SU1357854A1 - Instrument transducer of supervoltage electric power line current - Google Patents

Abstract

The measuring current transducer (IPT) of super high voltage power lines can be used in relaying and automation devices of super high voltage electric systems. It contains a measuring transformer (T) 2 current, switching unit 3, made in the form of four fully controlled AC switches, each of which can be made, for example, in the form of a bridge rectifier 4 with a power transistor 5, raising T 6 capacitors 7, noro-sagging T 8, load 9. IPT has increased measurement accuracy and reduced power consumption, i il. with y

Description

The invention relates to electrical measuring technology and can be used as a measuring transducer of non-alternating current in relay prohibiting and automatics devices for super high voltage electrical systems.

The purpose of the invention is to improve measurement accuracy and reduce power consumption by directly switching the secondary alternating current of the measuring current transformer, reducing the switching frequency and eliminating the ballast resistor in the Measuring circuit.

The drawing shows the electrical circuit of the proposed converter.

The converter contains a measuring current transformer 2 located at phase 1 of the transmission line and a switching unit 3 made of four fully controllable switches: alternating current, each of which can be performed, for example, as a bridge rectifier 4, the output of which is connected to the power transistor 5 The alternating current keys are connected to the bridge, with the secondary winding of the measuring current transformer 2 connected to one of its diagonals, and the primary winding of the increasing t is connected to the other diagonal of the bridge. ansformatora 6, the secondary winding of which is connected through a capacitor 7 to the primary winding of stepdown transformer 8. The output of the secondary winding-up transformer 6 is connected to a controlled phase transmission line 1, and the average primary ob- output, step-down transformer in skeins grounded. The secondary winding of the first transformer 6, the capacitors 7 and the primary winding of the step-down transformer 8 form the rest of the communication channel. A measuring circuit with a load of 9 is included in the secondary circuit of the step-down transformer.

The Converter operates as follows.

The current flowing through the phase I of the transmission line causes the current in the secondary winding of the current measuring transformer 2 to flow to the left, which through the switching unit 3 enters the primary winding of the transceiver.

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five

format 6. The transistors 5 switches of the alternating current unit of the switching unit 3 carry an alternating voltage of a rectangular shape with equal half-periods, and these transistors controlling the 5 switches of the alternating current are phased in such a way that in each half-period they are in a conducting state two: ranzistor 5 ac keys forming the opposite shoulders of the bridge of the switching unit 3, and the other two transistors 5 of the remaining two ac keys are in a non-conducting state.

. Thus, the primary winding of the step-up transformer 6 each half-period is connected to the secondary winding of the measuring current transformer, and the polarity of its connection is changed by opposite to each half-period. At the same time, the voltage applied to the primary winding of the second transformer 6 has a frequency equal to the switching frequency of the alternating current keys of the switching unit 3 and is modulated by the amplitude of a variable component proportional to the current flowing through the phase 1 of the power transmission line. The indicated voltage across the capacitive communication channel formed by the secondary 2 winding of the step-up transformer 6, the capacitors 7 and the primary winding of the step-down transformer 8, is transformed into the secondary winding of the first transformer 0 8, which causes the current to flow through the measuring circuit with load 9. In order to reduce the imbalance of the operation of transformers 6 and 8, the average output of the secondary winding of the step-up transformer 5 of the transformer b is under potential. scrap phase transmission lines, and the average output of the primary winding step-down transformer 8 at ground potential. In this case, the magnetic fluxes generated by the current flowing from phase 1 of the transmission line through the half-windings of transformers 6 and B and through the capacitors 7 to the ground are equal and directed oppositely, i.e., they do not affect the operation; - 6 and lowering 8 transformers. When choosing the frequency to ommuting the keys of the alternating current of the switching unit 3 is much higher than industrial0

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ac current frequency through the primary winding of the downstream transformer 6 approaches a rectangular one, and its amplitude is proportional to the instantaneous value

ka flowing. in the controlled phase of the power line. A similar form and amplitude has a current flowing through the load 9 of the measuring circuit connected to the secondary winding of the step-down transformer 8.

The elimination of mittels installed in the secondary circuit of the measuring current transformer 2 and direct switching of the secondary alternating current of the measuring current transformer 2 by switching unit 3, made using alternating current keys connected to the bridge, eliminates the possibility of current flow in addition to the secondary circuit. winding measuring current transformer 2. This increases the accuracy of the measurement and. It is necessary to introduce an additional ballast resistor in the measuring device, a positive circuit with a load of 9, which reduces the power consumed from the measuring transducer of the current 2 and, accordingly, from the transmission line. In addition, since the proposed device does not require the fulfillment of conditions

2

T)

n 4C.f

where S. is the load resistance 9;

-the transformation ratio of the transformer 8;

capacitance of capacitors 7 of the capacitive communication channel;

Editor O. Golovach

Compiled by S. Veysky Tehred M. Didyk

Order 5993/44

Circulation 730 Subscription

VNIIGSh State Committee of the USSR. for inventions and discoveries 113035, Moscow, Zh-35, RaushskA emb., 4/5

Production and printing company, Uzhgorod, st. design 4

15 o 5 o

five

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g - the key switching frequency of the switching unit 3, the switching frequency f can be significantly reduced, which also improves the measurement accuracy by reducing the influence of the parasitic parameters of the device elements, for example, the transformer windings of their own capacitors, the inertia of the switching unit keys.

Claims (1)

Invention Formula The measuring transducer for the transmission of ultra-high voltage power lines, containing the measuring transformer current a, located on the monitored phase of the line, switching unit, up and down transformers, the first of which is connected at the output of the switching unit, and the second is connected to the load of the measuring circuit, capacitive a communication channel consisting of two capacitors placed between transformers, with the average output of the second. The primary winding of the first transformer is connected to the controlled phase of the transmission line, and the middle primary output of the second transformer is grounded, characterized in that, in order to improve accuracy and reduce power consumption, the switching unit is implemented in the form of four AC switches connected to a bridge , to the terminals of one diagonal of which the secondary winding of the measuring current transformer is connected, and the primary winding of the first transformer is connected to the terminals of the other diagonal of it. Proofreader M.Sharoshi