Method for location of single-phase ground fault in branched aerial power line with insulated neutral conductor

FIELD: maintenance of aerial power lines with an insulated neutral conductor by contactless method, applicable for mobile location of a single-phase ground fault in a branched aerial power line with an insulated neutral conductor.

SUBSTANCE: the method provides for fixation of an emergency signal, then the electric and magnetic field strengths are measured as an emergency signal in succession in the point of branching and under each branch of the aerial power line, converted to harmonic components of the voltage and current signals proportional to them, with the aid of the Fourier transform for each harmonic the amplitude and the phase angles of the harmonic components of the voltage and current signals are determined, from the sequence of the values of the amplitudes of harmonic components of the voltage and current signals the i-th harmonic component with the maximum amplitudes of harmonic components of the voltage and current signals is separated, comparing them with the proportional maximum allowable amplitudes measured in the normal operating conditions of the power line, and according to the excess of the values of the amplitudes of the components of the voltage and current components of the separated i-th harmonic, the branch with a faulty condition, the direction to the point of the ground fault in it are determined according to the sign of the shift between the harmonic components of the voltage and current signals of the separated i-th harmonic, for the positive sign of the phase shift angle between the harmonic components of the voltage and current signals the direction of search "to the right" corresponds, and for the negative sign of the phase shift angle between the harmonic components of the voltage and current signals the direction of search "to the left" corresponds, the point of ground fault in this branch is determined according to the change of the sign of the phase angle shift between the harmonic components of the voltage and current signals of the separated i-th harmonic, measuring the strengths of the electric and magnetic fields, moving under the aerial power line along the faulty branch.

EFFECT: provided determination of the point of the single-phase ground fault within a short period of time with a high precision and convenience.

1 dwg, 6 tbl

The invention relates to maintenance of power lines with insulated neutral mobile, contactless and can be used to determine where the single-phase earth fault in extensive overhead power lines with insulated neutral.

There is a method of determining the place of single-phase earth fault in extensive overhead power lines with insulated neutral (see A.S. USSR №1413562 MCI), which fix the emergency signal containing harmonic components of the signal of known frequency f₀and the total interference transform alarm signals in voltage and current, advanced form of auxiliary signals, with their help transform the voltage signals and current amplified converted the alarm and using the Fourier transform get a sequence of values of the amplitudes of the voltages and currents of these harmonic components, which are judged on results.

In this way fix the alarm contact measuring voltage and current of the alarm and the total interference at the substations at which the measurement is carried out at a high voltage, which leads to stationary, bulky, power-consuming and expensive equipment, and the lack of automatic selection of the optimal frequency harmonic components of the signal reduces the accuracy of metering the deposits.

There is also known a method of determining the location of single-phase earth fault in extensive overhead power lines with insulated neutral (see kN.: Kuznetsov A.P. Determination of faults on overhead transmission lines. - M.: Energoatomizdat, 1989. - 94 S.: ill.), used as a prototype, which is fixed alarm with sensors electric and magnetic fields, containing harmonic components of the signal. From alarm allocate the 11th harmonic, the harmonic signal components of voltage and current increase and served on panoramicasul scheme, whichever are in opposite or the same signals of current and voltage arrow milliammeter, with zero in the middle of the scale, is deflected in the direction to the location of the ground fault.

In this way fix the alarm contactless measurement of harmonic components of the voltage signals and current alarm mobile method, i.e. moving under overhead power lines along its branches.

The main disadvantage of this method is the lack of automatic selection of the optimal frequency harmonic components of the signal. Analysis is possible only at frequencies for which there are filters. Analog processing methods harmonic components of the signal lead to complex and energem the th equipment, which leads to the increase of time searching for the location of the damage, as well as to the complexity of operation of the measuring equipment because of the larger number of controls and settings.

The authors were tasked to create a mobile, fast way to determine where the single-phase earth fault in extensive overhead power lines with insulated neutral, which is fixed alarm contactless measurement of harmonic components of the voltage signals and current moving under overhead power lines along its branches, and to ensure, through the introduction of automatic selection of the optimal frequency harmonic components of the signal, high accuracy and ease of measurement by use of numerical methods for the analysis of harmonic components of the signal.

The aim of the invention is to improve the speed, accuracy and ease of determining the place of single-phase earth fault in extensive overhead power lines with insulated neutral.

This objective is achieved in that the method of determining the location of single-phase earth fault in extensive overhead power lines with insulated neutral, which is fixed emergency signal containing harmonic components using the Fourier transform of the alarm receiving a sequence of values amplit the d and phases of harmonic components of signals of voltage and current, they will judge the results,

the novelty of that

consistently in location of branches and each branch overhead power lines as an emergency signal to measure the strength of the electric and magnetic fields transform them into them proportional harmonic components of signals of voltage and current, using a Fourier transform for each harmonic determine the amplitudes and phase angles of the harmonic components of signals of voltage and current, from the sequence of values of the amplitudes of the harmonic components of the voltage signals and current i allocate harmonic component with the maximum amplitudes of the harmonic components of signals of voltage and current, comparing them with proportional to the maximum amplitude measured during normal operation, power lines, and the excess values of the amplitudes of the harmonic components of the voltage signals and current i selected harmonics determine the branch with the emergency mode, the direction to the place of earth fault in it is determined by the sign of the phase angle between the harmonic components of the voltage signals and current i selected harmonics, while the positive sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “right”and for the negative sign of the angle is the phase shift between the harmonic components of the voltage signals and current corresponds to the search direction “left”, and the location of the earth fault in this branch is determined by the change of sign of the phase angle between the harmonic components of the voltage signals and current i selected harmonics, measuring the strength of the electric and magnetic fields moving under overhead power lines along the branches from the emergency mode.

The invention is illustrated as follows.

To determine the direction to the location of the ground fault record emergency signal containing harmonic components sequentially in place of branches and each branch overhead power lines. As an emergency signal to measure the strength of the electric and magnetic fields, which convert so as to provide automatic selection of the i-th frequency with maximum amplitudes of the harmonic components of signals of voltage and current. Compare the settings of the selected i-th harmonic of the maximum amplitudes of the harmonic components of the signal voltages and currents proportional to the maximum amplitudes of harmonic components of signals of voltage and current in the normal mode, power lines, and the excess values of the amplitudes of the harmonic components of the signal voltages and currents i selected harmonics determine the branch with the emergency mode, the direction to the place of earth fault in it is determined by the sign of the phase angle between the harmonic components of the voltage signals and current i selected harmonics, for the positive sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “right”and for the negative sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “to the left”, the place of earth fault in this branch is determined by the change of sign of the phase angle between the harmonic components of the voltage signals and current i selected harmonics.

The maximum amplitude of the harmonic components of signals of voltage and current determine in normal operation, overhead power lines, measuring the strength of the electric and magnetic fields and converting them into them proportional harmonic components of signals of voltage and current sensors magnetic and electric fields.

After performing a Fourier transform of the receive and memorize the series of values of amplitudes and phases of harmonic components of signals of voltage and current for a number of harmonics. To find the optimal number of harmonics with maximum amplitudes of the harmonic components of the voltage signals and current vector put the number of the amplitudes of the harmonic components of the voltage signals with amplitudes of harmonic components of the current signals. In the resulting series of values nachtergaele and the corresponding harmonic number. For this number of harmonics remember amplitude and phase of harmonic components of signals of voltage and current in emergency mode. If the resulting value of the i-th harmonic component with the maximum amplitudes of the harmonic components of the voltage signals and current in emergency operation exceeds proportional to the maximum amplitude of the harmonic components of the voltage signals and current in normal mode, it indicates a ground fault on this exhaust overhead power lines.

If this exhaust overhead power lines detected ground fault, then the number of harmonics corresponding to the i-th harmonic component of the signal with the maximum amplitudes of the harmonic components of signals of voltage and current in emergency mode, there are the phase angle of the harmonic component of the voltage signal and the phase angle of the harmonic component of the signal current from the ranks of the values of the phase angles of the harmonic components of signals of voltage and current. Direction to the place of the circuit is determined by the sign of the phase angle between the harmonic components of signals of voltage and current for the memorized number of harmonics in emergency mode.

According to the experimental data for the positive sign of the phase angle between the harmonic components of the voltage signals is I and the current corresponds to the direction of the search “right”, and for the negative sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “to the left”.

In the process of patent information research in the field of electrical equipment intended for maintenance of power lines, identical solutions were not found.

The method is as follows.

In normal operation, power lines, measure and record the electric and magnetic fields. The measurements were carried out at a safe distance equal to 8-10 m from the axis projection of power lines on the ground.

Recorded signals is converted into a proportional im harmonic components of the signal voltages and currents. Using the Fourier transform of the harmonic components of the voltage signals and the current is converted into a sequence of values of amplitudes and phase angles of the harmonic components of signals of voltage and current, from which i allocate harmonic component with the maximum amplitudes of the harmonic components of signals of voltage and current. The value of the maximum amplitudes of harmonic components of signals of voltage and current corresponding to the electric and magnetic fields in normal mode, take the reference and record.

After receiving information about the presence of the single is testing the ground fault from the substation brigade repair and maintenance of power lines sets, what is the exhaust from the substation transmission line has been shorted to ground. To do this, sequentially, starting from the substation and under each branch of the air hvtl, and then places the branching measure and record the electric and magnetic fields. The measurements were carried out at a safe distance equal to 8-10 m from the line axis projection of power lines on the ground.

Fixed tensions emergency signal is converted into a proportional im harmonic components of signals of voltage and current sensors magnetic and electric fields. Using the Fourier transform of the harmonic components of the voltage signals and the current is converted into a sequence of values of amplitudes and phase angles of the harmonic components of signals of voltage and current, from which allocate the i-th harmonic component with the maximum amplitudes of the harmonic components of signals of voltage and current. Compare i-th harmonic component with the maximum amplitudes of the harmonic components of the voltage signals and current in emergency mode is proportional to the maximum amplitude measured during normal operation of power lines.

On ground fault on this exhaust branch transmission lines indicates the exceeding of the maximum amplitudes of the harmonic components of the voltage signals is I and the current measured in the normal operating mode of the transmission line. Next, the number of harmonics corresponding to the i-th harmonic component of the signal with the maximum amplitudes of the harmonic components of signals of voltage and current in emergency mode, there are the phase angle of the harmonic component of the voltage signal and the phase angle of the harmonic component of the signal current from the ranks of the values of the phase angles of the harmonic components of the signal voltages and phase angles of the harmonic components of the current signals. Direction to the place of the circuit is determined by the sign of the phase angle between the harmonic components of signals of voltage and current, while the positive sign of the phase angle between the harmonic components of signals of voltage and current correspond to the search direction “right”and for the negative sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “to the left”.

When known damaged branches, power lines, such as instrument readings that are installed on the feeding substation, the search space earth fault you can start with damaged branches. Team on duty machine moves to any place of forking branches with alarm signal, which produces measure the electric and magnetic fields. As Dutch is ing magnetic field, you can use an inductor with a disconnected magnetic core, and as a sensor of the electric field zero-sequence - telescopic antenna or metal plate. Recorded signals transform and obtain the search direction. Towards the place of circuit judge whether the branch should move to the next branching branches with alarm.

If, in a subsequent branching branches with alarm the search direction points to the previous measurements, the location of the circuit located between the two measuring points. Moving along the line, follow the direction of the search. The point to change the search direction indicates the location of the ground fault.

The drawing shows extensive overhead power lines with insulated neutral, extending from the transformer substation.

In points 1, 2, 3, 4, 5 measurements of the emergency signal at regular intervals of time within 20 MS. This has resulted in a 32-point signal. The received signal was decomposed into a spectrum of amplitudes and phase angles of the harmonic components of signals of voltage and current. The spectrum contains 16 pixels.

To find the optimal harmonics with maximum amplitudes of the harmonic components of signals of voltage and current vector put the number of the amplitudes of the harmonic components of the voltage signals from recomendated harmonic components of the current signals. In the resulting series of values to find the maximum value and the corresponding harmonic number. For this number of harmonics are phase angle between the harmonic components of signals of voltage and current. Direction to the place of the circuit is determined by the sign of the phase angle between the harmonic components of signals of voltage and current, i.e. for a positive sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search "right"and for the negative sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search "to the left".

The obtained data of measurements and calculations are summarized in tables 1-6.

The proposed method of determining the place of single-phase earth fault in extensive overhead power lines with insulated neutral allows for a short period of time with high accuracy and convenience in comparison with previously known methods of determining the place of single-phase earth fault in extensive overhead power lines with insulated neutral to determine the location of a single-phase circuit.

In comparison with previously known methods of determining the place of single-phase earth fault in extensive overhead power lines with isolated neutral the proposed method enables you to search and what to predelete place single-phase circuit from any point, extensive overhead power lines with insulated neutral.

The method of determining the location of single-phase earth fault in extensive overhead power lines with insulated neutral, which is fixed emergency signal containing harmonic components of different frequencies, which transform using the Fourier transform in the sequence of the values of the amplitudes of the voltage and current of these harmonic components of different frequencies, which are judged on results, wherein sequentially in place of branches and each branch overhead power lines as an emergency signal to measure the strength of the electric and magnetic fields transform them into them proportional harmonic components of signals of voltage and current, using a Fourier transform for each harmonic determine the amplitude and phase the angles of the harmonic components of signals of voltage and current, from the sequence of values of the amplitudes of the harmonic components of the voltage signals and t is ka allocate the i-th harmonic component with the maximum amplitudes of the harmonic components of signals of voltage and current, comparing them is proportional to the maximum amplitude measured during normal operation, power lines, and the excess values of the amplitudes of the harmonic components of the voltage signals and current of the selected i-th harmonic, determine the branch with the emergency mode, the direction to the place of earth fault in it is determined by the sign of the phase angle between the harmonic components of the voltage signals and current of the selected i-th harmonic, while the positive sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “right”and for the negative sign of the phase angle between the harmonic components of the voltage signals and current corresponds to the direction of the search “to the left”, the place of earth fault in this branch is determined by the change of sign of the phase angle between the harmonic components of the voltage signals and current of the selected i-th harmonic, measuring the strength of the electric and magnetic fields moving under overhead power lines along the branches from the emergency mode.