INES-event
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REACTOR SCRAM DURING INSPECTION OF GROUND CONNECTION

Unit 4 at rated power. The inspection to identify the cause of previous activation occurrence of ground connection signaling at the 4th system of electric supply was performed. The workers simulated ground connection in the usual way as in the past. In this case, however, the activation of a new protection of condenser cooling pump occurred and both pumps tripped. It resulted in power decrease and activation of reactor protection at 10:28 a.m. due to turbine trip. The function of automatics and unit regulators was correct. Repeating the test procedure to determine the reason for false protection activation it was revealed that during ground connection an induction of spurious voltage in cable connecting pumping station and pumps protection occurs and as a consequence the protection is activated.

Location: BOHUNICE-4
Event date: Tue, 20-06-1995
Nuclear event report
Legenda & explanation