SU47365A1 - A device for metering reactive energy in three-phase networks - Google Patents

Description

To measure reactive electrical energy in three-phase current circuits, reactive electric meters are usually arranged according to the Bergtold principle, i.e. there are two current windings in each element (system), the number of turns of each of them is three times less than the number of turns current windings of a normal (active) electric meter.

It is now proposed to measure reactive electrical energy in three-phase current circuits in some cases to use special reactive electric meters having only one current winding in each of their elements. Such a reactive electric meter differs from a normal (active) electric meter in that the number of turns of its thick windings will be less than the number of turns of a normal electric meter, and the section will be 1/3 times larger than the latter. For example, if the number of turns of the thick winding of a normal (active) counter is 14, and its section is 2.26 mm (with a diameter T, 7 mm), then the number of turns of the proposed

the jet counter will be 8, and the cross section is 2.26 1/3 3.91 4.15 mm (with a diameter of 2.3 mm).

The essence of the invention is such a device in which the current winding of the meter is included in the secondary windings of two current transformers.

that the current in this winding is equal to the geometric difference of two linear currents. On the other hand, the voltage winding is connected between the third phase and the zero point of the network. Such an inclusion allows a shift between the current and voltage in the meter circuit to be equal to 9Cf. FIG. 1-b clarify the subject matter of the invention in cases of various uses of the device.

Single-winding reactive electric meters can be either three-phase or single-phase. They can be applied in the following cases:

Case 1. Three-phase circuit with a voltage of 380 volts with a uniform load of phases (see diagram in Fig. 1).

The terms used in the diagram are as follows:

7, 2 and 3 - wires of a three-phase circuit G, t - current transformers CA - active electric

Cp counter - reactive electric

counter

P - receivers. We denote further by: Vi, Vs and 1/3 are the phase voltages of this three-phase circuit

/12. 3 — phase current strengths and 9 — phase shift angles between these currents and the corresponding phase voltages — the geometric difference of the currents / 5 and / 2B of all the cases considered here is assumed, as in other methods of measuring reactive electrical energy (except for measuring its using a sinus electric meter) that

K, K 1 /, 1 / f,

where UV is the phase voltage for an arbitrary phase and

(1 / nd W.} (Y2, Y,) (Ug, yi) 120

Based on the diagram and diagram shown in FIG. 2, we have the readings of the Cp reactive electric meter

W ,,, cos (-y,), I ,, i - | /.cos (- /,), /, +

+ 4soz (-1 / z), (- / 2) g

 ./,cos(60°-cpO + + 4cos ()

 / icos (60 ° -cpi) + + + 2 co5 (120 ° -sr2) g

1 i- (/ 1 cos cfi 4- sin 9i / ocoscp24x / F / jSin cp2)

one/

(sossv v / Fsin a-coscp-f- | -) / sin co.

The total active (reactive) electrical energy of the entire circuit is found by multiplying the active (reactive) meter reading by three. The advantages of this method are as follows: 1) a lower cost of an energy-measuring installation than when using other methods for measuring reactive electrical energy; 2) the complexity of the circuit; 3) easy adjustment of a reactive electric meter; 4) invariability of the direction of rotation of said electric meter; 5) the possibility of manufacturing this electric meter from an ordinary single-phase 220-volt electric meter; 6) minimal losses in its windings.

Case P. Three-phase circuit with a voltage of 380/220 volts with a neutral wire (see diagram in Fig. 3). Here

SA, SL and CfJ - single-phase active electric meters

Wed Wed and Wed -reactive electric meters

The remaining designations are the same as in case I.

The readings of the electric meter Wed will be:

WP - (/ 1 cos cpi + v / r / i sin cpi -

/ 9 cos cp2 + / c / 2 sin cp2)

Similar to this expression, the readings of electric meters Cp and will be respectively

WP p- (/ 2 COS CRO + sin -

- / 3 COS Fz + sin sr) t. and

W7p 27 (3 cos srp + sin F, - / I cos cpi -f-sin cpi) t

The sum of readings of electric meters will be expressed as:

W / p Wp + Wp + W; UV (L sin sr, + H- / 2 sin srz + sin (pz),

that is, it will express the full reactive electrical energy of a three-phase circuit.

The advantages of the method are as indicated in paragraphs. 3, 4 and; 5 advantages of the previous case; and also in the ability to avoid the use of the deficient 400-volt three-phase electric meter Bergtold.

Case 111. Three-phase circuit of low (see the circuit in Fig. 4) or high (see the circuit in Fig. 5) voltage without a neutral wire.

Here

SA and SA - elements of an active two-element electric meter (RpoHa counter)

CP and Wed - jet counter

T „-phase voltage transformers Ta -tubular fuses

/ 7p - fuses 3 - ground

Everything else has the same designations. A diagram explaining the diagrams of FIG. 4 and 5 is depicted in FIG. b. Here, 12 and are the linear voltages between the respective wires (1 and 2 and 2 and 3), with Viz 23 1 where V is the linear voltage in general.

Designating through the part of the reading of the reactive electric meter, due to the element Cp, M - part of the reading of the reactive electric meter, due to the element, IV - on the basis of the diagrams and diagrams, we give the full reading of the electric meter:

Wi, cos (V ,,, I ,,) t /

 - and / 1С05 (1 /, з, / 1) + Лс051Цз (-4) 1 t

T / m

to"

  COS (90

tO + 1/3

+ 4cos (150 ° - 2) V 1 / - (/ j sin91-- (D cos cp2 +

/

/ 2 sin Uz

) W, cos (Vi ,, f ,,) t

 - J / 3COs (Fj2, / C) + / 2COSll /, 2 (- / 2) lU

V,.,

Jfi:

 , cos (90 ° -cp,) +

V

+ / 2 cos ().

VV

(/ I sin (ps - | 2- 2 cos fz f

from where

, + U7, - (Asincp, +

-j- / 2 sin cp2 -f- / 3 sin) Wp,

where Rf is the full reactive electrical energy of a given three-phase electric circuit.

The subject matter of the invention.

A device for metering reactive energy in three-phase networks using a single-phase meter, characterized in that the current winding of the meter is included in the secondary windings of two current transformers so that the current flowing through it is equal to the geometric difference of two linear currents, and the voltage winding is connected between the third phase and the zero point of the network in order to obtain a shift in 9sU between the current and the voltage in the meter circuit. , .З f