Novel fast and secure approach for reverse power protection in synchronous generators

摘要

The purpose of the reverse power (RP) protection is essentially to prevent severe damage to the generator prime mover. For this aim, directional relays are usually utilised. RP condition (RPC) leads to initial oscillations of power and frequency which might exceed the RP threshold and lead to mal-operation of the relay. Therefore, assigning a time delay is essential to reduce the oscillations. However, this strategy increases the relay trip time, which leads to enhancing the motoring time and the risk of damage to the prime mover. This study proposes a novel algorithm to detect RPC in synchronous generators, based on some easily accessible quantities including active power (P), load angle (delta), internal voltage (E-A), terminal voltage (V) and the phase difference between voltage and current (theta). This scheme utilises two criterions including the sign of theta and also comparing V with tangential component of E-A on V (E(A)Cos delta). This algorithm is independent of the size and type of load and is also capable of discriminating RPC with other potential faults. The performance of the proposed approach has been verified with Matlab software and the obtained simulation results show the fastest operation and highest reliability of the proposed technique compared to others.