Thermal analogue protection for capacitors

TLDR: In this paper, the primary winding of a potential transformer is connected across a series capacitor bank to protect it from high current faults and the secondary winding of the potential transformer connected to a thermal analogue device which reproduces the thermal characteristics of the capacitor and operates capacitor switching means when dangerous thermal conditions are reached.

Abstract: A capacitor protection system is provided having the primary winding of a potential transformer connected across a series capacitor bank to be protected and the secondary winding of the potential transformer connected to a thermal analogue device which reproduces the thermal characteristics of the capacitor and operates capacitor switching means when dangerous thermal conditions are reached. An inverse time voltage relay is also connected across the secondary winding to initiate protective capacitor switching responsive to high current faults. The thermal analogue device simulates the internal thermal conditions of the capacitor based on the principle that the power loss in the capacitor is proportional to the square of the voltage across the capacitor. Voltage comparison circuits are also provided between groups of capacitors in banks having multiple groups to detect blown fuses associated with respective capacitor groups.