RU2586995C1 - Method of compensating for touch voltage at operating site in repair of overhead transmission line - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention can be used in electrical engineering. According to method overhead line is connected at ends in distribution devices of substations, on of connected main earthing phase conductors derived repair overhead line with grounding circuit support, set additional grounding spaced from grounding circuit support at distance of not less than 15 m, in circuit of main earthing include current transformer, between main ground and additional grounding include current source, controlled current with current transformer secondary winding so that at each moment in time instantaneous value of controlled source of current is equal to instantaneous value of current through main grounding to support circuit and opposite to it by direction.

EFFECT: technical result is higher safety of works on overhead lines due to reduction of induced voltage in place of works to safe value.

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Description

The invention relates to the electric power industry and can be used to provide security measures during work on overhead power lines that are in the off position under the induced voltage.

The claimed invention relates to a priority area for the development of science and technology "Technologies for creating energy-saving transportation systems, heat and electricity distribution" [1. Smirnov Yu.G., Skidanova E.V., Krasnov S.A. Alphabetical subject index to the International Patent Classification in priority areas for the development of science and technology. M .: PATENT, 2008 - p. 97].

Rules on labor protection during the operation of electrical installations [2. Rules for labor protection during the operation of electrical installations. Registered in the Ministry of Justice of Russia on 12.12.2013 No. 30593 and published on 01/13/2014] security measures were identified during operations on overhead power lines, on which additional voltage is induced from neighboring operating lines. Safety measures are separately highlighted when working on such lines when grounding them in accordance with the general requirements of the Rules does not allow lowering the potential induced on the disconnected wires below 25 V. In accordance with the Rules, a list of lines that are disconnected under induced voltage is formed. The list includes overhead lines (their sections), the induced voltage value of which exceeds 25 V, as well as overhead lines built on double-circuit (multi-circuit) supports. The induced voltage values are obtained using a simplified calculation method or line measurements.

It is known that on any overhead line (OHL) running in parallel with other overhead lines, a third-party potential is continuously induced, due to the electromagnetic fields of the influencing lines. The potential value depends on the operating voltage, load currents, the distance between the phase conductors of the lines and the lengths of the sections of their parallel arrangement. The potential induced on each of these lines (induced voltage) can be arbitrarily represented as the sum of two components: electrostatic and electromagnetic.

The electrostatic (transverse) component on an ungrounded OHL can reach several kV. The electromagnetic (longitudinal) component leads to the appearance of a touch voltage at the place of work, caused by spreading on the ground through grounding at the place of work of the induced current. Grounding of overhead lines at least at one point leads to an almost complete disappearance of the transverse component.

The Rules [2, p. 38.45 (adopted as an analogue)] require measures to reduce the touch voltage, incorrectly referred to in many documents, including regulatory documents, as the induced voltage, to a value of no more than 25 V. If it is not possible to reduce this rule [2, 38.45] oblige the use of grounding VL only at the place of work, which is not always reliable, and this desire to reduce the contact voltage at the place of work to less than 25 V leads to a mortal danger in the event of loss of connection between the overhead wires and the gap dilution, which in this case leads to the appearance of kilovolts of the transverse component. For this reason alone, over the past 15 years, more than 15 people of linear personnel of electric grid enterprises have died. All this is described in detail in [3. Vanteev A.I. Issues of the safe organization of work on overhead power lines. Appendix to the journal "Energy". Issue 4 (184). 2014].

A known method of reducing the inductive effect of AC networks on wired communication communications [4. Patent RU No. 2298487, IPC В60М 1/06, В60М 3/00, publ. May 10, 2007], in which an additional adjustable source of compensating voltage is used, which is in antiphase to the supply (to induced) voltage. An additional adjustable source of compensating voltage is connected to an additional wire located parallel to the communication wires, grounded on one side. As a result of the addition of the electric fields of the supply (induced) voltage and the source of the compensating voltage, the electric influence of the network on adjacent wire communication lines is reduced to almost zero. The method adopted for the analogue.

Signs of an analogue that coincide with the essential features of the proposed method is the connection of an adjustable source of compensating voltage to the ground loop through an additional wire located parallel to the communication wires.

In this method, only the electric (electrostatic) component of the induced voltage is compensated and the electromagnetic component is not affected, which does not exclude the appearance of the induced voltage from the electromagnetic component.

A known method of compensating induced voltage at the place of work on a disconnected overhead power line [5. Patent RU No. 2541508, IPC H02J 3/00, publ. 02.20.2015], in which the phase conductors of the disconnected line at the place of work are connected with grounding wires with the grounding circuit of the line support at the place of work, characterized in that the power of the induced voltage source is preliminarily determined, an autonomous power source is formed with the possibility of controlling the magnitude and phase of the compensating voltage, measure the induced voltage at the place of work with a voltmeter, connect the line supports to the grounding loops and grounding wires adjustable power source, which sets the voltage equal in magnitude and is in antiphase to the measured induced voltage, and control the voltmeter for the value of the residual induced voltage, not exceeding 25 V. This patent is taken as a prototype.

The signs of the prototype, coinciding with the essential features of the proposed method, is the grounding of the phases of the disconnected line at the place of work and the use of an autonomous power source.

The disadvantages of the prototype are: 1. The use of the method only for the mode without grounding the overhead lines at the ends, which poses a serious danger due to the lower reliability of portable grounding relative to stationary grounding knives at the ends of the overhead lines. 2. Setting the power source before starting work without any adjustment in the future.

The invention is aimed at solving the problem of improving the safety of work on overhead power lines.

A positive result of the invention is to reduce the induced voltage at the place of work to values less than 25 V required by safety regulations by compensating for the induced current through the ground resistance at the site of work of the overhead power transmission line that has been repaired.

A positive result is achieved as follows: The overhead line to be repaired is earthed at the ends, at the work site they are connected by grounding conductors (main ground at the work site) the phase wires of the overhead line brought out for repair with the support ground loop at the work site, establish additional ground that is distant from the circuit grounding supports at a distance of not less than 15 m, include a current transformer in the main ground circuit, between the main and secondary groundings include a controlled current source the current (IUT), the current from the secondary winding of the current transformer, control the IUT so that at any moment the instantaneous value of the IUT current is equal to the instantaneous value of the current through the main ground and opposite to it. The ITU current compensates for the spreading on the ground from the support circuit of the induced current, and, consequently, the touch voltage.

The differences of the proposed method from the prototype prove the novelty of the technical solution described in the claims.

The new approach allows to increase the safety of work in electrical installations by reducing the contact voltage at the place of work to values lower than those required by safety regulations (25 V), which confirms the compliance of the claimed technical solutions with the patentability condition “industrial applicability”.

From the prior art, the distinctive essential features of the proposed method, described in the claims, are unknown, which confirms their compliance with the condition of patentability "inventive step".

The application of the claimed method allows to reduce the touch voltage at the place of work under any conditions on the influencing lines, and not only on them: 1. There is no danger of the appearance of the transverse component, since the overhead line is grounded at the ends with stationary grounding knives; 2. There is no dependence on the load current on the influencing lines; 3. There are no bursts from the flow of short-circuit currents along the influencing lines (bursts can appear not only as a result of short circuits on the influencing lines themselves, but also in any other places); 4. No effect from electrified railways; 5. No effect from atmospheric overvoltage. That is - this is a universal way.

The invention is illustrated by drawings, where:

- in FIG. 1 shows a single-line design of a double-circuit overhead line with grounding of the wires of the three phases of the disconnected line at the ends with stationary grounding knives and at the work site using portable grounding;

- in FIG. Figure 2 shows the transfer of the point of entry of the induced current to the installation site of the additional grounding.

The scheme includes: Overhead line (VL) 1, displayed for repair; VL 2 in operation - affecting VL; stationary grounding knives 3; grounding 4 at the place of work, which is, together with the grounding contour of the support, the main grounding; additional grounding 5; current controlled current source (ITUT) 6; current transformer 7; spreading of the induced current on the ground 8 - it is this current that causes the appearance of a touch voltage equal to the product of the induced current and the resistance of the grounding contour of the support; induced current 9; current 10 from ITUT, compensating for the spreading of induced current through the ground through the ground; support grounding circuit (main ground).

In FIG. 1, in a single-line version, a two-circuit overhead line is presented with grounding of the wires of the three phases of the disconnected line 1 at the ends with stationary grounding knives 3 and at the work site with portable grounding 4 - main grounding at the place of work. An additional grounding of 5 is installed at a distance of at least 15 m from the support ground loop; a current transformer 7 is installed in the main grounding circuit at the work site 4. An ITUT 6 is included in the secondary grounding circuit, controlled by the current from the secondary winding of the current transformer 7. Electromotive force, which is left in the overhead line 2, is induced on the wires for repair of overhead line 1, creating in the circuits on both sides of the workplace: ground 4 - overhead lines 1 on both sides of the work site - stationary ground 3 - earth induced current.

Spreading on the ground, this current causes the appearance of a touch voltage, which, according to safety rules, should not be more than 25 V. The current 10 from ITUT 7 compensates for the current 9, and, therefore, the touch voltage at the place of work.

In FIG. 2 shows that the application of the claimed method transfers the entry point of the current induced to the overhead lines to the installation location of the additional ground. The place of installation of additional grounding, near which a contact voltage of current spreading 12 now arises, can be fenced with a temporary fence with a signal tape, the radius of the fence according to safety rules is 8 m. But this place is located away from the place of work and does not interfere with their production. It is advisable to carry out additional grounding in order to reduce the required ITU power with the least grounding resistance. Here, it is possible to use an electrode driven into the ground with a length of about 2 m without the need for dismantling it (useful for the following cases of work in this place on overhead lines). It is also possible such a way to reduce grounding resistance, as watering the earth in the place of a clogged electrode with salt water, because this is usually a one-time job.

Using the proposed method of compensating for contact voltage at the place of work on the overhead power transmission line that has been repaired, it is possible to reduce the induced voltage at the place of work to values lower than those required by safety regulations (25 V), which will significantly improve the safety of repair work on air power lines.

Claims (1)

The method of compensating for contact voltage at the place of work on the overhead power transmission line for repair, in which the overhead line is earthed at the ends in the open switchgear of the substations, at the place of work, the main wires are connected to the ground wires of the overhaul repair line with the support ground loop, characterized in that establish additional grounding, spaced from the support ground loop at a distance of at least 15 m, include a current transformer in the main ground circuit Between primary ground and additional ground include current source, current controlled current transformer with a secondary winding so that at each time instant value current control source is equal to the instantaneous value of the current through the main circuit ground to support it and opposite in direction.

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