A Model Parameter Identification Based Bus-bar Protection Principle

A novel model parameter identification based bus-bar protection principle is proposed in this paper. An inductance model can be developed when an internal fault occurs on bus. By taking the inductance and the resistance of the model as the unknown parameters to be identified, the equivalent instantaneous impedance and the dispersion of the parameter can be calculated. Utilizing their difference, the external fault and the internal fault with different current transformer (CT) saturation extent can be distinguished correctly. Based on this, a new criterion with self-adaptive restraint characteristic for busbar protection is put forward. As the new principle is suitable for non-periodic component, fundamental component and harmonic component, it can operate more rapidly comparing with the traditional phasor based bus-bar protection principles. Moreover, the proposed principle has the inherent immunity to the impact of fault current flowing out when a fault occurs in the protection zone of the breaker-and-a-half bus-bar and is insensitive to fault resistance. Simulation results show that the presented principle has high sensitivity and reliability.