Valence Electrical Training Services

Why did my Frequency Test in Cycles Fail?

We added a new YouTube video, Why did my Frequency Test in Cycles Fail?. This video describes how two different relays with identical settings can have different time test results when performing any frequency test.

Relays that use time delays in seconds are easy to test because seconds is a universal unit that can only be interpreted one way.

Relays that use time delays in cycles are easy to test as long as the relay and the test-set use the same reference during a frequency test. Cycles use the generated frequency, or by the nominal (or system) frequency as a reference. If the relay and the test-set do not use the same reference, your timing test results will get worse the further you test frequency is from the system frequency.

This video is an excerpt from our online training course describing the basics of relay testing to provide a real-world example to explain why understanding the relationship between time and frequency is important for relay testers.

The online training courses are currently under development. Subscribe to our mailing list to get updates when we release new courses.

This video uses information from the  first chapter of The Relay Testing Handbook: Principles and Practice or the first of The Relay Testing Handbook series: Electrical Fundamentals for Relay Testing. You can purchase these books at our online store at

About the Author Valence Announcements

Valence Electrical Training Services is the independent source for protective relay training for relay testers. We offer: • Online Training Courses that can be completed at any location at any time • The Relay Testing Handbook series of books written for relay testers by a relay tester • Hands-On Training Classes where you come to us, or we come to your organization

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