We’ll finish off the relay settings in this video by looking at the global and port settings to make sure this relay is configured correctly for our application.
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Good advice on COM timeout settings. Never thought to check that before for those reasons. Thanks.
Hi Chris, in the lesson, you mentioned that directional setting to auto is good. Why is it good? Hope you can give some insight into this. I always thought that the directional element is only either yes or no. How does “auto ” work?
SEL uses a very complex logic scheme that uses impedance and sequence components to determine direction. I have seen some engineers set the DIR to “Y” when they don’t understand all of the complexities and inadvertently disable the protection elements that are supposed to be directional.
Therefore, only engineers who truly understand all of the complexities inside the element should set it to Y and apply all of the setting involved. If they don’t, it’s safer to let the relay determine direction in AUTO mode.
Thank you Lina for the explanation. I hope you don’t mind if I dwell a little further into the matter. I have come across some papers that suggested using negative & zero seq voltage to determine the fault direction & it seemed convincing, nevertheless the final RCA is a known angle. If the engineer chooses to allow the relay internal algorithm to decide on the direction of fault (auto), that means he won’t know the RCA/MTA setting as well as any specific region being omitted or not. In this case, how do you decide on the test points to conduct & how do you assess if a test pass or fail?
The directional angle in an SEL relay is not necessarily a straight line or fixed, as it is using simpler versions of directional control. Pre-fault values, fault values, and settings make for a dynamic characteristic that changes based on any of these variables. Change any one and the characteristic changes. While it would be possible to perform all the calculations to test the characteristic as you would with other directional control schemes, what do you gain by that amount of resolution?
What you really care about is that the relay will trip in the forward direction, which has a range somewhere between 45-89 degrees lag, and that it doesn’t trip in the reverse direction, which would be between 225-269 degrees lag. That’s much easier to prove with simple tests. Doing more would be similar to performing a pickup test on a 51 element. You can do it, but why would you want to?
Thank you for your reply. I understand your philosophy now.
Thank you, Chris for the heads up on the Time-out on ports using SEL protocol. This is good info.
I was curious though, if Timeout settings on ports using SEL protocol is a real CIP concern, I wonder why SEL doesn’t just set a default time-out value of 15 minutes for any ports on back of relay that are typically accessed remotely? Should this not be a pretty straight forward fix, or is there more to it than that?
I’m pretty sure SEL does have the ports set to time out automatically (they appear to have written most of the NERC CIP standard), however, relay testers and relay testing software find this annoying and turn it off. The warning here is to the relay testers to check and make sure that the timeouts are turned back on.
Noting the COM timeout settings is a new wrinkle in the brain for me as well, and when working on the grid, one must remember that we are a target for cyber attacks.