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Extended (?) CT ratio

Jam

Hi all,

I'm trying to calculate the Accuracy Limit Factor for some protection CTs but the ratio is specified as, for example, “5P20 extd. 1000%”… What does the “extd. 1000%” mean?

My first guess would be extending the 5% accuracy to 20x1000% = 200xIn under some condition, perhaps a specified burden.

The switchgear suppler is trying to help but is not desparately quick.

Thanks

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    Hmm. Usually magnetic saturation is your friend and prevents the the secondary side thing having its socks blown off in the event of a primary side "bolted fault", and I suspect this is another way of expressing this, as it is about the only thing that should be happening at that multiplier. But I'd expect to  see “Idyn” or something.

    Can you say who makes the CTs?

    Mike.

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    Hmm. Usually magnetic saturation is your friend and prevents the the secondary side thing having its socks blown off in the event of a primary side "bolted fault", and I suspect this is another way of expressing this, as it is about the only thing that should be happening at that multiplier. But I'd expect to  see “Idyn” or something.

    Can you say who makes the CTs?

    Mike.

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