Editing Current transformer (section)

=== Burden ===
The secondary load of a current transformer is termed the "burden" to distinguish it from the primary load.

The burden in a CT metering [[electrical network]] is largely [[electrical resistance|resistive]] [[electrical impedance|impedance]] presented to its secondary winding. Typical burden ratings for IEC CTs are 1.5&nbsp;[[volt-ampere|VA]], 3&nbsp;VA, 5&nbsp;VA, 10&nbsp;VA, 15&nbsp;VA, 20&nbsp;VA, 30&nbsp;VA, 45&nbsp;VA and 60&nbsp;VA. ANSI/IEEE burden ratings are B-0.1, B-0.2, B-0.5, B-1.0, B-2.0 and B-4.0. This means a CT with a burden rating of B-0.2 will maintain its stated accuracy with up to 0.2&nbsp;[[Ohm|Ω]] on the secondary circuit. These specification diagrams show accuracy parallelograms on a grid incorporating magnitude and phase angle error scales at the CT's rated burden. Items that contribute to the burden of a current measurement circuit are switch-blocks, meters and intermediate [[electrical conductor|conductors]]. The most common cause of excess burden impedance is the conductor between the [[Electricity meter|meter]] and the CT. When substation meters are located far from the meter cabinets, the excessive length of cable creates a large resistance. This problem can be reduced by using thicker cables and CTs with lower secondary currents (1&nbsp;A), both of which will produce less voltage drop between the CT and its metering devices.<ref name=SHEE11/>