AUTOMATION OF THE A D J U S T M E N T

OF E L E C T R I C I T Y METERS

V. I. Uvarov

AND TESTING

UDC 681.3.056 : 621.317.q85.089.6

The increased precision of induction-type electricity meters requires the improvements of the technical means used for their adjustment and testing.

The most widespread methods used for adjusting electricity meters consists of the wattmeter and stop-watch and the stroboscopic methods. The latter method is unsuitable for adjusting meters with loads of 5-10% of the nominal one, owing to cyclic variations of the meter disc speed [1]. The drawback of the wattmeter and stop- watch method consist of its inefficiency.

In order to raise labor productivity in adjusting electricity meters we have developed an installation whose schematic is shown in Fig. 1.

A photoelectric head PH which consists of an illuminating lamp with an appropriate optical device and a photoresistor, is attached to the tested electricity meter TM. The beam from the lamp is focussed onto the meter disc bevel and reflected from it to the photoresistor. Each time the disc bevel passes in front of the meter's inspec- tion window, the intensity of the photoresistor's illumination changes sharply. The first PH pulse starts the time intervals generator TIG, which transmits pulses with repetition periods equal to the nominal duration of one tested- meter disc revolution through the OR gate to the cathode-ray oscillographic CRO. The PH pulses are also fed to the gate. If the tested meter is defective the pulses from the photoelectric head and the TIG will have a phase

TM

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Translated from Izmeriternaya Tekhnika, No. 11, pp. 87-88, November, 1975.

�9 1976 Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. No part o f this publication may be repro- duced, stored in a retrieval system, or transmitted, in any.form or by any means, electronic, mechanical, photocopying, micro- filming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher /or $15.00.

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difference. The TIG also provides t ime pips for evaluating the meter error. The electr ici ty meter ' s adjusting e le - ments are used for obtaining coincidence of the pulse images on the CRO screen, and thus el iminating the meter exffor.

We also developed a semiautomat ic testing installation (Fig. 2) which implements the wat tmeter and stop- watch method and serves to test simultaneously several electr ici ty meters. It consists of the disc revolution counters DRC with the photoelectr ic heads PH and the t ime meters T M , which comprise transistorized logical units of the "Spektr" set. The operation of this installation's channel is described in detai l in [2]. The tolerated relat ive error 6 w of the tested electr ic i ty meter expressed in percentages on the testing installation is determined from the for- mula [3]

6w-- t n - t 100, t

where t is the actual duration of the electr ic i ty meter disc's single rotation; t n is its nominal (calculated) value for the given type of meter and testing condition.

Further investigations led to the development of an installation for determining the electr ic i ty meters ' re lat ive error immedia te ly and el iminating subjective errors from measurement results.

The installation consists of a disc revolution coumer, a standard and stopping unit, a unit of reference fre- quencies f= 10n/t n, a reversible counter, and a digital display board. Before testing is started, tile reversible counter is set to 10,000 and the start and stop triggers to their ini t ial position. In the course of testing the reference fre- quency pulses ( f= l0 n / t n) are subtracted from the counter setting for a given number of the electr ici ty meter ' s disc revolutions. At the end of this operation with t < t n the reversible counter reading is registered and the digital board displays the code of 6 x = - ( f t - 1 0 n ) .

For t = t n the reversible counter decades are emptied and the digital board displays zeros.

For t >t n tile reversible counter is emptied before the end of the operation. Theten-thousandth pulse of the f frequency trips the trigger, thus switching tile reversible counter to addition and making the board display a"plus" sign. At the end of the circuit 's operation the reversible counter registers and the digital board displays a code of 6 x = + ( f t - 1 0 n ) .

Thus, the indicatgr board displays immedia te ly the electr ici ty meter error with its sign.

The appl icat ion of the described devices for testing electr ici ty meters provides good results with stable supply sources.

1.

2.

3. 4.

L I T E R A T U R E C I T E D

N. G. Vostroknutov and A. M. tlyukovich, Electricity Meter Testing [in Russian], GEI, Moscow-Leningrad (1981). V. I. Uvarov, I z m e r i t e r . Tekh., No. 9 (1972). GOST 14767-69, "Electr ici ty meters. Methods and means of testing." I. P. Pichkhadze et al., Izmer i te l ' . Tekh., No. 12 (1972).

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