Burden is the total impedance placed across a CT or VT secondary by relays, meters and connecting leads, stated in volt-amperes at rated secondary current or voltage. A CT rated 15 VA at 5 A can drive 0.6 ohm and still hold its accuracy class. Long lead runs, especially with 5 A secondaries, eat into the burden and can push a protection CT into saturation during a fault.
Lead run from the yard CTs to the relay room is 300 m, that's most of the burden on a 5 A secondary, go 1 A next time.
Also heard as
- VA burden
- secondary load
Related terms
CT
Current transformer: an instrument transformer that scales large primary currents down to a standard secondary.
VT
Voltage transformer: an instrument transformer that steps high voltage down to a standard level for relays and meters.
X/R ratio
Ratio of reactance to resistance in the fault path, which sets how large and slow the DC offset in fault current is.