GB2248307A

GB2248307A - Detecting fraudulent consumption of electricity

Info

Publication number: GB2248307A
Application number: GB9021097A
Authority: GB
Inventors: Alan John Jones
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1990-09-28
Filing date: 1990-09-28
Publication date: 1992-04-01
Anticipated expiration: 2010-09-28
Also published as: GB9021097D0; GB2248307B

Abstract

In an arrangement comprising a meter (1) for metering electricity consumed in a load (3) connected to a supply (5), a device (11) is concealed within a cutout (7) for providing a concealed indication of the amount of electricity consumed in the load (3). In Figure 2 the device (11) comprises a current transformer (13), a rectifier bridge (15) and a mercury electrochemical elapsed time indicator (21). In Figure 3 (not shown) a voltage to frequency converter supplies pulses to a pulse counter. <IMAGE>

Description

ARRANGEMENTS INCORPORATING AN ELECTRICITY CONSUMPTION METER This invention relates to arrangements incorporating an electricity consumption meter.

More particularly the invention relates to arrangements comprising an electricity consumption meter for metering an amount of electricity consumed in a load connected to an electricity supply via the meter.

It is well known that such arrangements are susceptible to the taking of unmetered electricity by interference with the consumption meter itself or its associated wiring.

It is an object of the present invention to provide an arrangement incorporating an electricity consumption meter wherein the above problem is alleviated.

According to the present invention there is provided an arrangement comprising: an electricity consumption meter for metering an amount of electricity consumed in a load connected to an electricity supply via said meter; consumer equipment connected between said meter and said supply; and means concealed within said consumer equipment, additional to said meter, for indicating the amount of electricity consumed in said load.

One arrangement in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block schematic diagram of the arrangement; Figure 2 is a circuit diagram of a part of the arrangement; and Figure 3 shows a modification of the circuit diagram of Figure 2.

Referring to Figure 1, the arrangement comprises an electricity consumption meter 1 for metering an amount of electricity consumed in a load 3 connected to an alternating current electricity supply 5 via the meter 1, and a cutout 7 connected between the meter 1 and the supply 5 for disconnecting the load 3 from the supply 5. The cutout 7 includes a fuse 9 connected in the live path L between the supply 5 and load 3, which fuse 9 ruptures if the current in the live path L exceeds a predetermined value.

The part of the cutout 7 which carries the fuse 9 is removable from the remainder of the cutout 7 to enable the fuse 9 to be changed.

The neutral N and earth E paths between the supply 5 and load 3 are as shown in Figure 1.

Referring also to Figure 2, located within the removable part of the cutout 7, i.e. the part of the cutout 7 which carries the fuse 9, is means 11 additional to the meter 1 for indicating the amount of electricity consumed in the load 3. The means 11 is located within the removable part in such a way that when the removable part is secured to the remainder of the cutout 7 the means 11 is concealed. In this conection it is to be noted that removal of the removable part requires authorisation and that the removable part when secured to the remainder of the cutout 7 is secured in such a way that any attempt to remove it will leave a sign of such attempt.

The means 11 comprises a current transformer 13, a bridge rectifier 15, a burden resistor 17, a current limiting and scaling resistor 19, and an electrochemical elapsed time indicator 21. The primary winding 23 of the transformer 13 is constituted by a bar connection of the removable part of the cutout 7, which bar connection is in the live path L between the supply 5 and the load 3. The secondary winding 25 of the transformer 13 comprises a coil of toroidal form of approximately 1000 turns. The bar connection passes through the hole of the toroidal coil.

In operation alternating current induced in the secondary winding 25 is rectified by the bridge rectifier 15 and a voltage corresponding to the rectified current set up across the burden resistor 17 and the series combination of the current limiting and scaling resistor 19 and the electrochemical elapsed time indicator 21.

The indicator 21 comprises a length of capillary tube 27 containing two columns of mercury 29 separated by a droplet of electrolyte 31. Located in the droplet 31 is a solid index 33.

Alongside and parallel to the tube 27 is a linear scale 34. Each end of the tube 27 is sealed and accommodates an electrode 37, part of which is immersed in the column of mercury 29 at that end of the tube 27. The electrodes 37 are connected in the circuit of the means 11 as shown in Figure 2, the electrodes being connected by way of clip connections to enable easy replacement of the indicator 21 after use.

In operation of the indicator 21, the potential difference between the electrodes 37 causes electrolysis and hence transferal of the mercury of one of the columns 29 to the other at a rate proportional to the current flowing between the electrodes 37. The total amount of mercury transferred after a given time will thus represent the integral of the current flowing between the electrodes 37 over this given time. The amount of mercury transferred is indicated by the change in the position of the index 33 relative to the scale 34. The scale 34 is arranged to read ampere-hours for the current flowing in the live path L between the supply 5 and load 3, the resistor 19 serving as a scaling resistor since changing the value of resistor 19 for a given load current changes the current flowing through the indicator 21 and hence the rate of transferal of mercury.

The reading in ampere-hours of the means 11 after a given time is compared with the reading in watt-hours of the electricity consumption meter 1 for the same given time in order to determine if unmetered electricity has been taken. In this connection it is to be appreciated that the amount of electricity consumed in the load 3 as indicated by the means 11 is in terms of ampere-hours while such consumption as indicated by the meter 1 is in terms of watt-hours so that their comparison requires assumptions regarding the voltage supplied by the supply 5 and the power factor of the load 3.In practice it is practicable to make such assumptions and, in order to take into account the fact that such assumptions have been made and the accuracy of the means 11 itself, discrepancies between the indications of the means 11 and the meter 1 that are less than a predetermined amount are disregarded.

Referring to Figure 3, in a modification of the means 11 of Figure 2, the current limiting and scaling resistor 19 and the electrochemical elapsed time indicator 21 are replaced by a voltage to frequency converter 39 and a counter 41 as shown in Figure 3.

The converter 39 and counter 41 are powered by a battery 43. The converter 39 generates pulses at a rate proportional to the current flow in the live path L and these pulses are counted by the counter 41. The count of the counter 41 after a given time thus provides an indication in terms of ampere-hours of the amount of electricity consumed in the load 3 over that given time. The count of the counter 41 can be read in any conventional manner, for example a portable reading device 45 may be plugged into the counter 41.

It will be appreciated that whilst in the arrangement in accordance with the invention described by way of example the concealed means for indicating the amount of electricity consumed is carried in the removable part of a fuse type cut-out in other arrangements the concealed means may be housed elsewhere in a fuse type cut-out, or a cut-out of a different type may be used.

It will also be appreciated that in other arrangements in accordance with the invention the concealed means for indicating the amount of electricity consumed may be housed in consumer equipment other than a cut-out up-stream of the electricity consumption meter.

Claims

1. An arrangement comprising: an electricity consumption meter for metering an amount of electricity consumed in a load connected to an electricity supply via said meter; consumer equipment connected between said meter and said supply; and means concealed within said consumer equipment, additional to said meter, for indicating the amount of electricity consumed in said load.

2. An arrangement according to Claim 1 wherein said consumer equipment comprises a cut-out for disconnecting said load from said supply.

3. An arrangement according to Claim 2 wherein: a part of said cutout carries a fuse, the rupturing of which effects disconnection of said load from said supply; said part is removable from the remainder of said cutout to enable said fuse to be changed; and said means additional to said meter is located within said part in such a way that when said part is secured to said remainder said means additional is concealed.

4. An arrangement according to Claim 1 or Claim 2 or Claim 3 wherein said means additional to said meter indicates the amount of electricity consumed in said load in terms of ampere-hours.

5. An arrangement according to any one of the preceding claims wherein said means additional comprises an electrochemical elapsed time indicator.

6. An arrangement according to any one of the preceding claims wherein said means additional comprises an electronic counter.

7. An arrangement according to Claim 5 wherein said means additional includes a transformer, the primary winding of which is constituted by a connection in a conductive path between said supply and said load, said electrochemical elapsed time indicator providing the indication of the amount of electricity consumed in response to a rectified current derived from the secondary winding of said transformer.

8. An arrangement according to Claim 6 wherein said means additional includes a transformer, the primary winding of which is constituted by a connection in a conductive path between said supply and said load, said electronic counter providing the indication of the amount of electricity consumed in response to a rectified current derived from the secondary winding of said transformer.

9. An arrangement incorporating an electricity consumption meter substantially as hereinbefore described with reference to the accompanying drawings.