GB490633A - Improvements in or relating to testing arrangements for three-phase electric energy meters - Google Patents

Abstract

490,633. Current, voltage, and phasedifference measurements testing meters. SIEMENS & HALSKE AKT.-GES. Oct. 11, 1937, No. 27639. Convention date, Oct. 10, 1936. [Class 37] Apparatus for testing the connections of three-phase two-wattmeter metering systems comprises measuring-apparatus for each phase current and line voltage, as well. as means for checking the direction of rotation of the fields produced. The direction of field rotation may be checked by measuring the symmetrical positive and negative phase sequence components of the currents and voltages. Means for measuring the star point voltage are also provided. Current measurements can be effected by a transformer connection to the current windings, and the voltage measure. ments can be effected in a similar manner. In one arrangement three ammeters, four voltmeters and two field direction indicators are located in a common casing with the necessary terminal connections. Fig. 2 shows an apparatus in which only two instruments A, B are employed, two mechanically coupled doublepole three-way switches 8, 9 making the various. test connections. Three-pole two-way switches 15 .. 17 are also mechanically coupled. Voltage terminals 1 .. 3 connect the meter windings R, S, T, through transformers 12, 13, the transformer 14 being in the earth connection O. Current terminals 4 . . . 7 connect the windings R, T through transformers 10, 11, the connection at T being 180‹ displaced. The transformers 10 .. 14 are all wound to produce about 4 volts for measurement purposes. A centre-tapped choke 18, 19, resistors 20 . . . . 27 and condensers 38 . . . 31 also are provided. In positions I and II of switches 8, 9 normal current and voltage measurements are effected, whilst in position III of the switches the instruments A, B are connected as shown in Figures 3 and 4 into the complex potentiometers formed by the above-mentioned resistors and condensers across the transformer windings 12, 13. With the connections shown, the instrument A measures the positive phase sequence component of voltage and B the negative. By changing the position of switch 15 . . 17 to that shown in Figure 2, these oppositely rotating components can be indicated in respect of the meter currents.