Patent GB-740430-A (GB)
Title: Testing of electricity meters
Inventor: GLYDE THOMAS CHARLES WILLIAM
IPC: G01R35/04
Filed: 1953-10-23
Abstract: 740,430. Testing electricity meters; connection fittings. LANDIS & GYR, Ltd. Oct. 23, 1953. No. 29420/53. Classes 37 and 38 (1). [Also in Group XXXVII] Apparatus for testing electricity meters comprises a clamping member slidable into a locked position where its terminals engage the testmeter terminals and a cam closes a switch controlling the power supply to the testing circuits. The invention is described with reference to testing single-phase watt-hour meters by stroboscopic comparison with a standard meter and the 3-phase equipment disclosed includes solenoid - contactors selectively push - button operated to produce the test loads required. The invention provides rapid testing, Fig. 1, as meters supplied down delivery shoots 11 to a two-man test bench 10 are quickly clamped/connected and tested/adjusted and returned through dispatch shoots 12. In Fig. 1 a test meter 33 is clamped/connected at 49 on one of test sections 21 and the operator through viewing tube 26 sees on translucent screen 45, Fig. 2, the speed of meter 33 versus that of standard 15. The stroboscopic comparator system, Figs. 2 and 3, comprises light beam 35 extending via slit in mask 90 through apertures in standard meter disc 37 and thence via mirrors 38-4:0 and associated lenses to black-lined disc 41 of test meter 33. The light reflected from disc 41 is directed by mirrors 42-44 onto screen 45 and any error in test meter 33 is observed by the direction and speed of travel of vertical lines along screen 45. The test bench 10, Fig. 1, has load selector push-buttons common to the two test sections 21. The clamping member (Figs. 4-6).-When panel 49 comprising terminals 65-68 is pushed home so that terminals 65-68 engage the terminals on test meter 33 rods 50 slide along free-running rollers 51-53 and a bar 55 spring- controlled at 58 and bridging rods 50 is held by a latch 56 extending from a shaft 57 and a cam 87 on bar 55 closes power supply contacts 86. The shaft 57 has an arm 62 pinned to the armature 63 of a tripping solenoid 64 and the latter is energized at test completion to lift latch 56 as the operator presses the STOP push button. The thrust outwards of panel 49 by spring 58 when solenoid 64 operates is cushioned by abutment of pins 59 carried on bars 55 and sliding in slots 60 against spring buffers 61. The current terminals 65, 66 are resiliently mounted within the panel 49 by leaf springs 69 and the voltage terminals 67, 68 are of the plunger type with internal helical springs. The terminals 65-68 are connected to cables contained in rigid insulating tubes 70-73 and flexible leads connect the cables to the testing circuits. Testing circuits (Fig. 7).-With a meter 33 clamp/connected on each section 21 one of the operators presses START button 32 to energize and lock start contactor 74 via closed clamping member contacts 86; also to prepare contactors 75-77 and feed current coil supply transformer 81 and parallel-connect the voltage coils in test meters 33 and standard 15. Next FULL LOAD button 31 is pressed to trip-in and lock full-load contactor 75 and light indicating lamps 224; also to feed 3-phase voltage to 120 degrees spaced phase-shifting transformer terminals 79, B, Y, R, light the voltage-indicating lamps 83 and energize the current and voltage coils in the test and standard meters. The voltage coils are energized as voltage transformer 80 is 1/phase fed via auto-transformer 78 across 79R, X of phase shifter 79. After test-adjustment of each test meter 33 one of the operators presses the 0.5 POWER FACTOR button 30 whereby the full load contactor 75 reverses and the 0.5 power factor contactor 77 closes and locks and establishes test conditions as did the full-load contactor 75 except that indicator lamps 225 are now alight and the phase shifter 79 is now energized at 79R*, 79B*, 79Y*, for the required 60 degrees lag. When the meters 33 have been tested/adjusted on this load the LIGHT LOAD button 29 is pressed so as to open the power factor contactor 77 and close and lock the light-load contactor 76 and transfer the phase-shifter voltage to 79B, 79Y, 79R; also introduce load resistor 88 instead of 89, light indicator lamps 226 and make other appropriate circuits as before. Light-load adjustments are then effected and the whole series of tests repeated. Finally the STOP button is actuated to open the start contactor 74 and energize solenoids 64 so that the two clamping panels 49 are released by their springs 58 as stated above. The load buttons 29-31 and contactors 75-77 are interlocked so that only one contactor can be closed at one time. The voltage coils in the standard 15 are connected to supply by solenoid A in contactor 74 so that they remain warm during the intervals between mounting successive test meters. The auto-transformer 78 co-operating with phae shifter 79 provides through selected tappings the required compensation for phaseangle errors due to transformer windings &c. When the primary of voltage transformer 80 is energized the voltage across meter feed lines 85 is that selected by switch 19 plus a connection 20 which is adjustable.