US-12620535-B2 - Electrical switch for an on-load tap changer

US12620535B2US 12620535 B2US12620535 B2US 12620535B2US-12620535-B2

Abstract

An electrical switch for an on-load tap changer, said electrical switch comprising: at least three electrical contacts connected to a respective electrical conductor, a switch means configured to be movable between a plurality of positions, the switch means in each respective position physically contacting a respective combination of said electrical contacts to provide electrical contact between the electrical contacts in each respective combination of electrical contacts, the switch means including two electrically interconnected contacts or contact surfaces provided on a movable carrier element mounted on the operating member for movement along a said arcuate path, and the contacts or contact surfaces being provided at a same radial distance from the rotational axis and with a same spacing as the electrical contacts of each respective combination of electrical contacts.

Inventors

Jean Louis Gérard MATHAE

Assignees

HITACHI ENERGY LTD

Dates

Publication Date: 20260505
Application Date: 20230828
Priority Date: 20220829

Claims (11)

1 . An electrical switch for an on-load tap changer, said electrical switch comprising: at least three electrical contacts connected to respective electrical conductors, a movable switch assembly configured to be movable between a plurality of positions, said movable switch assembly comprising two electrically interconnected contacts or contact surfaces provided on a carrier element, such that in each respective position the movable switch assembly physically contacts a respective combination of said electrical contacts to provide electrical contact between the electrical contacts in each respective combination; a hermetically sealed housing providing an inner space enclosing the electrical contacts and the movable switch assembly, said electrical conductors extending from the electrical contacts inside the inner space of the housing to an outside of the housing, and a control assembly comprising an operating member extending from the outside of the housing into the inner space of the housing, the operating member being operatively connected to the movable switch assembly such that the operating member is able to move the movable switch assembly to the plurality of positions depending on a position of the operating member, wherein said inner space is under vacuum or is filled with an arc suppression gas, wherein the operating member comprises an arm rotatably attached to the housing for rotation about a rotational axis, wherein the movable switch assembly is attached to an end portion of the arm such that the movable switch assembly is movable between said plurality of positions along an arcuate path, wherein said contacts or contact surfaces of the movable switch assembly are provided at a same radial distance from the rotational axis and with a same spacing as the electrical contacts of each respective combination of electrical contacts.
2 . The electrical switch according to claim 1 , wherein said inner space is filled with an SF6 arc suppression gas.
3 . The electrical switch according to claim 1 , wherein the movable switch assembly is configured to be movable to a first position in which the movable switch assembly physically contacts a first one of said electrical contacts and a second one of said electrical contacts, and to be movable to a second position in which the movable switch assembly physically contacts said second one of said electrical contacts and a third one of said electrical contacts.
4 . An on-load tap changer comprising the electrical switch according to claim 1 .
5 . The on-load tap changer according to claim 4 , wherein the electrical switch is a diverter switch, wherein one of said electrical conductors is a neutral conductor, and wherein remaining conductors are connected to respective tap selector switches.
6 . The electrical switch according to claim 1 , wherein the carrier element of the movable switch assembly is mounted at an end portion of the operating member.
7 . The electrical switch according to claim 1 , wherein the movable switch assembly comprises one of said electrical contacts.
8 . The electrical switch according to claim 1 , wherein the control assembly is actuated by a motorized actuator.
9 . The electrical switch according to claim 1 , wherein the actuator is located outside the housing and drives the operating member through a sealed interface.
10 . The electrical switch according to claim 1 , wherein the movable switch assembly is movable to an intermediate position in which current flows via additional electrical contacts.
11 . The electrical switch according to claim 1 , wherein one of said electrical conductors is a neutral conductor, and the remaining electrical conductors are connected to respective tap selector switches.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a 35 U.S.C. § 371 national stage application of PCT International Application No. PCT/EP2023/073539 filed on Aug. 28, 2023, which in turn claims foreign priority to European Patent Application No. 22192667.8, filed on Aug. 29, 2022, the disclosures and content of which are incorporated by reference herein in their entirety. TECHNICAL FIELD The present disclosure relates to on-load tap changers and more specifically to an electrical switch for an on-load tap changer. BACKGROUND Electrical switches are often used in on-load tap changers (OLTC) for different functions, such as a main switch, a resistor switch, a pre-selector switch or a diverter switch. The specific design of the switches may vary; For example, some switches are designed to ‘make before break’ whilst some are designed to ‘break before make’. The on-load tap changers are often used with voltages at which the electrical switch is subject to arcing upon change of position of the electrical switch. Arcing causes wear of the electrical switch, and thus contamination of surrounding components of the OLTC and/or contamination of the electrical switch. For example, an insulating oil in the OLTC may become contaminated and lose parts of its insulating properties. SUMMARY Accordingly, an object of the present disclosure is to increase lifetime and reduce service need of an on-load tap changer. According to a first aspect of the present disclosure, this and other objects is achieved by an electrical switch according to claim 1, with alternative embodiments set forth in the dependent claims. The electrical switch is for an on-load tap changer and the electrical switch comprises at least three electrical contacts connected to a respective electrical conductor. The electrical switch further comprises a switch means configured to be movable between a plurality of positions, wherein the switch means in each respective position physically contacts a respective combination of said electrical contacts to provide electrical contact between the electrical contacts in each respective combination of electrical contacts. The physical contact governed by the switch means may either be a direct contact between contacts of each combination of contacts, or the physical contact may be provided by a portion of the switch means contacting the contacts of each combination of contacts to bridge between the combination of contacts. The electrical switch further comprises a hermetically sealed housing providing an inner space enclosing the electrical contacts and the switch means. The electrical conductors extending from the electrical contacts inside the inner space of the housing to an outside of the housing. The electrical switch further comprises a control means configured to control movement of the switch means. Also, the inner space is under vacuum or is filled with an arc suppression gas. The control means comprises an operating member extending from the outside of the housing into the inner space of the housing. The operating member is operatively connected to the switch means such that the operating member is able to move the switch means to the plurality of positions depending on a position of the operating member. The operating member comprises an arm rotatably attached to the housing for rotation about a rotational axis. The switch means is attached an end portion of the arm such that the switch means is movable between said plurality of positions along an arcuate path. The switch means comprises two electrically interconnected contacts or contact surfaces provided on a movable carrier element mounted on the operating member for movement along a said arcuate path, and the contacts or contact surfaces of the switch means are provided at a same radial distance from the rotational axis and with a same spacing as the electrical contacts of each respective combination of electrical contacts. For example, the electrical switch may be connected to a plurality of tap selector switches and to a neutral terminal/load via respective ones of said conductors. The movable switch means is operated between different positions to connect the load to different ones of the plurality of tap selector switches. This enables a current to be routed through a first tap selector switch whilst another tap selector switch is adjusted, wherein the electrical switch is subsequently operated to electrically connect the other tap selector switch and disconnect the first tap selector switch. By providing a hermetically sealed housing around the electrical contacts and the switch means and providing a vacuum or an arc suppression gas inside the housing, the electrical contacts and the switch means will be subjected to less arcing upon operation of the electrical switch. Since the conductors are routed from the inside of the housing to the outside of the housing, the conductors are still accessible from outside the housing, where some other