Analysis of failures and “blind spots” of ZYQ-11S/12S voltage switching box for PXH-831/801E protection screen

ZYQ-11S/12S voltage switching boxes are important components of PXH-831/801E protection screen. Bus P.T secondary alternating voltage at I and II sections of power substation will be switched in the box and then transmitted to corresponding protective devices. The author has analyzed carefully on several failures under special operating conditions of ZYQ-11S/12S voltage switching boxes. Lay out every possible incentive that may lead to accidents according to the device principle, examine and exclude one by one and then base on occurring characteristics of accidents to reveal the real cause with sufficient reasons - the device has “blind spot”. And therefore take relevant measures accordingly in practice to avoid of such incidents happening again.