Evaluation of numerical time overcurrent relay performance for current transformer saturation compensation methods

- Mathematical CT model implemented to study saturation effects.
- Methods to detect and compensate the CT saturation intervals.
- Environment to evaluate overcurrent relays for the compensation methods presented.

Current transformer (CT) core has non-linear magnetic characteristics and may achieve high flux values when exposed to high fault currents. In this case, the CT primary current is not fully reflected in their secondary side and the relay cannot operate in the desired time. Several papers have been published about computational methods to compensate saturation of CTs due transient conditions. However, the use of CT simulated signal for practical tests in protection relays is rare. This paper presents an environment that allows performing secondary tests in physical relays when computational methods are applied to minimize the effects caused by CT saturation. The CT model and saturation compensation methods are implemented in MATLAB. The secondary signals resulting of this modeling are converted to COMTRADE format to be loaded into injection test device in order to evaluate the overcurrent numerical relay response for each CT saturation compensation method presented.