RU2695890C1 - Method for monitoring state of power transmission line with shunt reactors disconnected in cycle of single-phase automatic reclosure and device for its implementation - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to relay protection and automation of ultrahigh-voltage alternating current lines with non-zero degree of compensation of working capacity, and can be used to determine firing arc extinction or presence of stable short circuit during dead-end pause of single-phase automatic reclosure (SPAR). To achieve said technical result, measuring voltage on disconnected phase and comparing with setting, storing obtained values of voltage on disconnected phase, measured given period of time back, according to measured at different times voltages values are calculated their difference and comparing the obtained value with the setting, determined based on the degree of compensation of the working capacitance of the line, and in case this value exceeds the value of the setting, an arc fading signal is generated.

EFFECT: technical result is improvement of reliability of determination of firing arc extinction, thus preventing activation of phase disconnected in SPAR cycle with stable short circuit on lines with shunt reactors by determination of vector of voltage increment of disconnected phase of power transmission line.

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Description

The invention relates to relay protection and automation of power lines (hereinafter, power lines) of extra-high voltage alternating current (hereinafter referred to as HV) with a non-zero degree of compensation of the working capacity and can be used to determine the fact of the extinction of the charge arc or the presence of a stable short circuit during a non-current pause of a single-phase automatic re-inclusion (hereinafter, OAPV).

If one or more shunt reactors (hereinafter, SH) are installed on the power line, and a non-zero degree of compensation of the working capacitance takes place, then the voltage restored after the extinction of the arc in the disconnected phase will have the character of beats. These beats are caused by the appearance of a free component with a frequency of ω _sv , which depends directly on the degree of compensation of the working capacity and can be found by the formula from the literature (Belyakov N.N., Kadomskaya K.P., Levinstein M.L., etc. ; Under the editorship of Levinshtein ML Processes during single-phase automatic re-inclusion of high voltage lines. - M .: Energoatomizdat, 1991. - 256):

Where,

- ω _CR - the angular frequency of the forced component of the voltage (rad / s);

- K _p - the degree of compensation of the working capacity.

The degree of compensation of the working capacity K _{p is} calculated by the formula:

Where,

- B _p - the total conductivity of the SHR connected to the line in the OAPV cycle (Sim);

- B ₁ - the transverse conductivity of the line in a straight sequence (Sim).

There is a method of determining the fact of the extinction of the arc by the voltage of the disconnected phase with the electrical removal of the voltage transformer to the middle of the line according to the zero sequence current (Belyakov NN, Kadomskaya KP, Levinstein M L and others; Ed. By Levinshtein M. L. Processes with single-phase automatic re-inclusion of high voltage lines. - M.: Energoatomizdat, 1991. - 256 p.). The method consists in measuring the voltage on the disconnected phase, the current of the zero sequence, calculating the compensated voltage and comparing it with the setting.

Compensated voltage is calculated by the formula:

Where,

- U _о.ф - voltage measured on the disconnected phase (V);

- I ₀ - measured zero sequence current (A);

- Z ₀ , Z ₁ - resistance of power lines in zero and direct sequences, (Ohm).

This corresponds to compensation for half of the maximum arc burning voltage. A coefficient of 0.5 increases the sensitivity of the LV (hereinafter, the voltage relay) during short circuit (hereinafter, short circuit) at the end of the power line by 2 times, but worsens it during the short circuit at the beginning of the power line, where the arc burning voltage is zero. The response signal of a voltage relay in a beat may be intermittent, with pauses in the minimum amplitude of the beat. This prevents the set of delay for operation, selected on the basis of the time of deionization of the medium, during which repeated breakdown of the arc gap is possible. This method determines the fact of the extinction of the arc only in the first period of the beats, therefore it is not suitable for the degrees of compensation of the working capacity at which the time of deionization of the medium exceeds the duration of one period of the beats.

The analogue has the following disadvantages:

- in the presence of compensation, sensitivity decreases during short circuit at the beginning of power lines;

- time limit for the duration of the beat period.

A known method of determining the fact of the extinction of the arc at a low degree of compensation of the working capacity, based on the measurement and comparison with a given duration between voltage transitions in the disconnected phase through zero (SU 1418840 A1, published 08/23/1988), adopted as a prototype. The method consists in measuring the voltage at each disconnected phase and comparing it with the setpoint determined by the isolation from close short circuits, recording the excess of the measured value over the setpoint during the time necessary to restore the strength of the air gap and to organize the repeated switching on of the disconnected phases, measuring the duration of the intervals between transitions through zero voltages of the disconnected phases and in case they exceed the setpoint, the value of which corresponds to the minimum The values of frequency in the system during the specified interval of time for monitoring the voltage value of the signal formed recharge arc extinction.

The method according to the closest analogue is carried out using a device containing a voltage transformer, with one output connected in series with the emergency phase voltage measuring unit, the output of which is connected to the input of the threshold element, the output connected to the first input of the AND logic element, the output connected to the “delay” element, the transformer voltage of another output connected in parallel with the input of the unit for measuring the duration of the time interval between voltage transitions through zero values, the output of which o connected to the input of the comparison unit, the output connected to the second input of the logical element I. Moreover, the unit for measuring the duration of the time interval between voltage transitions through zero values contains a block “pulse” generating pulses connected to the “delay” element connected to the “Memory” element ", An exemplary generator, connected to an input of an AND element by an output, connected to another AND element by an output, connected to an impulse counter input, connected to a comparison unit by an output, and containing the block setting the output connected to the input of the comparison element, the output of which is connected to the input of the block of the logic element AND, the unit for measuring the duration of time intervals between voltage transitions through zero values is connected to the second input of the comparison element.

The disadvantage of the method and device for its implementation is the insecurity of the electrical system of the power system from the undesirable effects of the emergency mode that occurs when the phase of the line is switched on for a stable short circuit; an increase in the duration of a dead-time pause of the OAPV, and, as a consequence, the low stability of the power system to emergency disturbances.

This is due to the sensitivity of the method to distortion of the voltage waveform during arc burning, which leads to a change in the durations between voltage transitions through zero; and also because of the impossibility of working with large values of the degree of compensation of the working capacity and the degrees of compensation greater than one.

The technical result is a reduction in the duration of the uninterrupted pause of the OAPV or preventing the turn-off of the phase disconnected in the OAPV cycle with a stable short circuit on the lines with shunt reactors, as a result of increasing the accuracy of determining the fact of the extinction of the arc in possible conditions of distortion of the waveform, and with large degrees of compensation of the working capacity also degrees of compensation greater than one.

The technical result of the proposed method is achieved by the fact that in the method of monitoring the state of the power line phase disconnected in the cycle of the single-phase automatic repeated switching on of the power line with shunt reactors, the method consists in measuring the voltage in the disconnected phase and comparing it with the setpoint, storing the obtained voltage values for the disconnected phase measured for a predetermined period time ago, according to the voltage values measured at different instants of time, their difference is calculated and the obtained value is compared with the setting, predelyaemoy based on the degree of working line capacitance compensation, and in case of exceeding this value the setting value, a signal is formed of the arc extinction.

The technical result of the claimed device is achieved by the fact that it contains voltage measuring transformers, a threshold element, additional voltage measuring transformers are introduced with 5, 6 and 7 inputs connected to the phases of the power lines 1 and switches 2, 3, 4, and the outputs connected to the inputs of the phase sorting unit 8, the outputs of which are connected to the inputs of the blocks of the Fourier filter 9, 10, 11, while the first block of the Fourier filter is connected to the output of the differentiator 18 connected to the threshold element 19; the outputs of the second 10 and third 11 blocks of the Fourier filter are connected to the inputs of the adder block 12, to the output of which a divider block 16 is connected, connected to the input of the multiplier block 17, connected to the second input of the differentiator block 18; interconnected buffers 13 and 14, to a common point of which a shift block 15 is connected, while one buffer 13 is connected to the output of the first block of the Fourier filter 9, and the output is connected to the block of the multiplier 17, and the second buffer 14 is connected to the output of the adder block 12 and to the second input of the divider block 16.

In the phases remaining in operation in the OAPV cycle, there is exclusively a voltage of a forced frequency ω _pr . While in the voltage of the disconnected phase after the extinction of the arc, in addition to the forced component, there is also a free component ω _sv . Having fixed the change in the frequency of the voltage of the disconnected phase relative to the frequency of the voltage of the included phases, we can determine the fact of the extinction of the arc. For this, it is proposed to use the phenomenon of rotation of the voltage vector of the disconnected phase, relative to the voltage vectors of the included phases. It is proposed to fix the fact of rotation by calculating the modulus of the difference of two samples of the vector at different points in time, that is, the increment of the vector over a certain period of time. The voltage vector of the disconnected phase during the beating makes a complete revolution in a time equal to the period of the beating. Over a period of time equal to half the beat period, the vector rotates 180 degrees relative to the position in which it was at the time the clock began. In this case, the modulus of the difference between the vectors of the current moment of time and the moment of time spaced half the beat period backward will be maximum and, taking into account the attenuation of the free component, close to twice the value of the module of the rotating vector. During arc burning, the modulus of the difference of vectors is theoretically equal to zero. Given the unsteadiness of the combustion process, the difference between the vectors will be significantly less than the voltage with compensation for half of the maximum arc voltage. Thus, the control unit of the extinction of the arc based on the proposed method is more sensitive to the voltage relay and upon successful extinguishing of the arc gives a continuous operation signal without pauses at the output.

To compensate for the deviation of the forced frequency of the power system from the nominal value, it is proposed to multiply the voltage vector of the disconnected phase, recorded in memory half the beat period back, by the rotation vector calculated from the sum of the voltage vectors of the included phases. To find this vector, the total stress vector of the included phases at the current time must be divided by the same vector, memorized half the beat period back. The sum of the vectors is used to reduce the angular error when measuring each of them individually.

An increase in the beat period corresponds to an approach to the resonance of stresses with frequencies ω _sb and ω _pr , and, consequently, an increase in the beat amplitude and the modulus of the rotating vector. That is, the difference of the vectors will have a sufficient value even at angles between them less than 180 degrees. Therefore, it is possible to limit the time setting to 0.14 s, because the modulus of the vector difference will be of sufficient value to provide the necessary detuning from the non-stationary mode of arc burning.

The essence of the proposed method lies in the fact that by measuring the voltage at the disconnected phase, as well as maintaining the voltage value at the disconnected phase of the measured predetermined period of time ago, calculating the difference from these voltages measured at different times, and comparing the obtained value with the set point, and in if this value is exceeded, the value of the setting, the formation of a signal about the extinction of the arc, a technical result is achieved.

In FIG. the functional diagram of a device for implementing the inventive method for controlling the extinction of an arc operating on the proposed method, where the following notation:

1 - phase power lines;

2, 3, 4 - switches;

5, 6, 7 - measuring voltage transformers;

8 - phase sorting unit;

8.1; 8.2; 8.3 - outputs of the phase sorting unit;

9, 10, 11 - Fourier filter blocks;

12 - adder block;

13, 14-buffers;

15 - block shear;

16 - divider block;

17 - block multiplier;

18 - block differentiator;

19 is a threshold element.

The method for monitoring the state of a power line phase disconnected in a single-phase automatic repeated switching-on phase with shunt reactors consists in measuring the voltage in the disconnected phase and comparing it with the setpoint. The voltage value for the disconnected phase is measured, the measured predetermined period of time ago. From the voltage values measured at different time instants, their difference is calculated and the obtained value is compared with the setting determined on the basis of the degree of compensation of the line working capacity. If this value is exceeded, the setting value is formed, a signal about the extinction of the arc.

A device for implementing the inventive method contains voltage transformers 5, 6 and 7, the inputs of which are connected to the phases of the power lines 1 and switches 2, 3, 4, and the outputs are connected to the inputs of the phase sorting unit 8. The outputs of the phase sorting unit 8 are connected to the inputs of the filter blocks Fourier 9, 10, 11. In this case, the first Fourier filter block 9 is connected to the output of the differentiator 18 connected to the threshold element 19. The outputs of the second 10 and third 11 Fourier filter blocks are connected to the inputs of the adder block 12, to the output of which the block divides For 16, connected to the input of the multiplier block 17. The output of the multiplier block 17 is connected to the second input of the differentiator block 18. The buffers 13 and 14 are connected to each other, and the shift block 15 is connected to their common point. In this case, one buffer 13 is connected to the output of the first block Fourier filter 9, and the output is connected to the block of the multiplier 17, and the second buffer 14 is connected to the output of the adder block 12 and to the second input of the divider block 16.

The method is carried out using the device as follows.

In the device, voltage measuring transformers 5, 6 and 7 are connected to the phases of the power line 1. With the permission of the automatic reclosure device, the phase sorting unit 8 redirects signals: with the 4-phase switch disconnected to the output of the phase sorting unit 8.1, and from the switched-on phases (switches 2 and 3) - to the outputs of the block sorting phases 8.2 and 8.3. The signals sorted by the phase sorting unit 8 are fed to the Fourier filter units 9, 10 and 11, which form digital voltage samples in complex quantities (hereinafter referred to as samples). The voltage samples of the included phases from the outputs of the Fourier filter blocks 10 and 11 are summed in the adder block 12. The voltage samples from the outputs of the Fourier filter blocks 9 and the adder 12 are written to the buffers 13 and 14, respectively. The shift unit 15 determines the voltage recorded a predetermined (setpoint) time ago, as a result of which, these values are the output values of the buffers 13 and 14. The current value of the total voltage from the adder unit 12 is divided in the divider unit 16 by the value extracted from the buffer 14. Thus Thus, the rotation vector is formed by the divider block 16, which is then multiplied in the multiplier block 17 with the disconnected phase voltage extracted from the buffer 13. The differentiator block 18 calculates the difference of the current voltage vector of the disconnected phase from the output of block 9 and the voltage rotation vector compensated by the output of the multiplier block 17. The threshold organ 19 compares the vector module with a given setting determined by the degree of compensation of the working capacitance K _p . When the value of the modulus of the vector of the set value is exceeded, the threshold element 19 generates a discrete signal at the output signaling the extinction of the arc. As a result, a stable short circuit or the fact of the final extinction of the arc with a self-eliminating short circuit is detected. This allows you to protect the electrical system of the energy system from the undesirable effects of the emergency mode that occurs when the phase of the line with a stable short circuit is turned on and to reduce the duration of the uninterrupted pause of the OAPV, and thereby increase the stability of the energy system to emergency disturbances.

Claims (2)

1. A method for monitoring the state of a power line disconnected in a cycle of a single-phase automatic repeated switching on of a phase of a power line with shunt reactors, which consists in measuring the voltage in the disconnected phase and comparing with the setpoint, characterized in that the obtained voltage values in the disconnected phase, measured for a specified period of time, are stored back, according to the voltage values measured at different instants of time, their difference is calculated and the obtained value is compared with the setting determined on the basis of the degree of compensation the working capacity of the line, and if this value is exceeded, the setpoint values form a signal about the extinction of the arc. 2. The device for implementing the method according to claim 1, comprising a voltage measuring transformer 5, a threshold element 19, characterized in that additional voltage measuring transformers 6 and 7 are introduced, with inputs connected to the phases of the power lines 1 and switches 2, 3, 4, and outputs connected to the inputs of the input phase sorting unit 8, the outputs of which are connected to the inputs of the input Fourier filter units 9, 10, 11, while the first Fourier filter unit is connected via an output to the differentiator unit 18 connected to the threshold element 19; the outputs of the second 10 and third 11 blocks of the Fourier filter are connected to the inputs of the input block of the adder 12, the output of which is connected to the input block of the divider 16, connected to the input of the input block of the multiplier 17, the output connected to the second input of the input block of the differentiator 18; interconnected input buffers 13 and 14, to the common point of which the introduced shift unit 15 is attached, while one buffer 13 is connected to the output of the first Fourier filter unit 9, and by output it is connected to the multiplier unit 17, and the second buffer 14 is connected to the output of the adder block 12 and to the second input of the divider block 16.

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