New methods of selective distinguishing between power swings and high impedance short-circuits, evolving short-circuits and other complicated faults which secure reliability of operation of distance protections

aim of project
Faults in a power system such as short-circuits and disconnections of power system elements cause disturbance of balance between electrical and mechanical power in the system. The disturbance causes power swings and, accompanying them, changes of electrical signals, which are measured by power system protections. Sometimes the changes may cause improper operation of power system protections and development of power system failure. In case of transmission networks, power system protections such as distance protections are connected to power swings. It is important to use additional power swing blocking functions for selective operation of these protections during power swings. Traditional power swing blocking functions do not always operate in accordance with the user’s expectations. Improper operation can be observed in cases of: single-pole automatic cycle, high impedance evolving short-circuits, long period short-circuits. In order to improve reliability of power swing blocking functions, producers of protections apply additional algorithms. Thanks to this (in the manufacturers’ opinion), new equipment should be more reliable than the traditional one, and it should operate properly in the above mentioned cases. The aim of the project is to analyze different types of power swing blocking functions used by diff erent manufacturers. Power swing detection algorithms and additional criteria to distinguish between short-circuits and power swings will be tested. New methods and algorithms for testing selected power system protections will be described.

expected results
Analysis of operation of methods of power swing blocking functions used in modern numerical distance protections. Description of new methods and algorithms for testing power swing blocking functions.