GB741392A - Improvements relating to electrical measuring apparatus - Google Patents

Abstract

741,392. High voltage measurements using capacitive voltage dividers; electric capacitors. HIVOLT, Ltd., and BRUCE, F. M. June 18, 1954 [June 18, 1953], No. 16888/53. Class 37. The very high A.C. voltage to be measured (e.g. 100 kilovolts) is applied between concave electrodes 1, 2, Fig. 2, and a proportional low-value measuring voltage (e.g. 1 volt) is tapped-off a probe electrode 15. and applied to a cathode-follower valve voltmeter, Fig. 3. The geometry of the electrodes 1, 2 provides a high degree of screening from external stray fields; also the rolled-over rims shown tend to reduce corona discharge or arcing. The electrode 2 adjacent probe 15 is mounted on a pedestal 5 which at 18 encloses the valve 20 and input &c. components shown to the left of the chain line in Fig. 3. The power pack, calibration, &c. components shown on the right of the chain line are contained in the measurement and control unit 8, Fig. 1, and the considerable length of the flexible connecting cable 7 per-' mitted by the use of the cathode follower valve 20 shown (high input and low output impedance) means that unit 8 may be located at a safe distance from the high A.C. voltage applied to electrodes 1, 2. The 3-position switch 12 in co-operation with rheostats 25, 27 and k.v. reading meter 9 provides for adjusting the anode and filament voltages of valve 20 to the correct value each time a measurement is made. The electrodes 1, 2 are of sheet metal and mounted on an insulating column 3 which encloses and holds the metallic probe electrode 15 and sensitivity is varied by moving the column 3 vertically and thus also the probe 15 and locking the column 3 by means of grub screw 33.