In a power grid, protection relays are critical components which are supposed to detect and disconnect faulty feeders. Unfortunately, they do not detect all faults. For example, the relay protection systems can be incorrectly configured or not sensitive enough for certain intermittent earth faults, why a faulty feeder may not be disconnected in a proper way leading to a high displacement voltage tripping the whole substation. The problem of unselective tripping is a hot topic of discussion and, among others, Vattenfall has drawn attention to the problem in a thesis which can be read here (in Swedish) SAIDI-påverkan på grund av oselektiva felbortkopplingar – en analys baserad på Vattenfall Eldistribution AB:s nät
dLab solution to unselective tripping is called dProtection which can be described as a dAnalyzer on-the-edge with the ability to send digital signals and thus commanding the circuit breakers directly, or indirectly via the protection relays, to operate. With dLab’s patented algorithm for detecting directional and intermittent earth faults, dProtection ensures that only the faulty feeder is disconnected in case of a fault, and not the entire busbar.
Read more about our customer Olofström and their use of dAnalyzer and dProtection here: New order: Olofström Kraft AB takes another step together with dLab | dLab (dlaboratory.com)
Read more about a real case where dLab detects intermittent earth faults that leads to an unselective tripping.