Current Transformer Burden

Burden is the load imposed on the secondary of the CT at rated current and is measured in VA (product of volts and amps). The accuracy class applies only to loads at rated VA and below, down to one quarter VA .

The burden on the secondary of a CT includes the effect of pilot leads, connections etc , as well as the instrument burden itself.

In situations where the meter is remote from the current transformer, the resistance of the pilot wires may exceed the meter impedance many times in these cases it is often economical to use 1 amp meters and CTs. 

Instrument Type Approximate Burden
Ammeter 0.5 - 5VA
Voltmeter 2 - 5VA
Frequesncy Meter 1 - 5VA
Protection Relay 0.2 - 30VA

The diagram below shows the burden imposed on the CT due to a run of pilot wire. It will be seen that a pilot loop of 2.5mm2 wire, 60 metres long (30 metres distance) has a load of 12.5 VA on a 5 amp CT but only 0.5VA on a 1 amp CT.

Lead -Burden -Chart

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Other parameters which need to be taken into consideration as part of the specification:



Related Information

pdfBurden - Application Note (373 KB) Download
pdfAccuracy Class - Application Note (410 KB) Download
pdfProtection Class - Application Note (575 KB) Download

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