RU2361229C1 - Method of determining cable fault site - Google Patents

Abstract

FIELD: physics; measurement.

SUBSTANCE: invention relates to electrical measurement techniques and can be used for determining site of damage in a cable. A test sinusoidal signal with frequency f is transmitted from a highly stable generator between the cable jacket and earth. A sensor is moved along the cable. At the receiving part the test signal with frequency f is recorded and compared with a signal at the same frequency from a highly stable reference generator, pre-synchronised with the driving generator. Difference in phase between the signal from the reference generator and signal recorded above the cable using the sensor is determined. Damage to the cable is determined from the change in phase difference between signals.

EFFECT: increased accuracy and efficiency of determination of site of damage in a cable.

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Description

The invention relates to electrical engineering and can be used to determine the location of cable damage.

A known method for determining the fault location of a core in a cable line, according to which an alternating current of the main frequency is applied to the damaged core at one end of the cable line, the main frequency signal and the auxiliary frequency signal are extracted over the cable line path, the selected signals are converted to signals with the same frequency and fixed phase shift of the converted signals. By changing the angle of the phase shift, one can judge the place of damage. (AS USSR, 928264, 1982, MKI G01R 31/08. Method for determining the location of a short circuit in a cable line. / Molokanov M.V., Spiridonov V.K., Shalyt G.M., Shchedrin M.B. )

The disadvantage of this method is that the flow of alternating current is provided by the presence in the circuit of the interrupt unit, as well as in the receiving device of two sensors, which leads to an increase in the cost of the device and the presence of a stationary power supply that ensures the operation of the interrupt unit at the near end of the communication line.

Closest to the proposed one is a method for determining the location of cable damage, including applying a test amplitude-modulated signal, moving the sensor along the cable, registering signals, converting the selected signals to signals with the same frequency and determining the phase shift, the value of which judges the location of the cable damage, amplitude -modulated signal is fed between the cable sheath and the ground, in the receiving part, signals with upper f ₁ and lower f ₂ side frequencies are isolated, the conversion of these with Ignals in signals with the same frequency are carried out by the condition mf ₁ = nf ₂ = const, where m and n are integers. (Patent No. 2207582, IPC G01R 31/08. Method for determining the location of cable damage. / Kandaev V.A., Sveshnikova N.Yu.)

The disadvantage of this method is the presence in the generator part of additional devices that modulate the signal, as well as the presence in the receiving part of additional devices for processing the amplitude-modulated signal, which complicates the implementation of this method of determining the location of cable damage and increases the cost of equipment, as well as the result of using additional converting the original signal devices accumulate error.

The purpose of the invention is to increase the accuracy and efficiency of determining the location of cable damage.

To achieve this goal in the proposed method for determining the location of cable damage, including the supply of a test sinusoidal signal from a highly stable oscillator (crystal), moving the sensor along the cable, registering a master oscillator signal, determining the phase shift between this signal and a highly stable reference oscillator signal of the same frequency located in the receiving part and previously synchronized with the master, a test sinusoidal signal is fed between the cable sheath and the ground; by the magnitude of the phase shift judge the place of damage to the cable.

The drawing shows a functional diagram of a device that implements measurements by this method.

The device consists of a generator and receiving parts. The generator part contains a highly stable master oscillator of the sinusoidal signal 1, the frequency divider is a driver 2, a power amplifier 3 and a matching device 4 connected to the cable sheath 5. One terminal of the master oscillator 1 is grounded. The receiving part contains a sensor-shaper 6, a selective amplifier 7, a highly stable reference oscillator 8, a frequency divider — a shaper 9, a phase shifter 10, a phase meter 11, an indicator 12.

The process of determining the location of cable damage is as follows.

Using a highly stable master oscillator 1 and a frequency divider — former 2, a test sinusoidal signal of frequency f is generated, which, after the necessary amplification, is supplied to the cable sheath – ground circuit through a matching device 4. The signal propagating through the cable creates an electromagnetic field on the earth’s surface.

The receiving part is used to register these fields and detect a phase shift at the site of damage. The magnitude of the phase shift is a function of frequency. The electromagnetic field is recorded by the sensor-driver 6. The generated signal is transmitted to the selective amplifier 7, tuned to the frequency f and amplifying this signal to the required value, which is then fed to the first input of the phase meter 11. Using a highly stable reference generator 8 and a frequency divider - driver 9 is formed reference sinusoidal signal with frequency f, using the phase shifter at the beginning of the line, a zero phase shift is established between the test and reference signals. Next, the reference signal is supplied to the second input of the phasemeter 11, which determines when moving the receiver along the cable path the phase shift between the reference and test signals. This phase difference is recorded by indicator 12. In this method, higher accuracy is achieved due to the presence of highly stable crystal oscillators. A highly stable signal is applied between the cable sheath and ground. In the receiving part, a signal of frequency f is extracted and the phase shift between the signal of the reference generator and the signal recorded above the cable by the sensor is determined. Cable damage is judged by the increment of the phase difference between the signals.

Claims (1)

A method for determining the location of a cable damage, including supplying a test signal from a master oscillator, moving the sensor along the cable, registering a master oscillator signal, characterized in that a sinusoidal signal with a frequency f from a highly stable master oscillator is supplied between the cable sheath and the test signal is recorded in the receiving part with a frequency f and compare it with a signal of the same frequency from a highly stable reference oscillator previously synchronized with the master, determine the shift phases between signals, the magnitude of which is judged on the place of cable damage.