PILOT WIRE DIFFERENTIAL PROTECTION APPARATUS FOR MULTI-END CIRCUIT BASED ON PHASE COMPARISON PRINCIPLE

摘要

A pilot wire differential protection apparatus and method for a power transmission and distribution lines including three or more connecting ends. The apparatus comprises: three or more TRANSLAY relays, which are sequentially connected at the corresponding connecting ends of the power transmission and distribution lines, respectively. Summation transformers of the respective relays are connected to an a phase, a b phase, a c phase and a neutral point at the connecting ends of the corresponding protected circuits, and a pilot wire first connecting terminal and a pilot wire second connecting terminal of the respective relays (are connected with each other in parallel, respectively. Respective phase comparators compare corresponding phases of U1 and t111 so as to obtain a phase difference, U1 is a voltage at a secondary winding side of the relay of the phase comparator, Ull is a voltage at a auxiliary transformer side of the relay of the phase comparator. A false state in the lines is judgedaccording to the phase difference Arg--.± . At each of the connecting ends, a pilots padding Ullresistor Rpp of the relay is adjusted so that Rpp + Rw = k * R0 is satisfied, k is a setconstant, Rw is a resistance on the pilot wire, and Ro is a linear impedance of the TRANSLAY relay. When ToTr or ToTr, a value of k satisfies a condition of— n* k —1 —I —(i1* k + n)* T0 I Tr + n —1 or a condition of FIGURE: FIG 5