RU2700809C1 - Selective automated system for diagnosing and monitoring the state of insulation of power cable lines - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to electric measuring equipment and can be used in electric installations, at electric stations and substations, electric networks and communication networks. Summary: selective automated system for diagnostics and monitoring of insulation state of power cable lines includes two measuring sets. One set is installed at the beginning of the controlled line, and the other set is installed at its end. Each measuring set contains zero-sequence current transformers by number of connections, zero sequence current sensors, zero-sequence voltage measurement transformer, zero sequence voltage sensor, current transformers by number of phases of protected connection, measuring voltage transformer, negative sequence current and voltage filters, microcontroller, personal computer, interface converter, power supply unit of microcontroller.

EFFECT: determination of insulation state and prediction of insulation service life.

1 cl, 3 dwg

Description

The invention relates to electrical engineering and can be used in electrical installations, at electrical stations and substations, electrical networks and communication networks to determine the state of insulation and predict the insulation resource.

A known method for determining the state and resource of insulation of an electrical installation (Tadjibaev A.I., Kaniskin V.A., Sazhin B.I., Kostenko E.M. et al. Method of determining the state and resource of insulation of an electrical installation // Rospatent,) according to the application No. 93-01 6114/10 of March 29, 93, published September 20, 95), which consists in determining the dielectric loss tangent at different frequencies, finding the reference value of the maximum dielectric loss tangent frequency and calibration characteristics at different temperatures for model electrical anovki, working temperature insulation, the maximum value of the tangent of dielectric loss angle frequency for controlled electrical find the difference of said values and determining the selected characteristic of the calibration and the remaining service life of insulation.

The disadvantage of this method is the need to use an exemplary electrical installation, which creates significant difficulties in the practical implementation of this method.

Known automated system for diagnosing and monitoring the state of insulation of power cable lines (RF Patent No. 112525. Automated system for diagnosing and monitoring the state of insulation of power cable lines / Poluyanovich NK, Stulneva AV, Dubyago MN Publ. 10.01.2012 Bull. No. 1), containing by the number of connections zero-sequence current transformers, zero-sequence current sensors, zero-sequence voltage transformer, zero-sequence voltage sensor, microcontroller, ne a dormant computer, characterized in that an interface converter is inserted into it, a microcontroller power supply, the outputs of the zero sequence current transformers are connected to the inputs of the corresponding zero sequence current sensors, the corresponding outputs of the zero sequence current sensors are connected to the first inputs of the microcontroller, the output of the zero sequence voltage transformer is connected to zero sequence voltage sensor input, zero sequence voltage sensor output NOSTA connected to second inputs of the microcontroller, interface converter connected to the first output of the microcontroller, the second output of the microcontroller is connected to a power supply, a personal computer input connected to the output interface converter.

The operation of the device is based on measuring the zero sequence current level (TNP) in a controlled connection and the zero sequence voltage in the cable line. When the phase insulation is weakened, the zero sequence current increases (the amplitude and phase of the zero sequence current). The data on the state of the cable line is processed by the microcontroller, in it the obtained data are compared with the permissible amplitude of the TNF vector and, if its value is exceeded, the angle between the TNR vector and the phase-to-phase voltage vector is determined, as a result of which it is determined whether the current generated corresponds to an insulation defect if it does not match, then an earth fault has occurred.

The value of this angle with the given ranges determines which phase the defect occurred in. The data obtained are processed in a mathematical model, and the system determines the distance to the defect and the resistance of the defect or, if the defect is only outlined, the system predicts the time after which the breakdown will occur.

This system provides the search for damage, the assessment of the state of power cable lines, by determining the resistance of the defect and the distance to the defect, predicting the planned damage to the cable line.

The disadvantage of this system is that it controls only phase isolation, which allows to detect the appearance and monitor the development of processes of phase faults to earth. But in electrical networks, there are often processes of reducing the electrical strength of interphase isolation, which ultimately leads to short circuits between the phases and disruption of power supply. Short circuits between phases (two-phase and three-phase) are not accompanied by the appearance of currents of zero sequence, therefore this device does not provide early detection of such damage and prediction of the life of interphase isolation.

Also, this system does not allow to determine with sufficient accuracy the place of occurrence of damage, since a decrease in the dielectric strength of the insulation can occur out of line at a small distance from its end, and in this case it is difficult to determine the true place of occurrence of damage.

Closest to the invention in use, technical nature and technical result achieved is an automated system for diagnosing and monitoring the status of insulation of power cable lines (RF Patent No. 2657290. Automated system for diagnosing and monitoring the state of insulation of power cable lines / Biryulin V.I., Kudelina D. B. Publ. 06/13/2018).

This system contains zero sequence current transformers; zero sequence current sensors; zero sequence voltage transformer; zero sequence voltage sensor; microcontroller; Power Supply; interface converter; Personal Computer; current transformers; reverse sequence current filter.

Monitoring currents and voltages of both the reverse and zero sequence allows you to determine the decrease in the electrical strength of the phase insulation relative to the ground and interphase insulation, but cannot accurately determine the place of occurrence of damage.

The technical task of the alleged invention is to determine the occurrence of damage on the protected line.

The task is achieved by the fact that in a selective automated system for diagnosing and monitoring the state of insulation of power cable lines, there are two measuring sets installed at the beginning and end of the protected line.

These kits measure the currents of the reverse and zero sequence, both at the beginning and at the end of the protected line. Comparison of these currents makes it possible to determine the occurrence of insulation damage only on the damaged line, since insulation damage outside the protected line (especially with damage close to this line) will be accompanied by the same values of the reverse and zero sequence currents, both at the beginning and at the end of the protected line. This will clearly localize the element of the electrical network with damaged insulation, which will reduce the time to search and eliminate the defect.

The invention is illustrated by drawings, where figure 1 shows two measuring sets installed at the beginning and end of the protected line. In FIG. 2 is a diagram of a measuring set of a selective automated system for diagnosing and monitoring the state of insulation of power cable lines, which shows: 1,3,5 - zero sequence current transformers; 2,4,6 - zero sequence current sensors; 7 - voltage transformer of zero sequence; 8 - zero sequence voltage sensor; 9 - microcontroller; 10 - power supply; 11 - interface converter; 12 - personal computer; 13 - current transformers; 14 - reverse sequence current filter. In Fig. 3, points 1 and 2 show the places of damage on the protected line and outside the protected line, respectively.

A selective automated system for diagnosing and monitoring the state of insulation of power cable lines operates as follows. In the normal state of insulation of the protected cable line or when external damage occurs (outside the protected line), the currents at the beginning and end of the line will be almost the same. If insulation damage occurs on the protected line, the current at the beginning of the line becomes greater than the current at the end of this line.

Constant comparison of current values provides continuous monitoring of the state of the line and responds only to damage to the phase and interphase isolation occurring on this line. Damages that occur outside the line will not lead to the triggering of this diagnostic and monitoring system of the insulation of power cable lines, even if the electrical parameters are approximately the same as the damage on the protected line, as if the damage points are located, as shown in figure 3 - point 1 on the protected line and point 2 outside the protected line.

A selective automated system for diagnosing and monitoring the state of insulation of power cable lines allows you to determine the location of damage to the insulation of cable lines, if the damage is located on the controlled line, the approximate distance to the place of the local insulation defect and the resistance of this defect are determined without turning off the equipment by changing the operating parameters of this line.

Claims (1)

A selective automated system for diagnosing and monitoring the state of insulation of power cable lines contains a measuring kit containing zero-sequence current transformers by the number of connections, zero-sequence current sensors, zero-sequence voltage transformer, zero-sequence voltage sensor, microcontroller, personal computer, interface converter, power supply microcontroller, outputs of current transformers of zero sequence and connected to the inputs of the corresponding zero-sequence current sensors, the corresponding outputs of the zero-sequence current sensors are connected to the first inputs of the microcontroller, the output of the zero-sequence voltage transformer is connected to the input of the zero-sequence voltage sensor, the output of the zero-sequence voltage sensor is connected to the second inputs of the microcontroller, the interface converter is connected to the first output of the microcontroller, the second output of the microcontroller is connected to the unit power supply, the input of a personal computer is connected to the output of the interface converter, current transformers according to the number of phases of the protected connection, voltage measuring transformer, current and voltage filters of the negative sequence, current transformers and voltage measuring transformers are connected to the inputs of the corresponding filters of the negative sequence, the outputs of the filters are connected to microcontroller inputs, characterized in that a second measuring set identical to the first is introduced into the system Wherein one set of measurement is set at the beginning of the controlled line and the second - to its end.

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