What is the influence of transition impedance on distance protection?
The influence of network distance protection and different action characteristic impedance relay is illustrated. In the actual power system, when the phase short circuit or grounding short circuit, short circuit usually has an impedance, the analysis and experiments show that the reactance is resistive, it is often called the transition resistance.The presence of transient resistance changes the impedance of the impedance relay and affects the correct action of the distance protection. In general, the measurement resistance increases, the protection range of distance protection is shortened, distance protection II protection sensitivity decreases, but sometimes it may cause protection over range action or reverse direction misoperation. In the unilateral power network, the transition resistance increases the measurement impedance and reduces the protection range. A dual power network, transition resistance, may increase the measurement impedance, or may reduce the measurement impedance. The larger the occupied area of an impedance relay in the +R axis, the smaller the transition resistance.
There is a transition resistance at the short-circuit point, which changes the measurement impedance of the distance protection and makes it malfunction.Transient resistance is a transient quantity, and becomes an important factor in transient protection in distance protection.Considering various filtering methods, setting zero sequence reactance line or DPFC algorithm, the transient overreach problem of excessive resistance can be avoided.
Transition resistance is a state of resistance in an instant. When an electrical equipment has an interphase short circuit or a relative short circuit, the resistance through which the short-circuit current flows from one phase to another or from one phase to the other. When the phase is short circuited, the transition resistance is mainly arc resistance. When grounding short circuit, the transition resistance is mainly the tower and its grounding resistance. As soon as the fault disappears, the transition resistance disappears.
