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What Are The Common Cable Faults? The Main Reason For Cable Failure
- Jun 25, 2018 -

Cable is an important medium for electricity transmission. During the use of cables, various types of faults often occur. This article will introduce you to the common faults of cables and the causes of cable faults, helping you better understand the faults of cables.

常见的电缆故障有哪些?电缆发生故障的主要原因

What are the common cable faults? The main reason for cable failure

Cable is an important medium for electricity transmission. During the use of cables, various types of faults often occur. This article will introduce you to the common faults of cables and the causes of cable faults to help you better understand the cables. Faults and regulations use wire and cable.


Common cable faults


Common faults in cable lines include mechanical damage, insulation damage, moisture insult, insulation degradation, overvoltage, and cable overheating. When the above fault occurs on the line, the power of the faulty cable should be cut off, the fault point should be found, the fault should be checked and analyzed, and then the repair and test should be carried out. The cut should be removed and the power supply can be restored after the fault is eliminated.


The most direct cause of a cable fault is a breakdown of insulation and breakdown.


The main causes of cable faults are:


a. Overload operation: Long-term overload operation will increase the cable temperature and insulation, resulting in breakdown insulation and reduce the construction quality. b. Electrical aspects: The cable head construction process fails to meet the requirements, and the cable head is poorly sealed. The moisture intrudes into the cable and the insulation performance of the cable decreases. When the cable is laid, no protective measures are taken. The protective layer is damaged and the insulation is reduced. c. The civil works include: The well pipe trench drains poorly, and the cable is immersed in water for a long time and damages the dielectric strength. The working well is too small and the bending radius of the cable is not enough, and it is destroyed by the external force of the extrusion for a long time. It is mainly the construction of machinery in the municipal construction that involves brute construction and excavation and cutting of cables. d. Corrosion: The protective layer is subject to chemical corrosion or cable corrosion for a long time, resulting in failure of the protective layer and reduction of insulation. e. Cable itself or poor quality of cable head accessories. Poor sealing of the head, dissolution of insulating glue, cracking, resulting in the resonance phenomenon of the station for the line break fault so that the line capacitance between the phase and the capacitance of the distribution transformer and the excitation inductance constitute a resonant circuit, thereby exciting the ferromagnetic resonance.


Breakage failure causes resonance damage


Breaking resonance Under severe conditions, the high frequency is superimposed with the fundamental frequency resonance, which can make the overvoltage amplitude reach 2.5 times of the phase voltage [P], which may cause the neutral point of the system to move, and the winding and the wire may overvoltage. Insulation flashover, explosion arrester explosion, electrical equipment damage. In some cases, the phase sequence of the load transformer may reverse, and overvoltage may also be transmitted to the low voltage side of the transformer, causing damage.


Measures to prevent overvoltage and disconnection from resonance


(1) Do not use fuses to avoid non-full-phase operation;


(2) Strengthen the inspection and maintenance of the line to prevent the occurrence of disconnection; (3) Do not hang the transformer on the line for a long time;


(4) using ring or dual power supply;


(5) Add phase-to-phase capacitance to the transformer side.


The principle is: the use of capacitors as energy-absorbing elements to absorb the energy in the transient process, thereby reducing the impact of disturbance intensity to suppress the occurrence of resonance .s a (o + 3C,,) 1C., with additional phase capacitance on the transformer side △ C Let [8] [Co + 3 (C U + A0)/Ca be increased to increase the equivalent capacitance C and the equivalent electromotive force Eo.


(6) Transformers with good excitation characteristics can help reduce the occurrence of breakage and overvoltage.