RU2617563C1 - Method of measurement of resistance to current spreading - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: method of measurement of resistance to current spreading, according to the invention, lies in the installation of the auxiliary potential electrode made of a material that provides the maximum external contact potential difference in relation to the ground. The external contact potential difference is determined using voltmeter with high internal resistance. The grounding and auxiliary potential electrode are connected through the high resistance load resistor and ammeter connected serially. The current flowing through load resistor is measured. Resistance to current spreading is calculated using Ohm's law for the complete chain.

EFFECT: reduction of the complexity and cost of measuring the current spreading resistance.

2 dwg, 1 tbl

Description

The invention relates to the field of electric power and can be used to measure resistance to current spreading.

The well-known "Method and device for measuring the resistance of the ground electrode" according to the patent of the Russian Federation No. 2321009, IPC G01R 27/20 (2006.01), publ. 03/27/08, Bull. No. 9. The method consists in measuring the resistance of the grounding device in a minimum period of time, excluding the operation of the protection against earth fault from earth fault phase wire.

The disadvantage of this method is the narrow scope of its application, due to the fact that the analogue method requires the presence of a phase wire of an electric network with a voltage of 220 V and a digital thyristor meter for ground fault current.

Also known is the "Method of measuring the resistance of the grounding device during power supply by cable line" according to the patent of the Russian Federation No. 2761012 of 09/10/12, Bull. No. 25, which allows to assess the conformity of the resistance of the grounding device to the requirements of the PUE without disconnecting the electrical installation. The method includes measuring with current clamps the current in the zero core of the cable line and at the same time the current flowing through the grounding device.

The disadvantage of this method is its narrow scope, due to the fact that in the analogue method, the measurement of the resistance of the grounding device is possible only under the assumption that an electric current is constantly flowing in the cable line.

There are various methods for measuring the resistance of the grounding device (S.I. Kostruba Measurement of the electrical parameters of the earth and grounding devices. Monograph. - M .: Energoatomizdat, 1983. V.S. Azarov, Yu.M. Kupriyanovich. Operational control of electrical safety conditions on substations. - M.: Publishing House of Moscow State Educational Institution).

The essence of the known methods of measuring the resistance of the grounding device is to conduct a measuring electric current through the grounding device, determine the value of this current, determine the value of the electric potential on the grounding device and calculate the desired resistance of the grounding device according to the formula based on Ohm's law.

The main disadvantage of all known analogues is the high complexity in measuring resistance to current spreading.

Closest to the technical nature of the present invention is a method of measuring the resistance of the grounding device by the method of ammeter and voltmeter selected by the prototype. A diagram explaining the essence of the traditional method of measuring the resistance of the grounding device is shown in FIG. one.

The closest analogue (prototype) includes the following sequence of actions:

disconnect from the grounding device 1 zero protective conductor (PE, PEN or N) of the electrical network;

an auxiliary current electrode 7 is driven through the grounding device 1 and the auxiliary current electrode 7 driven into the ground 2 at a sufficiently large distance from the portable source of the measuring electric current (generator) through an ammeter 3, which shows the value of the measuring current I (internal measuring current source 8);

measure with a voltmeter 4 connected between the grounding device 1 and the auxiliary potential electrode 5 driven into the ground at a sufficiently large distance, the electrical voltage U generated at the grounding device;

determine the desired resistance of the grounding device 6 according to the following formula, known from Ohm's law, for an incomplete circuit, that is, without taking into account the internal resistance of the current source:

where U is the voltage measured by a voltmeter, V;

I is the current measured by an ammeter, A.

However, the disadvantage of the prototype method is that it requires a portable source of measuring electric current (generator), a current electrode that needs to be driven into the ground, and then removed from the ground, and the presence of a coil with connecting wires, which makes the method relatively complicated and relatively dear.

The proposed method is based on the known results of practice [http://meandr.org/archives/24328] and their theoretical generalization [http://elektroprovodnik.ru/soedinenie-mednyx-i-alyuminievyx-provodov.html; http://electricalschool.info/main/390-pro-raznost-potencialov.html; http://fazaa.ru/uroki-elektrotexniki/ximicheskie-istochniki-elektricheskoj-energii.html, accessed October 31, 2015].

The technical result from the use of the claimed method is to reduce the complexity and cost of measuring resistance to current spreading.

The technical result is achieved by the fact that in the known method for measuring the resistance to current spreading, which consists in disconnecting the zero protective wire of the electrical network from the grounding device, an auxiliary potential electrode is installed, characterized in that the external contact potential difference between the grounding device and the auxiliary potential electrode is determined using a voltmeter with high internal resistance, connect the ground to the auxiliary potential electrode through a high-resistance load resistance and a series-connected ammeter, measure the current flowing through the load resistance, calculate the resistance to current spreading, applying Ohm's law for a complete circuit.

The claimed technical solution is illustrated by the following drawings:

FIG. 1 is a diagram illustrating a conventional method for measuring current spreading resistance.

FIG. 2 is a diagram explaining the proposed method.

The claimed method is implemented as follows.

It is known [http://www.xumuk.ru/encyklopedia/914.html, Eremin V.V., Kargov S.I., Uspenskaya I.A., Kuzmenko N.E., Lunin V.V. Fundamentals of physical chemistry. Theory and objectives: a textbook for universities, Galvanic cells and batteries // Brockhaus and Efron Encyclopedic Dictionary: 86 vols. (82 vols. 4 ext.). - SPb., 1890-1907, http://dic.academic.ru/dic.nsf/enc_tech/268.], That two conductors that are heterogeneous in terms of the material used and placed in the electrolyte are a galvanic cell whose parameters are:

U is the potential difference between the electrodes of the galvanic cell;

R _int - internal resistance of the source, that is, the desired resistance of the earth.

A fragment of the data on the pairwise potential difference for dissimilar materials is presented in the table:

One of the options for the pair with the maximum potential difference is zinc-copper. In this case, the potential difference also substantially depends on the quality of the medium between electrodes heterogeneous in materials, that is, a fragment of the earth's surface (earth). It (earth) can be considered as a kind of electrolyte with various properties, on which the internal resistance of the galvanic cell under consideration, that is, the desired earth resistance, depends.

In FIG. 2 is a diagram explaining the essence of the claimed method.

At a certain distance from the measured grounding 1, an auxiliary potential electrode 5 of material forming a pair with respect to the ground electrode with maximum potential difference is mounted in the ground 2. In general, the potential difference at the terminals 1 ', 5' depends on the quality of the earth between the two electrodes (a kind of electrolyte: water and soluble minerals in various combinations).

The voltage at the terminals 1 ', 5' is measured with a voltmeter 4 and stored. Parallel to the voltmeter, terminals 1 'and 5' are connected in series with a circuit of high-resistance load resistance R _N and ammeter 3. The current is measured and its value is stored. According to the Ohm law formula for the complete chain

By mathematical transformation, we obtain the expression for R _int (internal resistance of the galvanic cell, that is, the earth resistance is 6 R _s )

The stored values of U, I, R _{n are} substituted into the expression and the internal resistance of the galvanic pair is calculated, that is, the total ground resistance R _{int (s)} 6. The earth resistance 6 R _{int (s)} is represented by an equivalent circuit from a plurality of parallel connected resistances (R ₁ , Ri, R _{n + 1} ), each of which can be represented by a set of series-connected resistances.

Thanks to the use of a single auxiliary electrode and the application of Ohm's law for a complete circuit, the complexity and cost of measuring the resistance to current spreading are reduced, thereby achieving the formulated technical result.

Claims (1)

A method for measuring the resistance to current spreading, namely, that the zero protective wire of the electric network is disconnected from the grounding device, an auxiliary potential electrode is installed, characterized in that the external contact potential difference between the grounding device and the auxiliary potential electrode is determined using a voltmeter with high internal resistance, connect the ground and auxiliary potential electrode through a high-resistance load resistance and Tel'nykh included ammeter measuring the current flowing through the load impedance, calculated impedance current spreading, applying Ohm's law to complete the circuit.

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