SU1638674A1 - Device for cable insulation damage detection - Google Patents

Abstract

The invention relates to electrical engineering and can be used to test and determine the location of insulation damage in cable lines. The purpose of the invention is to simplify the device. The device contains 1 pulse voltage generator (GIN) and damage indicator 2 (SP). GIN contains a source of 3 direct current, the cumulative configurator 5 h pulse transformer 10, the secondary winding of which is connected to the conductors of the cable. The PI contains an inductive current sensor (IDT) 11 with an intensifying link consisting of a series-connected threshold element (PE) 12 and a capacitor 13 loaded with a signal element 1, (ESS) 14. The IDT superimposes on the cable obop and the storage capacitor 5 GIN It is discharged to the primary sheath of the pulsed transformer 10. A high pulsed voltage through the secondary winding is applied to the cable insulation. If there is insulation damage on the cable section on the capacitor 13, the voltage is proportional to the aperiodic component of the current in the cable, and the SC 14 will indicate a breakdown of the insulation. FROM 12 provides stabilization of input voltages. The exact location of damage is determined by moving the IDT along the cable path. 1 h, para. f-ly, 3 sludge in LL i w 00 ze 1 Јb

Description

The invention relates to instrumentation engineering and can be used to determine the location of insulation damage in cable lines, mainly high voltage, in mines, explosive rooms and field conditions of open pit mining.

The aim of the invention is to simplify a device for determining damage to cable insulation.

Fig. 1 is a circuit diagram of the device; Figures 2 and 3 are time diagrams of currents illustrating the operation of the device, respectively, in the absence and presence of insulation damage.

The device (FIG. 1) contains a pulse voltage generator 1, a fault indicator 2. The pulse voltage generator 1 contains a DC source 3, a current-limiting resistor 4, a storage capacitor 5, a switching thyristor 6 with an additional resistor 7 a capacitor 8, a push-button 9 in the control electrode circuit, and a pulse transformer 10 whose primary winding is connected through the switching thyristor 6 to the storage capacitor 5. Damage indicator 2 turns on the current sensor 11 with an indication circuit formed by an integrating element consisting of a series-connected threshold element The device 12 and the capacitor 13, loaded with the signal element 14. To control the pulse supply, an additional signal element (alarm device) 15 connected to the threshold element 12 is used.

A current transformer with a broken magnetic conductor is used as a current sensor 11. The threshold element 12 is formed from two in series and counter-connected semiconductor zener diodes of two silicon diodes connected in parallel and counter. The signal element 14 may be a micro-ammeter or a signal lamp, such as a LED with a transistor voltage and current amplifier. The signal element 15 responds to the pulse voltage at the threshold element 12. The pulse voltage generator 1 is connected to the terminals for connecting a monitored

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cable, damage indicator 2 is applied by the current sensor 11 to the sheath of the cable being monitored.

The device works as follows.

The pulse voltage generator 1 is connected by the secondary winding of the transformer 17 through terminals for connecting the test cable to the cores of the cable 16, the storage capacitor 5 through the current limiting resistor 4 is charged from the DC source 3. Damage indicator 2 is applied by the current sensor 11 to the sheath of the cable under test. When the button 9 is pressed, the thyristor 6 opens and the capacitor 5 is discharged to the primary winding of the pulse transformer 10. A high pulse voltage is induced in the secondary winding of the transformer 10, which is applied to the insulation of the cable to be monitored 16. In the absence of insulation damage, a current flows in the cable damped oscillatory process. In the sensor 11, an emf is induced, under the action of which a current proportional to the current in the cable flows through the threshold element 12 and the integrating capacitor 13. The EMF value of the current sensor 11 significantly exceeds the maximum voltage at the threshold element and the integrating capacitor. The integrated signal (UK) on the capacitor 13 is fed to the signal element 14 with a high internal resistance, for example, a microammeter, which has a significant inductance. i

As with good insulation

cable, the charge and discharge currents are equal, then the voltage U "on the integrating capacitor after the oscillation process decays will be zero and the signal element 14 will show that there is no damage to the cable insulation in the area behind the current sensor overlay. At any part of the cable behind the fault site, the shock is symmetric damped with respect to the time axis, therefore, when a current sensor 11 is installed here and the test voltage is applied to the cable, the circuit works as in the absence of damage, t, e. only the pulse indicator is turned on. In the area between

where the pulse voltage generator 1 is connected and where the insulation of the cable is damaged, the current 1K has a different character and is an oscillating damping process with an aperiodic component. When a current sensor 11 is installed in this region, a voltage proportional to the aperiodic component of the current in the cable arises on the integrating capacitor at the end of the oscillatory process, and the signal element 14 indicates an insulation breakdown in the cable. To determine the exact location of damage to the insulation of the cable, the current sensor 11 is moved along the cable, for example, in the direction from the connection point of the pulse voltage generator 1 until the signal disappears on the signal element 14, which corresponds to the breakdown point.

Claims (2)

1. A device for detecting cable insulation damage, containing a pulse voltage generator, an output connected to terminals for connecting a monitored cable, and a damage indicator including a current sensor and a signal element whose input is shunted by an integrating capacitor, in order to simplify devices, the damage indicator 5 days equipped with a threshold element connected in series to the circuit of the current sensor and integrating capacitor. 2. The device according to claim 1, about the fact that it contains an additional signal element connected in parallel with the threshold element. Mk 2 Compiled by V.Gaynov Editor M.Tsitkina Tehred S.Migunova Order 927 Circulation 426 NIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5, Raushsk nab. V, fig.Z Corrector S.Cherni Subscription