GB2447135A

GB2447135A - Sub-metering in an electrical distribution board

Info

Publication number: GB2447135A
Application number: GB0803573A
Authority: GB
Inventors: Michael David Sargent; Keith Wray Ball; Andrew Purdie Baker; Terence Edward John Lovett
Original assignee: Schneider Electric Ltd
Current assignee: Schneider Electric Ltd
Priority date: 2007-02-28
Filing date: 2008-02-27
Publication date: 2008-09-03
Also published as: GB0803573D0; GB0703865D0; AU2008200915A1; AU2008200915B2

Abstract

An electrical distribution board assembly (10) comprises a chassis (12), an incoming terminal (14), and a bus conductor (16) extending along the chassis (12) for distributing electrical power from the incoming terminal (14) to an array of outgoing conductor terminals (18). The array of outgoing conductor terminals (18) is subdivided into at least two sub-arrays (26a, 26b), the bus conductor (16) providing a metering point (28) between the sub-arrays (26a, 26b). This allows for more economical metering of groups of circuits in an electrical installation.

Description

I

Improvements in or relating to Electrical Distribution Boards The present invention relates to an electrical distribution board assembly.

An electrical distribution board distributes electrical power from one or more incoming power supply terminals to a number of outgoing power supply terminals. Typically, the electrical distribution board is a housing which comprises a number of circuit breakers. 1 0

Present building regulations require users of electricity in small, medium and large commercial and industrial buildings to be able to identify their energy usage. Moreover, the building regulations state that it is reasonable for the end user to identify 90% of the energy usage of their building(s). It is also reasonable for the end-user to be able to identify where the energy is being used, e.g. sub-metering of power, lighting circuits etc. Conventional practice for monitoring electrical energy usage is to retrofit a commercially available electricity meter and transformer combination to the distribution board. This can be placed around the incoming power cables to the distribution board, or the outgoing power cables from the distribution board to the load. Alternatively, such electricity meter and transformer combinations may be installed within the distribution board as part of a new installation.

While this practice is effective at accurately monitoring the energy usage of the distribution board, it is limited in that it is only possible to monitor the total energy usage of the distribution board. If a user wishes to identify the energy usage of particular circuits of the distribution board they are required to add an electricity meter and transformer combination to each of the individual outgoing power circuits. This may be more detailed than the user needs, and is of course expensive. Alternatively, a number of distribution boards each having an energy metering facility at their incoming side are connected together. This results in a complicated system which is expensive and time consuming to install.

It is an object of the present invention to provide for more economic metering of groups of circuits in an electrical installation.

According to a first aspect of the present invention there is provided an electrical distribution board assembly comprising: a chassis; at least one incoming terminal; at least one bus conductor extending along said chassis for distributing electrical power from said incoming terminal to an array of outgoing conductor terminals; wherein said array of outgoing conductor terminals is subdivided into at least two sub-arrays, said bus conductor providing a metering point between said sub-arrays.

The provision of a metering point between sub-arrays allows for monitoring power consumption in one group of outgoing circuits separately from another, without unduly increasing the size or cost of the installation.

Preferably, said bus conductor is a busbar.

The assembly may be provided with a sensing device at said metering point, the sensing device in use providing a metering signal to a metering device.

The sensing device may be a current transformer encircling said bus conductor at the metering point.

The sensing device may be a current transformer in close proximity to said bus conductor at the metering point. The coupling of the sensing device to the bus conductor is by electromagnetic induction, in that case, rather than by electrical contact.

The current transformer may comprise a body having an aperture for passage of the bus conductor.

The assembly may further comprise at least one additional sensing device at a metering point associated with said incoming terminal, the additional sensing device in use providing a second metering signal to a metering device, whereby energy consumption of the whole array and a sub-array can be metered simultaneously.

In a preferred embodiment, said electrical distribution board assembly comprises a plurality of incoming terminals and a plurality of bus conductors extending in parallel along said chassis for distributing multi-phase electrical power from said incoming terminals to said array of outgoing conductor terminals, and each busbar provides a metering point between said sub-arrays.

Preferably, each bus conductor is a busbar.

The assembly may be provided with a respective sensing device coupled to each bus conductor at said metering point, the sensing devices in use providing a metering signal to a metering device.

The sensing devices may be current transformers encircling their respective bus conductors at the metering point.

The bus conductors at the metering point may be spaced more widely than within the sub-arrays. This will provide space for mounting of a current transformer or other sensing device, for example, without unduly increasing the size of the whole assembly.

Where the bus conductors are bus bars, at least one of said bus bars may be made in sections, joined together between the sub-arrays. In one embodiment, each bus bar is made in three sections, comprising a straight section within each of said sub-arrays and a joining section connecting the two straight sections together between the sub-arrays.

In a three-phase embodiment, the joining sections of two bus bars are curved to increase spacing between the joining sections relative to the straight sections, thereby to provide said metering point.

The assembly may further comprise a metering device connected to receive said sensing signal from the sensing device and to provide a readout of energy consumption in one or more of said sub-arrays of outgoing circuits.

In a preferred embodiment, the metering device is located in a metering unit on a separate chassis adapted for mounting beside the distribution board assembly chassis and connected to receive said metering signal from the sensing device(s) coupled to the bus conductor(s) at said metering point(s).

The metering unit may comprise an additional metering device for receiving sensing signals from a sensing device associated with the incoming terminals.

Said electrical distribution board assembly may be adapted such that it is electrically connectable to another similar electrical distribution board assembly. This permits a modular expansion of the distribution board to suit a larger electrical installation.

Preferably, each electrical distribution board assembly is electrically connected by one or more busbars extending along said chassis.

According to a second aspect of the present invention there is provided an electrical distribution board comprising: at least one electrical distribution board assembly according to the first aspect; a first electrical energy metering system coupled to the bus conductor between said sub-arrays of said at least one electrical distribution board assembly; and a second electrical energy metering system coupled to said incoming terminal(s).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:-Fig. 1 is a perspective view of an electrical distribution board comprising an electrical distribution board assembly according to a first aspect of the present invention, together with associated metering unit; Fig. 2 is a top view of the distribution board of Fig. 1; Fig. 3 is an enlarged view of the busbars and current transformers of Fig. 1 at a metering point between sections of the distribution board; and Fig. 4 is an enlarged view of the electrical metering devices of the metering unit in Fig. 1.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Figs. 1 and 2 illustrate an electrical distribution board 1 which includes an electrical distribution board assembly 10 comprising a chassis 12 (in the form of a chassis pan assembly), three incoming terminals 14a-14b, three busbars 16a-16b (an example of a bus conductor) and an array of outgoing conductor terminals 18. A metering unit, to be described later, is provided on a separate chassis 34 (in the form of a chassis pan assembly). 1 0

The chassis pan assembly 12 is a plastics moulding or formed metal chassis, in the general form of a rectangular board which is adapted to be mounted on a wall or rack via mounting points 20. Cover and outer housing parts may also be provided, though these are not part of the invention and not shown.

The incoming terminals 14a-14b are located towards the bottom of the chassis pan assembly 12. Although three incoming terminals 14a-14b are illustrated in Figs. 1 and 2 for an assembly 10 supplying three-phase power, it should be appreciated that the assembly 10 may comprise one, two, four or more incoming terminals depending on the required type of power supply. A neutral terminal is also shown, in this example. In the installed state, individual conductors (cables) which are not shown in the drawing will lead power into the terminals 14a-14c.

Within the distribution board assembly, busbars 16a-16b extend along the length of the chassis pan assembly 12. The busbars 16a-16b distribute electrical power from the incoming terminals 14a-14b to the array of outgoing conductor terminals 18. Again, although three busbars 16a-16b are illustrated in Figs. 1 and 2, it should be appreciated that the number of busbars will correspond to the number of incoming terminals explained above.

The outgoing conductor terminals 18 are adapted to feed miniature circuit breaker devices 23 mounted on DIN or similar mounting rails 22. The miniature circuit breaker devices 23 may be simple switches, but are typically current-sensitive circuit breaker devices. An outgoing terminal of each miniature circuit breaker is available for the connection of a cable to carry power out to an individual load circuit within the wider installation.

Each terminal 18 is connectable to a respective one of said busbars 16a- 16c, by operation of a switch 23. In this way, the unused terminals 18 are not live, only the ones connected into a miniature circuit breaker 24. In the three-phase example shown, the outgoing terminals 18 of each sub-array are connected to the three phases in a repeating sequence. A set of three adjacent miniature circuit breakers 24 will thus receive a full set of three phases.

Such arrangements, and variations thereof, are well known in the field and no further description is given here. In contrast to conventional arrangements, however, the array of outgoing conductor terminals 18 in this example is split into a first sub-array 26a and a second sub-array 26b.

As illustrated in Fig. 3, the busbars 16a-16b are exposed in the space between sub-arrays 26a, 26b. The bus bars are also splayed outwardly in this region to increase their spacing and define a metering point 28 between the two sub-array 26a, 26b. The metering point 28 allows for monitoring power consumption in outgoing circuits connected to one sub-array separately from the other, without unduly increasing the size or cost of the installation.

In the embodiment illustrated here, the assembly 10 is shown with sensing devices in the form of three current transformers 30 circumferentially mounted around their respective busbars 16a-16b at the metering point.

To facilitate assembly, and to maximize sharing of components with other product lines, each of the busbars in this example is made in three sections: two straight sections extending within the respective sub-arrays, and a joining section connected between the other sections by a bolted or riveted connection. The current transformers can be fitted to these joining sections before final assembly into the distribution board. One or more of the joining sections may provide the splaying necessary to provide space for the current transformers. An insulating cover (not shown) will be provided over the metering point, to prevent accidental contact with the live conductors.

As illustrated best in Fig. 4, two digital metering devices 32a and 32b, are mounted together with a second set of current transformers 36 on a second chassis pan assembly 34. The second chassis pan assembly with these components comprises a metering sub-assembly or module, which can be supplied as a separate unit for use with the novel distribution board assembly provided on chassis pan assembly 12. In the finished installation, incoming cables pass over the chassis pan assembly 34 and through the second sets of current transformers 36.

Each electrical meter 32a, 32b is connected to receive metering signals from the current transformers 30 and 36, respectively. The lower set of current transformers 36 meter the total power consumption of both sub-arrays 26a, 26b, and hence meter 32b records the total consumption of all outgoing circuits connected to the terminals 18 in the distribution board.

This part of the arrangement is conventional. At the same time, however, upper current transformers 30 meter the power consumption of the outgoing circuits connected to terminals of the upper sub-array 26a only.

A simple subtraction of the upper power consumption from the total power consumption gives the power consumption of the lower sub- array 26b, so that the user can know not only his total energy usage, but also the usage of each group circuits. By connecting only the lighting circuits to the upper sub-array 26a, for example, the meter 32a will tell how much energy is consumed for lighting.

Furthermore, although only the electrical distribution board 1 has been illustrated as comprising only one assembly 10, it should be appreciated that any suitable number of assemblies 10 may be included in an electrical distribution board 1. For example, each assembly 10 is adapted such that it is electrically connectable to another similar assembly 10. Each assembly may be connected by simply connecting together busbars 16a- 16b. Therefore, it is possible to monitor a large number of sub-arrays by simply including the required number of assemblies 10 in the distribution board 1. This avoids an unnecessarily complex system, which is also less expensive than previous options. If desired, an assembly 10 can be made with three or more subsets of outgoing terminals, and two metering points between them.

Modifications and improvements may be made to the above without departing from the spirit and scope of the present invention. For example, although current transformers 30 have been described and illustrated above for monitoring the power consumption, it should be appreciated that Other sensing devices, whether of contact or non-contact type, may be employed.

Also, although the above assembly 10 has been illustrated and described as a three-phase power supply, it should be appreciated that the assembly could equally operate with a single-phase, two-phase, or poly-phase power supply.

In the metering arrangements, two simple meters 32a, 32b are illustrated, each connected to its own sensing device in the form of the current transformers 30, 36. In other embodiments, a single metering device may provide multiple channels, which can be read out sequentially. A more sophisticated metering device could even be configured to perform the subtraction mentioned above. I0

Furthermore, although the current transformers 30, 36 have been illustrated and described above as being discrete independent devices, it should be appreciated that the current transformers 30, 36 may be in the form of a single device which comprises three apertures which are adapted to receive the busbars 16a-16b. The operation of the single device remains the same as the discrete independent devices.

Also, although the metering device has been described above as providing a readout of energy consumption, it should be appreciated that the meter may readout other characteristics such as amps, voltage, power factor, which may be sensed by the device.

Claims

Claims 1. An electrical distribution board assembly comprising: a

chassis; at least one incoming terminal; at least one bus conductor extending along said chassis for distributing electrical power from said incoming terminal to an array of outgoing conductor terminals; wherein said array of outgoing conductor terminals is subdivided into at least two sub-arrays, said bus conductor providing a metering point between said sub-arrays.
2. An electrical distribution board assembly as claimed in claim 1, wherein said bus conductor is a busbar.
3. An electrical distribution board assembly as claimed in claim I or claim 2, wherein said assembly further comprises a sensing device at said metering point, said sensing device in use providing a metering signal to a metering device.
4. An electrical distribution board assembly as claimed in claim 4, wherein said sensing device is a current transformer encircling said bus conductor at said metering point.
5. An electrical distribution board assembly as claimed in claim 4, wherein said current transformer comprises a body having an aperture for passage of said bus conductor.
6. An electrical distribution board assembly as claimed in claim 4, wherein said sensing device is a current transformer in close proximity to said bus conductor at said metering point, and wherein said current transformer is coupled to the bus conductor by electromagnetic induction.
7. An electrical distribution board assembly as claimed in any of claims 3 to 6, wherein said assembly further comprises at least one additional sensing device at a metering point associated with said incoming terminal, said additional sensing device in use providing a second metering signal to a metering device, whereby energy consumption of the whole array and a sub-array can be metered simultaneously.
8. An electrical distribution board assembly as claimed in any preceding claim, wherein said assembly comprises a plurality of incoming terminals and a plurality of bus conductors extending in parallel along said chassis for distributing multi-phase electrical power from said incoming terminals to said array of outgoing conductor terminals, and each bus conductor provides a metering point between said sub-arrays.
9. An electrical distribution board assembly as claimed in claim 8, wherein each bus conductor is a busbar.
10. An electrical distribution board assembly as claimed in claim 8 or 9, wherein said assembly comprises a respective sensing device coupled to each bus conductor at said metering point, said sensing devices in use providing a metering signal to a metering device.
11. An electrical distribution board assembly as claimed in claim 10, wherein said sensing devices are current transformers encircling their respective bus conductors at said metering point.
12. An electrical distribution board assembly as claimed in any of claims 8 to 11, wherein said bus conductors at said metering point is spaced more widely than with said sub-arrays.
13. An electrical distribution board assembly as claimed in any of claims 9 to 12, wherein at least one of said busbars is made in sections, joined together between said sub-arrays.
14. An electrical distribution board assembly as claimed in claim 13, wherein each busbar is made in three sections, comprising a straight section within each of said sub-arrays and a joining section connecting said two straight sections together between said sub-arrays.
15. An electrical distribution board assembly as claimed in claim 14, wherein said assembly comprises three busbars and said joining sections of two busbars are curved to increase spacing between said joining sections relative to said straight sections, thereby to provide said metering point.
16. An electrical distribution board assembly as claimed in any of claims 3 to 15, wherein said assembly further comprises a metering device connected to receive said sensing signal from said sensing device and to provide a readout of energy consumption in one or more of said sub-arrays of outgoing circuits.
17. An electrical distribution board assembly as claimed in claim 16, wherein said metering device is located on a separate chassis adapted for mounting beside said distribution board assembly chassis and connected to receive said metering signal from said sensing device(s) coupled to said bus conductor(s) at said metering points(s).
18. An electrical distribution board assembly as claimed in claims 16 or 17, wherein said metering device comprises an additional metering device for receiving sensing signals from a sensing device associated with said incoming terminals.
19. An electrical distribution board assembly as claimed any preceding claim, wherein said electrical distribution board assembly is adapted such that it is electrically connectable to another similar electrical distribution board assembly.
20. An electrical distribution board assembly as claimed in claim 19, wherein each electrical distribution board assembly is electrically connected by one or more busbars extending along said chassis.
21. An electrical distribution board comprising: at least one electrical distribution board assembly according to claim 1; a first electrical energy metering system coupled to the bus conductor between said sub-arrays of said at least one electrical distribution board assembly; and a second electrical energy metering system coupled to said incoming terminal(s).
22. An electrical distribution board assembly as hereinbefore described with reference to the accompanying drawings.
23. An electrical distribution board as hereinbefore described with reference to the accompanying drawings.