New swing-blocking methods for digital distance protection

The article firstly reviewed the shortcomings in the existing swing blocking schemes of current distance protection relays. Two new schemes, which take full advantage of the calculation ability of the digital relays, were then proposed. The new schemes can assert a reliable blocking during power swings, while also are able to trigger with very little delay even on faults happening during swings. The new schemes trip faults with a minimum actual delay time depending on at what time the fault occurs and the actual swing frequency.