Current transformer selection guide
Current transformer selection guide
Current transformer selection guide
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<strong>Current</strong> <strong>transformer</strong> <strong>selection</strong> <strong>guide</strong>DETERMINATION OFTHE CUSTOMER’S NEED(cont’d)Rated burdenTake the rated burden which is immediatlely above the effectivepower supplied by the CT.The rated burden for accuracy power are:2.5 VA - 5 VA - 10 VA - 15 VA - 30 VA.Safety factor in metering (SF)The SF value will be selected depending on the short time currentwithstand of the receivers: 5 ≤ SF ≤ 10An ammeter is usually guaranteed to support a short time current of 10 I ni.e. 50 A for a 5 A device.To ensure that the appliance is not destroyed should a fault occur in theprimary the current <strong>transformer</strong> must be able to saturate before 10 I n in thesecondary.For this reason, a SF of 5 is sufficient.In accordance with the standard, our CT’s have an SF ≤ 10. However,depending on the characteristics of the current consumer, a lower SF valuemay be requested.10date11/92- B•1•4 -revised08/95page 9
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