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LTPU on relays?

LTPU on relays?

LTPU on relays?

(OP)
Hello Everyone,

I have a question on providing settings for overcurrent relays. When providing settings for 51 element is it required to keep in mind CT saturation. For example - A 50:5 CT is connected to a relay which has a pickup setting available from 0.5 -20 x CTR. Can the pick up be set to 20?

RE: LTPU on relays?

There isn't enough provided information to answer that question, although the ANSI method of designating CTs may be different.

Details of:
  • CT Specification (e.g. 50P20F20 or 5P20 20VA)
  • Connected Burden
  • Maximum expected primary current
Would need to be considered before being able to advise on whether or not the CT would saturate before the pickup point is reached, at least for an IEC application.

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