GB829641A - Improvements in and relating to electrical protective relays - Google Patents

Abstract

829,641. Protective cut-out arrangements. ENGLISH ELECTRIC CO. Ltd. Aug. 17, 1956 [Aug. 19, 1955], No. 23955/55. Class 38 (5). In an impedance relay having an operating coil 14 energized from current terminals 12a, 12b through a variable impedance 15, the restraining winding 18 is connected directly across voltage terminals 13a, 13b, whilst the polarizing windings 16 are connected between the voltage terminal 13b and the junction between the coil 14 and the impedance whereby the windings 16 are energized by a voltage equal to that across 13a, 13b minus the drop across the impedance 15, which drop is proportional to the line current. The arrangement has the offset characteristic denoted by circle F, Fig. 5, the degree of offset being adjustable by the impedance, but this adjustment does not affect the " reach." The windings 14, 16, 18 are arranged on a 4-pole core 11a . . . 11d to influence an armature 10. A capacitor 17 forms a resonant circuit with the windings 16 to maintain a transient flux should the voltage signal fall to zero. In a modified arrangement (Fig. 6, not shown), the impedance is replaced by the primary of a transformer, the secondary (shunted by a variable resistance) being connected in the circuit of the windings 16. In a modified form of Fig. 6 (Fig. 7, not shown) the transformer core is formed by the relay core limb 11a, the winding 14 serving as the primary and the limb having a further winding serving as the secondary and connected to the windings 16.