Patent GB-741436-A (GB)
Title: Testing device for multiwire cables
IPC: G01R31/02
Filed: 1953-04-07
Abstract: 741,436. Detecting faults in multiple cables. IBM DEUTSCHLAND INTERNATIONALE BURO MASCHINEN GES. April 7, 1953 [April 8, 1952], No. 9362/53. Class 37. In apparatus for testing multiconductor plug connected electric cables, there are provided plural testing relay circuits arranged for connection to the individual strands of a cable and operative to sequentially test for interruption of, transposition of, and short-circuit between the several cable strands, whereby the relay circuits operate a signal display in the absence of any fault, and energize distinctive visible and/or audible signalling devices indicative of any detected fault. Fig. 1 shows a form of the apparatus wherein the ends of a 5-way cord under test are plugged into sockets each comprising contacts 1 to 5 so that the conductors are respectively in series with relays R1 to R5. Contacts A, B in series with the main supply are mechanically closed and relay VR is energized over contacts PRd, VRE1# and VRE2a to close contacts VRa, so that the R relays in series with continuous conductors are energized, while those in series with broken conductors are de-energized. Operation of one or more such relays energizes relay PR through the parallelled normally open contacts R1c to R5c and prepares a circuit through contacts R6d, contacts PRc, and VRE 1a to the parallelled contacts R1d to R5d which are opened when all the conductors are continuous so that relay FR is inoperative and a green lamp GL is energized through contacts PRa and FRa. If one or more conductors is broken, relay FR is energized over contacts R1d to R5d and holds over contact FRc to de-energize lamp GL at contact FRa and energize relay VR by closing contact FRd. Contact VRb closes and energizes fault lamp FL1, while closure of the appropriate one of contacts R1b to R5b by deenergization of the relay R in series with the broken conductor energizing through contact FRb the appropriate indicator lamp L1 to L5 denoting the faulty conductor. In the absence of any disconnection the energization of relay PR opens contact PRd after a time delay, and since relay FR is de-energized relay VR is also de-energized so that relay R13 is energized over contact PRc and holds over contact R13a. Contacts R13b, R13c close, relay R15 is energized to close contacts R15b and R15c, and relay R10 is thus energized. In the absence of transposition between the conductors joined to contacts 5, relay R10 is energized and contacts R10b, R10d switch the relay R9 for energization in series with contacts 4. Contact R9a switches out contacts 5, and in the absence of transposition between the conductors joined to contacts 4, the conductors joined to contacts 3, 2 and 1 are similarly and successively switched for testing in series with relays R8, R7 and R6 until in the absence of transposition therein the latter is energized and the lamp GL remains energized. If a transposition occurs such that e.g. there is no connection between contacts 4, relay R9 is de-energized. Relay R10 remains energized so that lamp L4 is energized through contact R10c to indicate the conductor concerned. Contact VRE1c is closed by the already energized relay VRE1 and contact FRa is opened by the already energized relay FR which holds over contact FRc, so that lamp GL is de-energized and lamp FL2 is energized. Energization of relay R6 in the absence of transpositions closes contacts R6c to energize relay VRE2 which holds over contacts VRE2a. Relays R13 and VRE1 are de-energized in sequence by opening contacts VRE2 and R13d, so that relay R6 is de-energized by opening contacts VREle and R13c. Contacts VRE2b are now closed to connect all the conductors of the cable in series with their associated sockets 1 to 5 and with test relays R1 to R5, so that any short circuit between the conductors de-energizes the relay or relays interposed between them. In testing for insulation the cord conductors are connected as before, joining the respective sockets of pairs 1-5 so that relay R6 is energized to close contacts R6c to energize relay VRE2 which changes over contacts VRE2a to hold energized. Relays R13 and VRE1 are de-energized by opening contacts VRE2 and R13d, opening contacts VRE1e and R13c to de-energize relay R6. All the conductors and sockets 1-5, and relays R1-R5 are series connected by closure of contacts VRE2b so that if a short-circuit exists the appropriate interposed relay R1- R5 is de-energized. Fault lamp FL3 is then energized over closed contacts VRE2, R6d, PRc, contacts VRE1a, and the contact R1d- R5d closed by de-energization of its relay by the short-circuit. Relay FR is also energized to energize the appropriate lamp L1-L5 over closed contacts VRE1g, FRb, VRE1h, and the appropriate closed contact R1b-R5b. In the absence of a fault, the " clear lamp GL is energized over normally closed contacts FRa and PRa since relays PR and FR are then deenergized. Fig. 2 shows a simplified modification for testing a 4-conductor cord which is connected between the pairs of sockets 1 to 4, and contacts A, B are closed mechanically. Switching sockets a2c2, c3c4, a4a5, a6a7 and c7c8 are short-circuited, and relay R6 is energized. Relay 5 is also energized to turn over contacts R5a, R5b, contact R6a closes and voltage is applied between sockets 1 and 4 across the 4-cord conductors in series with coils I of relays R1, R2, R3 while coils II are energized in balancing parallel opposition thereto so that relays R1, R2, R3 are deenergized in the absence of faults. Contacts R1a, R2a, R3a remain open and relay R4 is de-energized, so that lamp GL is energized, indicating no fault. If an interruption, shortcircuit, or transposition is present either one or more of relays R1, R2, R3 are de-energized or the magnetic effects of coils I and II do not balance out. Relay R4 is then energized through one or more of contacts R1a, R2a, R3a to turn over contact R4b whereby lamp GL is de-energized and fault lamp FL is energized. In a further modification for high voltage testing of the insulation of the conductors, the shortcircuits between switching sockets a2c2, c3c4, a4a5, a6a7 and c7c8 are removed and sockets a1 to a9 and c1 to c8 are interconnected with corresponding sockets in the apparatus shown in Fig. 3, which is supplied between terminals HS+, HS - with a direct voltage at e.g. 1200 v. from a transformer energized voltage multiplying rectifier circuit (Fig. 4) wherein the positive HS+ is earthed and a potentiometer comprising resistors W1, W5 and a multielectrode stabilizing valve SV is connected across the rectified output. An amplifying pentode V is connected across the stabilizer in series with a relay F with its screen energized from a stabilizer electrode and its central grid connected to the junction of resistors W2, W4 in series with the negative HS -, so that when the output current is zero the pentode is cut off by the voltage drop across Wl while any output current due to an insulation fault produces a drop across W2 which causes the pentode to conduct and energizes relay F. The conductor cord is as before connected between the pairs of sockets 1-4 (Fig. 2) and contacts A, B are closed mechanically. The mains voltage energizes relays HP1, HP2 over contacts Sa, sockets a1 and c2, and contacts HP1a, HP1c close while contacts HP1b, HP1d open. Coil NI of two-coil relay N, shown as NI, NII, is energized through contacts Sa, HP1a, X in position a, Pa and relay HS is energized through contacts ALa, HP1c, Nd. Contacts HSa, HSc apply the high voltage from terminals HS+, HS - to the arms I and III of a rotary selector switch. Initially the high voltage is short-circuited over contact Pc to energize the fault relay F, which energizes relay X over contact Fa. Contact X closes to position c before opening from position a, and relay P is energized over closed contacts Sa and HP1a to hold over closed contacts Ub and Pd through coil PH. Relay N simultaneously holds over its coil NII in circuit with closed contacts Nb, X in position c, HP1a and Sa. Contact Pc opens to remove the short-circuit across HS+, HS - and fault relay F is deenergized since the arms of rotary switches I, III lie on the unconnected contacts O. Relay X is de-energized, but relay P holds over coil PH and since contact Pa is opened the coil N1 of relay N is de-energized. Since coil NII is also de-energized at open contact Xc, contact Nd opens to de-energize relay HS and disconnect the high voltage source at contacts contacts HSa, HSc. The rotary switch magnet DW is impulsed over closed contacts Sc, HSb, Pb, Na, Ua, and the arms move to position 1. Relay U is energized over contacts DW and opens contacts Ub to de-energize the holding coil PH of relay P which closes contacts Pa and opens contacts Pc. The coil NI of relay N is energized, and the high test voltage is applied between sockets a3, c5, connected to strands 1 and 2. In the absence of faults the test operation is repeated through six successive steps of the selector switches during which the test voltage is applied successively between sockets a3, a5 of strands 1, 3; sockets c8, a3 of strands 1, 4; sockets a5, c5 of strands 2, 3; sockets c8, c5 of strands 2, 4, and sockets a5, c8 of sockets 3, 4. The selector switch arms then move to contacts 7 at which relay S is energized over selector switch II. Contact Sa opens to de-energize relays HP1, HP2 to terminate the high voltage test and stop the rotary selector back to zero. Relay R6 (Fig. 2) is energized over contacts HP1b, Sd, closes contacts R6a to R6d and initiates the test sequence already described with reference to Fig. 2. If however the high voltage test sequence reveals an insulation fault between two conductors, relay F is energized to close the circuit of relay X over contact Fa while relay HS is energized over contacts Nd closed by energization of coil NII of relay N. Relay P is energized over contact X in position c and relay N is m