Category Archives: Electrical Networks

Understanding Magnetising Inrush in Transformers

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 »

Understanding MV Switchboard Power Supply Modes

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 »

Polarization Index (PI) and DAR Tests: Assessing Electrical Insulation Quality in 2025

Insulating materials are fundamental to the safe and efficient operation of electrical systems, serving to separate conductive parts from non-conductive ones and prevent unintended current flow. In high-voltage equipment such as motors, generators, transformers, and cables, insulation integrity directly impacts reliability, with studies estimating that up to 98% of electrical failures originate from insulation degradation due to factors… Read More »

What are the Differences Between Substation and Switchyard?

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 »

Tan Delta Test: Generator Insulation Guide

The tan delta test, formally known as dissipation factor or power factor testing, is a fundamental diagnostic technique in high-voltage electrical systems. It quantifies the dielectric losses in insulation materials, offering critical insights into their condition and susceptibility to failure. In the realm of generators, this test is primarily applied to stator windings, which endure continuous electrical, thermal,… Read More »

Directional Earth Fault Protection for Compensated Neutral Networks (ANSI Code 67N)

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 »