Power Transformer Differential Relay Reliability Assessment Using False Trip Root Cause Analysis

Power transformer is vital element in power grid. Its failure may affect on the continuity of supply of electrical energy to the consumers. A differential relay, which is generally used for protecting this power transformer, may be affected by the disturbances such as inrush current, current transformer saturation and over-excitation due to external faults. Accordingly, false trips (mal-operation) of protection system may be resulted in. This research work proposes root cause analysis based on fault tree analysis to be used for assessing disturbances that lead to false trips. When the critical root causes are identified, mitigation measures are used. The model of security can help to quantify analytically the reliability of the considered protection system.