基于模型参数识别的母线保护原理

Model-parameter Identification Based Bus-bar Protection Principle

提出一种基于模型参数识别的母线保护新原理。将母线内部故障状态等效为一个电感电路模型,发生故障时可实时计算出模型参数的等效瞬时阻抗值及参数的离散度,并利用其在母线区内、外故障及电流互感器(current transformer,CT)不同饱和程度时的幅值特点,构造出具有自适应制动特性的母线保护判据。当母线外部故障伴有CT饱和发生时,该判据能可靠制动,无需闭锁母线保护;而当母线内部故障且CT饱和时,保护能快速动作,具有较高的动作可靠性和灵敏度。与传统的母线保护相比,该保护无需滤波,对各次谐波及非周期分量都适用,动作速度更快。在3/2断路器接线的母线区内故障有汲出电流的情况下,保护的灵敏度不受影响,数字仿真和动模数据验证了其可靠性和有效性。

A novel model-parameter identification based bus-bar protection principle is proposed. An inductance model can be developed when the internal fault occurs on bus, and the inductance and the resistance of the model are taken as the unknown parameters. By calculating the equivalent instantaneous impedance and the dispersion of the parameters, and utilizing their difference, the external fault and the internal fault with different current transformer （CT） saturation degrees can be distinguished correctly. According to this, a new criterion with self-adaptive restraint characteristic for bus-bar protection is put forward. As the new principle is suitable for non-periodic component, fundamental component and harmonic component, it can operate more rapidly compared with the traditional bus-bar protection principles. Moreover, it can be applied to the bus-bar with one-and-a-half breaker arrangement and the protection performance won’t be affected even when an internal fault occurs with current flowing out the bus. Simulation results show that the presented principle has high sensitivity and reliability.