This article focuses specifically on directional earth fault protection (ANSI 67N) for electrical networks with an impedance-grounded neutral. We’ll be releasing more articles soon that explore how directional earth protection behaves in other grounding systems. The goal is to give you a complete, system-by-system view of how earth fault protection works. Stay tuned—there’s much more coming. In this… Read More »
Distance protection schemes play a vital role in ensuring reliable and speedy fault clearance on transmission lines. The fundamental idea behind distance protection is to measure the impedance between the relay location and the fault point, enabling the relay to detect faults within set zones. Conventional time-stepped distance protection, for instance, sets an instantaneous Zone 1 reach to about… Read More »
An interposing relay (sometimes called an interface relay or isolation relay) is essentially a relay used to interface two circuits that have different electrical characteristics (e.g. different voltages, current levels, or common references). It “interposes” itself between a control circuit (e.g. PLC, sensor output) and a load or another circuit that may not be directly compatible. Key roles… Read More »
Magnetising inrush is a transient electrical phenomenon that primarily occurs when a power transformer is energized. It is not indicative of a fault but rather a normal response of the transformer’s magnetic core to sudden application of voltage. However, it poses significant challenges for transformer protection systems, which must distinguish this temporary surge from actual faults to avoid… Read More »
Medium Voltage (MV) switchboards are critical components in electrical distribution networks, responsible for controlling, protecting, and isolating electrical equipment. The power supply modes for these switchboards vary based on the required level of redundancy, reliability, and operational flexibility. These modes determine how supply sources connect to the busbars and feeders, ensuring continuity of power while minimizing downtime during… Read More »
In electrical power systems, substations and switchyards form critical nodes that ensure the efficient, safe, and reliable transfer of electricity from generation sources to consumers. While often discussed interchangeably in casual contexts, they exhibit distinct characteristics based on their functions, equipment, and placements within the grid. This comprehensive overview draws from engineering principles and industry practices to delineate… Read More »
Directional earth fault protection, identified by the ANSI code 67N, is a specialized protection function used in electrical networks with a compensated neutral, typically employing a Petersen coil earthing system. This protection is designed to detect and isolate earth faults (single-phase-to-ground faults) in such networks by distinguishing the fault current in a faulty feeder from the capacitive currents… Read More »