Calibrating current transformer circuit using portable lamp transformer

Whether the 10% error of the current transformer is qualified or not has a direct impact on the relay protection in the power system. If it is not qualified, it will cause the current protection to refuse to operate, which will cause the accident to expand, so it must be calibrated regularly. The method of calibrating the current transformer using a portable lamp transformer is as shown in the figure. Operation method: close the knife switch QS, slowly adjust the voltage regulator TA, the voltage of the street light transformer T gradually rises, and the readings of the ammeters PA1 and PA2 slowly increase. When the reading of PA2 increases to the action value I of current relay KA1, read the value I1 of ammeter PA1. If the error can meet the following formula: It means that the current transformer TA1 is not saturated, it is qualified. Otherwise, replace the current transformer and re-inspect it. The verification is that the current transformers on L1, L2 and L3 must not be live, that is, when the power supply is out.