Patent GB-261496-A (GB)
Title: Improvements in or relating to the protection of electric line sections
IPC: H02H3/04
Filed: 1925-09-04
Abstract: 261,496. Rushen, P. C., (Siemens & Halske Akt.-Ges.). Sept. 4, 1925. Cut-out arrangements.-In order to isolate any faulty section of a sectionalized line, each section has associated with it an instrument which measures the resistance of the section and when, on fault in the section, the volts therein fall off the pointer of the measuring instrument is electromagnetically depressed so that it makes contact with a conducting sector and trips the circuit-breaker at once or in a time independent of the resistance of the section. The connections of the instrument for indicating the fault are shown in Fig. 7. The fall in volts on fault opens a no-volt or other relay 230 thereby deenergizing a coil 231 which lets fall a stirrup 202. This stirrup depresses the pointer 201 of the instrument which measures the quotient of the voltage and current, that is, the resistance or impedance of the circuit, and if the circuit is faulty the pointer lies over one of the contacts 203 and becomes engaged therewith to complete the circuit of the corresponding drop indicator 205. If the circuit is not faulty the pointer is depressed into engagement with the contact 204 whereby an alternative supply circuit is closed for the coil 231. In this way the stirrup is raised and the pointer is able to take up a new position if the nature or location of the fault has changed since the indication of its first occurrence was given. Besides giving the indication (at B for example) of a fault, the pointer completes the circuit of a relay 11, Fig. 1, which closes the tripping circuit of the main circuitbreaker 15. In order to prevent action when supply to the section is regularly cut off (no fault existing on the section) a current-operated relay 7 has its contacts 6 located in the circuit of the coil 231 so that, when there is no current in the section, the stirrup cannot be actuated. The no-volt relay is indicated in Fig. 1 at 3, 4 and this can be replaced by a relay whiah depends for its action on the resistance of the line. The stirrup itself may have a conducting portion for engagement with the conducting pointer. As applied to a sectionalized line, Fig. 4, in which each section has a circuitbreaker at each end of it, each circuit-breaker is controlled independently by two coils, the upper coils in the Figure operating with a retardation of one second and, in association with their corresponding measuring instruments, serving to trip the circuit-breaker when the resistance of a section falls to three-quarters of its normal value, while the lower coils operate with a timelag of two seconds and, in association with their measuring instruments, operate when a fault develops in a portion including a whole section and half of the neighbouring section. By these means it is ensured that the circuit-breakers on either side of a section open on fault on the section. In order to ensure that no circuitbreakers on sections next to the faulty section are tripped, the measuring device may be provided with a two-part stirrup one part of which is depressed at a time so that together with time-lag relays the circuit-breakers in the faulty sections only are affected.