RU152421U1 - DEVICE FOR MEASURING RESISTANCE OF EARTH GROUNDERS OF U-SHAPED SUPPORTS OF ELECTRIC TRANSMISSION AIR LINES WITHOUT DISCONNECTING THE GROUND PROTECTION ROPE - Google Patents

Abstract

A device for measuring the resistance of grounding conductors of U-shaped supports of overhead power transmission lines without disconnecting the lightning protection cable, comprising detachable clamp meters, a current source, a voltmeter, current and potential electrodes, characterized in that the clamp meters have two magnetic cores made of a nanocrystalline alloy having a high magnetic permeability, with secondary windings connected in series.

Description

Application area

The inventive device relates to electrical engineering and can be used to monitor the condition of grounding conductors of U-shaped supports of overhead power lines without disconnecting the lightning protection cable.

State of the art

A device for measuring the resistance of grounding conductors of overhead power lines, containing the device F-4103, connected to the measuring current and potential electrodes in a single-beam or two-beam circuit [1, p. 12]. The disadvantage of this device is the impossibility of its use for measuring the resistance of the grounding poles of the supports of overhead power lines with a voltage of 110 kV, on which a lightning protection cable is connected to the support.

The reason for this is that part of the measuring current passes through the ground electrode of the test support, while all the generator current passes through the auxiliary current electrode. This is explained by the fact that part of the generator current is sucked off from the ground electrode of the studied support to neighboring supports, passes through their ground electrodes, and returns to the generator through an auxiliary current electrode.

The known method and the measuring schemes implementing it, which allows the measurement of the resistance of the grounding poles of the supports of overhead power lines with a voltage of PO kV without disconnecting the lightning protection cable [1, p. 20]. In this case, a resistance meter (for example, the F-4103 device) with additional current and potential electrodes is used.

Measurements are carried out in three ways. A significant drawback is the measurement error of up to 25%. In addition, numerous measurements and subsequent processing of their results, significantly increase the time of measuring the resistance of the grounding support.

A device for measuring the resistance of grounding conductors of overhead power transmission lines, comprising: a current source, clamp meters (detachable current transformers) included in the current meter, voltmeter and potential probe cable [1, p. 26]. The disadvantage of this device is the lack of sensitivity when measuring the resistance of grounding conductors of reinforced concrete supports overhead power lines.

The closest in technical essence to the claimed is a device containing: detachable clamp meter 1 with a magnetic wire made of nanocrystalline alloy 5BDSR with high relative magnetic permeability (µrel = ~ 50,000), current source 2, voltmeter 3, current electrode 4 and potential electrode 5 [2]. The disadvantage of this device is the large error in measuring the resistance of grounding conductors of U-shaped reinforced concrete supports of overhead power lines. Clamp meter 1 (Fig. 1) can be located only on one reinforced concrete rack, measuring the current (I ₁ ) flowing from this rack to the ground. In this case, part of the current (I ₂ ) will drain into the ground at another rack. The additional error arising from not taking into account the current I ₂ is:

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The technical result consists in increasing the accuracy of measurement by a device for measuring the resistance of grounding conductors of U-shaped supports of overhead power lines without disconnecting the lightning protection cable and is achieved by using current-measuring devices in the known device

pincers with two magnetic circuits, the secondary windings of which are connected in parallel, which allows you to measure all the current flowing from the support into the ground.

Utility Model Disclosure

In FIG. 2 shows the structure of the proposed device for measuring the resistance of grounding conductors of U-shaped supports of overhead power lines without disconnecting the lightning protection cable.

The device contains a detachable clamp meter 1, a current source 2, a voltmeter 3, a current electrode 4 and a potential electrode 5.

Detachable clamp meters 1 are put on the first and second racks of the monitored U-shaped support of the power line 6, the current generator 2 is connected to the support 6 and the current electrode 4, the voltmeter 3 is connected to the support 6 and the potential electrode 5.

The measurement of the resistance of grounding conductors of the U-shaped supports of overhead power lines without disconnecting the lightning protection cable is carried out by the method of "ammeter-voltmeter". To do this, measure the current flowing from the support into the ground, and the voltage drop that it creates. Through the ratio of these values, the grounding resistance is determined.

The measurement of current and voltage must be carried out simultaneously, since the amount of current flowing into the ground depends not only on the currents created in the reinforced concrete support by the generator 2 (Fig. 2), but also on the current flowing from the lightning protection cable along the support into the ground. The magnitude of this current depends on the mode of operation of the power line and is subject to strong fluctuations. Therefore, at the same time, it is necessary to measure all the currents flowing from the support into the ground. Otherwise, the result of the measurement will be the current and voltage drop measured for a different current value. As a result, an additional error appears, the value of which will depend on the value of the current in the lightning protection cable.

The use of clamp meters with two magnetic cores, the secondary windings of which are connected in parallel, allows you to simultaneously measure all the current flowing down the U-shaped reinforced concrete support in

ground: I = I ₁ + I ₂ (Fig. 2). With the help of ticks, the total total current is measured, including the current flowing from the ground wire through the support into the ground. A voltmeter simultaneously measures the voltage drop created by this current.

When using clamp meters with one magnetic circuit, measurements have to be carried out alternately in each of the two pillars of the support. During the measurement, the total current of the U-shaped support can change due to the current flowing from the ground wire through the support into the ground, resulting in an additional error.

The above arguments are confirmed by the data of tests carried out on the existing supports of the transmission line “CHP-4-Bakhta”, the results of which are summarized in table 1.

Device Description

Before starting the measurement, two rod electrodes are driven into the ground at a distance of 20-30 meters from the base of the support. Through one of them, the current electrode 4, closes the circuit of the flow of current flowing through the support 6 into the ground. The second potential electrode 5 serves to measure the voltage drop across the resistance of the grounding device of the test support. Electrodes 4 and 5 can be located both along one line (single-beam pattern) and at the vertices of an isosceles triangle (double-beam pattern). In both cases, the distance between them should be at least 10 meters to minimize electromagnetic interference in the connecting wires.

The test current is supplied to the body of the support 6 by connecting the generator 2 with one output to the metal element of the support 6, and the second output to the current electrode 4.

The current flowing to the ground through the grounding device of the considered support 6 is measured using current-measuring clamps 1 with two detachable magnetic cores made of nanocrystalline alloy with high magnetic permeability and covering reinforced concrete pillars of the support. The secondary windings of the magnetic cores of the clamp meter 1 are connected in parallel, which allows you to measure all the current flowing down the U-shaped support into the ground (Fig. 2):

I = I ₁ + I ₂

The voltage drop on the grounding device of the support should be measured as the potential difference between the metal elements of the support 6 and the point of zero potential, which is used as a potential electrode 5.

Grounding resistance is determined by Ohm's law:

where U is the voltage measured by a voltmeter;

I-current measured by clamp meters.

Information sources

1 Celebrovsky Yu.V., Mikitinsky M.Sh. Measurement of grounding resistances of supports V L. - M .: Energoatomizdat, 1988.

2 Application for PM No. 2014111033/28 (01764), priority: 03/21/2014, publ. 08/20/2014, IPC G01R 27/20. A device for measuring grounding without disconnecting a lightning protection cable. Authors: Bessolitsch A.V., Golgovskikh A.V., Petrov N.V.

Claims (1)

A device for measuring the resistance of grounding conductors of U-shaped supports of overhead power transmission lines without disconnecting the lightning protection cable, comprising detachable clamp meters, a current source, a voltmeter, current and potential electrodes, characterized in that the clamp meters have two magnetic cores made of a nanocrystalline alloy having a high magnetic permeability, with secondary windings connected in series.

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