GROUND FAULT DETECTION SYSTEM FOR UNGROUNDED POWER SYSTEMS

摘要

The fault detection system (10) includes at least one valid zero sequence voltage source, either from a local relay or a remote relay on a protected line. Zero sequence current is selected between total (vector sum from both ends of the protected line) measured zero sequence current or calculated zero sequence current. A zero sequence impedance-based calculation (80) is then made and the result is compared against a threshold value to produce a trip decision. The trip decision is then applied through a normal tripping circuit or a slow tripping circuit (40), depending upon selected circuit conditions, involving the local and remote ends of the line.