SU750398A1 - Method of locating core short-circuiting in cable line - Google Patents

Description

(54) METHOD FOR DETERMINING LOCATION OF RESIDUAL IN A CABLE LINE

one

The invention relates to electrical measuring equipment and can be used to determine the location of damage to the insulation of a conductor in power cable lines during single-phase or interphase closures.

The closest in technical essence is a method for determining the location of a conductor closure in a cable line, including the effect on one of the cable ends on a damaged and intact conductor, respectively, an alternating audio current and high-frequency current pulses sent through a half-period of an audio current, grounding the non-damaged conductor at the other end of the cable, fixing the phase shift of signals induced by the electromagnetic fields of alternating current currents Zy sound current relative to high-frequency im- parcels: current pulses flj

The disadvantage of this method is the low sensitivity and accuracy of determining the location of damage.

The purpose of the invention is to increase the sensitivity of the method and accuracy of determining the location of damage.

This is achieved by the fact that in a known method, including the impact of alternating currents on a damaged and undamaged core at one end of a cable, grounding an intact core on the other end of the cable, fixing the phase shift of signals induced by electromagnetic fields of alternating currents, alternating current frequencies are different constant multiplicity in time, and the signals induced by the electromagnetic fields of alternating currents are converted into signals with the same frequencies.

The drawing shows a block diagram of the device that implements this method.

Claims (1)

The device contains a source of operating current 1, a source of auxiliary current 75 75 and a reception unit 3 consisting of receivers 4 and 5 of operating and auxiliary signals, frequency converters 6 and 7, respectively, and a meter 8 phase. The method is implemented as follows. Let the power electric cable 9 be damaged - short circuit of one of the cores to the shell. A current with a frequency D from the operating current source 1 is sent to the damaged core of cable 9 along the core-to-ground circuit, and a current with a frequency jfe from the auxiliary current source 2 is sent to the intact core of cable 9 via the core-core circuit. In order to ensure a better passage of the auxiliary current, the intact core at the far end of the cable 9 is connected to ground. The frequencies of the working and auxiliary currents are related by the in-tp B ratios. The multiplicity of the frequencies of sources 1 and 2 of the working and auxiliary currents must be constant and stable over time, since it is only under this condition that the frequency of the received signals can be easily converted conversion ratio) required for the control of the phase shift of the operating current. Receiver unit 3 is mixed along cable 9. Receivers 4 and 5 of the working and auxiliary signals, respectively, are selective to frequencies / p and f Lo, signals induced by magnetic fields generated by the working and auxiliary currents flowing through the wires of the cable 9 are transduced. Converters 6 and 7 frequencies transform the induced, signals with the same frequencies fp -, and the phase meter 8 controls the phase shift between the converted signals Auxiliary current flowing through the intact GIP monotonously changes the phase failure along the cable 9 regardless of the location of damage. Therefore, in a relatively small area of the damage location in the cable 9, the change in the phase of the auxiliary current is negligible and the phase shift can be taken equal to H The operating current flowing in the damaged core changes its phase shift at the fault location. If there is a transient resistance at the site of damage, a current induced by the core-sheath capacity will flow past the site of damage. A current of currents will flow in front of the damage site: the current due to the transient resistance of the damage, plus the current running past the damage site. The phase angle of the operating current will be Q in front of the damage point. © OMff 90 after the damage point of Mra. where (is the phase angle due to the flow of current through the transient resistance at the fault sites. Receivers 4 and 5 of the working and auxiliary signals will induce signals whose phase shifts are proportional to the phase shifts of the working and auxiliary currents. To convert the frequency of the induced signals to fp values in converters The 6 and 7 frequencies should have the following conversion factors: the signals converted by the frequency will change the measurement scale of the phase angles, and the phase angles will have the following e values: for the operating current to the fault location - ((90 p after the fault location p 90 p {For the auxiliary current along the entire length of the UV-J "/ S line The phase meter 8 will determine the phase angles: before the rotation Y -Y after the damage A) Changing the phase shift angle at the damage point of the cable 9 will amount to). The distinct difference in the magnitude of the monitored phase shifts to the location and after the damage location and a sharp change in the phase shift angle at the damage location make it possible to unambiguously determine the location of the damage — the location of the core closure to ku cable 9, i.e. single phase damage. This method can also be applied to determine the location of damage when a core with a cable is closed. In this case, only the inclusion of the operating current source 1 is changed. A current with a frequency p is sent to the damaged cores along a core-core circuit. Since 575 wires of cable 9 have a twist, the magnetic flux caused by the current flowing through the core-wire circuit changes its direction in accordance with the structure of the fluid along cable 9. Therefore, phase measuring gauge 8 will monitor the phase shift angle There is a sign every half-step of twisting the wires. The change in the sign of the phase shift angle is immediately behind the site of damage, since no further current flows through the circuit of damaged cores and, consequently, the site of core-core damage (i.e., interphase damage) is uniquely determined. So, the described method allows, by the most drastic change in the phase shift angle, with high accuracy to determine the location of the conductor closure in the cable line. 8 The invention method of determining the location of the conductor closure in the cable line, including the effect of alternating currents on the damaged and intact. conductors at the sdn of the cable ends, grounding the intact conductors at the other end, the cable, fixing the phase shift of the signals induced by the electromagnetic fields of alternating currents, characterized in that in order to increase the sensitivity and accuracy of determining the location of damage, the frequency of alternating currents is chosen different with constant multiplicity in time, and the signals induced by the electromagnetic fields of alternating currents are converted into signals with the same frequencies. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 5О4987, cl. Q 01 R 31 / O8, 1973.