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Power Transformers

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Breakers & Relays

Partial Discharge & Circuit Breaker Asset Management

Detecting and avoiding preventable failures BY JAY GARNETT, Doble Engineering Company While metal clad switchgear can be very reliable, sometimes operating for over 50 years, throughout the aging process, this group of electrical disconnect switches, fuses and circuit breakers can experience issues...

Breakers & Relays

Circuit Breaker Time and Motion Testing

Determining mechanical condition of high-voltage circuit breakers BY JOZEF LEVI, Doble Engineering Company Life expectancy of a newly installed high-voltage circuit breaker is approximately 40 years. Throughout its life, under normal circuit conditions, the circuit breaker will operate less than...


Zensol new instrument for OLTC testing

According to CIGRE A2.34, the dynamic resistance measurement or DRM (OFFLINE) is a test that offers diagnostics for several diverter or selector switch malfunctions such as: contact problems, broken springs, broken transition resistors, poor contact pressure, inadequate transition time, momentary open circuit, and synchronism motion issues.

Zensol’s DRM principle

Tap windings are powered with a DC voltage source. The current fluctuations are recorded during the switching process. The schematic below shows the principle of the...

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