Energy Metering in a Deregulated Environment William Amuna

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Charlene Henderson
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1 Energy Metering in a Deregulated Environment William Amuna

2 ABSTRACT Metering is very essential and accurate metering could determine the profitability of any company in the energy sector. The power sector in Ghana will soon be deregulated. At present there is the Volta River Authority (VRA), which is mainly responsible for the generation and transmission of electricity and a few Independent Power Producers (IPP S) and metering is simple and straightforward. This scenario will definitely change with deregulation. This paper seeks to evaluate the present metering systems in the Transmission and Distribution networks in Ghana, evaluate their adequacy or otherwise and see what changes need to be done under deregulation. The paper would examine the following: Metering in the Transmission System (Open access system) Metering in the Distribution System Proposals for effective metering under Deregulation. KEYWORDS: Energy Metering, Deregulation, Telemetering, Distribution.

3 PRESENT METERING SYSTEM IN GHANA Type of Customers The present system is such that the VRA supplies power in bulk to the Electricity Company of Ghana (ECG) a distribution company, a number of mines, Volta Aluminum Company (Valco), which operates an aluminium smelter and other industries (Bulk Supply Customers). The ECG supplies power to its customers namely industrial, commercial and residential customers. Type of Metering Generally the generating stations use secondary connected feraris energy meters of Class 1.0 accuracy and accuracy of bulk supply meters range from class 0.2 to class 1.0. and the distribution system utilizes meters of Class 2.0 accuracy. The VRA network is interconnected in the east with the network of Togo Benin through a double circuit 161kV line and in the west with the network of La Cote d' Ivoire through a 225 kv transmission line (tie line) on which static energy meters of Class 0.2 accuracy are employed for metering. Type of Meters Energy meters currently in use are mainly Ferraris meters, some of which have maximum demand indication whilst others do not have. Recently, digital meters have been introduction in both transmission and distribution networks. Time of use meters are not being employed but there has been the introduction of prepaid meters in the distribution system. Type of billing Valco, tie line, ECG and Togo Benin are billed solely on the energy (kwh) consumed. Whereas the mines and other industries are billed by both the energy consumed and the maximum demand. There is also a poor power factor surcharge that is slapped on industries operating on poor power factor. In the distribution network, residential and commercial customers are billed by the energy (kwh) consumed. There are however some customers without meters who are billed on estimated energy consumed (Flat Rate). Sources of metering errors Inaccurate metering can lead to loss of revenue, wrong values of Transmission and Distribution losses and wrong data for planning purposes. The possible sources of errors in metering are

4 Low class meters (accuracy class and capabilities). Low class instrument transformers. Unmatched instrument transformer/meter accuracies. Lack of supervision of meters resulting in unregistered energy when meter is faulty. Drift in accuracy of Ferraris meters. DEREGULATED ENVIRONMENT Under deregulation, the structure of the power system in Ghana would change. Some of the anticipated changes include: The existence of Independent power producers (IPP) in addition to the VRA. The possible introduction of a meter company that may be a competitive company or owned by a utility to provide billing services. The introduction of local distribution companies. The possible introduction of energy services companies to provide energy retailing services. Open access to transmission system. Under this regime, there will be concerns for the amount of energy being injected by an IPP into the grid, the amount of energy being wheeled, costing of energy, frequency and power factor concerns, line loading, time of use metering (tou), etc. The companies will be in competition and the ability of a company to stride on will depend largely on accurate billing and cost reduction techniques that it will employ. PROPOSED METERING SYSTEMS: Generation systems: The IPPs will need high precision metering to measure the amount of energy they produce. It is recommended that they use Digital meters of the following specifications. Accuracy Class 0.2/kWh, 1.0/kVarh. Mode of Measurement Bi directional. Demand measuring capabilities. Date and time stamping. Tariff programming capabilities. Time of use capabilities.

5 Pulse output for Telemetering. Automatic meter reading capability. Load profile capabilities to help in system planning studies: Self Supervision capabilities to alert when there is a problem with the meter. In order to achieve the desired results of measurements, the instrument transformers for metering should have accuracies of Class 0.2 to match the energy meters. IPPs should also consider the possibility of back up metering and put in place check meters to the primary meters. The check meters could also be used for billing when the primary meters are faulted. Check meters should have a separate potential transformer (PT) supply. Transmission system The energy meters recommended for use by the Grid Company to meter its BSP Customers (Bulk Supply point meters) should have the following specifications: Type Digital Accuracy Class 0.2 to 0.5 (kwh) 2.0 kvarh) Mode of measurement Single/Bi directional Demand measurement Capabilities Date and time stamping Tariff capabilities Time of Use capabilities Pulse output for telemetering Load profile capabilities. Self supervision. Instrument transformer accuracies should match that of the meters. Distribution systems Specifications of meters for Industrial Customers should be similar to those of the transmission network. For residential customers, the one household one meter policy should be adopted to ensure that every customer is metered. If Ferraris meters are to be used, it is recommended that meters with lifetime of years be used to reduce cost. These meters should have suspension magnetic bearings. Existing traditional Ferraris meters could also be retrofitted with the addition of pulse generators if automatic meter reading (AMR) is required. Though its initial cost is high, Prepaid energy metering should be encouraged since it will significantly

6 improve the cash flow of utilities and also reduce the non payment of bills by consumers. Generally, the accuracy class of such prepaid meters should be from class 2.0. The situation where some customers do not have meters and are billed by estimated energy consumed has no place in a deregulated environment except when a proper energy audit is undertaken on the customer. Electronic meters Electronic meters are preferred to Ferraris meters because in addition to recording energy and demand, they could have features like power factor measurements, Date and Time stamping, multi tariff structures and would normally be equipped with communication capabilities to allow for AMR. They hardly drift in accuracy. Telemetering A telemetering system should be put in place by the Meter Company so that all energy data can be acquired at the end of each day. This will provide means of knowing energy generated by the various IPP s and energy used by consumers. A telemetering system is very expensive to put in place but the VRA already has one in place [1]. Steps should be taken to make it fully functional so that it can be used. It is advisable that all energy meters have an integrating period of 15 minutes to conform with the existing energy meters used by the Volta River Authority Meter checks The accuracy of the energy meters in use should be checked to ensure that accuracies have not drifted. It is recommended that meters (except residential meters) be checked once every year as is done now in VRA and ECG. Standards used for the checks should be acceptably high and the standards should be checked every three years. The VRA has the K2005 standard of accuracy 0.01 that can be used to check other standards for a fee.

7 COST IMPLICATIONS OF NEW METERING SYSTEM All this discussion will be of no use if the cost implications of the suggested schemes are not analysed. The most expensive meters will be that of the Class 0.2 meter. The cost of these meters is estimated at about $4000 for the type of meters in use by VRA. The cost of the other meters recommended in this paper will be in the range of $50 to $3000. Depending on the energy consumed by the Customer, the payback period for instituting these schemes will range from 3 months to 36 months. For instance, VRA changed a class 1.0 meter to a class 0.2 digital meter and there was an increase in energy registration of 0.8%. Sample calculation Energy as registered by BSP meters at Takoradi for the month of February 2000 was kwh. The increase in energy registered, which is 0.8% of this total energy would be kwh. This is equivalent to $4150 at present tariff levels. The cost of a class 0.2 Energy meter is about $4000. Typical meter prices PHASE DESCRIPTION CLASS PRICE Single Electromechanical 2 $50 Single Digital (Pre payment) 2 $80 Three Electromechanical 1 $100 Three Digital (Direct connection) 1 $339 Three Digital (CT connection) 1 $237 Three Digital 0.5 $583 Three Digital (combimeter) 0.2 $4000 BENEFITS will provide reliable data for forecasting, scheduling and capacity planning Reduced cost on meter maintenance Improved return on investment More accurate system loss values. Improved security of metering installations

8 CONCLUSION In conclusion, it can be said that energy companies in a deregulated environment should ensure high accuracy metering since for very large loads, a small change in accuracy could mean a large loss of energy registered and hence revenue to the utility. For all types of customers, cost/benefit analyses can be done to ascertain the financial implications of installing a higher accuracy meter. At the design stage of projects, Instrument transformer accuracy classes should be chosen such that they will match well with energy meter accuracies in order to obtain more accurate and effective metering. It should also be noted that, the Ferraris meters generally drift in accuracy with time and digital meters, which have constant accuracies, are recommended for use by utilities, especially in a deregulated environment. REFERENCES 1. William Amuna, J Amoako Baah, "Automatic Meter Reading, The VRA Experience", Arab Electricity 97 Proc., Bahrain. 2. Sam Chungyang, " Metering in China", 3. Deregulation in the Power Industry Notes from Penn State University Lectures.

9 Speaker: Position: Company: Country: Biographical Information William Amuna System Metering and Instrumentation Engineer Volta River Authority Ghana William Amuna graduated with a B.Sc. (Hons) Electrical Engineering degree from the University of Science and Technology, Kumasi, Ghana in He has worked for several years as a Protection and Control Engineer with the Volta River Authority and at present he is the System Metering and Instrumentation Engineer. He also undertook a course in Advanced Power Systems Engineering at the Pennsylvania State University College of Engineering, Pennsylvania, USA.

10 Company: Country: Company Background Information Volta River Authority Ghana

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