SU1764005A1 - Device for detecting place of one-phase fault to ground - Google Patents

Description

one

(21) 4864363/21

(22) 09.09.90

(46) 09/23/92. Bul No. 35

(71) Pskov branch of the Leningrad State Technical University

(72) AAIvanov and R.A.Polnsky (56) USSR Copyright Certificate No. 554511, cl. О 01 R31 / 08, 1977.

Kuznetsov A.P. Determination of places of damage on overhead power lines. - M., Energoatomizdat, 1989 - library of electrician, vol. 618, pp. 81-82. The device Wave-M is a prototype. (54) DEVICE FOR SEARCHING OF SINGLE-PHASE LOCATION ON EARTH

(57) Use: The invention relates to electrical measuring equipment and can be used to find a place for a single-phase earth fault in aerial electrical networks with insulated neutral. The essence of the invention: the device contains 1 magnetic sensor (1), 3 inductors (2-4), 3 filters (5-7), 3 quadrants (8-10), 1 summing amplifier (11), 1 square root calculator (12 ). 1 gain corrector (13), 1 amplifier (14), 1 control unit (15), 1 indicator. The inductors are arranged so that their magnetic axes are mutually perpendicular to each other. 1 hp f-ly, 1 silt

The invention relates to the field of electrical measuring equipment and can be used to find the location of a single-phase earth fault in aerial electrical networks with insulated neutral.

A device is known for finding the location of a single-phase earth fault, which contains a high-harmonic sensor of a magnetic field, a controlled signal amplifier, an indicator, a controlled-signal gain gain corrector in the form of a zero-sequence electric field sensor and a regulator (see AS No. 554511, cl. G01 R31 / 08 publ. BIMg 14.1977).

The main disadvantage of this device is the dependence of its readings on the spatial position of the magnetic sensor (or the same device, since the sensor is mounted in the device case) relative to the line wires, which reduces the accuracy

measurements and leads to an increase in the time of finding the place of damage.

The closest in technical essence to the claimed invention is a device for finding the location of a single-phase earth fault (Wave-M device), containing a magnetic sensor made in the form of two inductance coils with open-ended magnetic cores, two filters, amplifiers of a monitored signal , the gain corrector of the monitored signal in the form of a zero-sequence electric field sensor and a regulator (see A. Kuznetsov. Determination of places of damage on aerial lines lektroperedachi -. M .: Energoatomizdat, 1989. - P. 81-82).

The main disadvantage of this device is also the dependence of its readings on the spatial position

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a magnetic sensor with respect to the wires of the line, which reduces the accuracy of measurements and leads to an increase in the time of finding the place of damage.

The aim of the invention is to improve the measurement accuracy by eliminating the dependence of the device readings on the spatial position of the magnetic sensor.

The goal is achieved by the fact that the device for finding a single-phase earth fault location, contains a magnetic sensor, made in the form of two inductors with open magnetic cores, two filters tuned to the frequency of the monitored signal, the first and second amplifiers of the monitored signal, the corrector gain controlled a signal consisting of a zero-sequence electric field sensor, a voltage follower, a third amplifier, a rectifier and a controller, a control unit and an ikator, with the electric field sensor being connected via a voltage follower to the input of the third amplifier, the output of which is connected to the first output of the corrector, which in turn is connected to the first input of the control unit, and through a rectifier connected to the first input of the regulator, the control unit of the second input is connected to the output of the second amplifier, and the first and second outputs are connected respectively to the input of the indicator and to the first input of the second amplifier, a third filter is additionally tuned to the frequency of the monitored si square quadrant calculator, the first amplifier of the monitored signal is summed, and the magnetic sensor contains a third inductance with an open magnetic core, while the inductance coils are arranged so that their magnetic axes are mutually perpendicular to each other, the terminals of the coils are connected respectively to inputs of the first, second and third filters, the outputs of which are connected respectively through the first, second and third quadrants to the corresponding inputs of the summing amplifier Whose output is the square root calculator via connected to the input of the corrector, connected to the second input of the regulator, the second output equalizer connected to the output of the regulator and connected to the second input of the second amplifier.

Distinctive features of the proposed invention are that the third filter tuned to the frequency of the monitored signal, three quadrs and the square root calculator are added to the device for finding the location of a single-phase earth fault, the square amplifier has the first amplifier of the monitored signal, and the magnetic sensor contains the third coil inductance with an open magnetic core, while the inductance coils are arranged so that their magnetic axes are mutually perpendicular to each other, The coils are connected to the inputs of the first, second, and third filters, respectively, whose outputs are connected via the first, second, and third quadrants, respectively.

5 corresponding inputs of a summing amplifier, the output of which is connected to the input of the corrector through the square root calculator, to which the second input of the controller is connected, the second output of the corrector

0 is connected to the output of the regulator and is connected to the second input of the second amplifier.

The proposed device has significant differences, since other known technical solutions with similar

5 signs the applicant did not find.

When implementing a device, the identified distinctive features in conjunction with other signs provide a positive

0 effect, which consists in increasing the accuracy of measurements, since the dependence of the readings of the device on the spatial position of the magnetic sensor is excluded.

5 In FIG. 1 shows a functional diagram of the device; in fig. 2 is a sector diagram illustrating the operation of the device.

The device contains a magnetic sensor 1, consisting of three 2,3,4 inductance coils with open magnetic cores, which are made of permallo, as recommended when measuring the characteristics of low-frequency weak magnetic fields (see Panin VV, Stepanov

5 B.M. Measurement of pulsed magnetic and electric fields. - M .: Energoatomizdat, 1987. - P. 21). The inductors are arranged so that their magnetic axes are mutually perpendicular to each other. findings

Each of the coils 0 is connected to the inputs of one of the three filters 5-7, tuned to the frequency of the controlled harmonic component of the ground-to-ground current. It is most expedient to use the clock of 250, 350, 550 Hz.

The outputs of the filters are connected through quadrants 8-10 to the corresponding inputs of summing amplifier 11. Quadratures are designed to squad the voltages allocated by the filter. A summing amplifier provides the summation and amplification of squared voltage signals.

The square root calculator 12 connected to the output of summing amplifier 11 is designed to form a voltage proportional to the magnetic field of the magnetic field at the frequency of the monitored signal at the location of the device. Integral multipliers K525PS2, included according to the square-cutting scheme and the square-root extraction laughter, can be used as quadrants 8-10 and the square root calculator 12 (see Putnikov VS Integral electronics in measuring devices. - L .: Energoatomomizdat, 1988. - P. 131-132). Since the analog integral multipliers are a functionally complete device, their introduction into the device circuit for finding the location of a single-phase earth fault has practically no effect on its dimensions and weight. Connecting these chips also does not cause much difficulty.

The mutually perpendicular arrangement of the coils of the magnetic sensor and the use of quadrs, the summing amplifier and the square root calculator make it possible to eliminate the dependence of the device readings on the spatial position of the magnetic sensor.

In general, the EMF induced in a separate coil of the sensor by the magnetic field created by any of the harmonic components of the ground fault current is maximum when the magnetic induction vector B is parallel to the magnetic axis of the coil and Minimum when B is perpendicular. In all other cases, the EMF is intermediate and directly proportional to the projection of the magnetic induction vector on the magnetic axis of the sensor. This explains the influence of the position of the magnetic sensor on the measurement results in the presence of one or two (as in the prototype) inductors in it (see Panin VV, Stepanov BM. Measurement of pulsed magnetic ... - C. sixteen). If the magnetic sensor, as proposed, consists of three mutually perpendicular coils, then the EMF induced by the magnetic field in each of them will be determined (with their identical technical characteristics) by the corresponding projection of the magnetic induction vector on the magnetic axis of the coil (Fig. 2) . The square root of the sum of the squares of the three EMF coils is always directly proportional to the absolute value

(module) of the vector B at a given point in space or, equivalently, at the location of the device. This is true for any harmonic component, including the controlled one. Consequently, the voltage signal at the output of the calculator 12 square root, proportional to the indicated module of the magnetic induction vector, will not depend on the spatial distribution of the magnetic sensor. Therefore, the accuracy of measurements using the proposed device will be higher than that of known devices.

5 It should be noted that, based on design considerations, the inductors of a magnetic sensor may have different technical characteristics, for example, the length and cross section of the core or

0 number of turns. This is easily taken into account by an appropriate selection of the transfer coefficient of the summing amplifier for the individual inputs and does not affect the measurement results.

5 The square root calculator 12 through the monitored signal gain corrector 13 is connected to the input of the second amplifier 14, which is designed to change the sensitivity of the device produced by switching the amplifier gain using the control unit 15.

The control unit consists of a switch of the mode of operation and sensitivity of the device and the power button (see

Kuznetsov A.P. Locating damage. nor on overhead power lines.

- M .: Energoatomizdat, 1989. - p. 79,81-82).

A galvanic cell or battery may be used as a power source. The unipolar-to-bipolar voltage converter, necessary for powering the microcircuits, can be performed by any of the known circuits, in

5 including as in the prototype. FIG. 1 power supply not shown.

As an indicator 16, either a rectifier loaded on a series-connected resistor and a micro-ammeter is used, as is the case in the known devices for searching for ground fault locations (see Kuznetsov A. P. Determining the damage points on overhead power lines. - M .: Energoatomizdat.

5 1989. - p. 76-85), or instead of a microammeter, an analog-to-digital converter with digital indication can be used. In the second variant, the size and weight of the device will be reduced, which is essential from the point of view of ease of operation.

Corrector 13 of the monitored signal amplification contains a zero-sequence electric field sensor 17 connected via a voltage follower 18 to the input of the third AC amplifier 19. The output of this amplifier is connected to the first input of the control unit 15 and through the rectifier 20 is connected to the first input of the regulator 21.

The electric field sensor 17 (electric antenna) is a metal plate embedded in the housing of the device.

The regulator 21 is a voltage divider, the upper arm of which forms a constant resistor, and a field-effect transistor is used as the lower, the gate connected to the output of the rectifier 20 (see Goroshkov BI Radioelectronic devices: Reference book. - M,: Radio and Communication, 1985. - p. 81, Fig. 2.13).

The device works as follows. When one of the phases of the line is shorted to earth, the zero sequence currents, which contain, in addition to the main component of 50 Hz, higher harmonic components, create a magnetic field around the wires of the line, which affects the inductances 2-4 of the magnetic sensor 1. EMF induced in these coils As a result of this magnetic field effect, the inputs to the filters 5-7, which separate the signals at a frequency controlled by the harmonic component, are applied. The selected voltage signals are squared using quadrants 8-10 and then amplified and summed using summing amplifier 11. From this total voltage, the square root is extracted by the transmitter 12 and, thus, a voltage is finally formed that is directly proportional to the vector modulus magnetic induction at the location of the device.

The voltage generated at the output of the transmitter 12 is fed through the regulator 21 of the equalizer 13 to the input of the second amplifier 14. From the output of this amplifier, the voltage signal amplified in accordance with the gain control set by the control gain unit 15 and depending on the gain ratio of the regulator 21, then fed through the control unit 15 to the indicator 16.

The use of corrector 13 for amplifying the monitored signal reduces the dependence of the device’s indications on the distance between it and the proppdm line, as well as on

transient resistance values at the point of closure.

The voltage signal of the sender 17 of the electric field is fed through the voltage follower 18 to the input of the third amplifier 19. The amplified signal is rectified by the rectifier 20 and fed to the first (control) input of the regulator 21. which automatically, depending on the value

0, the output voltage of rectifier 20 varies the transfer coefficient. Moreover, with decreasing (increasing) voltage of the electric field and, consequently, the voltage on the sensor 17, the transfer coefficient of the regulator 21 increases (decreases) as the field-effect transistor inside it starts to close (open). In turn, the voltage signal of the sensor 17 increases as

When approaching the wires of the line and, conversely, decreases with distance from them. In addition, at the same distance to the wires, the voltage value of the sensor 17 also depends on the magnitude of the transient resistance of the resistance at the point of closure. As the value of this resistance decreases, the voltage signal increases as the zero sequence voltage in the line increases, and vice versa. So

In this way, the presence of the corrector 13 also provides for a partial stabilization of the readings of the device with changes in the magnitude of the transition resistance at the location of the earth fault.

5 If necessary, the signal from the output of the amplifier 19 can be supplied by means of the control unit 15 directly to the input of the indicator 16, which allows it to monitor the strength of the electric field and the presence of a ground fault and wire breaks.

Compared with the prototype of the proposed device will improve the accuracy of measurements, and thereby reduce

5 time to find the place of single-phase earth closure.

Claims (2)

Claim 1. Device for finding the location of a single-phase earth fault, containing a magnetic sensor made in the PID of two inductors with open magnetic cores, two filters tuned to the frequency of the monitored signal, the first and second amplifiers of the monitored signal, the correction gain of the monitored signal consisting of a zero-sequence electric field sensor, a voltage follower, a third amplifier, a rectifier and a regulator, a control unit and an indicator, The electric field sensor is connected via a voltage repeater to the input of the third amplifier, the output of which is connected to the first output of the corrector, which in turn is connected to the first input of the control unit, and through a rectifier connected to the first input of the regulator, the control unit is connected to the second input the output of the second amplifier, and the first and second outputs are connected respectively to the input of the indicator and to the first input of the second amplifier, characterized in that. that, in order to improve measurement accuracy, a third filter tuned to the frequency of the monitored signal, three quadrants and a square root calculator were added, the first amplifier of the monitored signal is summed, and the magnetic sensor contains a third inductance with an open magG 1 T 17 18 FIG. I 0 five core coil, while the inductors are located as follows. that their magnetic axes are mutually perpendicular, the leads of the coils are connected respectively to the inputs of the first, second and third filters, the outputs of which are connected respectively through the first, second and third quadrants to the corresponding inputs of the summing amplifier, the output of which through the square root calculator is connected to which is connected to the second input of the regulator, the second output of the corrector is connected to the output of the regulator and connected to the second input of the second amplifier. 2. The device according to claim 1, characterized in that a digital indicator with an analog-to-digital converter at the input is used as the indicator. FIG. 2