Conference: The West African Power Industry Convention
Location: Abuja, Nigeria
Presenter: Lucas Scaraffiotti
Abstract: Presented by Lucas Scaraffiotti at The West African Power Industry Convention
In electricity distribution networks, energy flows are always metered at end-user delivery points (residential, commercial and industrial) and usually also at MV feeders outgoing from HV/MV sub/stations. The difference of energy registrations between these two levels provides the efficiency (or total losses) over the area distributed from every HV/MV sub/station. Each single result averages losses over tens of thousands of customers and hundreds of distribution (MV/LV) transformers, so this is mapping the system efficiency at a very poor resolution level.
In order to bring workable visibility in the efficiency map, the intermediate level of the distribution transformer (MV/LV) station also has to be monitored by a Check Meter. This will offer, at an affordable cost, a powerful x100 zoom into the efficiency map, thus enabling the implementation of an efficiency improvement policy along with many other side benefits.
This new Check Meter must be carefully designed to meet the environment of the Distribution Transformer (DT): installed in public places, little available space, availability of communications, wiring and installation of CTs. Basically the Check Meter is a load profiling multi-energy (active, apparent, import and export) meter with AMR capabilities. A periodic reading will provide very accurate daily, weekly or monthly active energy delivered from this DT. The other task is to build, verify and maintain a database linking this DT with its LV customers connected downstream.
On the LV customers side, three main types of meters are in use: commercial meters usually featuring Time Of Use and automatic End Of Billing capabilities, conventional meters read manually around end or beginning of the month and, finally, more and more PrePayment meters where kWh data are time-stamped at purchase and not at consumption. These customer consumptions, despite not exactly synchronous, may be normalized – in daily average consumption for instance. Then total metered consumption over such population downstream a DT – typically several hundreds customers – can be aggregated and cumulated monthly or quarterly with a pretty fine certainty thanks to statistic effect smoothing time jitter of raw data. A modern software system, of course, is needed to consolidate, process and report such amount of data.
Once delivered and metered figures are available, the software system reports the total loss for each distribution sub-segment, down to the LV Distribution Transformer. With known technical losses documented for every sub-segment, non-technical losses may be extracted. As a result, the efficiency policy has a powerful tool to identify, localize and benchmark the LV losses, set up improvement programs and measure their results.
Two side-benefits of the Check Meter may be quoted. First, the meter can provide valuable information about the loading of its DT, thus contributing to technical losses reduction program and also preserving the assets. Secondly, the Check Meters also enable the narrowing down of losses estimation on the Medium Voltage level, using specific algorithms for MV networks.