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EP-3871302-B1 - SWITCHGEAR COMPRISING A PASSIVE ARC PROTECTION

EP3871302B1EP 3871302 B1EP3871302 B1EP 3871302B1EP-3871302-B1

Inventors

  • BAYER, BARDO
  • Manjunatha, Aravind Ponnathapura

Dates

Publication Date
20260506
Application Date
20181026

Claims (5)

  1. Switchgear, comprising a frame (1) and at least a bus bar (3) to transmit electrical current, wherein an arc attractor is arranged and wherein the arc attractor is an electrode (5) and/ or is a sacrificial electrode, characterized in that at least a flexible insulation (6) is arranged, which is not a rigid insulating material, wherein the flexible insulation (6) is a protective layer, configured to protect the frame (1) against heat effects of an arc attracted to the arc attractor or from the arc, wherein the flexible insulation (6) is attached on a rear side of the arc attractor or wherein the flexible insulation (6) is a wrapping on top of the arc attractor.
  2. Switchgear according to claim 1, characterized in that the flexible insulation (6) is an elastomer or comprises an elastomer.
  3. Switchgear according to claim 1 or 2, characterized in that the arc attractor is embodied as a metallic structure and/ or is a metal fin structure.
  4. Switchgear according to one of the preceding claims, characterized in that the arc attractor is in the form of metal strips or metal bars.
  5. Switchgear according to one of the preceding claims, characterized in that the switchgear is a low voltage or medium voltage switchgear.

Description

The invention is related to a switchgear according to the preamble of claim 1. WO 2004/057 718 A2 discloses a device comprising an insulation plate consisting of a glass mat base laminate or a "hard mat". DE 1 191 458 B teaches to arrange a bare horn for an electric arc on a bus bar. US 2011/0149482 A1 teaches to connect a red glass insulator with an arc attractor. US 2017/0054278 A1 teaches to provide ground fault frame bodies in a horizontal direction in plural numbers. US 5,705,773 A shows a tee boot 1 which is in a "T" configuration and is arranged around a bare joint area formed by bus bars and a riser. DE 72 32 011 U teaches to use a plate based on sodium silicate containing water which is arranged in sandwich manner between two plates of metal or is attached on one side of a metal plate. A potential risk of failure exists for a bare bus bar system during internal arc fault tests, especially at 400 V and 100 kA and at 690 V and 65 kA. Internal arc faults in switchgears are usually avoided either by insulations or managed by either providing dedicated arc-escape routes, e.g. pressure relief flaps. Additionally or as an alternative the switchgear can be made mechanically and thermally robust to withstand an arc. The insulating components are usually rigid or solid. This makes it difficult, to install them in tight spaces, which are usually present in compact switchgears. The currently existing assemblies or procedures make use of solid parts and/or moulded insulating parts. They provoke difficulties as follows: mounting of the parts in the available space, challenges to use the parts or components at the required area or surface, which needs to be protected, expensive requirements for molds, no readily available off-the-shelf components etc. Further, one of the existing methods of construction is to completely insulate bus bar systems, which are classified as arc-ignition protected zones. In other current assemblies active arc fault protections are used. By using current constructions, there is a high probability of the arc finding metal parts of the frame or enclosure, hence burning and causing damage. The internal arc usually runs along a main bus bar in the direction of energy flow and usually burns at the ends of the bus bar. The insulating angle, which covers the final few millimeters of the bus bar is providing a semi-enclosed area for the arc to burn. The partitions within the insulating angle are helping in arc-elongation. However, with higher rating of the arc faults, namely higher kA ratings, the arc has a tendency to jump from the dedicated arc-burning region to the neighboring frames, enclosures and to burn causing holes, which could endanger the switchgear safety. Additionally, in spite of the insulating angle, there could be radiative heat effects on the enclosures and on the adjacent regions. The object of the invention therefore is to control and localize arc damages and to create a switchgear, which provides arc-fault containment. The object of the invention is achieved by means of the features of claim 1. According to this claim in the switchgear an arc attractor and at least a flexible insulation are arranged. According to the invention it has been found, that present constructions or arrangements of swichgears do not use any dedicated arc attraction mechanism, neither is there any flexible protection mechanism for the metal and cladding. According to the invention it further has been found that an arc attractor, preferably a sacrificial electrode, along with flexible insulation material either individually or in conjunction with solid insulation materials can be utilized to increase the arc quenching as well as the thermal withstand capability of the switchgear, thus making it arc-resistant. According to the invention a dedicated arc attractor provides a dedicated arc-burning location. The protection can be increased by means of a flexible insulation. The main concept of the invention is to provide a dedicated and safe arc-burning zone together with an arc attracting mechanism, and a flexible protection mechanism. A switchgear, in which this concept is realized, is safer than those of the state of the art, because a damage due to an arc is contained and localized. The arc is guided into dedicated locations for localized burning. The arc attractor also leads to a continuous arc-fault current, which results in a more consistent current value and in cases of presence of an up stream protection, helps in current detection and tripping. The arc attractor is an electrode and/ or is a sacrificial electrode. A sacrificial electrode can be made of cost-efficient materials. The switchgear has potential to be cheaper than switchgears of the state of the art. Further, advantageously, the arc attractor is embodied as a sacrificial metallic structure and/ or is a sacrificial metal structure. Such a structure may be positioned in such a way that it provides a safe region for the burning of the arc.