WO2011001188A2

WO2011001188A2 - System and apparatus for monitoring electricity supply system

Info

Publication number: WO2011001188A2
Application number: PCT/GB2010/051101
Authority: WO
Inventors: Hugh Smeaton
Original assignee: Hugh Smeaton
Priority date: 2009-07-03
Filing date: 2010-07-05
Publication date: 2011-01-06
Also published as: GB201201392D0; WO2011001188A3; GB2485498A

Abstract

The invention relates to an electricity distribution network and in particular the provision of metering apparatus at a location or locations in the network intermediate the end consumer and the source of the electricity. The metering apparatus is typically located at substations in the supply network and monitors at least one parameter relating to the electricity at that location and transmits data relating to that parameter to allow the data to be used in conjunction with further data, typically received from metering apparatus at the end consumers to allow analysis of the network to be performed.

Description

System and Apparatus for Monitoring Electricity Supply System

The invention to which this application relates is a system and apparatus which allows the monitoring of electricity supply systems and, in particular, to allow losses within the systems to be identified and thereafter acted upon to thereby allow a resultant reduction in electricity loss to be achieved.

It is known that in conventional electricity supply systems in the UK approximately 7% of electricity which is generated is lo st and a higher percentage of loss occurs in other parts of the world, such as 30% of all electricity which is generated. The loss can occur, for example, through theft, by unauthorised tapping of the power lines.

There is an increasing demand from environmental bodies and governing bodies, as well as the generating companies, to reduce these losses both with respect to the financial and economic cost and also the environmental impact of generating electricity which is sub sequently lost.

The aim of the present invention is therefore to provide a means of monitoring electricity supply within the supply network so as, firstly, to be able to identify that losses have occurred, and secondly to act on the losses with respect to the particular location of the same so as to allow the losses to be reduced.

In a first aspect of the invention there is provided an electricity supply network, said network provided to supply electricity to a number of premises, and wherein at least one meter is provided at a location intermediate the source of the electricity and said premises and said at least one meter is capable of monitoring at least one parameter relating to the electricity supply at that said location and transmitting and/or receiving data relating to the same.

Typically said premises are provided with at least one meter capable of receiving and transmitting data relating to electricity consumption at the premises and the said at least one meter located upstream is a further meter in addition to tho se provided at the premises. Typically all of the meters are capable of transmitting data relating to the electricity consumption.

In one embodiment, comparison means are provided to allow data from the meters at the plurality of premises, to be retrieved and processed as a first set of data and compared with data received from the at least one further meter at the location upstream in the supply network.

In one embodiment, the location upstream is a sub station and yet further, the meter is connected to one or more current transformers at said substation.

In one example, the sub station is an 1 1000/ 41 5 volt transformer sub station.

In one embodiment, the substation is provided with twin transformers and meters are provided to allow the monitoring o f and provision of data representative o f the loads on each of the transformers. In one embodiment, if the identified load on one of the transformers falls below a predetermined level, then the said transformer can be switched off until the load on the remaining transformer is identified as exceeding a particular level. Typically the meter data is provided at given time periods so as to allow the operation of the transformers to be determined with respect to the particular loads at a given time. In one embodiment, the comparison between the readings from the meters at the plurality of premises and the meters at the said one or more upstream locations, is performed continuously or, alternatively, at predetermined time intervals so as to allow a detailed record to be constructed of the electricity load at the respective meters at given times and/or to identify differences between the readings from a plurality of meters and the one or more meters at the upstream location so as to identify any electricity loss intermediate said meter locations and, if so, the extent of the lo ss and/or time of the loss.

In one embodiment, a plurality of meters are provided at a number of locations in the network upstream of the premises which are being supplied thereby allowing the network to be split into a series of sections, with at least some of said sections being monitored using the meter apparatus herein described and allowing comparison between meter readings to identify electricity loss in specific network sections.

In addition to identifying loss through theft, it is also po ssible in accordance with the invention to identify loss which is due to malfunction or poorly performing apparatus within the network and therefore identify the said components of the network which may need to be replaced.

In a further embodiment, the provision of the meters at the sub station location, allows the occurrence and duration of unbalanced loading to be monitored and, if the same occurs over a prolonged period of time, the network operator can take action to reduce the unbalanced load and thereby reduce the lo ss which can be created by unbalanced loads due to the fact that the loss varies with the square of the current. In a further aspect of the invention, there is provided a method of monitoring the performance of an electricity supply network, said method comprising the steps of obtaining data relating to the electricity supply to one or more premises by providing meter apparatus at said one or more premises, providing at least one further meter at at least one location upstream of said premises in the supply network, obtaining data from said further meters relating to the electricity supply at that location, comparing the first set of data retrieved from the meters at the premises with the second set of data obtained from the meters upstream in the network, and identifying differences between the said sets of data.

In one embodiment the comparison is made to identify whether electricity supply lo ss has occurred in the network intermediate the respective locations of the meters providing the first and second sets of data. In addition or alternatively the data in the first or second sets can be used to analyse and determine behavioural characteristics of the apparatus and/or electricity supply at the meter location.

The present invention therefore provides the ability for the electricity network operator to manage the demand for electricity and allow them to take action when electricity loss and /or supply malfunction is found to be occurring.

In a further aspect of the invention the meter apparatus at the location upstream of the premises in the electricity supply network is used to provide data relating to the identification of the phase of the electricity supply which is being monitored by that meter apparatus. Typically, the phase identification occurs at a location which is either of a sub station, a distribution pillar or link within the network.

The ability to identify the phase which is being monitored by a specific meter, means that the balancing of the load on the distributor feeding that single phase can be managed more accurately if the phase has been identified.

It should also be noted that any unbalances in the load between phases of the electricity supply, transfer upwardly from the location towards the grid in the network with not only increased losses in H kV feeders but in the transformers themselves.

In a further aspect of the invention there is provided an electricity supply network, said network including one or meters at a first location in the network to meter the electricity supply, and readings from said one or more meters are compared to the total of the meter readings taken for the supply of electricity to industry, commerce and/or households.

In one embodiment the said first location is as the system steps down from the national grid to the 33,000 volts substations.

In a yet further aspect of the invention there is provided a system which consists of a consumer 3 phase and single phase meter, a current multiplexer to measure currents from CT's and measure and log AC voltage and the time current and voltage crossover and wherein a plurality of district control processing means are provided to accept data from secondary sub-station meters located within the network and be capable of communication back to the sub-station meter.

In one embodiment the number of channels provided in the current multiplexer is selected with respect to the type of sub-station it will control. This unit will also measure and log AC voltage and the time current and voltage crossover.

In one embodiment the communication means between the sub station meter and the control processing means will be selected to suit the operating environment and/or network parameters. Typically secondary sub-stations do not have telephone lines and therefore some form of communication means may be required to be provided. One option is to use the same communication means as is used to communicate with the meter at the consumer premises.

In one embodiment there is provided a district control system for a district of an electricity supply network said system allowing analysis of the load flows in the HkV and 33kV networks to generate an audit trail of current and power factor through the network. Typically eth system also includes means to allow a control method to be used in conjunction with the date received from the meters at the substation to allow optimisation of the 11 kV switching for the supply network.

In one embodiment during planned or emergency load shedding, the method can be based on the actual load flows on the network together with the 24 hour history of load flows.

Conventionally the network is open i.e. 11000/415kV sub-stations feed a dedicated number of secondary sub-stations and similarly a grid sub-station feeds a dedicated number of primary sub-stations. However the lack of CT's on HkV switches means that full online data is not available to trace all load flows.

Specific embodiments of the invention are now described with reference to the accompanying drawings wherein;

Figures 1 and 2 illustrate, schematically, part of an electricity supply network in accordance with an embodiment of the invention; Figure 3 illustrates a three phase supply layout.

Referring firstly to Figures 1 and 2 electricity is provided along the power line 4 in the network section shown from a generating location 6. The electricity is carried along the grid 9 to a sub station location 8 which, in one embodiment, can include first and second transformers. Also, in accordance with the invention, there is provided metering apparatus 10, the form of which will be described subsequently. From the substation, the electricity supply is stepped down in voltage as shown in Figure 2 and distributed via power lines 12, 14, 1 6, 18, 20 to premises 22, 24, 26, 28 as shown in Figure 1 . In accordance with the invention, each of these premises 22-28, are provided with metering apparatus 30.

The metering apparatus 10, 30, is provided of a type which allows data to be transmitted from the metering apparatus, typically via a power line carrier system, to a processing facility to provide data which is indicative of the electricity supply such as, for example, measuring the load. Typically, each metering apparatus is capable of receiving data and transmitting data, with the data, most typically, being carried along the power lines 12-28 and/or power line 4 to and from the processing facility. Typically, each of the meters will record the kilowatts per hour and input voltage values of the electricity supply at that location.

A meter interface unit can also be provided which allows relays, typically 15 amp relays, to be provided to allow load shedding circuitry to be connected to the meters as required.

The metering apparatus 10, at an upstream location such as the sub station 8, is typically capable of providing three phase monitoring of the electricity supply with, again, power line carrier communication being used and will be capable of logging the current, voltage and phase angle of the supply from the sub station along power line 12.

The processing facility (not shown) is capable of transmitting to and receiving a first set of data from the meters apparatus 30 and a second set of data from the meter, 10 and processing the received data and comparing the data from the respective meter locations in the network to identify discrepancies in the electricity supply between the said locations.

The supply network with which the invention is used is, in one embodiment, an H kV ring network which can cope with 5MW of load. As, in accordance with the invention, the electricity supply coming out of the primary substations is metered in, for example, half hour recording periods, then accurate load distribution monitoring of the supply is possible. Thus as a result of the invention, the loading o f the H kV network can be monitored to indicate locations where the network is not operating correctly and requires upgrading and/or the identification of where uneven loading amounts between sub stations and/or at different periods of the day can be identified so as to allow the more accurate and efficient management of the operation of the sub stations to meet the variations in load due to demand variations at given time intervals.

In one embodiment, the measurement of the phase angle in the sub station or other location means that it is necessary to take all three phase voltages to the substation meter apparatus. Due to high volt levels in the substation, for safety reasons, a single phase supply unit is preferable. However, in the instance that three phases are provided these phases can be identified electrically in the meter at the upstream location and this data can be transmitted to the connected meters at the premises such that each meter at each premises, can recognise the particular phase that it is being supplied by. This data can also be transferred to the processing facility to thereby allow the data for meters supplied by each particular phase, to be collated and then compared with the data for that specific phase collated from the meter at the location upstream.

High voltage faults are often easy to find and fix. However faults in the distributor line to premises such as households are often difficult to find and can lead to premises being without power for many hours or days while the fault is located and repaired. In accordance with the invention in one aspect the meters at the second location such as the premises locations are provided with triggers which detect when the power supply falls below a certain level, say 200 Volts, which is indicative of a fault having occurred. When this is detected the meter will start to log the voltage supply over time.

In practice the meters which are closest to the sub station on the distributor or branch supply line will have the highest of the detected voltage levels and the detected voltage levels in sub sequent meters located away from the substation will drop, typically successively. However the meters which lie on the branch line downstream of the location of the fault will not detect a drop in voltage and so reference to the detected voltages at the respective meters will allow the identification o f the location of the fault along the distributor line as lying between a meter with a detected voltage drop and the next meter which has not detected a drop. This therefore allows fault location to be more quickly identified.

Typically the electricity which leaves the 1 1 ,000/ 41 5 volt sub stations in the network comes out in four core cables which connect to the transformers via fuses. There is typically 41 5 volts between the three phases (red, yellow, blue) and 240 volts between any of the three phases and the neutral, as a fourth conductor is referred. This is illustrated in Figure 3.

Industry and other relatively large consumers are typically provided with a three phase supply, whilst households and lower users typically receive a single phase supply. Large electrical motors are all operated with a three phase supply while small motors such as fridge and deep freezers are single phase operated.

In one embodiment the lo sses which are identified using the method of the invention are transformer losses. In one embodiment the particular area of interest is with regard to those sub stations which have two transformers. In accordance with the invention by detecting the amount of electricity which is consumed at specific times it will be possible to selectively operate one or two of the transformers, with, for example only one transformer being connected to the 1 1 KV network in times of low use, such as summer, as opposed to the present where both transformers are operated all the time regardless of the electricity usage at that period of operation. However losses on a normal I OOOKVA transformer are 25KW i.e. £2.50 per hour at domestic rates which represent significant expense in terms of lost revenue. It should also be possible to carry out similar savings on the 33/ 1 1 KV transformers with larger savings, but of course there are much fewer of these.

In one embodiment if the sub station meters fed from the primary supply are coded in the same way as the meters at the premises then this allows the identity of the loading along the network. In another embodiment power factor losses are identified in accordance with the invention. Where the connected load to the network at the users location is electrical heat or filament lighting the power factor or efficiency is 100%. However when the load is an electric motor or a transformer such as those used by PC's, printers, scanners etc this efficiency can drop. In industry or large commercial premises it is normal for the electricity supply company to measure the power factor and charge the user on this basis. However the exact method of charging varies from one supply company to another. The power factor at the grid metering is 0.95-0.96.

Dependent on how the power factor is measured at the gird sub stations this may provide the full picture. It is normal to compute the power factor with reference to KWH and KVARH and theses values can be averaged every half hour and the half hour averages averaged over 24 hours. For example if it is applied in the same way as high users voltage metering and averaged over a month this approach will mask errors as there is a considerable off peak space and water heating load overnight when the rotating industrial load is low and this will distort the power factor calculations.

In a further embodiment of the invention the unbalanced loads in the network are identified. When the current carried in the three phase conductors is balanced then no current flows in the fourth or neutral conductor and this is known as a balanced load but this only happens with say three phase motors and never happens on the electricity network. Even in industrial or commercial installations, the load taken from the network is never balanced. However at present there is no way of being able to identify what this level of unbalance actually is as present metering does not measure or record the loads on the individual phases of the supply. In most cases the single phase domestic load is connected to the same distribution cables hence a balanced load on the distribution cables and sub station transformers is not only never balanced but not measured in the sub station. As an example if there is provided a load of 100 amps on the red phase, 200 amps on the yellow phase and 300 amps on the blue phase of a supply this will give an average load of 200 amps. However the losses of a 200 amp balanced load would be 200² = 40,00OR x 3 = 120,00OR.

However in the practical situation of the load being unbalanced, the unbalanced lo sses would be 100²R + 200²R + 300²R = 10,000R + 40,00OR + 90,00OR = 140,00OR i.e. an increase o f 16.66%. In addition further lo sses occur in the neutral conductor plus an unbalanced load increases the losses in both H KV and 33KV networks and transformers thus leading towards potential losses of approximately 20%. The provision of metering at the end user and at at least one location further upstream as well as the metering o f the each of the phases would allow the unbalanced load losses to be identified and actions taken to balance them.

In a further aspect of the invention there is provided a solution to the problem by providing a network management system for the supply network which include an integrated metering system using intelligent meters at consumer locations and at at least one location on the network upstream from said consumer locations.

In one embodiment, in an industrial situation, there is provided metering for a three phase supply which logs at predetermined time intervals, such as half hourly intervals, the KW on all three phases on the supply and the voltage and power factor on all three phases. Typically the current in each phase is either measured or alternatively calculated from the other readings. The meters are provided with a data communication system such as a Power Line Carrier (PLC) system to allow data representative of the readings to be transmitted to a monitoring location. At household premises, a single phase meter can be provided to measure a voltage current and phase angle and record these at predetermined intervals, again such as half hour intervals. Once more a data communication means is provided to allow the data to be transmitted to a monitoring location.

In one embodiment the single phase meter can have two output ports to allow it to command remote connection and disconnection of two 15 amp circuits. The meter typically will also have an electronic address which will relate to the distributor and substation that feeds it.

As part of the network, the substation can be provided with a three phase meter which is used to measure phase voltages, phase currents and phase angles on each phase. It typically has an electronic address and PLC communication capability to a landline or mobile phone interface.

In one use of the invention there is provided a network monitoring control system provided to operate at a district level so that each meter in the system shall be electronically addressed to the sub station feeding the meters. Typically the monitoring method allows the following to be identified by the monitoring means:

1. The load on the substation at predetermined time intervals which will allow transformers to be switched off in twin transformer substations during summer periods and only brought back on when required.

2. By totalling the consumer meter readings and comparing to the substation readings, the network losses in each substation can be calculated. In the case of stolen electricity, the time of theft will be known within a predetermined time period and, by looking at the voltages down the distributor from consumer readings, it should be possible to close in on the source and location of theft.

3. The profile of the voltage readings will allow close analysis of copper losses and also atomise the interconnections of the 41 5/240 volt network in towns and cities. By checking the power factors at both consumer and sub station locations, it will be possible to determine the degree o f the problem and take up with the consumers who are identified as creating the problem.

In the case of phase unbalance loads can be moved in industrial and commercial premises. With domestic consumers loads can be "swung" into blocks of flats with three phase supplies and/or ground supplies can be shifted by jointing.

As loads vary, full time monitoring may not be attractive but the monitoring of substations on an annual basis would be of use. With regard to the 1 1 KV network, there needs to be metering installed within the same and typically, in each primary sub station with the meters therein tied into the secondary sub stations which are fed by the primary substations. This could help to optimise network upgrades and/or handle major faults which occur.

Similarly with the H KV or 415V distributors the system can be used to quickly establish the scale and location of the fault and also check that everyone is supplied once again once the fault has been located and repaired.

In one practical embodiment in a network each consumer is provided with a meter with a unique serial number together with an electronic address required for metering purposes. When the meter is connected to the network it broadcasts a message to its host sub-station to identify itself and of course the phase that it is being fed from and then sends out data at regular intervals, say Vi hourly readings. The host sub-station stores this data for a period of time typically chosen by the network operator such as a 24hr period.

The documentation for meter reading purposes is sent to the associated network company who logs this data into the district controller. From existing records the district controller now knows the geographical location of the meter hence the distributor that feeds it. This means that between the host sub-station meter and the district controller, the geographic location of the meter, the distributor that feeds it and the actual phase for single phase meters is known. Ideally this data should be fed by the district controller to a mimic diagram that identifies the distances between sub-stations and consumers. Thus data is important in terms of using data to help optimise network upgrades or automate LV fault location. An alternative option is to quantify distance and cross-section area of cables between consumer and sub-station at the time the consumer is logged onto the system

The invention therefore allows the provision at the substation of at least one meter which knows the power, phase angle and phase load of every consumer fed by the substation, at regular time intervals such as every half hour. The meter then totals the load registered in the consumers meters in terms of kW, PF and consumer's voltage. It then summates the consumer's data and compares this to the energy leaving the sub-station every half hour and has pre-set trigger points, such as

I)If the difference between energy recorded on consumer's meters and that sent out falls below pre-set levels either in total or specific half hourly periods.

2)Phase imbalance not only in terms of quantity of phase imbalance but the length of time it runs.

3)Power factor and variations over the preset log time. 4)If consumer's voltage falls or rises above preset limits (i.e. loss of neutral).

5)Load patterns equivalent to illegal usage patterns such as in terms of cannabis farms can best be identified in meters at the sub-station so as to more quickly help locate them.

In practice if the district control gets an alarm from a sub-station meter it can interrogate the meter and download its readings. As it knows the location of every consumer on each phase, the loads drawn and the voltages at each consumer's meter this data can be used to help locate not only excess losses but the time they take place.

With regard to phase imbalance this can come from 3-phase consumers or un-balance from single phase consumers. The phase imbalance will vary over the length of a 3-phase distributor and also over time.

There is no possibility of ever getting anything like even phase imbalance and of course load patterns will vary with time. However the system provides all the data required to help improve the situation by tariffs to three phase consumers, balancing loads by switching in such as blocks of flats. It will be an on-going process with the usual law of diminishing returns.

With regard to power factors the system can accurately locate in terms of value the power factor, the source of poor power factor and the length of time it runs

Primary and Secondary substation metering can be achieved by a multiplexer reading across inputs from the yellow phase and rogowski coils on the protection CT's. As the input to the primary is from delta wound transformers to get kWH figures it requires a 2watt meter method. This can successfully be done at the multiplexer and can be easily done by feeding raw current voltage and crossover time to the area computer. Primary sub- stations have mostly telephone line communication and can be run online or on a dial up basis.

In addition to the above uses the provision of the meters at the substations in accordance with the invention allow the monitoring of consumer voltage at the remote ends of networks to allow transformers to run on tap2 during summer periods when windmills could be toiling. This of course saves energy in terms of losses and generation. In addition, fault location can be more quickly achieved such as for example, with a 1.6 rating power factor, 400 amp fuses at the substation seldom blow instantaneously. The specification calls to time stamp voltage dips. The sub-station meter or district computer can use the voltages from consumers meters along a distributor to help locate distribution faults.

Thus the provision of meters with communication means at substations and particularly secondary substations allows processing means to build up a picture of network loads by summating the loads on secondary substations to build up the loads on primaries. At the end of the day the system allows the network company to trace every amp entering the system to its eventual destination. It will identify the source of network losses and if both primary and secondary substations are quipped in accordance with the invention all or the majority of losses on the network can be traced and identified.

Claims

1. An electricity supply network, said network provided to supply electricity to a number of premises, and wherein at least one meter is provided at a location intermediate the source of the electricity and said premises and said at least one meter is capable of monitoring at least one parameter relating to the electricity supply at that said location and transmitting and/or receiving data relating to the same.

2 A network according to claim 1 wherein said premises are provided with at least one meter capable of receiving and transmitting data relating to electricity consumption at the premises and the said at least one meter located upstream of the premises is a further meter in addition to those provided at the premises.

3 A network according to claim 1 wherein the parameter which is measured is electricity consumption and the meter is capable of transmitting data relating to the same.

4 A network according to claim 1 wherein comparison means are provided to allow data from the meters at the plurality of premises, to be retrieved and processed as a first set of data and compared with data received from the at least one further meter at the location upstream in the supply network.

5 A network according to claim 1 wherein the said meter is located at a substation in the network.

6 A network according to claim 5 wherein a meter is provided at each substation in the network. 7 A network according to claim 5 wherein the meter is connected to one or more current transformers at said sub station.

8 A network according to claim 5 wherein the sub station is an 1 1000/415 volt transformer substation.

9 A network according to claim 5 wherein the meter is provided to monitor and provide data representative of the loads on the transformers at the sub station.

10 A network according to claim 1 wherein data from the meter is transmitted at given time periods so as to allow the operation of the network to be monitored.

1 1 A network according to claim 1 wherein a comparison between the readings from meters at the plurality of premises and the meters at the said one or more upstream locations, is performed to create a record of the electricity load at the respective meters at given times and/or to identify differences between the readings from a plurality of meters and the one or more meters at the upstream locations so as to identify any electricity loss.

12 A network according to claim 1 wherein the meter apparatus at the location upstream of the premises provides data relating to the identification of the phase of the electricity supply which is being monitored by that meter apparatus.

13 A network according to claim 12 wherein the phase identification occurs at a location which is either of a sub station, a distribution pillar or link within the network. 14 An electricity supply network, said network including one or meters at a first location in the network to meter the electricity supply, and readings from said one or more meters are compared to the total of the meter readings taken for the supply of electricity to industry, commerce and/or households.

15 A network according to claim 14 wherein said first location is as the system steps down from the national grid to the 33,000 volts sub stations

16 A network according to claim 1 wherein the said meter is provided with a code or electronic address to enable the identification of the distributor and sub station to which the same is connected.

17 A network according to claim 1 wherein the said at least one meter is used to monitor a three phase supply and log each of the three phases on the supply and the voltage and power factor on all three phases.

18 A network according to claim 1 wherein the said meter is provided with a data communication system in the form of a Power Line Carrier (PLC) system to allow data representative o f the readings to be transmitted from the meter to a monitoring location.

19 A network according to claim 18 wherein the data is transmitted along the existing power supply system cables.

20 The meter typically will also have an electronic address which will relate to the distributor and sub station that feeds it. 21 A network according to claim 1 wherein meter is fitted at a sub station and is a three phase meter which is used to measure phase voltages, phase currents and phase angles on each phase.

22 A network according to claim 1 wherein said network includes a 3 phase and single phase meter, a current multiplexer to measure currents from the meters and measure and log AC voltage and the time current and voltage crossover and wherein a plurality of control processing means are provided to accept data from one or more secondary sub-station meters located within the network and which are capable of communication back to the sub-station meter.

23 A network according to claim 22 wherein the number of channels provided in the current multiplexer is selected with respect to the type of sub-station it will control.

24 A method of monitoring the performance of an electricity supply network, said method comprising the steps of obtaining data relating to the electricity supply to one or more premises by providing meter apparatus at said one or more premises, providing at least one further meter at at least one location intermediate the said premises and the electricity source in the supply network, obtaining data from said further meters relating to the electricity supply at that location, comparing the first set of data retrieved from the meters at the premises with the second set of data obtained from the meters upstream in the network.

25 A method according to claim 24 wherein the comparison is made to identify whether electricity supply loss has occurred in the network intermediate the respective locations of the meters providing the first and second sets of data. 26 A method according to claim 24 wherein the data in the first or second sets can be used to analyse and determine behavioural characteristics of the apparatus and/ or electricity supply at the meter location.

27 A method according to claim 24 wherein the unbalanced loads in the network are identified