Patent GB-552516-A (GB)
Title: Improvements in and connected with electric wiring systems
IPC: H01R9/24
Filed: 1941-10-06
Abstract: 552,516. Indicating faults. CRABTREE & CO., Ltd., J. A., McLOUGHLIN, H. F., HILL, W. E., MORGAN, R. W., and WINTLE, T. D. G. Oct. 6, 1941, Nos. 2212/42 and 16223/41. Divided out of 552,503. [Class 37] [Also in Group XXXVII] An arrangement for indicating and locating earth faults comprises a pair of lamps P1, which may be located on the dashboard of an aeroplane, and a portable lamp M1 and switch T, Fig. 9, connected across the mains, for example a ring main energized by the generator of an aircraft, adapted to supply apparatus L<SP>1</SP>, L<SP>111</SP> over distribution boards 1, 2 and junction boxes 3, 4. Each board comprises a pair of busbars a with group isolating switches I, J, and subcircuit isolating switches s, s<SP>1</SP>, and in addition normal control switches may be provided, Figs. 7, 8 (not shown). Each board includes also a socket in which the portable lamp M1 can be successively inserted so as to bridge the mains. The switches I, J are then opened and the failure of the lamp to light indicates the faulty circuit. The other board is then isolated and the switch T operated to show which side is faulty. Thus in Fig. 9 a fault would be indicated in the negative side of the board I with the switch T in the lower position. The switches s in the positive side are all opened, and the switches s<SP>1</SP> opened in turn until the failure of the lamp to light shows that the fault is cleared. The fault is then located by reclosing the switch s<SP>1</SP> and disconnecting all the joints until once again the lamp fails to light. In the event of there being another fault, the other switches s<SP>1</SP> are reclosed in succession in reverse order whereupon the fault, if any, will be indicated by the lamp lighting, which method can also be applied if the other fault is on another board. The Specification shows that even if the normal control switch is open, an indication will still be given, Fig. 8 (not shown). Switchboards.-The mains v engage in sockets u in an insulating block l and are connected by links w having upstanding sockets x for receiving the plug of the indicator M 1. Links y are connected between links w and plates Z, Fig. 12, forming one fixed contact of the switch I or J, the other contact Z<SP>1</SP> of which is connected to the appropriate busbar a. The sub-circuit leads f end in plugs e inserted in sockets d secured on insulating blocks g and serving as one contact of the sub-circuit switch s or s<SP>1</SP>. The other contact comprises a part of a clip h for a fuse i in an insulating holder j, the other clip being connected to the busbar. The switches are all fingeroperated and comprise a spindle o with a transverse hole r receiving a round-ended pin q which is urged against the fixed contacts by a spring S'. Circuit is broken by depressing the spindle, which is then rotated through 90 degrees to prevent the circuit being re-made, or the spindle can be locked in depressed position by rotation into engagement with recesses in the block l. The strap y of the positive side may have a socket II co-operating with a socket x in the positive side to indicate millivolt drop in the shunt and hence the current taken by the branch circuit. Certain of the leads f are directly connected by conducting links k. Specification 552,502 is referred to.