Page 149 - Practical Power System and Protective Relays Commissioning

148 Practical Power System and Protective Relays Commissioning

FIGURE 14.7 Inductive gas insulated system voltage transformer.

FIGURE 14.8 Capacitive gas insulated system voltage transformer.

14.7 SURGE ARRESTER

Zinc oxide surge arrester elements suitable for immersion in SF 6 are sup-
ported by an insulating cylinder inside a GIS enclosure section. This makes a
surge arrester for overvoltage control as shown in Fig. 14.11. Insulation coor-
dination studies usually show there is no need for surge arresters in a GIS,
however some users specify a surge arrester at transformer and cable connec-
tions. Predominantly, the outdoor bushing surge arresters are used.

14.8 CONTROL SYSTEM
The local control of the GIS components (CB, disconnectors, and earthing
switches) is undertaken through a local control cabinet (LCC). Additionally,
all interlocking and annunciator and alarms are controlled via the LCC.