Patent GB-263247-A (GB)
Title: Means for cutting out a faulty line section in an electrical distribution system
IPC: H02H3/06
Filed: 1925-10-08
Abstract: 263,247. Nankivell, F. J. Oct. 8, 1925. Protective arrangements; automatic circuitbreakers.-An arrangement for isolating a faulty line section in a sectionalized distribution system which may be made up of a ring main (supplied from both ends) and of branch feeders (fed from one end only) as indicated in Fig. 1, comprises means for opening, by automatic or manual control from the main station, all the section switches when the main switch opens on fault, and automatically or manually controlled means for reclosing the section switches in succession beginning with the one nearest to the station and proceeding to the switch on the faulty section. This switch, in closing to a. preliminary position on the fault, actuates auxiliary locking- out relays which render dead the switch-closing means (for example, a motor) before, owing to the fault, it is tripped open again together with the main station switch. When the station switch is again closed, the section switches close in succession (automatically or under hand control) up to the switch on the faulty section and this switch is prevented from closing. In the case of a ring main, the closure of the section switches proceeds round both ways of the ring until the section switches at the two ends of the faulty section are reached and these switches being locked out the faulty section is completely isolated. The auxiliary relays which prevent the reclosure have contacts which give an indication (at the station) as to which section is faulty. Fig. 4 shows the main switch E, with main switch F and one of the sectionalizing switches S together with the relays and other gear associated with each of the sectionalizing switches. The station switch S, as shown, is of the pivotedblade type and auxiliary switches c6, c13 are operated by cams K1, K2 on the switch shaft. The motor M is put into operative driving gear with the switch by the action of an electromechanical relay R controlled by voltage coils VC1 and VC2 and a current coil c c. It derives its energy from one or other of the transformers P1, P2 connected across the supply. The relay R1, acting through the cam T and links t, brings the pawl p into engagement with the switchdriving segment. When the relay R, owing to cessation of supply or other cause is de-energized, the switch is put out of gear and opens under its own weight. The relay system includes selective relays R2, R3, a closing relay R4, and a lock-out relay R5 which, in the event of fault, is locked out by excess current in the transformer CT1 while the section switch is still in the preliminary closed position X1. In order to isolate a section it is necessary, after the main switch F has tripped open by the action of the tripping coil H (while the section switch on the faulty section is still only in its preliminary closed position J with the result that all section switches again assume the off position), to reclose the main switch, whereupon, owing to the lockedout condition of the relay R5 indicators SD1, SD2, for example lamps, energized through the back contacts C14 of the relay from the potential transformers PI, P2 may be employed. Or, in order to obtain at the main station an identifiable indication from the lock-out relay of each section the indicating currents which supply SD1, SD2 may be arranged to supply a motor m, Fig. 5, driving a coding contact c<15> in the circuit of a high-frequency oscillator b, for example, a buzzer. This supplies an oscillating circuit L1 coupled to a tuned circuit L2 connected to the supply mains. The characteristic impulses for each relay are transmitted to a tuned receiving circuit L3, L4 at the station so as to be recognizable. The completely automatic arrangement described may be replaced by a semi-automatic system controlled from the central station by dispensing with the electromechanical relay R, and employing superimposed high-frequency currents and tuned circuits whereby the section switches may be opened or closed by frequencies sent out from the main station, one for closing and one for opening each section switch. In this arrangement, the section switches are normally maintained in driving gear with their motors by springs and are disengaged by tripping coils connected at y, Figs. 4 and 9, to a tuned tripping circuit L7, Fig. 9, responsive only to one particular frequency sent out from the device Z at the station. The closing frequency is introduced at the points z, Figs. 4 and 9, and is of different frequency.