DEVICE FOR PROTECTION OF ELECTRIC INSTALLATIONS WITH VOLTAGE TRANSFORMERS AGAINST FERRORESONANCE Russian patent published in 1995 - IPC

FIELD: protection of electromagnetic transformers. SUBSTANCE: device for protection of electric installations with voltage transformers against ferroresonance includes unit for fundamental harmonic, subharmonic unit which inputs are connected to secondary winding of trasformer and outputs - to control unit via OR gate and time delay element. Output of control unit is linked to resistor unit placed between neutral of voltage transformed and its secondary winding. With emergence of ferroresonance on fundamental harmonic or on subharmonic unit of fundamental harmonic unit operates and signal is sent through logic OR to input of time delay element. After operation of the latter signal "Ferroresonance registration" appears which is also fed to resistor unit via control unit. Consequently the latter is coupled to secondary winding of voltage transformer. Factor-of-merit of circuit drops abruptly and suppression of ferroresonance tales place. EFFECT: enhanced efficiency and reliability of protection against ferroresonance. 1 dwg