Automatic CT Injection Kit

Electrical Engineering

A circuit breaker in a substation must operate flawlessly to keep the system healthy. It should trip within the minimum time when the relay detects any fault in the transmission system. This is possible when the C.T. ratio of the relay system, trip timing, and over-current setting of the respective circuit breaker is correct. If the relay overcurrent setting and C.T ratio don’t match the need for circuit Breaker rating the circuit breaker might not operate on time and the system might get damaged due to overcurrent or any undetected fault. A circuit breaker operates correctly when C.T and relay settings are rightly set according to the level of the transmission system. To check this reliability of the C.T a test called C.T injection is carried out, where C.T is disconnected from the system and fed varying high current through dimmer stat, and the secondary of C.T is measured and calculated with the primary current. (eg: primary to secondary current ratio 500/1, 200/1). Other settings in the relay are peak current setting overcurrent setting trip time setting. (eg: Peak current setting: 100 A, over current setting:- 150%, trip time setting :-10 ms). This setting may vary for different circuit Breakers in the different substations and different power level INTRODUCTION Automatic CT injection kit works in place of human workers, requires only an operator to signal the Arduino Uno kit wirelessly while changing the relay settings according to requirement and supervising the working of assembly, and finally deciding whether the circuit breaker trips on time according to outcome data and passing a judgment whether it is suitable for bringing in operation in bus bar system or to be repaired or replaced. This testing is called CT injection and our project “Automatic CT Injection Kit” focuses on safety from electrical accidents, reduction in time consumption, and reduction in per testing cost by automation of this testing process by introducing servomotors and microcontrollers to operate in place of human workers, each component is assigned a special work which is done by human labor

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