OMICRON Magazine

that it was capable of eliminating all the line faults correctly. But with ground faults, some of the tests failed, depending on their respective system topologies. The protection concept defined the ground fault protection settings as follows: › The capacitive current amplitude requires tripping in the event of a ground fault. Ground fault protec- tion receives the same threshold value for all injections. › The timed tripping for the ground fault protection was designed to make it possible for one or both of the feeders to supply power during operation with an open or closed busbar coupling. however, during the test the busbar coupling triggered non-selectively, as the trip times were not correctly parameterized: 0.2 s for the line to ground loop instead of 0.4 s. In the case of a ground fault and its oper- ating state, this deviation can lead to a power supply loss for half of the connected loads. Even in clear network layouts, as in this example, the devil is often in the details. The system-based test was able to uncover incompat- ible parameterization because it provides an integrated overview of the entire protection system and quickly discovers inherent errors. It is essential that the tests pay ad- ditional attention to the way the entire system is working together. By supplementing conventional tests, system-based test cases have proved to be a simple yet powerful tool for demonstrating the reliability of a protection system as a whole. 12