakdown repairs or maintenance. Not much is being done about failed equipment replacement. Consumers depend on their own contributions in the neighborhood or some donations from rich people and at other times govt interventions to get their failed transformers replaced. The industry should however evolve a more sustainable approach to asset management e.g. giving consumers credit in return for capital investment.
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4.5 There is urgent need for aggressive revamp of distribution infrastructure across the country and stake holders should brace up for this if we want to set the power sector up and running. The power sectors is not doing well because of this lack of vibrant or commercially viable distribution system to complement the efforts at generation and transmission.
4.6 The recurring problems in distribution have always been that of overloading and over-
stretching of L V reticulations lines. Revamp efforts should therefore target at delivering on the specified grid supply to the consumers. We should build more Relief and Injection Substations , evaluating the losses at all times to ensure that correct specified voltage reach consumers facilities. 4.7 It is the collective responsibility of all stake holders in the power sector to see that the Discos are operating efficiently. Govt, the Gencos, Transmission and the Discos themselves should be part of the rehabilitation project. This is more so because, the companies were sold as they were with many of the infrastructures getting worse than they inherited them. And because many did not carry out any technical audit of what they were buying, everyone is forced to continue in business with whatever they met. With the low revenue base, it will be impossible for the Discos alone to reposition distribution for profitability. 4.8 When this is done and when the system becomes financially resilient enough to take on most
and make the operators plough back on profit to service consumers and the market.
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4.9 On metering, prepaid metering with efficient vending system should be our focus
because much as the unbundled power sector is now commercial and service driven, we must not lose sight of the fact that consumers might have also come to terms with the sector and are equally waiting to pay for only quality services. M etering is a direct measure of the system market worth and service quality. 4.10 We should be doing away with the extortion called estimated billing. Govt should fund the CAPM I Programme (ie Credited Advance Payment for M etering Implementation). Govt should import meters or procure meters from local smart meter manufactures that can meet the demand as a way of increasing local content in the industry. The Discos in turn should sell the to off-takers (at controlled rates but allowing the Discos to charge reasonable handling charges
Under the CAM PI arrangement, consumers get energy credit for paying for the meters and they net off the credited sum against their energy bills. The meters become Disco property after the credit sum has been liquidated.
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4.10 There are no credible efforts at providing meters - no credibility because everyone knows we need meters but very little is being achieved in this regard. Last month the NERC was calling on consumers not to pay any more estimated bills. This could be a way of forcing the Discos to meter everyone if the average Nigerian consumer will heed such calls. But it is virtually impossible to enforce such sanctions because the Discos are just struggling to survive. A close look at the billing system and tariff structure shows a consumer tariff that is much like a “take or pay tariff” with consumers getting billed whether they were supplied electricity or not. One plausible way out of this is to carryout a system revamp that will guarantee sales and provide the much needed revenue. 4.11 Discos should show more support for consumers efforts at getting electricity meters for
Sometimes another officer in the same Disco will tell you they can’t trace your payment for meter etc and so you continue to wait. A funded CAPMI program could solve many of these metering
even when they supply no electricity to the consumer and there is this talks about debts on account
in most cases. 4.12 There is need for constant operators training with advent of new equipment design that are in vogue to provide a more proactive network management e.g. operators should make full use of on- load tap changers installed to tackle the incidence of low voltage in the distribution lines that can be compensated for by on-load tap-changing techniques.
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5.1 The Power Sector to me remains a lucrative sector of our economy. This is because electricity is an all time essential utility in our homes, factories, business establishments or schools and we do have the market for
5.2 There is general dearth or shortage of power engineers in the country. These are electrical engineers that specialize in interconnected power systems, comprising heavy current engineering (distribution), they are specialists in electric machines (synchronous generators, synchronous and asynchronous motors and transformers) and high voltage engineering (transmission) and they are trained to have in-depth knowledge on power and machine operations, maintenance and protection. Local and overseas training should be encouraged at the graduate and post graduate levels for our people in these areas to man the industry otherwise we will continue to import manpower from overseas. On–the-Job-Training (OJT) is also recommended for those already employed in the industry. 5.3 Our power system of today was designed and built by engineers like us; though many came in as contractors from other countries, many of our professionals participated in these projects and even today it is our engineers that understand what our power system is like. Engineers should continue be at the helm of affairs to keep it running. Engineers should be allowed to man many of the top decision making positions in the sector so that efforts could be aimed at solving the basic problems in the sector by way of directing the finances of the organized sector to the much needed areas. M any govt projects and efforts in the sector today does not reflect the urgent needs in the sector. The Electric Power Sector is much too technical for politicians or any other ancillary support professionals to head and direct. 5.4 Though there is general technical manpower shortage in the sector, I do not believe that the various issues identified above are beyond our technical capabilities. Govt and other key players in the power sector should fix distribution as a matter of deliberate policy.
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Nigeria Head Office: Lilleker Bros. Bros Nig. Ltd 11, Queen Elizabeth Road P.O. Box 347 Zaria Telephone: 069-333129, 335066 Fax: 069-330881 e-mail: office@lillekernigeria.com UK Office: Lilleker Bros Ltd 30 M oorgate Road Rotherham S60 ZAG Telephone: 01709 374073 Telefax: 01790 364517 e-mail: info@lillekerbros.com Calabar M ain Office: Lilleker Bros. Bros Nig. Ltd 69 M CC Road Calabar P.O. Box 640, State Housing Estate Calabar Telephone: +234-806 917 8449 e-mail: trevor.ralton@lillekernigeria.com Calabar Project Office: Cross River State Water Board Compound Plot 147 Ndidem Usang Iso Road, Calabar Telephone: +234-803 384 0741; +234-807-137-3129 e-mail: percy.ezonfade@lillekernigeria.com percy.ezonfade@gmail.com