GB2616474A

GB2616474A - Testing interface

Info

Publication number: GB2616474A
Application number: GB2203404.5A
Authority: GB
Inventors: Sludden Dominic
Original assignee: Balfour Beatty PLC
Current assignee: Balfour Beatty PLC
Priority date: 2022-03-11
Filing date: 2022-03-11
Publication date: 2023-09-13
Also published as: GB202203404D0

Abstract

A low voltage switchgear testing interface 100 for live testing a low voltage busbar 110 of an electrical installation. The testing interface 100 has a test point 120, such as a socket, to receive a plug of a testing device. The test point 120 is spatially offset or physically separated from, and electrically connected to, the busbar 110. The testing interface 100 also has electrical connection means 130, such as a wire or rigid conductor, adapted to electrically connect the test point 120 to the busbar 110. The busbar 110 may extend in any longitudinal direction or may curve or may adjoin another busbar. The electrical connection means 130 may include a fuse carrier (140, fig.2) or a disconnector switch (230, fig.3). The installation may have multiple busbars (110a-c, fig.2) each with a test point (120a-c, fig.2). Each test point may have dual sockets to form a Kelvin connection for performing dead, or de-energised, tests on the busbars.

Description

TESTING INlERFACE

FIELD OF THE INVENTION

The invention relates to the field of infrastructure installations, and more specifically to the field of electrical infrastructure installations.

BACKGROUND OF THE INVENTION

Electrical infrastructure installations require frequent testing in order to ensure that they are functioning as intended and to determine if maintenance is required.

Currently, for low voltage (LV) switchgear installations, live testing of the installations is performed by simply probing or attaching a testing device directly to the live conductors, referred to as busbars. Typically, a transparent plastic screen is provided between the busbars and the operator performing the test, with small openings to allow the testing device to pass through, as a safety measure.

In particular, live testing of LV switchgears requires attaching of probes to the main busbars usually through an TEC 60529 IP2x transparent plastic barrier (e.g. Perspex shield/screen). However, this is not always practical as the shield provides a protective barrier, but it also hinders the operator's movement and access to the busbars. Common problems involve tools and equipment, or parts thereof, falling within the busbars or being accidentally left in the switchgear. Metallic objects falling into the busbar chamber, or being left in the chamber accidently, may cause an arc fault.

Energized, or live, testing caries a significant risk. This risk is amplified when the switchgear is connected to systems with high short circuit magnitudes and associated arc fault incident energy. For example, a system with 2,500,000 Volt-amperes (VA) Dynl 1 6% impedance 11,000 / 400 V distribution transformer and 11,000 V short circuit level of 500,000,000 VA results in the 400V main switchboard having 38,000,000 VA (55,000 A) symmetrical short circuit current and that is without any other parallel power sources. Main 400V switchboards are for some installations rated 100kA short circuit withstand or greater.

The arc fault incident energy in these installations is extremely dangerous.

There is therefore a need to provide a means of testing an LV switchgear installations that is safer and more efficient for the operator performing the test, particularly under live testing conditions.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a low voltage switchgear testing interface for live testing a low voltage busbar of an electrical installation, the testing interface comprising: a test point adapted to interact with a testing device, wherein the test point is spatially offset from, and electrically connected to, the busbar; and electrical connection means adapted to electrically connect the test point to the busbar.

By providing a test point that is spatially offset from the busbar, but connected by way of electrical connection means (e.g. electrically conductive wire), an operator is no longer required to directly access or interact with the live busbar when carrying out routine test procedures. Accordingly, the safety of such testing procedures may be greatly increased.

In other words, the invention provides a means of spatially separating a point at which an interface of a testing device (such as a contact, plug, socket or probe) is used from the busbars of the switchgear when carrying out a test, thereby improving the safety of the procedure for live testing the busbars. Such separation may also facilitate the provision of one or more safety/protective barriers between the test point and the busbar(s).

In an embodiment, the electrical connection means may include a fuse carrier electrically connected between the test point and the busbar, wherein the fuse carrier is adapted to receive a fuse. In this way, the safety of the testing interface can be further improved by including a fusing arrangement which prevents surges in current from reaching the operator at the test point.

In an embodiment, the fuse carrier may be rated for 80kA or more. For example, in an embodiment, the fuse carrier may be rated for 120kA. In another embodiment, the fuse carrier may be rated for 100kA In an embodiment, the electrical connection means may be double insulated between the fuse carrier and the busbar. In this way, the safety of the testing interface may be further improved.

In an embodiment, the electrical connection means may further comprise a shroud between the fuse carrier and the busbar. In this way, the safety of the testing interface can be further improved.

In an embodiment, a length of the electrical connection means between the fuse carrier and the busbar may be shorter than a length of the electrical connection means between the test point and the fuse carrier.

In an embodiment, the fuse carrier may comprise an indicator for indicating whether a fuse has blown. In this way, an operator may be quickly and efficiently informed that a fuse of the testing interface has blown, which may be indicative of a fault in the testing circuit or system. The fuse carrier may also comprise a switching arrangement. Thus, the fuse carrier may comprise a switched fuse disconnector.

In an embodiment, the electrical connection means may further comprise a switch adapted connect or disconnect the busbar to/from the test point. That is, a switchable arrangement for selectably (electrically) isolating (i.e. disconnecting) the busbar and the test point may be provided. In this way, the operator may isolate the testing interface from the live busbar, which may improve the safety of the testing interface further. The disconnector may be operated locally or remotely. Such a control arrangement may further improve safety by preventing unauthorized and/or unintended electrical connection between the busbar and the test point.

In an embodiment, the test point may comprise a Kelvin connection. In an embodiment, the test point may comprise dual sockets for receiving a testing device (e.g. test plug, text socket, or testing probe). In this way, it may be possible to perform dead, or non-energized, tests on the switchgear.

In an embodiment, the testing interface may comprise a plurality of test points, wherein each test point is associated with one of a plurality of low voltage busbars.

In an embodiment, the busbar may comprise a conductive element extending in a longitudinal direction. In an embodiment, the test point may be spatially offset from the conductive element in a direction that has a perpendicular component with respect to the longitudinal direction. In some embodiments, the test point may be laterally and/or vertical offset from the busbar.

According to examples in accordance with an aspect of the invention, there is provided a low voltage switchboard comprising: a busbar for conducting an electric current; and a low voltage switchgear testing interface according to a proposed embodiment. In an embodiment, the busbar may be rated for a voltage of up to 1000V AC and 1500V DC.

According to examples in accordance with an aspect of the invention, there is provided a method for performing a live testing a low voltage busbar, the method comprising: providing a test point adapted to interact with a testing device, wherein the test point is spatially offset from, and electrically connected to, the busbar; providing electrical connection means between the test point and the busbar; providing a testing device to a test point of a low voltage switchgear testing interface, wherein the test point is physically separated from, and electrically connected to, the busbar.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 shows a schematic representation of a testing interface according to an aspect of the invention; Figure 2 shows a schematic representation of a testing interface according to a further aspect of the invention; Figure 3 shows a wiring diagram of a testing interface according to an aspect of the invention; and Figure 4 shows a wiring diagram of a testing interface according to a further aspect of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

As discussed herein, a busbar is a conductive strip or bar, typically a metallic strip or bar, which is usually housed inside switchgears, panel boards and busway enclosures for local high current power distribution.

As discussed herein, a switchgear refers to a control unit for an electrical power system to control, regulate and activate/deactivate the system.

A low voltage switchgear as discussed herein refers to a switchgear not exceeding 1000V AC or 1500V DC between conductors, e.g. low voltage switchgear according to British Standard BS EN 61439-2.

A low voltage switchgear as discussed herein refers to a switchgear not exceeding the voltages described above and typically rated for up to 10,000A of continuous current, up to 200kA short-circuit withstand current and up to 100kA short-time withstand current (for up to 30 cycles). In practice, low voltage switchgear is typically limited to 6300A continuous, or a 100kA short circuit withstand for] second. A common standard is 2500A and 50kA for 1. By way of further example, British Standard BS EN 61439-2 defines the specific requirements of power switchgear and controlgear Assemblies (PSC Assemblies), the rated voltage of which does not exceed 1,000 V AC or 1,500 V DC.

The invention provides a low voltage switchgear testing interface for live testing a low voltage busbar. The testing interface comprises a test point adapted to interact with an interface (such as a socket, plug or probe) of a testing device, wherein the test point is spatially offset from, and electrically connected to, the busbar and electrical connection means adapted to electrically connect the test point to the busbar.

Accordingly, there is provided a means of performing live testing of the busbars of a switchgear with greatly improved safety for the operator performing the tests. Further, as the remote test point removes the need for the plastic barrier that is typically provided to separate the operator from the busbars, the testing process is also made more convenient and efficient by the invention.

Put another way, proposed embodiments may remove a need for a tester to directly contact the busbar with a testing device (e.g. by maneuvering the testing device through a restricted hole in a plastic shield). Such embodiments may therefore provide a more convenient and efficient testing process, whilst also improving the safety for the operator. Further, the proposed invention provides a means of directly measuring the live busbar, without requiring intervening voltage transformers and current transformers, whilst still providing a spatial separation between the operator and the busbar. In other words, the test point provides an electrical connection to the busbar without requiring the physical proximity of the operator in order to achieve it.

Figure 1 shows a schematic representation of a testing interface 100 for live testing a high current, low voltage busbar 110 according to an aspect of the invention. The testing interface may form part of a low voltage switchboard, which may be rated to a voltage of up to 1000V AC and 1500V DC.

In the example shown in Figure 1, the testing interface 100 comprises a test point 120 adapted to interact with an interface (e.g. socket adapted to connect to the test point) of a testing device operated by a user. As can be seen in Figure 1, the test point is spatially offset (laterally) from the busbar and electrically connected to the busbar by way of electrical connection means 130 (e.g. a wire or rigid conductor). The test point may comprise a 4mm banana type socket, which provides a safe connection to a plug of the test equipment and may be rated up to 1000Vac and up to 32A.

The live, or energized, testing procedures for a busbar of a low voltage switchgear may include one or more of: a polarity check, which may be conducted between positive or negative conductors of a DC circuit or the Live and Neutral conductors of an AC circuit; an Earth electrode resistance measurement; an Earth fault loop impedance measurement; a fault current measurement; and a voltage drop measurement. Accordingly, by providing a test point that is spatially offset from the busbar, the tests and measurements outlined above may be completed in a manner that is far safer and more convenient for the operator.

The test point 120 may also be utilized for performing dead, or de-energized, tests on the busbar 110.

In the example shown in Figure 1, the busbar 110 comprises a conductive element extending in a longitudinal direction Although Figure 1 illustrates the busbar extending in a vertical direction, it should be noted that the busbar may extend in any longitudinal direction, may curve or may adjoin to another busbar according to the application of the switchgear comprising the busbar.

The test point 120 is shown as being spatially offset from the conductive element in a direction that has a perpendicular component with respect to the longitudinal direction in which the busbar extends.

By way of illustrative example, in a three dimensional space defined by three orthogonal axes: an x-axis; a y-axis; and a z-axis, the busbar 110 may extend in a longitudinal direction along the z-axis. In this case, the test point 120 may be disposed along (i.e. spaced from the busbar along): the x-axis; the y-axis; a combination of either the x-axis or the y-axis and the z-axis; a combination of both the x-axis and the y-axis; or a combination of all of the axes. In other words, the test point may be provided at any position spatially offset from the busbar.

Figure 2 shows a testing interface 100' for live testing a plurality of low voltage busbars 110a, 110b and 110c according to a further aspect of the invention.

In the example shown in Figure 2, the testing interface 100' comprises a plurality of test points 120a, 120b, 120c adapted to interact with a testing device operated by a user. Each of the plurality of test points connects to one of the plurality of busbars 110a, 110b and 110c. As can be seen in Figure 2, the test points are spatially offset from the busbars as described above and electrically connected to the busbars by way of electrical connection means 130a, 130b and 130c (e.g. electrically conductive elements).

In addition, the testing interface 100' shown in Figure 2 further comprises fuse carriers 140a, 140b and 140c, each of which are electrically connected between the test points and the busbars by way of the electrical connection means. The fuse carriers are adapted to receive a fuse in order to protect the test point from current surges (e.g. caused by Short circuit or overcurrent), thereby further increasing the safety of the operator when performing the tests. In addition, the fuse carriers may protect the sockets, cable and test gear from over current and short circuit. The fuse carrier may be rated for 100kA or more short circuit withstand, for example up to 120kA short circuit withstand and the fuses may be cartridge typel0x38mm gG, or general purpose, fuses rated for up to 100kA. The fuse carriers may further comprise an indicator, such as a neon indicator, to identify if a fuse has blown and to enable the operator to address the issue before attempting to perform a given test.

Figure 3 shows a wiring diagram 200 of a testing interface for live testing a low voltage busbar in a low voltage switchgear according to an aspect of the invention.

In the example shown in Figure 3, the switchgear comprises three live busbars LI, L2 and L3, one Neutral busbar N and one Earth busbar E. As in the examples described above, each of the busbars are electrically connected to spatially offset test points 210a, 210b, 210c, 210d and 210e by way of electrical connection means (e.g. electrical conductors adapted to provide respective electrical connections between the busbars and the test points). The test points 210a, 210b and 210c that are electrically connected to the three live bus bars comprise fuse carriers 220a, 220b and 220c as described above. In the example shown in Figure 3, fuses have not been provided for the electrical connections means connecting the test points 210d and 210e to the Neutral busbar and the Earth busbar. Instead, removable links have been provided in the fuse carriers.

The electrical connection means may be double insulated, and may further comprise a shroud, between the fuse carrier and the busbar. For example, the fuse carrier may be encased in a container/compartment. In addition, the length of the electrical connection means between the fuse carrier and the busbar may be shorter than a length of the electrical connection means between the test point and the fuse carrier and may be made as short as possible.

Also, in the example shown in Figure 3, each of the electrical connection means further comprises a disconnector 230a, 230b, 230c, 230d and 230e between the busbar and the test points. Accordingly, the test points may be entirely isolated from the busbars if necessary, for example, for maintenance of the test points themselves or for replacing a fuse of a fuse carrier. The disconnectors may be adapted to be moved between two configurations: an first, open (i.e. disconnected) configuration (in which a respective test point is electrically isolated from the corresponding busbar); and a second, closed (connected) configuration (in which a respective test point is electrically connected to the corresponding busbar). The disconnectors further may be operable to move between the open and closed configurations responsive to locally and/or remotely provisioned control signals.

Figure 4 shows a wiring diagram 300 of a testing interface according to a further aspect of the invention.

The arrangement of the testing interface shown in Figure 4 is largely similar to the testing interface shown in Figure 3; however, each test point 310a, 310b, 310c, 310d and 310e in the example shown in Figure 4 comprises dual sockets in order to form a Kelvin connection for performing dead, or de-energized, tests on the busbars.

As will be appreciated in light of the examples provided above, the invention provides a means of performing safe testing of a busbar of a switchgear of an electrical installation, which can be incorporated into new switchgear installations or retrofitted into existing switchgear installations. Further, the invention eliminates the chances of testing devices, or other testing equipment, and personal protective equipment from falling into busbar chambers or being left within the switchgear due to the removal of the need for the plastic barrier between the busbar and the operator.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS: 1. A low voltage switchgear testing interface for live testing a low voltage busbar of an electrical installation, the testing interface comprising: a test point adapted to interact with a testing device, wherein the test point is spatially offset from, and electrically connected to, the busbar, and electrical connection means adapted to electrically connect the test point to the busbar.
2. A low voltage switchgear testing interface as claimed in claim 1, wherein the electrical connection means comprises a fuse carrier electrically connected between the test point and the busbar, wherein the fuse carrier is adapted to receive a fuse.
3. A low voltage switchgear testing interface as claimed in claim 2, wherein the fuse carrier is rated for 80kA or more.
4. A low voltage switchgear testing interface as claimed in claim 3, wherein the fuse carrier is rated for 120kA.
5. A low voltage switchgear testing interface as claimed in any of claims 2 to 4, wherein the electrical connection means is double insulated between the fuse carrier and the 20 busbar.
6. A low voltage switchgear testing interface as claimed in any of claims 2 to 5, wherein the electrical connection means further comprises a shroud between the fuse carrier and the busbar.
7. A low voltage switchgear testing interface as claimed in any of claims 2 to 6, wherein a length of the electrical connection means between the fuse carrier and the busbar is shorter than a length of the electrical connection means between the test point and the fuse carrier
8. A low voltage switchgear testing interface as claimed in any of claims 2 to 7, wherein the fuse carrier comprises an indicator for indicating whether a fuse has blown
9 A low voltage switchgear testing interface as claimed in any of claims Ito 8, wherein the electrical connection means further comprises a disconnector between the busbar and the test point.
10. A low voltage switchgear testing interface as claimed in any of claims Ito 9, wherein the test point comprises a Kelvin connection.
11. A low voltage switchgear testing interface as claimed in claim 10, wherein the test point comprises dual sockets for receiving a one or more plugs of the testing device.
12. A low voltage switchgear testing interface as claimed in any of claims 1 to 11, wherein the testing interface comprises a plurality of test points, wherein each test point is associated with one of a plurality of low voltage busbars
13. A low voltage switchgear testing interface as claimed in any of claims 1 to 12, wherein the busbar comprises a conductive element extending in a longitudinal direction.
14. A low voltage switchgear testing interface as claimed in claim 13, wherein the test point is spatially offset from the conductive element in a direction that has a perpendicular component with respect to the longitudinal direction.
15. A low voltage switchboard comprising: a busbar for conducting an electric current; and a low voltage switchgear testing interface as claimed in any of claims 1 to N.
16. A low voltage switchboard as claimed in claim 15, wherein the busbar adheres to British Standard BS EN 61439.2.
17. A method for performing a live testing a low voltage busbar, the method comprising: providing a test point adapted to interact with a testing device, wherein the test point is spatially offset from, and electrically connected to, the busbar; providing an electrical connection means between the test point and the busbar; providing a testing device to a test point of a low voltage switchgear testing interface, wherein the test point is physically separated from, and electrically connected to, the busbar.