SU1308912A1 - Universal instrument transducer of three-phase network active power - Google Patents

Abstract

This invention relates to a measurement technique. The purpose of the invention is to increase the conversion accuracy and increase the output signal of the converter. The converter contains multipliers 1 ... 3, adder 4, voltage input blocks 5 ... 7, current injection blocks 8 ... 10, current measuring transformers 11 and 12, and removable jumpers 13 and 14. Current input block 9 is executed from two identical galvanically isolated input circuits and the formation of new functional connections enable one to achieve the set goal. 2 Il. a (C (L

Description

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The invention relates to a measurement technique and can be used for the conversion of active power into three-phase Tpek and four-wire networks into a unified signal.

The aim of the invention is to improve the accuracy and increase the output signal of the converter.

FIG. 1 shows the functional diagram of the meter at. power conversion in a three-wire network; in fig. 2 - the same, when converting power in a four-wire network.

The active power transducer for power conversion of a three-wire network consists of multipliers 1-3, adder 4, voltage input blocks 5–7, current input blocks 8–10, current measuring transformers 11 and 12, removable jumpers 13 and 14, and the outputs of multipliers 1 - 3 are connected to the inputs of adder 4, the output of which is the output of the converter, the first inputs of multipliers 1 - 3 are connected to the outputs of the voltage input blocks 5-7, respectively, the first inputs of which are connected to phases A, B and C controlled network, respectively , and the second ones are connected together and form a separate terminal, the second inputs of multipliers 1–3 are connected to the outputs of blocks 8–10 of current input, the first inputs of blocks 8 and 10 of current input are connected to the beginnings of secondary windings of measuring transformers 11 and 12 of current A and C, respectively The ends of which are connected to the first and third inputs of current input units 9, the second input of current input units 8 is connected by a removable jumper 13 to the second input of current input units 9, the fourth input of which is connected by a removable jumper 14 to the second input of current input units 10.

I. Transformation of active power

in a three-phase three-wire network, it proceeds as follows.

The input signals of the voltage input units 5-7 are proportional to the difference in the phase voltages of the network and the neutral-to-network voltage bias, i.e., since the ends of the input terminals of these devices form an artificial neutral. The output signals of blocks 8 and 1.0 of the current input proportion12 2

the phase currents of the phases A and C are rational, and the output signal of the current input unit 9 is the algebraic sum of the currents of the phases A and C taken with the opposite sign, i.e. phase B current

- (1d + 1) 1 ,.

since in a three-wire three-phase circuit the sum of the currents of the three phases is equal to zero

The output signal of the adder 4 is proportional to k t (Ug-Uo) io | + (Ug- -U,) i, + (U, -U „) i, k (Uio + U ib + U ic). since the component of the output signal UQ (i (., + ig + ip) is zero, and its average value is proportional to the active power of the three-phase network

and

Bblx

-sr. (RD + Pb + PC) kP,

When converting the power in the four-wire network (Fig. 2), the inputs of the current input trees 8-10 are connected directly to the secondary windings of the measuring current transformers 11,12 and 15, while the second input circuit of the current injection unit 9 is not used.

Claims (1)

Invention Formula A universal measuring transducer of active power of three-phase networks, containing three multipliers, the outputs of which are connected to the inputs of a cmamator whose output serves as the output of the converter, three voltage input units, the outputs of which are connected to the first inputs of the multipliers, and the first inputs to the phase conductors of the monitored network, and three current input units, the outputs of which are connected to the second multiplier inputs, the first inputs of the first and third current input units are connected respectively to the beginnings of the measuring output windings current transformers of the first and third phases of the monitored network, characterized in that, in order to increase accuracy and increase the output signal of the converter, the second current input unit is made with two identical galvanically isolated input circuits, the second to fourth inputs of which are connected by removable jumpers to the second inputs the first and third input current blocks respectively, and the first and third are connected respectively 313089124 With the ends of the output windings, the inputs of the voltage input units of the connecting current transformers are not connected together and brought to a separate first and third phases, with the second output terminal.