Experimental and EMTP Modeling of Numerical Transformer Protection for Enhancing Relay Transient Performance: A Case Study

This paper aims to present modeling and simulation of numerical differential protection for power transformer using Alternative Transient Program ATP/EMTP and its MODELS environment. The model presents the design, modeling and implementation of a numerical percentage differential relay that can be used in the protection of power system components, such as transformers, and transmission line. The relay design provides the characteristic of the percentage differential relay and evaluates its performance. To validate the performance of the modeled relay, simulations of a simplified power system in ATP/EMTP with parameters obtained from a real 30/11 KV power transformer has been carried out and compared against Siemens 7UT-612 differential relay. The advantages of modeling protection relays are to provide a good a indication of the system performance against protection system, also in addition provide indication of the relay response for different power system operating conditions such as external faults, internal faults, and switching inrush currents. Numerical differential protection in power system network gives the ability to capture and analyze the recorded transient operation conditions, and optimize relay setting due to each transformer characteristic and its location in the network.