A Universal Relay Protection Coordination Model for Synchronous Machine Based on Transient Stability

摘要

This paper develops a universal relay characteristic model which represents loss of field and out of step characteristics for power system transmission and planning relay coordination. The model, along with its proposed automated apparent impedance computing methodology, examines the relay coordination settings under transient events. The Eastern North American Power System (ENPAS) has been used in this study to provide the simulation data and apparent impedance trajectories for the studied generator coordination. In order to maximize grid reliability, the generator owners and transmission operators should ensure proper coordination between plant equipment and transmission protection systems, by verifying that the relay settings are both secure and reliable. The objective is to assure that generators remain on line to provide short term support during adverse grid conditions. A system stability study is required to evaluate generator and system response to power system faults and to subsequently evaluate if protective relays cause undesirable generator trips for recoverable events, particularly for the loss-of-field and out-of-step protection which may sometimes have default typical setting values or obsolete settings due to system growth. The typical relay settings may be acceptable in many instances. However, were these settings reliable and secure? The answer can only come from a stability study. The mathematical method presented in this paper deals with transient simulation data to coordinate the loss-of-field and out-of-step relay protection settings. The challenges in loss-of-field and out-of-step protection coordination include various system conditions and post analysis of simulation data. The approach discussed in this paper utilizes a mathematical algorithm to analyse simulation data instead of the conventional R-X diagram superimposed with apparent impedance trajectories. The universal relay protection model provides an algorithm to interpret the results of the stability studies, and thereby simplify coordination of relay setting. It requires the user to pre-set the loss-of-field and out-of-step relay protection, then compares the settings with transient data to quickly coordinate with stability study. This model also precisely calculates the apparent impedance time traveling in different zones. Furthermore, an adaptive mho offset could be recommended by the model, if the relay trips incorrectly for the stable, recoverable swings or does not trip correctly for unstable conditions.