GB2301192A - Electricity meter - Google Patents

Abstract

An electricity meter is provided with a sealable main terminal cover 28, which covers both its input and its output terminals 18-24 in the usual way. The cover is provided with a separately sealable access port 34, which can be opened to provide access via the main cover to the output terminals only 22,24, without breaking the seal on the main cover or providing access to the input terminals 18, 20.

Description

ELECTRICITY X TERS This invention relates to electricity meters, and is more particularly but not exclusively concerned with domestic electricity meters.

At the present time, domestic electricity meters typically comprise an upper portion containing the main metering components of the meter within a sealed casing, and a lower portion which contains the input and output terminals of the meter and which is separately sealed by a removable terminal cover. Normally, the casing is sealed by the meter manufacturer or the electricity distributor immediately after the meter has been tested and found to comply with its measurement accuracy requirements, while the terminal cover is sealed by or on behalf of the electricity distributor only after the meter has been connected in the electricity supply circuit of a consumer whose electricity consumption is to be measured by the meter.Sealing is typically achieved by passing a wire through co-operating holes in the casing (or terminal cover) and in the head of the bolt or screw securing the casing (or terminal cover) to the meter, and then crimping the ends of the wire in a special lead, copper or plastics seal, such that removal of the casing (or terminal cover) requires cutting the wire and therefore leaves evidence of the removal in the event that the removal was unauthorised.

It is an object of the present invention to provide an electricity meter with more versatile sealing arrangements.

According to the present invention, there is provided an electricity meter having a sealable casing and separately sealable terminal cover means providing access to the input and output terminals of the meter, wherein the terminal cover means is adapted to provide separately sealable access to the output terminals of the meter.

Thus the terminal cover means may comprise first and second sealable terminal covers for the input and output terminals respectively. Alternatively, the terminal cover means may comprise a sealable terminal cover which covers both the input and the output terminals and sealable access means in the terminal cover for providing access to the output terminals only. In this latter case, the meter advantageously includes a terminal compartment containing the input and output terminals, the compartment including a dividing wall which separates the input terminals from the output terminals and against which the terminal cover abuts when closed, whereby the dividing wall prevents access to the input terminals via the output terminal access means.

The invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 shows an electricity meter in accordance with the present invention; Figure 2 is a partly cutaway perspective view of a terminal cover forming part of the meter of Figure 1; and Figures 3 to 5 show alternative embodiments of the terminal cover of Figure 2.

The electricity meter shown in Figure 1 is indicated generally at 10, and comprises an upper casing portion 12 which contains the main metering components of the meter and a totalisator or other display 14, and a lower terminal portion 16 which contains the input and output terminals of the meter. The metering components may be electromechanical or electronic, in the latter case typically comprising a current sensing shunt connected to an electronic metering circuit of the kind described in United Kingdom Patent No 1 603 648, while the input terminals and the output terminals typically comprise a live input terminal, a neutral input terminal, at least one live output terminal and a neutral output terminal: these terminals are shown in dotted lines at 18, 20, 22 and 24 respectively in Figure 1.

The casing portion 12 is secured to a plastics base (not shown) by two recessed screws 26. Once the meter 10 is certified, eg by the manufacturer or the electricity distributor, as meeting its measurement accuracy requirements, the casing portion 12 is sealed in position by sealing the screws 26 as described hereinbefore, so that attempts at unauthorised access to the interior of the casing portion are readily detectable.

The terminal portion 16 is closed by a removable terminal cover 28, which is secured by a screw 30 to an upstanding portion of the base: this upstanding portion is shown in dotted lines at 32, and serves as a dividing wall to separate the input terminals 18, 20 from the output terminals 22, 24, as will be explained in more detail hereinafter. The terminal cover 28 is removable independently of the casing portion 12, ie without affecting the sealing of the casing portion, and is typically sealed in its closed state by sealing the screw 30 as described hereinbefore, once the meter 10 has been installed, ie connected in the electricity supply circuit of a consumer whose electricity consumption is to be measured by the meter.

With increasing de-regulation of the electricity supply industry, it is becoming increasingly likely that the electricity distributor, the meter installer and the party who connects the meter output terminals to the consumer's circuit will all be different parties. It is therefore important to be able to provide an "audit trail" indicating which party performed each function. The present invention assists in this by providing the terminal cover 28 with a separately sealable access aperture 34 and co-operating closure member (or door) 36, which are disposed above, and provide access only to, the output terminals 22,24.The access aperture 34 and door 36 are shown in more detail in Figure 2, where it can be seen that the door 36 is secured to a rib 40 extending across the middle of the aperture, by means of a screw (shown at 42 in Figure 2) which screws into a tapped hole 38 in the rib 40 and which is yet again sealed as described hereinbefore.

In use, with the electricity distribution circuit up to the meter having already been installed (the circuit including a safety cut-out such as a fuse), the meter installer would render the circuit safe via the cut-out and then instal the meter 10 by connecting the live and neutral wires of the circuit to the terminals 18 and 20. The installer would then perhaps test the operation of the meter 10 with a dummy load, before closing and sealing the terminal cover 28 and door 36 as described earlier. At this point, the customer's circuit is not connected to the output terminals 22, 24. The seals used by the installer are typically unique to the installer, so identifying him.

Finally, the aforementioned party who connects meter output terminals to the customer's circuit (who may be different from the meter installer) will check the customer's circuit, then open the door 36, complete the connection of the customer's circuit to the output terminals 22, 24 of the meter 10, and re-close and re-seal the door 36 with his or her own seal. It will thus be readily apparent subsequently which party made the various connections to the meter.

It will be appreciated that the door 36 provides access only to the output terminals 22, 24 because the terminal cover 28, when in its closed position, abuts the aforementioned dividing wall 32 to which it is secured, thus preventing access to the input terminals 18, 20 (which access could be used, for example, to fraudulently bypass the meter).

Figures 3 to 5 show various alternative ways of implementing the access aperture 34 and door 36 of Figure 2.

Thus in Figure 3, the door 34 has a tongue 44 which engages under the edge of one end of the aperture 34, and is secured by its screw 42 to a tapped hole 46 provided adjacent the edge of the other end of the aperture.

In Figure 4, the central rib 40 in the aperture 34 is provided with an upstanding loop 50 (instead of the tapped hole 38). The loop 50 projects through an aperture 52 in the door 36 between two further loops 54 on each side of the aperture 52, the loops 50, 54 thus forming one continuous loop or passage through which a sealing wire is passed to seal the door 36 shut.

In the Figure 5 implementation, the aperture 34 in the terminal cover 28 is enlarged to include part of the side wall of the terminal cover. The door 36 is correspondingly enlarged, and thus has a part 56 which is at right angles to the main part 58 and which fits into the portion of the aperture 34 in the side wall of the terminal cover 28. The main part 58 of the door 36 has flanges 60 on each side, which slide under corresponding flanges 62 on each side of the aperture 34 as the door 36 is slid into the aperture from the end thereof in the side wall of the terminal cover, thus producing a flush fit of the door in the aperture. A tongue 64 at the opposite end of the door 36 from the angled part 56 engages under the edge of corresponding end of the aperture 34 (as in the Figure 3 implementation), which edge has similar tongues 66 which engage under that end of the door, on each side of the tongue 64. Finally, corresponding holes 68, 70 in the terminal cover 28 and the door 36 respectively enable the door to be wire-sealed in its closed position.

Claims (8)

1. An electricity meter having a sealable casing and separately sealable terminal cover means providing access to the input and output terminals of the meter, wherein the terminal cover means is adapted to provide separately sealable access to the output terminals of the meter.

2. An electricity meter as claimed in claim 1, wherein the terminal means comprises first and second sealable terminal covers for the input and output terminals respectively.

3. An electricity meter as claimed in claim 1, wherein the terminal cover means comprises a sealable terminal cover which covers both the input and the output terminals and sealable access means in the terminal cover for providing access to the output terminals only.

4. An electricity meter as claimed in claim 3, wherein the meter includes a terminal compartment coxItaining the input and output terminals, the compartment including a dividing wall which separates the input terminals from the output terminals and against which the terminal cover abuts when closed, whereby the dividing wall prevents access to the input terminals via the output terminal access means.

5. An electricity meter substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.

6. An electricity meter substantially as herein described with reference to Figures 1 and 2, as modified by Figure 3, of the accompanying drawings.

7. An electricity meter substantially as herein described with reference to Figures 1 and 2, as modified by Figure 4, of the accompanying drawings.

8. An electricity meter substantially as herein described with reference to Figures 1 and 2, as modified by Figure 5, of the accompanying drawings.