Probabilistic analysis of current‐transformer dimensioning: A criterion for determining the level of exposure to saturation

Abstract

Summary Saturation of the current transformer (CT) results in maloperation of current‐dependent protective relays. While enhancing in the core area may prevent the saturation, it simultaneously increases the size, the weight, and, subsequently, the price of the CT, which is desirable for neither the CT manufactures nor the operators. This paper conducts a probabilistic analysis to investigate the impact of influential factors on CT saturation for CT dimensioning. The main aim of the probabilistic analysis is to identify the busses of the power network in which they may be highly exposed to the CT saturation phenomena. The proposed probabilistic framework is performed based on the time‐domain fault analysis. In the probabilistic time‐domain fault analysis, the effects of fault location, fault type, and fault resistance are investigated. Also, the effects of load and generation are considered probabilistically. On the basis of the selected random variables (RVs), the probability density function (PDF) of the voltage of the knee point (VKP) is obtained. Also, a new criterion so‐called depth of saturation (DofS) is introduced that shows the level of exposure to saturation phenomena for each bus. The results show that the proposed probabilistic framework helps to find a general observation to VKP of each CT from the CT‐dimensioning aspect. Also, the proposed probabilistic framework provides some useful information about the probability of saturation area in the power system.

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