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Anonymous Poster #1

Numerical relay setting

01/13/2023 1:34 PM

Settings for numerical 50/51 relays seem quite different from electromechanical 50/51 relays. How to do the calculation for numerical relays parameter settings for transformer protection?

And how can I get sure that the settings are correct? Is there any ways to check that the settings are going to work apart from etap software or any kind of software. Because I don't have access to these software. I have access to the transformer damage curve in excel sheet.

Thank you.
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SolarEagle
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Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33392
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#1

Re: Numerical relay setting

01/13/2023 4:46 PM

Relay 50N operates instantaneously on overload trip... Relay 51N operates based on IEC 60255 Standard Normal Inverse IDMT (Inverse Definite Minimum Time) trip characteristic.

https://pacbasics.org/transformer-differential-protection-application-example/

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rwilliams
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Join Date: Jul 2016
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#2

Re: Numerical relay setting

01/14/2023 6:27 PM

The instructions for the relay will explained how the relay operates. The Time Current Curves published for your model will compare directly to the time current curve for an induction disk electromagnetic relay, which should present the same dilemma you perceive with the digital relay, had you not been familiar with that technology previously. Tap 6, Time Dial 3, 50A instantaneous element on Extremely Inverse Time analog relay will have a digital analog.
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