Design & Development of Safety Features and Mechanism Adaptation in Air Insulated Switchgear

Abstract

Electricity has become an integrated part of our life. At the generation point, electric power in Megawatts is transferred from transmission line to distribution line where it gradually reduces to Kilowatts. From distribution lines the electricity is supplied to industrial and domestic areas. Medium Voltage Switchgear is an equipment used in uninterrupted power supply for switching and protection in distribution line. Air Insulated Switchgear (AIS) considered in this dissertation is an indoor product. In any switchgear, Internal Arc (IAC) is the biggest threat. It is high power discharge between conducting parts due to sudden fall in resistance. It causes heat explosion which causes severe damage in surroundings. Safety features are designed and developed to minimize the chances of accident. The Circuit Breaker (CB) considered in this dissertation is having metallic enclosure and is withdrawable type. The racking of CB is done manually with the help of racking handle. In case of malfunction, during this phase the operator in highly vulnerable to IAC. A safety feature is developed to motorized the racking system which ensures that the operator can remotely access racking of CB. Other safety feature which is planned to develop in this dissertation is to make a viewing system for contact engagement of isolating contacts. Misalignment of contacts leads to lower resistance in the path of current which causes hot-spots at the contacts. These hot-spots are the reason of deterioration of life of switchgear and also cause IAC. This dissertation also consists of the study of adaptation of helical spring operated mechanism (HSOM) in the circuit breaker. It includes linkage design and torque comparison of closing, opening and contact loading springs for closing operation. This study shows the feasibility of kinematic linkage designed and opening spring.