GB397823A - Improvements in and relating to circuits for relays in alternating current systems - Google Patents

Abstract

397,823. Protective arrangements ; e 1 e ctromagnetic relays. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A.- (Assignees of Meyer Akt.- Ges., P. ; 5, Lynarstrasse, Berlin.) Nov. 23, 1931, No. 32430. Convention date, Nov. 22, 1930. Void [Published under Sect. 91 of the Acts]. [Class 38 (v).] A protective relay 5, Fig. 1, is operated by the anode current of a valve 3 when the potential at the secondary 2 of a line current transformer exceeds that of a battery 4 by a sufficient amount. In Fig. 3, condensers 9, 19 give opposite potentials to the grid of a valve 3, proportional to currents at J1, J2, so that a relay 5 is operated when the ratio of the currents is excessive. The relay may be arranged to operate when the ratio of the difference to the sum of the currents is excessive, or, if the condenser 19 is given a voltage proportional to the voltage of the circuit when the impedance of a circuit is low. In a modification the grid of the valve is made positive to operate the relay, only when a reversal of current takes place. If, in the arrangement shown in Fig. 3, a resistance is placed in series with the rectifier 8, or if a potential divider or regulating transformer operated at uniform speed by a motor is placed in parallel with the secondary of the transformer 1, the relay may be given impedance time characteristics. In a modification a resonant circuit is used to obtain a time feature. In Fig. 10, the time element is introduced in the circuit of the voltage transformer 11. Upon operation of an initiating relay a switch 29 is moved to the left so that a potential proportional to that of the line is applied to a resistance 21 and the relay has a logarithmic time-impedance characteristic. In Fig. 11 an arrangement is shown in which the grid of the valve 3 is subjected to a voltage # sin # - #J, where # is a voltage proportional to that of a line which is displaced in phase by an angle # from a current J to which the voltage #J is proportional, a resistance 25<11> being provided, so that the relay 5 has a time reactance characteristic. The cores of the transformers may be constricted at suitable parts to vary the characteristics of the relay. In Fig. 15, the circuit of the relay 5 is closed by a switch operated by a coil 36, when the ratio of voltages proportional to the voltage and current in a line is below a certain value.