Introduction to Common Test Procedures


Introduction to Common Test Procedures

Most relay testers use the same test procedures created for electro-mechanical relays. Let’s take a look at them and see how they apply to digital relays.

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Matthew Connellan May 4, 2017 at 10:41 am

This is great and all and you say that it will save time, but imagine all the time lost trying to convince a customer that this test is equivalent to doing both tests separately the same way it has “always been done”. If this customer is a utility then you will not only lose the time it took to argue this with them, you will then also lose the time it will lake to go back and do the test again exactly the same as the old way because the argument will have been lost before it began.

Chris Werstiuk (Administrator) May 4, 2017 at 5:50 pm

Thanks for your comment.

I hear this excuse every once and while, but strangely only from relay testers. I have never heard it once from a customer. To put this in perspective, a back of the napkin calculation puts me at over 200 job sites all across North America after I started using these techniques. I never had to spend a single second convincing anyone about anything I was doing. These job sites include major utilities (such as PG&E and Xcel Energy), regional transmission and distribution companies, multi-national power equipment suppliers like SIEMENS and Hyundai, smaller power plants, nuclear plants, refineries, hospitals, and factories. The most time I ever spent with a customer explaining HOW I was testing occurred when a commissioning engineer looked over my shoulder to make sure that I was actually testing the relay to their specifications, and they usually left me alone after the first relay.

Do your customers still perform 3,000-6,000 mile tune-ups on their modern trucks? I doubt it. Modern cars typically suggest 5,000 to 10,000 mile intervals. Why don’t they do frequent tune-ups anymore? Probably because someone realized that it was costing them a lot of unnecessary time and money. It’s the same arguments for these test procedures, except they save your customer time, money,and future problems that they wouldn’t find until it is too late.

Part of a relay tester’s job is to de-mystify the relay for your customers and train them in the most up to date procedures that will give them the most benefits. I used to occasionally get testing specifications that required a “flick test” to test CT polarities. Do you think I went a found a lantern battery and potentially left their CTs saturated just to meet their requirement? No. I would call the customer and explain what a flick test was, why it was a bad idea, and that we had brand new fancy test equipment that could perform that test and more. They removed that specification and replaced it with a generic “polarity test” description.

What do you do if your customer requests a winding resistance test with a “Wheatstone bridge?” Do you try to find one, figure out how to get it calibrated, and then figure out how to use it? Or do you explain to them that no-one makes them anymore, and we have better technology?

In the end, this course is designed to help relays testers become relay testing craftsmen, not button pushers that continue to perform obsolete tests because that’s the way it has “always been done”. There are plenty of other resources for the button pushing path.

Over here in my part of the world, there’s no need to test the IDMT part of the curve that’s already been superseded by an instantaneous line. It’s just logic. We do it exactly like what you did in the video.

Chris Werstiuk (Administrator) July 25, 2021 at 8:35 am

Glad to hear it!

I’m a long-time tinkerer but I’m fairly new to relay commissioning. As a mathematical purist, I’ll argue all day that you need three points to plot a curve, but my experience with relays is that, unless the relay has failed, the curve characteristics of a modern relay can be found buried in the relay instruction manual. My question to anyone is, when testing TOC, do must customers consider 2 test points adequate?
We use mainly use Doble test sets for 3 phase current and voltage testing, and once everything is hooked up, it’s not difficult to run 3 or [pick a number] points in our tests to see if the TOC curve for a particular relay matches the fault coordination study numbers.
Thoughts? Comments? Additons? Subtractions?

Chris Werstiuk (Administrator) June 29, 2022 at 5:27 pm

You should always perform three timing tests on a inverse element, but some/many utilities treat digital relays like they are a calculator and will only perform one timing test. Some only perform one timing test on an electro-mechanical relay so that they are less likely to have to calibrate the relay and will spend less time performing the calibration if they have to.

Somebody yells “It keeps tripping on ground fault…”
“The relay is doing its job.” If I had a nickel for every time…

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