Research on Control of Fault Current Exceeding Standard and Equipment Development

The operational strategy of the electromagnetic ring network delivers high power supply reliability, but it also brings about the issue of fault current exceeding the norm, posing a threat to the power grid's safety. Taking a substation of an electromagnetic ring network as an example. The analysis commenced with an examination of the short-circuit current distribution across various branches in the event of 220kV busbar faults, resulting in the proposal of three different solutions for short-circuit currents. The optimal plan involves installing a fault current limiter (FCL) at the low-voltage side of the primary transformer. This paper carries out an impact analysis on relay protection and system stability. Finally, the equipment development and current limitation test of the FCL are carried out. The outcome illustrates that the FCL has the ability to confine the three-phase fault current of the 220kV busbar between 64.5kA and 52.4kA, with a current limitation depth of 18.7%. After adding the FCL, the impact on relay protection is overall controllable and will not affect the stability of system operation. The core component of the FCL, the fast switch, has a just split time of 0.6ms, and the fast fault detection algorithm makes the control device export less than 3ms, the current limitation test shows that the FCL can limit the expected maximum short-circuit current peak value of 17.5 kA to 8.5 kA. Incorporating FCL in branch that experience high fault currents is a financially viable and reliable solution to the issue of fault current exceeding the standard.