Current transformers near high-current busses

WHEN CURRENT TRANSFORMERS are applied in the vicinity of busses carrying large currents, the transformer accuracy may be very seriously affected. This is particularly true on systems which normally carry over 2,000 amperes and may carry 10 or 20 times this current during faults. A current transformer designed to operate protective relays during such a fault may be rendered completely useless by improper installation. For instance, Figure 1 gives the accuracy of a certain current transformer with the primary return conductor at several different spacings.