GB9717817D0 - Improvements relating to high voltage electric installation - Google Patents

Abstract

In response to failure mode short circuit current through a high voltage surge arrester 60, a disconnect device 65 operates to disconnect the surge arrester 60 by releasing one end of a connection lead 64, and the short circuit current through the arrester 60 is transferred to an arc gap between arcing horns 68, 69. This overcomes the problem that failure of the arrester can be a fire hazard if sparks or incandescent particles are emitted by the failed arrester. Disconnect device 65 may be an explosive type so that ionised gas emitted when it operates increases the conductivity between arcing horns 68, 69 to facilitate transfer of the short circuit current to the arc gap. The falling end of lead 64 tends to drag the ionised gases into the arc gap to assist in this process. Alternatively or additionally, transfer of current to the arc gap may be assisted by moving horns 68, 69 closer together - eg. upper horn 69 may be carried by a spring or gravity actuated plunger released by disconnect device 65. Alternative arrangements have a disconnect device (7, Figs.1A,1B; 23, Fig.2) which releases a spring biased rod (9) or a spring member (27) to short out the arrester (1 or 21) which may be connected in series with a spark gap (13,14,15). Another arrangement has an arrester (40, Fig. 3) connected in series with a closely coupled high voltage HRC fuse (44) which disconnects the arrester in response to a failure current therein before the arrester produces sparks and incandescent particles. In a further arrangement an arrester (50, Fig.4) is connected in series with a fuse (51) and a spark gap (52), the fuse and spark gap normally being shunted by a disconnect device (53) which responds to failure current in the arrester by removing the shunt so that the fault current then flows through the fuse and spark gap causing the fuse to disconnect the arrester.