GB2502101A

GB2502101A - Power distribution link box containing an interrupter

Info

Publication number: GB2502101A
Application number: GB1208603.9A
Authority: GB
Inventors: Brian Andrew Richard Mckean; Benjamin Colin Sigsworth; Andrew Michel
Original assignee: E P S UK Ltd
Current assignee: E P S UK Ltd
Priority date: 2012-05-16
Filing date: 2012-05-16
Publication date: 2013-11-20
Anticipated expiration: 2032-05-16
Also published as: GB201208603D0; GB2502101B

Abstract

A power distribution link box (1, figure 1), typically installed below ground, in a low voltage electricity supply network contains a link connector comprising a first connector stalk electrically connected to an input conductor and a second connector stalk electrically connected to an output conductor. A remotely-operable switch 5 is received on the stalks and comÂprises first and second terminals (15, figure 4) and clamping means (16, 17, 18, figure 4) for clamping each terminal (15) and its respective stalk together, an interrupter 8 mounted between the first and second terminals, an actuator (9, figure 3) for the interÂrupter 8, and control circuitry for controlling operation of the actuator (9) in response to receipt of an external signal.

Description

A POWER DISTRIBUTION LINK BOX, AND AN ELECTRICITY SUPPLY

NETWORK INCLUDING SUCH A LINK BOX

Field of the Invention

This invention relates to power distribution link box, and to an electricity supply network including such a link box.

Background to the Invention

In an electricity supply network, local area low voltage distribution to do-mestic customers in particular is segmented through 3-phase underground link boxes, containing removable solid links to permit a segment of the network to be isolated for the purpose of fault location, for example. While the link boxes provide a simple and effective means for a visiting engineer to disconnect a small part of the network from, or reconnect it to, a particular substation or a feeder pillar, this represents a labour-intensive operation, as the engineer has to travel to and locate each individual link box. In addition, there can be risks as-sociated with the reinsertion of the links if the circuit is still connected to the 415V AC supply.

A further factor which is complicating the control of the electricity supply network is the increasingly widespread installation of photovoltaic panels on domestic properties, since these are usually configured to supply electricity back into the grid when the output exceeds that required by the premises at which it is installed. Since an individual property will be connected to a single phase of the network, and since the installation of panels is dependent on ac- tion by the owner of the premises, it is possible for a significant imbalance be-tween the phases to arise. There is therefore a need for the electricity supply companies to be able to reconfigure the low voltage distribution network dynam-ically to minimise the adverse effects of the creation of such imbalances.

Summary of the Invention

According to the invention, there is provided a link box in a low voltage electricity supply network, containing a link connector comprising a first con- nector stalk electrically connected to an input conductor and a second connect-or stalk electrically connected to an output conductor, a remotely-operable switch being received on the stalks and comprising first and second terminals and clamping means for clamping each terminal and its respective stalk togeth-er, an interrupter mounted between the first and second terminals, an actuator for the interrupter, and control circuitry for controlling operation of the actuator in response to receipt of an external signal.

The interrupter is suitably a vacuum interrupter, and the actuator is pref- erably linked to the interrupter through a lever providing a mechanical ad-vantage.

The clamping means may each comprise a cam rotatable in one direc-tion to pull the respective terminal into engagement with the stalk to clamp it, and in the other direction to urge the terminal away from the stalk, thereby re-leasing it.

Preferably, the remotely-operable switch comprises a movable indicator linked to the interrupter to provide a visual indication of the state of the inter-rupter.

The invention also provides an electricity supply network comprising at least one link box according to the invention, connected between a plurality of consumers and one or more supply substations, and a remote control station arranged to transmit to the link box a control signal to open or close a remotely-operable switch therein. Preferably, the network comprises a plurality of such link boxes, and the remote control station is configured to transmit a said control signal to a selected one of the link boxes.

Brief Description of the Drawings

In the drawings, which illustrate an exemplary embodiment of the inven-tion: Figure 1 is a top plan view of a link box with the cover removed; Figure 2 is an enlarged view from above and to one side of one of the remotely-operable switches in the link box; Figure 3 is a side elevation of the switch shown in Figure 2; and Figure 4 is an enlarged detail view of the connectors of the switch shown in Figures 2 and 3.

Detailed Description of the Illustrated Embodiment

Referring first to Figure 1, the link box is of generally conventional form, and comprises a water-resistant enclosure 1 which, in use, will typically be bur-ied at least partially below ground. The enclosure 1 is provided with opposed cable inlets/outlets 2, 3 (it will be appreciated that the terms inlet" and "outlet" as used herein are not intended to indicate direction in the sense of load and supply). The cables will carry a 3-phase AC supply at 415V, for supplying do- mestic and small commercial customers in a local area, and the phase conduc-tors are connected to respective link sockets arranged side-by-side in a central block 4. In a conventional installation, each link socket will be occupied by a pair of conductor stalks upstanding therein, which are engageable by a remov- able conductor link so that, when required for fault location and isolation pur-poses, links can be removed to isolate a particular circuit or even an individual phase circuit. In the link box of the invention, each conductor link is replaced with a remotely-operable switch 5, shown in more detail in Figures 2 and 3.

The switch 5 comprises a support body 6, the lower part of which carries a pair of terminal clamps 7 arranged to engage and clamp on to the connector stalks, as will be described in more detail hereinafter with reference to Figure 4.

A vacuum interrupter 8 is connected across the terminals, and is operated by a magnetic actuator 9 (Figure 3), controlled by a control circuit board mounted in a housing 10 located between the clamps 7. The control circuit board receives switching command signals via a Power Line Carrier transmitted over one or more of the supply conductors from a terminal unit installed in a nearby substa-tion or feeder pillar. It will be appreciated that the switching command signals can be received by the control circuit board via any suitable communications media. It will further be appreciated that the interrupter may take the form of a vacuum interrupter, vacuum switch, vacuum contactor or any other suitable vacuum switching device.

The actuator 9 is mechanically linked to the interrupter 8 through a lever 11 configured to give a mechanical advantage, ensuring that a greater force is delivered to the interrupter, ensuring rapid and positive opening and closing of the switch. An extension 12 of the lever is operatively connected to a slidable indicator 13, visible through an opening 14 in the body, to provide an indication of whether the switch is in the open or closed state; it is important for safety considerations that the switch should only be installed on to the stalks when the in the open state.

Referring now to Figure 4, the clamps 7 each comprise a flexible copper terminal 15 connected at its upper end to one side of the interrupter 8. An actu-ating rod 16 passes slidably through the lower part of the body 6 and is fixed through and to the terminal 15 on one side of the body. The rod 16 is connect- ed on the other side of the body 6 to a cam arrangement 17 operated by a slot-ted wheel 18 rotatable by a screwdriver or like tool. Rotation of the wheel 18 in one direction causes the cam arrangement 17 to draw the rod 16 towards it, thereby drawing the lower end of the terminal 15 towards the body 6. The stalk in the link box can thus be clamped between the terminal and the body, ensur- ing a good electrical connection between the stalk and the terminal 15. Rota-tion in the opposite direction will release the clamping pressure, permitting the switch 5 to be withdrawn from the link box.

The use of the switches 5 permits greater flexibility in control of the local supply network. Not only can the different segments of the network be remotely switched for fault isolation and repair purposes without the need for the engi-neers to visit each link box, but dynamic control of the network can be achieved to permit balancing of loads and supply when power is returned to the grid from domestic generation sources such as photovoltaic panels.

Claims

CLAIMS1. A link box in a low voltage electricity supply network, containing a link connector comprising a first connector stalk electrically connected to an in-put conductor and a second connector stalk electrically connected to an output conductor, a remotely-operable switch being received on the stalks and com- prising first and second terminals and clamping means for clamping each termi-nal and its respective stalk together, an interrupter mounted between the first and second terminals, an actuator for the interrupter, and control circuitry for controlling operation of the actuator in response to receipt of an external signal.
2. A link box according to Claim 1, wherein the interrupter is a vacu-um interrupter.
3. A link box according to Claim 1 or 2, wherein the actuator is linked to the interrupter through a lever providing a mechanical advantage.
4. A link box according to any preceding claim, wherein the clamping means each comprise a cam rotatable in one direction to pull the respective terminal into engagement with the stalk to clamp it, and in the other direction to urge the terminal away from the stalk, thereby releasing it.
5. A link box according to any preceding claim, wherein the remotely- operable switch comprises a movable indicator linked to the interrupter to pro-vide a visual indication of the state of the interrupter.
6. A link box according to any preceding claim, comprising three link connectors, one for each phase of a three-phase supply, each link connector having a respective one of said remotely-operable switches.
7. A link box according to any preceding claim, wherein the control circuitry is adapted to receive a control signal via one or more of the in-put/output conductors.
8. A link box in a low voltage electricity supply network, substantially as described with reference to, and/or as shown in, the drawings.
9. An electricity supply network comprising at least one link box ac-cording to any preceding claim, connected between a plurality of consumers and one or more supply substations, and a remote control station arranged to transmit to the link box a control signal to open or close a remotely-operable switch therein.
10. A network according to Claim 9, wherein the network comprises a plurality of such link boxes, and the remote control station is configured to transmit a said control signal to a selected one of the link boxes.