Study for the performance of high speed switchgear for protection of in-house generation system

In large industrial plants and factories, it has become popular to use in-house generation systems connected to utility power systems. Especially, co-generation systems have been introduced to many consumers such as hotels and hospitals. However, when a fault occurs on the transmission line, voltage on the internal power system drops instantaneously until its clearance. To enhance the load's reliability, a new switchgear system has been developed. This equipment consists of static switchgear applying thyristor, disconnecting switches, and a control circuit. This control circuit has functions to detect voltage drops and voltage synchronization. This equipment is installed in series with the circuit breaker which connects the buses of the consumer's own power generation system, and executes high speed tripping and reclosing when the voltage on the consumer's bus drops instantaneously. In this paper, artificial test results of this equipment is presented. From these results, it is confirmed that this equipment can restrain voltage drop of the important loads within one cycle by means of tripping the short circuit current within one cycle when the voltage drops under the setting value. Then, comparison between measured results and simulated results by EMTP is represented. From this comparison, it is confirmed that verification of this equipment's performance using EMTP is effective. Then, influence of voltage drop (20% and 50%) on loads is investigated by simulating transient voltage change of the generator.