Method of measuring distance to single-phase short circuit to ground in electric circuit

IPC classes for russian patent Method of measuring distance to single-phase short circuit to ground in electric circuit (RU 2258233):

G01R31/08 - Locating faults in cables, transmission lines, or networks (emergency protective circuit arrangements H02H)

Another patents in same IPC classes:

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Method of measuring distance to single-phase short circuit to ground in electric circuit / 2258233

Device can be used for remote measurement of distance till site of damage - steady single-phase to ground, for example, at melting ice on ground by alternative or direct current. Method is based on measurement and storage of value of current, which passes through grounding electrode. The electrode is connected in turn at least two times to different points of circuit at the side of power line where it was short circuited onto ground. Distance to place of short circuit is subsequently calculated from the values and known parameters of electric circuit. Error in measurement of distance is reduced at big transient resistance due to rejection of usage of parameters of higher frequency mode.

Device for determining the place of one-phase ground in the networks with insulated neutral / 2260812

Proposed device is related to ensuring the normal functioning of the railroad high-voltage lines of longitudinal electric power supply with insulated neutral. A current transducers is switched into one from undamaged phases, closed with the damaged phase on the near end of line. The switch is located on the far end of line and has possibility closing and breaking of the undamaged and damaged phases with the current transducer. The measuring part is carried out with successively switched arithmetical device, functional corrector and indicator. The device has also a stabilized constant-current source, intended for supplying two measuring circuits by the current of equal value. The constant-current source is switched between the ground and phases, closed on the near end of line. This measuring part has also a control device and voltmeter with parallel connection to the stabilized constant-current source. The control device ensures possibility to control the voltmeter operation for realization of the peaking-difference function of this voltmeter in the modes with broken and closed switch. Besides the control device has possibility to control the arithmetical device, obtaining the information from the voltmeter on fulfillment the subtraction function of voltage, obtained in the second mode, from the first mode voltage, loaded preliminary into memory. The arithmetic device has possibility to realize the division of obtained voltage difference by the current, measured with current transducer, and to transmit the division result into the functional corrector. The last has possibility to take into account the line parameters and to convert the division result into a signal, convenient for readout on the indicator of information about the distance from substation up to the place of phase ground.

FIELD: electric engineering.

SUBSTANCE: device can be used for remote measurement of distance till site of damage - steady single-phase to ground, for example, at melting ice on ground by alternative or direct current. Method is based on measurement and storage of value of current, which passes through grounding electrode. The electrode is connected in turn at least two times to different points of circuit at the side of power line where it was short circuited onto ground. Distance to place of short circuit is subsequently calculated from the values and known parameters of electric circuit. Error in measurement of distance is reduced at big transient resistance due to rejection of usage of parameters of higher frequency mode.

EFFECT: reduced error of measurement.

5 cl, 7 dwg

The invention relates to power engineering and can be used to remotely determine the distance to the fault is single-phase earth fault of a transmission line, for example, when the melting of the ice constant or alternating current.

Known way two-way remote measurement to determine the distance to the point of earth fault [arzhannikov E.A., Cohen A. M. Methods and devices for the detection of faults on power transmission lines. - M.: NTF power progress", 1998, - 64 S., p.10-17]. According to this method, when shorted to ground, measure and memorize (fixed) value of the fault current to earth on both sides of the damaged power lines and for two fixed values of current and known parameters of the electric network calculate the distance to the fault. Theoretically, the method of two-sided measure excludes the impact of the transition resistance at the circuit, which may be different in a wide range.

The disadvantage of the method described above is the need of TV shows recorded values of a current from one end of the transmission line to another to perform the calculation of the distance to the fault.

There is a method of remote unilateral determination of the distance to fault ground the transmission line [RF Patent for the invention №2153179. The method of determining the distance to the fault-to-ground transmission lines (Dyakov A.F., Levchenko I.I., Alliluev A.A., Satsuk E.I.), IPC 7 G 01 R 31/08, 2000]. According to this method, when shorted to ground transmission line, which melts the ice, connect the power supply rectifier and fixed on one side of the line mode settings: the constant component of current and voltage and the value component of the high frequency voltage and current, and on these values and the known parameters of the transmission line calculate the distance to the fault. This method eliminates the influence of contact resistance and does not require TV shows the set values of voltage and current.

The disadvantage of the method described above is the need to use special equipment to highlight the high frequency component of current and voltage, as well as the accuracy of measuring the distance to the point of earth fault because of the inaccuracy of accounting increment in running resistance of the line conductor - earth at high frequency relative to its value at DC.

Known selected as a prototype method for determining the distance of a single-phase earth fault in the electrical network [Lukianenko M. Determination of the distance to the phase space for which akania on the ground in aircraft electrical networks with voltage of 10 kV. The dissertation on competition of a scientific degree of candidate of technical Sciences. - Minsk: Belarusian national technical University, 2003, to 22 C.], namely, that when shorted to ground transmission line connecting the power source high frequency between the line and ground, is fixed on one side of the line alternately, at least two times, the values of the mode parameters - voltage, active and reactive components of current flowing through the earthing at two different high frequencies, and these values and the known parameters of the transmission line calculate the distance to the point of snapping.

The disadvantage of this method is the need to connect to damaged power lines of the power source high frequency and significant error in the determination of the distance to earth fault at the big transition resistance that often occurs in the winter when melting of ice on power lines. Much of the error in the determination of the distance to the circuit used in this method depends on changes in the design parameters of the transmission line on the same high frequency relative to their values on other high frequency.

Object of the invention is to provide a method for determining the distance of novotneho ground fault in an electrical network, based on the unilateral fixing of the mode parameters that do not require connection to damaged power lines of the power source high frequency and ensure the reduction of errors in the determination of the distance to earth fault at the big transition resistance due to the non-use mode settings high frequency.

The problem is solved using the method of determining the distance of a single-phase ground fault in an electrical network, namely, that when shorted to ground transmission line is measured and remember (record) on one side of the line alternately, at least two times the value of current flowing through the earthing, and on these values and the known parameters of the electric network calculate the distance to a single-phase earth fault, which differ according to the invention, by the fact that the ground in which record is current, in turn, at least twice, connect to different points in the network to different poles on one side of the line with DC or different phases from one side of the line alternating current.

The invention is development, which is that to fix the value of the constant current flowing through the ground conductor connected to the electric network of outposts and the s current, use a current transformer with a linear characteristic, for example a current transformer with a split magnetic core, pulsed secondary current whichrestore primary constant current i(t) in accordance with the formula:

where n_TTT_Wthe transformation ratio and the time constant of the secondary circuit of current transformer with a linear response.

This allows to simplify the measuring equipment needed to determine the distance to ground fault in the DC network.

The invention has another development, which is that to determine the distance to the point of earth fault in a network with alternating current fixed value of the modulus of the AC current passing through the earth lead connected to the network, and the influence of the angle of phase shift between the recorded currents when connecting the earth lead to different points in the network into account by successive calculation of the k+1 time relative distance n to the point of snapping, the transition resistance at the circuit, and the phase angle between the currents as long as the difference between the n_(k+1)and n_kwill not be less than the margin of error of calculation.

This reduces the amount of measurement equipment for pixelenemy AC.

Figure 1 shows a diagram of the alternate dimension and memorizing (commit) values of current flowing through the earthing switch when it is alternately connected to different points in the network from one side of the line.

Figure 1 is displayed: 1 - earthed network, 2 - damaged line or phase transmission line, 3 - communication network (dashed line), 4 - place circuit 2 on the ground, 5 - high-voltage switching device, 6 - grounding device to which alternately connect the device 5 different points a and b network 1 on the one hand lines 2, 7 - primary measuring Converter current flowing through the earthing switch 6, 8 - fixing ammeter.

Also indicated in figure 1: L - length of the damaged line 2; n is the relative distance to the designated circuit To the transmission line.

Figure 2 and figure 3 shows the circuit network 1 for two positions of the switching device 5: figure 2 - earthing switch 6 and the measuring equipment 7, 8 is connected to point A, figure 3 - earthing 6 and measuring equipment 7, 8 is connected to a point In the electrical network 1.

In addition, figure 2 and figure 3 indicated:

U₀₁U₀₂- voltage on the respective contacts of the device 5 in the mode prior to their inclusion;

R_P- contact resistance in place of the circuit 4 together with the resistance, good discharge performance is eat earthing switch 6 and the resistance of the earth between 4 and 6;

Z_AK, Z_VKequivalent resistance of the electrical network 1 between points a and K, and K, respectively, in the actual emergency mode, when all EDS in network 1 are assumed to be zero;

I₁, I₂- fixed current value.

The proposed method is implemented with regard to its development as follows.

After the occurrence of a ground fault single phase line 2 and the device 5 through the grounding device 6 and the measuring equipment 7, 8 is held and fixed current value, for example, I₁. After the switch 5 in another position is fixed I₂. These currents are included in the equation:

where U₀₁U₀₂, Z_AK, Z_VKdepends on known parameters of the electric network 1 and the unknown values of n. The value of R_Palso unknown.

One equation is determined- in functions from unknown value n, and another equationcalculate the value of n is the desired relative distance to ground fault.

Thus, the proposed method eliminates the influence of contact resistance in place of the circuit in the same way as in method two-way remote measurements, while measurements provided is on one side of the transmission line, i.e. you don't need a TV program recorded current values, but also decreases the accuracy of measuring the distance to the point of earth fault in comparison with the above-described method, remote unilateral measure by eliminating the use of mode options increasing frequency.

According to the development of a method to determine the distance to ground fault in an electrical network with a constant current record integrating locking ammeter 8 the value of a constant current I₁and I₂as the steady-state DC component of the current i(t):

where i_W(t) - secondary pulse current with a linear characteristic of the current transformer 7, for example, with a split magnetic core,

n_TTT_Wa well - known transformation ratio and the time constant of the secondary circuit of this transformer current.

According to another development of the method for determining the distance of a ground fault in an electrical alternating current is fixed by means of the clamping ammeter 8 the modulus value of the alternating current flowing through the earthing switch 6 connected to the network, and the influence of the phase angle between the currents I₁and I₂take into account by successive calculation of the k+1 time relative distance n to the point of snapping, perehodnogo resistance R _pand the phase angle between the currents I₁and I₂as long as the difference between the n_(k+1)and n_kwill not be less than the margin of error of calculation.

These development methods allow you to reduce the amount of measurement equipment for fixing the values of direct and alternating current.

A specific example No. 1 implementation of the claimed invention to determine the distance to the point of earth fault in an electric network DC when melting of ice on a "phase - two phase" shown in schemes 4 and 5. In the wiring diagram figure 4 used the same notation that in figure 1. Circuits for two positions of the connection device 5 are combined in figure 5. Figure 5 indicated:

E_E, R_Ewell - known equivalent EMF and internal resistance of the power supply network with a constant current;

R is known, the resistance of one phase of a transmission line 2;

R_P- unknown contact resistance in place of the circuit.

Unknown value of n is calculated by the formula

where I₁andI₂- fixed value of DC for two positions of the switching device 5 connecting the earth lead 6 sootvetstvenno to point b and A;

To_sh- coefficient depending on the connection diagrams phase the wires of the transmission line. For the scheme "phase - two phase" K_sh=1,5 if locked to earth single phase, as shown in figure 4, when closed on the ground that one or both parallel connected phase To_sh=3.0V. For the scheme "phase - phase" K_sh=2,0.

According to the development of the method for measuring the I₁and I₂use a current transformer 7 is a split magnetic core and integrating clamping ammeter 8.

A specific example No. 2 implementation of the claimed invention to determine the distance to ground fault in an electrical AC when melting of ice on power lines by the method of "two-phase short circuit" shown in schemes 6 and 7. In the wiring diagram 6 used the same notation that in figure 1. Circuits for two positions of the switching device 5 are combined in Fig.7. 7 indicated:

E_E, Z_Ewell - known equivalent EMF and internal resistance of the power source network alternating current;

Z_L, Z_Mwell - known private and mutual resistance line electropedic. Unknown value of n is calculated by the formula

whereand- integrated value of AC for two positions of the switching device 5, the connection is found earthing 6 respectively to the point a and b;

well - known alternating current for melting the ice.

A formula consists of complex values ofandand fixed modules of these currentsandtherefore, to determine n use the proposed development method for electrical networks with alternating current.

According to this developing method, calculated in the first step, the value of n₍₁₎by the above formula. Substituting into it instead of the integrated values of the currents of their modules

The value of n₍₁₎expect resistance:

Because

then in the second step, calculate the angles of phase shift ϕ₁₍₂₎that ϕ₂₍₂₎from the formulas:

and then substitute these values into the formula for n and calculate n₍₂₎. The calculation is repeated k+1 times as long as the difference between the n_(k+1)and n_(k)will not be less than the margin of error of calculation.

Ways is is possible to implement the installation of ice melting DC substation 220 kV "Dagomys" the North Caucasus region.

1. The method of determining the distance of a single-phase ground fault in an electrical network, namely, that when shorted to ground transmission line is measured and remember on the same side of the line alternately, at least two times the value of current flowing through the earthing, and on these values and the known parameters of the electric network calculate the distance to a single-phase earth fault, characterized in that the earthing switch, in which measure and memorize the value of the current, in turn, at least twice, connected to different points of the network to different poles on one side of the line with a constant current or different phases from one side of the line alternating current.

2. The method according to claim 1, characterized in that for fixing the value of the constant current flowing through the ground conductor connected to the electric circuit with constant current using a current transformer with a linear characteristic, the pulse of the secondary current which i_W(t) to restore the primary constant current i(t) in accordance with the formula

where n_TTT_BTthe transformation ratio and the time constant of the secondary circuit of current transformer with a linear response.

3. The method according to claim 1, characterized in that for determining the distance is to the point of earth fault in a network with an alternating current of fixed value module AC passing through the earth lead connected to the network, and the influence of the angle of phase shift between the recorded currents when connecting the earth lead to different points in the network into account by successive calculation of the k+1 time relative distance n to the point of snapping, the transition resistance at the circuit, and the phase angle between the currents as long as the difference between the n_(k+1)and n_kwill not be less than the margin of error of calculation.