FIELD: AC, DC, and ripple current measurement technology for relay protective gear. SUBSTANCE: measurement technology includes following procedures: main magnetic flux is built up in ferromagnetic core by means of primary winding deposited on it which carries current under measurement and opposing magnetic flux is created by means of secondary winding deposited on mentioned core which carries compensating current; polarity of compensating current derivative is periodically reversed and value of current under measurement is found from low-frequency component of compensating current; in addition, mentioned periodic reversal of polarity of compensating current derivative is effected in case instant value of this current goes beyond following limits: 
and 
, where Imax and Imin are limit values of current measurement range; W1 and W2 is turn number of primary and secondary winding, respectively; Hs is magnetic field intensity in ferromagnetic core corresponding to its saturation limit; L is length of central magnetic line of force. EFFECT: reduced additive error , improved sensitivity, simplified design of device implementing this technique. 3 dwg
