Between R1 and R2 and across the current transformer loop is a third resistor R3. (In general, R1 and R2 are of equal value and R3 is generally of higher value than R1 and R2 in order to obtain the desired sensitivity.) In normal operation, in the absence of faults, a current circulates in the loop through R1 and R2 and if there is no difference in current in the two current transformers there is