Analysis of secondary voltage loss caused by 220kV bus voltage switchover

For researching the interaction among converter buses in MIDC(Multi-Infeed Direct Current) system,the converter bus voltage interaction formula of MIDC is deduced based on power flow equation of AC/DC system.

It offers steps of the secondary circuit to avoid miss operation when the alternating voltage losing, especially a measure to improve the double busbar voltage switch circuit with two position relay.

In order to address the problems of the alarm setting value of the direct-current equipment in current transformer substations, this paper analyzes the checking charge-discharge results of the batteries and then proposes recommendable values of the direct-current busbar voltage alarming value,so as to offer help to the safe and reliable operation and the maintenance of the direct current system.

According to the principle of backup power switchover unit of LFP-965, LFP-965 unit can not distinguish two buses without voltage synchronously when public busbar voltage transformer and line voltage transformer are employed at the same time.

This article introduces an event about protection action causing by the decrease of busbar voltage in Xiaolangdi hydropower station, in order to make people pay attention to voltage management to ensure the safety and stability of power grid and generating units.