In recent years, problems in the secondary voltage switching circuit of protection devices have led to incorrect operations of protection devices from time to time, often accompanied by large-scale power outages, seriously endangering the safe operation of the power grid. This is a weak link in relay protection work. To improve the safety and stability of the power grid, this paper takes typical accidents where abnormal secondary voltage switching circuits cause incorrect operations of protection devices as examples, analyzes the problems exposed in the secondary voltage circuit of protection, and proposes countermeasures, hoping to attract the attention of protection and operation personnel at all levels. The faults in the secondary voltage switching circuit of protection are mainly due to inadequate maintenance of auxiliary contacts of disconnecting switches, poor quality inspection of switching relays, and problems in the DC power supply circuit of switching relays.
Strict acceptance work must be carried out before commissioning, and any non-compliance with anti-accident measures must be resolutely rectified; during operation, if abnormal conditions occur, the operation should be suspended, and the dispatcher should be reported. At the same time, careful inspection and analysis should be conducted, and only after clarifying the situation and obtaining unified instructions from the dispatcher can the operation continue. For the voltage switching circuit, the auxiliary contacts of disconnecting switches and switching relays must be inspected annually, with focus on the contact parts to ensure good contact. Especially, the frequent occurrence of poor contact in auxiliary contacts of disconnecting switches requires clear regulations for primary maintenance personnel. An important reason why the secondary voltage circuit is prone to problems is the neglect of its regular inspection and requirements. Therefore, clear regulations must be established. This paper introduces the problems in the secondary voltage switching circuit of protection, the lessons to be learned, and preventive countermeasures, aiming to plug the loopholes in the secondary switching circuit, enhance the reliability of the secondary voltage circuit operation, reduce the hidden dangers of incorrect relay protection operations, and improve the level of safe and stable operation of the power grid.
