Abstract: In a 500kV substation, when the breaker No.5011 was switched on to charge the main transformer without load, the breaker No.5032 was tripped. The accident was investigated and analyzed, and the conclusion was obtained that the action of the breaker No.5032 was caused by the interference. When the equipment of the 500kV EHV power grid is being manipulated, the electromagnetic interference, which caused by the static electric field and the magnetic field around the equipments, the corona and the electromagnetic radiation, often is larger, and the operating voltage of the 500kV breaker is lower; therefore, it is easy disturbed. According to the analysis of this accident, more rigorous requirement of the normative setting of the antijump relay was put forward. 

Key words: tripping, interference, anti-jump relay