Transformer Snubber Assembly

What is a Transformer Snubber? It is a set of capacitors, surge arresters, fuses, and resistors typically found on medium voltage dry type transformers. What are Snubbers designed for? The main application has been to reduce damage to transformers during energizing applications. Energizing medium voltage transformers produces transient voltages. These transient voltages are a cause […]

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General Electric Multilin Protective Relaying

Multilins SR745 & SR750 Model Power Supply Issues: Recently, I have been tasked to perform some relay testing on multiple General Electric SR relay models. But in particular, the issues experienced have been with the original model SR745 (Transformer Protection Relay) and the SR750 (Feeder Protection Relay) models. Here are examples of the Original and […]

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Transformer Oil – What is it, and why sample?

Transformer oil is a liquid that is stable at high temperatures and has excellent electrical insulating properties. Typical motor oil that most people think of, is not the type of oil in a transformer. Transformer oil keeps the transformer cool. It also insulates the transformer and allows electrical components to be more compact than free air apparatus. […]

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Electromechanical Relay – Contact Cleaning

Electromechanical Relay – Contact Cleaning Equipment owners often wonder the importance of maintenance on any variety of equipment. Some owners would even say that electrical maintenance is a waste of money. I have a demonstration of an electromechanical relay with dirty contacts. When watching the video, notice the contact below the coil begins to vibrate. […]

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Electromechanical Relay – Basic Operation

Electromechanical Relay Operation Above is a brief video of an electromechanical relay operating at 3 different fault magnitudes. These fault magnitudes are based off of the relay setpoint – 200% fault, 400% fault, and 600% fault. The relay set point is based off of the CT ratings and the bus/cable/load ampacity ratings. Electromechanical Curve Shape […]

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Torque – Does it matter?

Does torque matter? The short answer, absolutely! Most electricians don’t realize that a bolt and nut is not a means for AC Current to flow through. The actual resistance of the bolt is a much higher resistance that the resistance of two sandwiched pieces of copper. When a bolt is torqued to spec, it firmly […]

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