SU1613974A1 - Apparatus for measuring currents proportional to modulus of resistance of insulation of three-phase electric power line with insulated neutral - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the insulation modules of the insulation of phase conductors with respect to earth in ac electric networks with insulated neutral. The purpose of the invention is to expand the functionality by defining the insulation resistance modules of individual phases. The device contains a load 1 supplied from the winding 2 of a power transformer, a zero-sequence current transformer with a toroidal core 3, a zero-sequence current transformer with a core 4, phase wires 5, 6, 7, dielectric holders 8, 9, three sections 10, 11, 12 secondary winding of core 3, three sections 13, 14, 15 of the secondary winding of core 4, resistors 16, 18, 20, analog dividers 17, 19, 21. The goal is achieved by addition of a second zero-sequence current transformer with secondary divided into three independent sectors with leads, placed on the load input, with the beginnings and ends of the leads of each sector of the secondary windings of the first and second zero-sequence current transformers, covering the same-phase line wire, are interconnected through their own resistor; which are connected to the first input of their analog divider of the measuring unit, the second input of each of which is connected to its controlled phase line wire. 1 il.

Description

The invention relates to a measuring technique and can be used to measure the modules of the resistance of the insulation of phase conductors relative to the earth in AC electrical networks with insulated neutral.

The purpose of the invention is to expand the functionality.

The drawing shows a circuit diagram of a device for measuring currents proportional to the modules of the insulation resistance of a three-phase transmission line.

A device for measuring currents proportional to the resistivity modules: the left (3-phase insulation of an electrical transmission line with an insulated neutral) supplying the load 1 from the winding 12 of the ciffloBoro transformer, contains a zero-sequence current transformer installed on the winding 2 of the power transformer toroidal core 3, and at the load input 1 - a zero-sequence current transformer with core | 4c; phase windows 5, 6, and 7 of the three-; 1) power transmission line placed along vertices of the inscription1; (equilateral equilateral triangle in dielectric holders 8 and 9, respectively. The secondary winding of core 3 is divided into three sections 10, 11, and 12 with leads, each; of which covers the core section 3 of 120 °, to the middle of each which connects their phase conductors 5, 6 and 7. The secondary winding of the core 4 is also divided into three sections 13, 14 and 15 with conclusions, each of which occupies the core sector 4 to 120, to the middle of each of which adjoins. ; your own wire 5, 6 and 7, respectively. The beginning and end of section 10 of core 3 are combined with the beginning and end of section 13 of core 4 through: a resistor 16, one of which is grounded, and the second output is connected to the first input of the analog divider 17 "The beginning and end of section 11 of core 3 through a resistor 18, one output of which is grounded, and the second output is connected to the first input of the analog divider 19, combined with the beginning and end of section 14 of core 4, the beginning and end of section 12 of core 3 are combined with the beginning and end of section 15 of core 4 through a resistor 20, one output of which is grounded , but. The second terminal is connected to the first input of the analog divider 21, Analog dividers 17, 19 and 2 contain operational amplifiers 22, 23 and 24, respectively, in the feedback circuits of which analog multipliers 25, 26 and 27 are installed, respectively

but,

each connected to its own output

house to the inverting inputs of the operational amplifiers 22, 23 and 24, respectively, with one of the inputs

| Multiply spruce 25, 26 and 27 are connected to the outputs of amplifiers 22j 23 and 24, respectively, and the second inputs of multipliers 25, 26 and 27 are the first inputs of analog dividers 17, 19 and 21, respectively.

The inverting inputs of the amplifiers 22, 23 and 24 are the second inputs of the analog dividers 17, 19 and 21, respectively, and are electrically connected to the phase conductors 5, 6 and 7 of the monitored line.

The device works as follows.

The magnetic fluxes from the current of the phase wire 5 are induced in sections 10 of 13 EMF, and those, in turn, are the currents in them, which are described by the following relations

1 (L1r + 1ud + SBC ° of section 10 of core 3; IC / DI + Kg, in section 13 of core

4, where I d - working current phase wire

five; Ivjp- leakage current through the insulation

right 5;

-6С total current through the insulation of wires 6 and 7о

ABOUT

Since sections 10 and 13 of cores 3 and 4 are differentially connected, the current through resistor 16 is

 : UAssA bs Jvft5

0

five

With the differential inclusion of sections 10 and 13 for accuracy of fit.

phase leakage current will not affect the resistance of the connecting circuits, since the resistor 16 will always have only the difference of the currents in sections 10 and 13, and the rest

the values are compensated. The voltage drop across the resistor 16 will be proportional to the current module through the insulation of the wire 5 (phase A). This voltage drop is applied to one of the inputs of the analog multiplier 25, and the inverting input of the operational amplifier 22 is supplied proportional to the voltage of the wire 5 relative to land „

As a result, the output of the analog divider 17 in terms of Vits is a voltage level proportional to the insulation resistance module of the wire 5 (phase A) relative to the earth.

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Claims (1)

SUMMARY OF THE INVENTION A device for measuring currents proportional to the insulation resistance modules of a three-phase power line with an insulated neutral, comprising a first zero sequence current transformer installed at the terminals of a winding of a power transformer. in the form of a toroidal core designed to pass phase wires located at the vertices of an inscribed equilateral triangle and forming the primary winding, while the secondary winding of the zero-sequence current transformer is made of three independent sections with leads spanning each core sector of 120 °, to the middle of which is adjacent phase wire, and all sections of the secondary winding are connected to the measuring unit, characterized in that, in order to expand the functional capabilities, he additionally introduced a second zero-sequence current transformer with a secondary winding, divided into three independent sectors with leads located on the load input, while the beginning and ends of the terminals of each of the secondary winding sectors of the first and second zero-sequence current transformers, covering one named phase wire lines, interconnected, through their own resistor, the output of each of which is connected to the first input of its analog divider of the measuring unit, the second input of each of which is connected to an appropriate monitored phase conductor line.