Research On Pilot Relaying Scheme For Double-circuit Transmission Lines On The Same Pole

Double-circuit transmission lines on the same pole(DLSP)are widely used on power systems due to its economy and large transmission capacity over single-circuit line.With the influence of mutual coupling between two circuits and the complexity of fault types, many protective devices widely applied to single circuit lines can't fully meet the special need of DLSP.Aiming at the characteristics of DLSP, a pilot relaying scheme synchronized by GPS signal is developed based on distributed parameter line model and phase-mode transformation theory. All kinds of faults on double-circuit transmission lines can be detected exactly and rapidly.Moreover, it could provide fault location information as an additional function.In this paper,methods of getting phase-mode transformation matrixes and decoupling for DLSP are introduced based on mode theory firstly. The effect of mutual inductance between two circuits to relaying and fault location is eliminated by decoupling. Secondly, criterion of pilot relaying is derived based on distributed parameter line theory.Effect of line parameters'distribution to relaying and fault location is eliminated.Otherwise,online parameter calculation is adopted to improve fault location precision. Finally, simulation results carried on EMTP software under various faults show the proposed relaying scheme is reliable, and fault location is accurate.