Method of measuring remoteness of single-phase short circuit in three-phase power line

FIELD: electrical measurement technology.

SUBSTANCE: first phase with damage insulation is found and power line is switched off of three-phase power line. Second and third phases with non-damaged insulation are closed to ground by means of jumpers at beginning and end of power line at known distance from start point of power line. Single-phase ac source is removed from beginning of power line between first phase with damaged insulation and ground. Voltage between first phase with damaged insulation and ground at beginning of power line is measured, then current is measured in first phase as well as phase angle between the voltages and current. After it distance to single-phase short-circuit is determined.

EFFECT: increased precision of measurement.

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The invention relates to electric networks, namely a three-phase transmission lines with isolated or compensated neutral and unilateral power, and can be used, for example, to determine the distance of a single-phase earth fault in three-phase power lines for power supply Autolock on electrified Railways.

Especially the performance and operation of high voltage transmission lines for power supply Autolock on the Railways is described in [1]. These three-phase transmission lines are isolated in the case of unilateral power.

The first feature of the three-phase power lines for power supply Autolock Railways compared with three-phase power lines other purpose is the fact that for 20-40 km to its wires at intervals of 1-3 km connect single-phase load. Each connection point is attached to only one load. For balancing the transmission line load at different locations connected to different phases. However, in this number due to the different power loads and their changes in time of the complete symmetry is not achieved. Download a different phase of such a transmission line may differ by 10-30 percent, which is many times revised the asymmetry of the three-phase power lines for other purposes.

The second feature are small differences in the values of current remote short circuit of the load current. So, under normal load phases 4-6 and wires type PSO-5 current deaf short circuit due to damage at the end of the transmission line is 6-10 And, if the closure occurs through transient resistance, and even less [1].

The third feature is that when the remote closures, as long transmission lines and small values of the currents) currents transverse capacitive conductivity between the phase with damaged insulation and phase with intact insulation to be commensurable with the short circuit current.

The fourth feature is that on electrified Railways single-phase AC power line to supply the Autolock is close to the contact network. Single-phase contact network brings all the wires of this line is approximately the same voltage due to electromagnetic effects. This effect is significantly greater than from any other three-phase transmission line.

These features can significantly affect the accuracy of determining the distance of a single-phase earth fault on the parameters of the emergency mode. It is known that in a network with isolated neutral parameters ABAP is logo mode when the circuit of one phase to ground (phase or line voltages and currents at the beginning of the line) do not have any information about the remoteness of damage. Therefore, the measurement of the parameters of the emergency mode with a three-phase transmission line with single-phase earth fault in the forced transfer mode single-phase short circuit by connecting the zero point of the supply transformer with earth [1, C. 120].

The essence of the method is illustrated in figure 1. To justify the way are 2 and 3.

There is a method of determining the distance of the fault location isolation of a single phase transmission line by a ground fault zero point of the transformer supplying the three-phase power supply line for power supply Autolock, measurement of the phase voltage U₁and current I₁wires with damaged insulation and calculate the parameter Z₁by the formula

on the basis of which to judge the distance of the fault location isolation [1, S. 121 and 122].

Also known variant of this method of determining the distance of the fault location isolation by earth fault not the zero point, and the other phase with intact insulation, measure the line voltage U₁₂between these phases and the current I₁wires with damaged insulation and calculate the parameter Z₁₂by the formula

on the basis of which the judge about the remoteness of the damage from the Azii [2].

Both variants of this method have one major drawback, namely, that when shorted to ground through a large contact resistance proportionality between the parameter Z₁or Z₁₂and the distance to the fault disappears, the error in determining the distance of the damage becomes very large and does not provide the required accuracy and reliability of measurements [1, p.123].

There is a method of determining the distance of the fault location isolation of a single phase transmission line with grounded neutral by measuring the voltage U, current I and the phase angle ϕ between them and the calculation of the parameter N by the formula

on the basis of which the judge about the remoteness of damage to insulation, and as the voltage of the U phase voltage is used, and as the current I - value I=I_f+C₀3I₀where I_f- phase current wires with damaged insulation, I₀- current zero-sequence, K₀- compensation coefficient current zero-sequence [3, p.6-8].

The error in the determination of remoteness of damage in the presence of contact resistance in this way, compared with the previous reduced. However, the error due to the presence of asymmetric, irregularly connected loads, currents priest who echnol capacitive and inductive conductivity of a contact network influence remains quite large.

There is a method of determining the distance of a single-phase circuit three-phase transmission line [4], in which the following sequence of operations: determine the first phase transmission lines with damaged insulation shutting on the ground, disconnect the power line from the power source; perimysium between a short-circuited wire of the first phase with damaged insulation and the second phase with intact insulation at the end of the transmission line at a known distance L from the power source with a jumper; unlock the feeding end of the third phase with intact insulation using, for example, a switching device; connect the earth wire of the third phase with intact insulation in the beginning and the end of the transmission line jumpers; connect to ground zero point or the conclusion of the second phase with intact insulation power source through a switching device; connecting the first phase with damaged insulation and the second phase with intact insulation to the power source; measure voltage U₁₂on the findings of a power source between the first phase with damaged insulation and a second phase with intact insulation, as well as the values of the currents I₁and I₂these phases; determine length l_kto place single-phase circuit according to the formula

where L is the distance from the power source to the opposite end of the line;

z - resistivity direct sequence 1 km of three-phase transmission line.

This method is adopted as a prototype, it provides higher accuracy than the previous one, but when using it, there are errors due to the fact that the currents I₁and I₂stored components, due to single-phase loads connected between the first phase with damaged insulation and a second phase with intact insulation, and also due to the presence of capacitive cross conduction between the first and second phases, and between the second phase and earth.

The technical result is to increase the accuracy of determining the distance of the place of single-phase earth fault.

The invention consists in that for determining the distance of the place of single-phase ground fault three phase transmission lines with isolated or compensated neutral one-way powered emergency settings mode by determining the phase with damaged insulation, turn off the power line, connect to the first phase with damaged insulation of one of the poles of the power source and measurement parameters emergency mode in case of single-phase earth fault on Oprah is elaut the first phase with damaged insulation, disconnect the transmission line from a source of three-phase voltage close to the ground the second and third phases with intact insulation with the help of jumpers at the beginning and end of the transmission line at a certain distance from its beginning, include at the beginning of the transmission line between the first phase with damaged insulation and ground source single-phase AC voltage, measure the voltage between the first phase with damaged insulation and earth at the beginning of the transmission line, the current in the first phase and the phase angle between voltage and current, set the value of the constant coefficients a and b depend on the specific parameters and the length of the transmission line, according to the formula

and determine the distance to a single-phase earth fault by the formula

where x₁a well - known value of the inductive component of the resistivity contour wire single phase-to-ground, Ohms/km;

z₂₃a well - known modulus value of specific resistance of the path is equivalent to wire two phase-to-ground, Ohms/km;

α₂₃a well - known argument value of specific resistance of the path is equivalent to wire two phases-land”,⁰e.;

z_ma well - known modulus value of specific resistance of mutual induction between TLDs what I circuits wire-to-ground, Ohm/km;

α_ma well - known argument value of specific resistance of mutual induction between two circuits wire-to-land”,⁰e.;

L is the known distance from the beginning to the end of the transmission lines, km;

l_to- determine the distance from the beginning of the line to place single-phase circuit, km;

U is the measured voltage between the first phase with damaged insulation and earth at the beginning of the line, In;

I₁- the measured value of the current of the first phase with damaged insulation, And;

ϕ - the measured value of the phase angle between voltage U and current I₁,⁰e.

Parameters x₁, z₂₃that α₂₃, z_mthat α_mdepend on the design of the transmission line and the brand used wires. For each line the values of these parameters are known.

The invention is illustrated by the scheme shown in figure 1. In the diagram, the following notation:

1 - the first phase transmission lines with damaged insulation at the point K on the destruction of l_kfrom the three-phase power source;

2, 3, respectively the second and the third phase transmission lines with intact insulation;

4 - three-phase power source;

5 - switch three-phase;

6, 7, 8, 9, respectively, the first, the WTO is Aya, the third and fourth grounding straps;

10 is a three - phase disconnector;

11, 12 - additional jumper;

13 - source single-phase AC voltage.

When shorted to ground at a point To the wires of the first phase 1 with damaged insulation perform the following operations:

1) define the first phase transmission lines with damaged insulation shutting on the ground, in a known manner, for example, by means of three voltmeters [1, s];

2) disconnect the power line from the power source 4 in a known manner by means of a three-phase switch 5 and switch 10;

3) close to the earth phase 2 and 3 with intact insulation in the beginning and end of a transmission line with jumpers 6, 7, 8, 9;

4) include at the beginning of the transmission line between the first phase with damaged insulation and ground source single-phase AC voltage, for example, 13;

5) measure voltage between the first phase with damaged insulation and earth at the beginning of the transmission line, the current in the first phase and the phase angle between voltage and current;

6) set the value of the constant coefficients a and b depend on the specific parameters and the length of the transmission line, according to the formula

7) determine the distance to a single-phase earth fault by the formula

where x₁a well - known value of the inductive component of the resistivity contour wire single phase-to-ground, Ohms/km;

z₂₃a well - known modulus value of specific resistance of the path is equivalent to wire two phase-to-ground, Ohms/km;

α₂₃a well - known argument value of specific resistance of the path is equivalent to wire two phases-land”,⁰e.;

z_ma well - known modulus value of specific resistance of mutual induction between two circuits wire-to-ground, Ohms/km;

α_ma well - known argument value of specific resistance of mutual induction between two circuits wire-to-land”,⁰e.;

L is the known distance from the beginning to the end of the transmission lines, km;

l_k- determine the distance from the beginning of the line to place single-phase circuit, km;

U is the measured voltage between the first phase with damaged insulation and earth at the beginning of the line, In;

I₁- the measured value of the current of the first phase with damaged insulation, And;

ϕ - the measured value of the phase angle between voltage U and current I₀,⁰e.

Operations 1, 2, 4 are known, the remaining operations are new. A positive effect (increasing precision) is achieved by simultaneous disconnection from source PI is project lead wires 2 and 3 with intact insulation and connecting them with the earth at the beginning and end of the line, when you do this:

- disables all, without exception, single-phase and three-phase consumers, which excludes the presence of a component of the load current I₁;

- completely eliminates the capacitive effect of the transversal conductivity, therefore, the component of the leakage current in the current I₁no;

- increases the shielding action of grounded wires 2 and 3, since there are two of them, which reduces the resistance of the screen and reduces the inductive influence of the contact network [5, s-436];

- eliminates the effect of arc resistance or contact resistance in the damaged spot on the accuracy of determining the distance of the earth fault. The proposed method will still work if the earth close, not two, but only one phase with intact insulation (second or third). However, the accuracy of the l_kthis reduces. When shorted to ground, only one phase with intact insulation in the formula for determining And should be replaced by z₂₃at z₁and α₂₃on α₁.

Justification of the method

The rationale of the proposed method is based on the diagrams in figure 2 and figure 3, where indicated:

1 - the first phase (wire) transmission lines with damaged insulation at the point K on the destruction of l_kfrom the power source (beginning of line);

2, 3, respectively W heaven and the third phase (wire) transmission line of length L with intact insulation;

4 - source single-phase AC voltage;

23 is equivalent to wire two phases (second and third) with intact insulation.

Specific resistance of 1 km loop wire single phase-earth” denotes z₁. As for the wires any three-phase line is a transposition, then the coefficients of mutual induction M and the resistance of the mutual induction z_mfor each pair of paths accepted the same. Formulas for calculating values of z₁and z_mgiven in [5, 6].

Calculation circuit transmission line with ground fault phase 1 at the point To and disconnected from the three-phase power source phases 2 and 3, closed on the ground at the beginning and end of the transmission line shown in figure 2,and. While phases 2 and 3 are connected in parallel. It is known that two circuits wire-to-earth” can be replaced with a single path is equivalent to wire two phase-to-ground [5]. Due to the transposition of the wires of the transmission line inductive effect of the current I₁phase 1 with damaged insulation on the wires phases 2 and 3 equally, so the impedance z₂₃path is equivalent to wire two phase to ground is.

Settlement scheme, in which the wires 2 and 3 are replaced by an equivalent 23 shown in figure 2,B. Consider two circuits, the first of which includes the source 4,the wire 1, place the circuit To the earth and the source 4, and the second is path equivalent to wire two phase - to-ground. For them, fair the following equations in accordance with the second law of Kirchhoff

where I₁, I₂₃- currents of wires respectively 1 and 23;

R_d- contact resistance in place of the circuit.

The value of the current in the ground on a plot of l_k. let I_N. Obviously

Using expression (2) in the first equation of system (1) exclude I₂₃and the second I₁. Get

This system of equations corresponds to the equivalent circuit shown in figa, which is converted in the diagram shown in figb, where

For the circuit shown in figb, in accordance with the second Kirchhoff's law and taking into account expressions (4) are

Denote

Taking into account the notations (6), we have instead of (5)where

Becausewhere I₁that ϕ - module and argument of the complex value; z_ethat α - module and argument of the complex value z_ethen, using fo the mule Euler, instead of (7) we get

Since l_toreal by definition, the member with the factor j is equal to zero, i.e. Usin(ϕ-α)+I₁R_dsinα=0. It follows

Since l_tomaterial, taking into account the expression (8) we get

where x_e- inductive resistance component z_e.

The value of x_eis determined from the expression (6):

where

Substituting equation (10) in (9), we obtain the quadratic equation, the solution of which has the form

Given the expression (11), we denote

which coincides with the expressions for a and b given in the claims. Substituting expression (13) in (12), we obtain

which coincides with the expression for l_todescribed in the claims.

This proves the principle of operation and performance of the proposed method.

Sources of information

1. Herman L.A., Veksler M.I., Solomon I.A. Device and the supply line Autolock. M: Transport; 1987. 192 C.

2. Figurov H.E., Taptykov E.G. the Definition of the remoteness of the circuits in high-voltage lines Autolock. //Relay protect the TA and automation devices supply rail./ Interuniversity collection of scientific works. VIP. Rostov-on-don, RIIGHT. 1978. S-86.

3. Eisenfeld A.I., Aronson, VN, The głowacki VG Locking indicator of the resistance of the FIS. - M.: Energoatomizdat, 1987. - 64 S.

4. RF patent №2186404. Methods and apparatus for determining the distance of a single-phase circuit three-phase transmission line (options).//Figurov H.E., Bochev A.S., Bodrov P.A./ CL 7 G 01 R 31/08, the Application 11.04.2001 No. 2001109809/09 (0102263). Epubl, Bull.№21.

5. Marquardt's CG the Supply of electric Railways. M.: Transport, 1965. 464 S.

6. Losev D.B, Chernin A.B. Calculation of electrical parameters in single-ended modes of electrical systems. M.: Energoatomizdat, 1983. 528 S.

The method of determining the distance of the place single-phase circuit three-phase transmission lines with isolated or compensated neutral and unilateral power by determining the phase with damaged insulation, turn off the power line, connect to the first phase with damaged insulation of one of the poles of the power source and measurement parameters emergency mode, wherein when the occurrence of single-phase earth fault define the first phase with damaged insulation, turn off the power line from the source of three-phase voltage close to the ground the second and third phases with intact insulation with the help of jumpers in the beginning and the end of the transmission line at a certain distance from its beginning, include at the beginning of the transmission line between the first phase with damaged insulation and ground source single-phase AC voltage, measure the voltage between the first phase with damaged insulation and earth at the beginning of the transmission line, the current in the first phase and the phase angle between voltage and current, set the value of the constant coefficients a and b depend on the specific parameters and the length of the transmission line according to the formula

and determine the distance to a single-phase earth fault by the formula

where x₁a well - known value of the inductive component of the resistivity contour wire single phase-to-ground, Ohms/km;

z₂₃a well - known modulus value of specific resistance of the path is equivalent to wire two phase-to-ground, Ohms/km;

α₂₃a well - known argument value of specific resistance of the path is equivalent to wire two phase to ground alrd.;

z_ma well - known modulus value of specific resistance of mutual induction between two circuits wire-to-ground, Ohms/km;

α_ma well - known argument value of specific resistance of mutual induction between two circuits wire-to-earth", lgrad.;

L is the known distance from the beginning to the end of the transmission lines, km;

l_to- determine the distance from the beginning of the line to place single-phase circuit, km;

U is the measured voltage between the first phase with damaged insulation and earth at the beginning of the line, In;

I₁- the measured value of the current of the first phase with damaged insulation, And;

ϕ - the measured value of the phase angle between voltage U and current I₁, elsrud.