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# Generator Protection

## Generator Protection

(OP)
What is the percentage of error limit for a ratio test to a CT class C800, 10000:5?

### RE: Generator Protection

At 100A and 800V secondary the error will not exceed 10%.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

### RE: Generator Protection

Dear Mr. Melco001 (Electrical)(OP)28 Apr 22 21:07
[color #204A87]"... What is the percentage of error limit for a ratio test to a CT class C800, 10000:5?...."[/color].
1. General: a) Usually CT ratio are <10000/5 A. It is not impossible.
b) For C class CT, refer to IEEE C57.13 for detail.
c) For an equivalent IEC standard, see IEC 60044-1 (or later current edition).
2. As per IEEE C57.13, for a C800 class, 5A secondary CT
a) Limit of ratio error at rated current not exceeding 3% ; and,
b) Limit of ratio error at 20 times rated current not exceeding 10% ; and,
c) Will deliver a Secondary voltage of 800V to a standard burden of (4 ohm + 18.400 mH) at 20 times the rated current without exceeding the limits , see above a) and b).
3. An equivalent per IEC 60044-1 (or later current edition); a C800 class CT is equivalent to IEC 200VA 5P20.
Note: A 200VA 5P20 CT is considered very high burden, usually not required. But is possible.
Che Kuan Yau (Singapore)

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