In-service protective relay meter tests are THE MOST important tests that should be performed on every digital relay. All of your offline relay testing is meaningless if: The CT/PT ratios are incorrect. The relay isn’t connected to its input signals (CTs/PTs). The relay is looking in the wrong direction. The
A reader submitted a question through the Ask Chris form. I’ve expanded the original question from “what are the differences between relays, contactors and motor starters?” to “What is the difference between contactors, motor starters, relays and circuit breakers?” We’ll look at the history of electrical protection in this post
Situation after CT Primary Injection: New 230kv breaker Testing CT’s, 4000/5, by high current injection injecting 80 amps A phase to ground the secondary leads are shorted in a junction box A-B-C-N / additionally a voltage is connected to test instrument form test set The secondary readings are A = 0.096
Here is another excellent, but dated, video that covers a lot more than its title. It starts with an excellent introduction to CTs and PTs (http://youtu.be/T5U5M3RYx9Q) Then some Phasor Diagram basics at 26:10 (http://youtu.be/T5U5M3RYx9Q?t=26m10s) Then it discusses transformer connections and one method for calculating phase shifts at 30:18 (http://youtu.be/T5U5M3RYx9Q?t=30m18s) It
Instrument transformers are specially designed to transform high system voltages and currents into smaller voltages and currents for remote metering and protection. Instrument transformers can be extremely accurate to allow the relay to protect the electrical system and still be isolated from dangerously high currents and voltages.I wrote and co-wrote some
I wrote an article for the NETA World magazine in 2004 that covers several different manual techniques for Current Transformer Testing that should help even the most experienced technicians. Here’s a summary of the current transformer testing paper. Back to the Basics – Current Transformer Testing (CT) As test equipment becomes more
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