Electrical faults do not always cause a fuse or circuit breaker to operate. On both single-phase and three-phase supplies, abnormal voltage, phase loss, incorrect phase sequence and changes in load current can remain unnoticed while equipment continues to run.
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Industry: Electrical distribution
Undervoltage and Overvoltage Explained – Protecting Three-Phase Equipment
Electrical equipment is designed to operate within a specified voltage range. When the supply remains above or below these limits, equipment performance, reliability and service life can be affected. Undervoltage can result in increased motor current, reduced torque and difficulty starting, while overvoltage can increase electrical and thermal stress on ...
Read moreTesting and Verifying Earth Leakage Relay Trip Times
Correctly testing an Earth Leakage Relay (ELR) requires more than applying a current equal to its selected trip level. The test current, intentional time delay, relay operating time and response of the associated switching device must all be considered. An unsuitable test method can make a correctly operating ELR appear ...
Read moreHow to Select Earth Leakage Relay Trip Levels and Non-Operate Time Delays
Every electrical installation has different protection requirements, which means there is no single "correct" trip level or time delay for an Earth Leakage Relay (ELR). The optimum settings are influenced by the location of the relay within the electrical distribution system, the size of the current transformer (CBCT), the type ...
Read moreUsing Type A Earth Leakage Relays with Variable Speed Drives
VSDs have become a standard method of controlling motor speed in industrial and commercial applications. By varying the frequency and voltage supplied to a motor, VSDs can improve energy efficiency, reduce mechanical stress and provide greater process control. However, the use of VSDs can also introduce additional leakage currents. This ...
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