Method for locating single-phase ground fault in three-phase power transmission line

IPC classes for russian patent Method for locating single-phase ground fault in three-phase power transmission line (RU 2244941):

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

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FIELD: instrumentation engineering; three-phase single-ended insulated- or compensated-neutral supply mains.

SUBSTANCE: proposed method involves detection of first failed phase on occurrence of single-phase ground fault, disconnection of power-transmission line from power supply, shorting-out of first failed phase and conductor of second serviceable phase at certain distance in end of power transmission line, grounding of neutral point of power supply or lead of one of its serviceable phases, connection of power transmission line to power supply, and measurement of emergency parameters. Chosen out of emergency parameters are current through first failed phase, current through second serviceable phase, and phase angles of these currents relative to voltage between mentioned first and second phases. Distance to point of single-phase ground fault is found from expression interrelating mentioned parameters.

EFFECT: enhanced measurement accuracy, facilitated location of single-phase ground fault.

1 cl, 1 dwg

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, including due to the different power loads and their changes over time, 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 ground fault is switched to the mode of the single-phase short circuit by connecting the zero point of the supply transformer with the ground or in the mode of two-phase short circuit to earth by connecting with earth a different phase with intact insulation.

The essence of the proposed method is illustrated by a drawing.

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 Z₁according to the formula

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

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, measurement of 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 insulation [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, I_about- current zero-sequence. To₀- compensation coefficient current zero-sequence [3, 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 is C-unbalanced, unevenly connected loads, currents transverse capacitive and inductive conductivity of a contact network influence remains quite large.

The known method 1 determine 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, grounding to the ground zero point or one of the intact phases of the power source and measurement parameters emergency mode, in which the following sequence of operations [4]:

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

2) disconnect the power line from the power source in a known manner by means of a three-phase circuit breaker;

3) 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 certain distance from the power source with a jumper;

4) unlock the feeding end of the third phase with intact insulation using, for example, a switching device;

5) connect the earth wire of the third phase with intact and what Alecia at the beginning and end of the transmission line jumpers;

6) is connected to the ground zero point or the output M of the second phase with intact insulation power source through a switching device, and the point M can be located either on the right or left of the switch;

7) connect the first phase with damaged insulation and the second phase with intact insulation of the transmission line to the power supply using the switch;

8) measure the voltage at the terminals of the power source between the first phase with damaged insulation and a second phase with intact insulation, as well as the value of the currents of the wires of these phases, using current transformers and voltage transformer;

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

where U₁₂the voltage at the terminals of the power source between the first phase with damaged insulation and a second phase with intact insulation;

I₁-current of the first phase with damaged insulation;

I₂the current second phase with intact insulation;

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

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

The disadvantages of this method are:

1) the complexity of the implementation and the complexity of the algorithm. The complexity of implementing zaklyuche which are necessary to install three jumper and converted a three-phase separator (10, 11, 12 figure 1 of the patent [4]), since the known method 1 assumes that each phase of the disconnector has an individual drive and can be opened or closed regardless of the position of the disconnector in other phases (phase control). At the same time, the high-voltage disconnectors transmission line for power supply Autolock equipped with a standard three-phase disconnectors, all the phases of which are controlled by one actuator and can be either all on or all off [1]. The industry produces three-phase circuit breakers for a voltage of 6-10 kV (this voltage is applied in the above-mentioned transmission lines) with phase control.

2) the complexity of the algorithm is that in the numerator and the denominator requires operations with vector quantities.

In the proposed invention is applied typical three-phase disconnector, the third phase transmission lines with intact insulation separately from the other two phases is not turned off, instead of the three used only one jumper, see formula (algorithm) to calculate the distance to the fault takes into account all peculiarities of the electric circuit, is obvious and new, provides high accuracy.

The technical result is to increase accuracy and simplify the definition of the remoteness of defesnive 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 by determining the phase with damaged insulation, earth fault zero point or one of the intact phases of the power source, shorting at the end of the line short-circuited wires faulted phase and the second of the intact phases and measurement of parameters of the emergency mode, when a single-phase earth fault define the first phase with damaged insulation, turn off the power line from the power source at a known distance at the end of the transmission line perimysium between a short-circuited wire of the first phase with damaged insulation and the wire of the second phase with intact insulation, connected to the ground zero point or the conclusion of the third phase of the power source, connect the power line to the power supply, measure the current of the first phase with damaged insulation, the current second phase with intact insulation and phase angles of these currents relative to the voltage between the said first and second phases of the transmission line, and determine the distance to a single-phase earth fault by the formula:

where l_k- be the tion from the supply end to place single-phase short circuit;

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

I₁module current of the first phase with damaged insulation;

ϕ₁is the phase angle of the current I₁relative voltage between the first and second phases;

I₂module current second phase with intact insulation;

ϕ₂is the phase angle of the current I₂with respect to the same voltage;

α - the argument is dependent on the design parameters of a transmission line.

The invention is illustrated in the drawing, where the following notation:

1 - wire of the first phase with damaged insulation of the transmission line;

2, 3 - wire, respectively, the second and third phase with intact insulation of the same transmission line;

4 - power;

5 - three-phase circuit breaker;

6 - three-phase disconnector;

7 - switching device;

8, 9, 10 - transformers;

11 - voltage transformer;

12 - jumper (zahratka).

When shorted to ground at a point To the wires of the first phase 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 by means of three voltmeters connected to the voltage transformer [1, s];

2) disable the line e is peredachi from the power source 4 in a known manner by using a three-phase switch 5 and switch 6;

3) perimysium between a short-circuited wire of the first phase 1 with damaged insulation and the second phase 2 with intact insulation at the end of the transmission line at a known distance L from the power source 4 with a jumper 12;

4) is connected to the ground zero point of the power source 4 or (shown dotted) output M of the third phase with intact insulation of this source using a switching device 7, and the point M can be located on both the left and right of the disconnector 6;

5) include the switch 6 and the switch 5;

6) measure the current of the first phase with damaged insulation, the current second phase with intact insulation and phase angles of these currents relative to the voltage between the said first and second phases of a transmission line using a measuring current transformers 9,10 and voltage 11;

7) determine the distance to a single-phase circuit using the above formula.

Operations 1, 2, 4, 5, operation 3, 6, and 7 are new.

The positive effect is due to two interrelated factors: the simultaneous exclusion of operations (a) - disconnection of the supply end of the third phase with intact insulation and the installation of two grounding jumpers in this phase at the beginning and end of the line and b) use a different formula (alternative algorithm for computing removed the barb damage). The destruction of the prototype of such essential characteristics as “unlock the feeding end of the third phase with intact insulation and connect it to the ground near the power source and at the opposite end of the transmission line leads to the necessity to use a new significant feature - mentioned formula to determine the distance of the damage. When this new type of formula (algorithm) is not obvious and is new.

The proposed method and the formula (algorithm) determine the distance of the place of single-phase earth fault completely rebuilt (insensitive) from electromagnetic influence of the contact network and the transition resistance at the injury site. As is known, these two factors cause the largest error in determining the distance of the fault location in transmission lines for power supply Autolock, reaching 100 percent or more. The proposed method for these factors does not respond, what ensures its high accuracy.

The possibility of carrying out the invention is ensured by the fact that the method operates well-known technical means without their reconstruction in comparison with typical designs (switch, circuit breaker, switching device, the current transformers and voltage, wire line, the power sources in the form of the transform is ora). The proposed formula (algorithm) contains only simple operations of elementary mathematics, easy to implement modern microprocessors.

Theoretical justification of the formula (algorithm) given in the Appendix.

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. In kN. Relay protection and automation devices supply rail. Interuniversity collection of works. Rostov Institute of engineers W-d transport, VIP. Rostov-on-don, RIIIT, 1978, s-86.

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

4. Patent RU 2186404. Methods and apparatus for determining the distance of a single-phase circuit three-phase transmission line (options). /Appguru, Associ, Pastrav. CL. 7 G 01 R 31/08. No. 2001109805/09. Appl. 11.04.2001, publ. 27.07.2002, bull. No. 24.

The method of determining the distance of the place of single-phase ground fault in a three-phase transmission lines with isolated or compensated neutral one-way powered by determining if the occurrence of single-phase earth fault in the first phase with handicapped the insulation, disconnect the transmission line from the power source, shorting between a short-circuited wire of the first phase with damaged insulation and wires of the second phase with intact insulation on a known distance at the end of the transmission line, connected to the ground zero point of the power source or the output of one of its phases with intact insulation, connect the transmission line to the power source and measurement parameters emergency mode, characterized in that as the intact phase, connected to the earth, choose the third phase with intact insulation, and of the parameters of the emergency operation measure the current of the first phase with damaged insulation, the current second phase with intact insulation and phase angles of these currents relative to the voltage between the said first and second phases of the transmission line, the distance to the place of single-phase ground fault is determined by the expression

where l_to- the distance from the feeding end to the place single-phase circuit,

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

I₁module current of the first phase with damaged insulation,

ϕ₁is the phase angle of the current I₁relative voltage between the first and second phases,

I₂module is Oka second phase with intact insulation,

ϕ₂is the phase angle of the current I₂with respect to the same voltage,

α - the argument is dependent on the design parameters of a transmission line.