Electrical Engineering - What is the purpose of calculating knee point voltage for Current transformers?

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What is the purpose of calculating knee point voltage for Current transformers?

Total Answers and Comments: 4

Last Update: October 04, 2009 Asked by: rohitasruti

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Submitted by: cvk

The purpose of calculating knee point is to select CT with operating point below knee point as above knee point CT tends to saturate and cause mal operation of protection relay. Knee point calculation is done for CTs usedÂ for differential protection and REF.

Above answer was rated as good by the following members:
imran_aramco

March 31, 2007 00:24:34

s kumar

RE: What is the purpose of calculating knee point volt...

The main purpose of calculating the knee point voltage is to identify the core saturation characteristics .This is mainly done on protection CT's

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October 05, 2007 04:42:07

cvk

RE: What is the purpose of calculating knee point volt...

After knee point saturation of the CT occurs. Hence the CT has to work below the knee point. By selecting a CT suitably for operating point below the knee point proper operation of the protection (like differential REF where protection class CTs are used) can be ensured.

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October 05, 2007 05:52:35

cvk

RE: What is the purpose of calculating knee point volt...

The purpose of calculating knee point is to select CT with operating point below knee point as above knee point CT tends to saturate and cause mal operation of protection relay. Knee point calculation is done for CTs used for differential protection and REF.

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Overall Rating: +1

October 03, 2009 22:34:01

GeeK_Percy

Member Since: October 2009 Contribution: 8

RE: What is the purpose of calculating knee point voltage for Current transformers?

Purpose of collecting Knee voltage is to use the circuit as an operating or as an metering circuit.

Operating circuit works far below knee voltage.

Metering circuit works at the verge of saturation.

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