SU1594445A1 - Method of determining active and reactive components of insulation resistance of three-phase four-wire mains with grounded neutral - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used in the operation of low-voltage three-phase networks with grounded neutral and neutral wire. The purpose of the invention is to increase credibility. For the implementation of the method, an additional parallel active-capacitive circuit connecting the neutral of the power transformer with the measured phase is formed, passing the conductors of this circuit along with the rest of the network conductors through the core window of the zero-sequence current transformer so that the direction of the leakage current in it in the measured phase, then the values of the resistor and capacitor in this circuit are changed until the EMF value at the output of the secondary winding of the transformer becomes p an apparent zero, after which the exposed values of the resistor and capacitor in this circuit is judged on the values of resistive and capacitive insulation resistance phase tion.

Description

The invention relates to electrical measuring equipment, in particular, to methods of phase measurement of active and reactive components of insulation resistance, and can be used in the operation of three-phase low-voltage, networks with grounded neutral.

The purpose of the invention is to increase credibility.

The drawing shows a schematic diagram of the device for implementing the proposed method.

The diagram shows a three-phase four-wire power line.

a three-phase load 2 and a single-phase load 3 supplied from the winding 1 of a power transformer and having active insulation resistances of the phases relative to the earth (Cd, Rg, cX also capacitive resistances of insulation of the phases

(SA, CB, Cc).

  In the device for implementing the method, the neutral winding 1 of the power transformer is connected to ground through resistance 4. The phase conductors A, B and C, as well as the neutral wire N are passed through the window of the core 5 of the zero-sequence current transformer, to the output of the secondary equipment 1

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the coil 6 of which is connected by an oscilloscope 7, an additional conductor 8 is passed through the window of the core 5, connecting the neutral of the power transformer with a common point of three parallel active-capacitive circuits connected via key 11.c with a conductor h oaz A between winding 1 of a silo transformer and sertse-chnik 3. A second circuit consisting of adjustable; capacitor 12 and a resistor 13 is connected via a key 14 with a conductor | se The 5 ”; third circuit. consisting of the regulator 15 and the resistor 16 is connected via a switch 17 to the conductor C of the method winding 1 with a serial transformer and a core 5., capacitors 9. 12 and 15 are tank stores, and the resistors O, 3, and 16 are the resistive magazines.

The essence of the method is as follows.

; Without creating an update

a small chain, TOB. with the disabled is: 14–14 and the level of the 11; 11k per bypass of the secondary winding is 6 ggtrans (the current current zero-order sequence is proportional to the total leakage current through the insulation ic ic eti |

 Phase leakage currents 1 ,,,, Ivn З I «-: zamyatsya through the neutral transducer and resist 4 f.ia seM.rnOs their phase separation is possible only by creating an additional circuit 5 in the window of the core The memory is directed opposite to the analogous magnitude 3 of the measured phase. For this, for example, for phase Aj, a circuit is created connecting the transformer’s neutral with the same phase, passing it through the window of the core 5 and connected to the phase And so that the leakage currents in phase A and B of the additional tseggi were sent to meetings about. In this case, in the measuring circuit, the leakage currents in phase 1 are redistributed. Since the measuring regulated capacitor 9 and the resistor 10 are inserted into the additional circuit and they are connected to a pair, through the neutral of the transformer with active and capacitive resistance and C / s Isolation of Phases A 5; then they can be read with an analog model of these components; Resistances of Isolation of Phase A ,, With an additional circuit of the dp phase; the equation of the symmetric components through Target Core 5 will look like this 3 about m;

 S 1y / - to,

t

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  IV (K.

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15 g dvs K: K - coeff: ipienta, proportional to the resistance of the additional ωgge and the insulation resistance of phase A

20 K

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The right 4, rieir expressions, represents itself: rest 11, under the action of which the secondary winding of the current transformer of the current zero voltage will induce an emf in the case of failure of insulation of the insulation resistance and additional resistance: : NejiK from resistor 10 and capacitor 9. Since the active and reactive components of the conductivity of the phases {A are constant at the moment., the condition of equality of the resistor 10 Jb of the capacitor 9 with certain values of the insulation resistance of phase A is zero ED value With the output of the secondary circuit of the current transformer zero ps; :: traditionality; setting a zero value of the emf at winding 6 on the oscilloscope 7 by changing the values of resistor u and capacitor 9 (by switching the resistor box and the store of capacitances), achieve the following: what; ta -1 values of the resistor 10 and AND; the capacitor 9 becomes equal to the av: resistive resistance and phase isolation capacitances. A „These are the magnitudes of the flux at zero emf on the 7c oscilloscope

The real estate d, l real zincin method works in the following way,

In the original state, the keys 11, 14 and 17 are disabled. To determine the k-tivny and capacitive components, the counterlegtik of phase A isolation includes a key 11 and, mainly on an oscilloscope 7, rotate the handles of the resistor i S

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Claims (1)

The method of determining the active and reactive components of the insulation resistance of the phases of a three-phase four-lead network with a grounded neutral, measure the value of the emf induced in. the secondary winding of the zero-sequence current transformer by passing through its window the core of the network conductors, according to the values 9 EMF is judged on the measured components of the insulation resistance, characterized in that, in order to increase reliability, the additional conductor that forms a parallel resistive-emitting bone circuit connecting the neutral of the power transformer to the measured network phase is passed through the window of the voltage circuit, so that the direction of the current in it is opposite to the leakage current and the measured phase, then the 15, the values of the resistor and the capacitor alternately in each phase of the network until the EMF value at the output of the secondary winding of the transformer becomes zero, after which the values of the resistor and capacitor This circuit is judged on the values of active and capacitive insulation resistance of each phase of the network.