Author: Noyafa–CCTV Tester
What types of cable faults can be tested by the cable fault tester? At present, power cable faults may involve three types of cable fault types that can be tested by cable fault testers. At present, power cable faults may involve three types of faults: 1. Conductor fault (core wire and metal shielding layer) 2. Main insulation fault 3. Sheath fault (sheath fault).
However, due to the wide variety of power cables, the structure and organization are not the same, and according to the needs of different departments, there can be different classification methods, which can be simply summarized as the following situations. 1.1 Cable faults are classified by fault location 1. Main insulation fault. Damage to the insulation between the conductor core wire of the cable and the ground or metal shield causes various types of faults.
Generally speaking, most of the faults of 35KV and below cables belong to this type of fault. 2. Sheath failure. It generally refers to the fault caused by damage to the metal sheath (layer) or insulating sheath of the cable. In practice, the fault of the insulating sheath between the metal sheath and the earth can be found.
Such failures are mostly leaky failures. Sheath failure is only involved in single-core power cables with high voltage levels of 35KV and above. 3. Main body failure.
A complete transmission cable consists of two parts: the cable body and the cable joint, so the fault of the cable must occur in the cable body and the cable joint. The body of the cable can have different types of failures, usually due to product quality and external damage. 4. Connector failure.
When using a cable for power supply, no matter the length of the cable, there must be two connectors at the end. For the long-distance power supply cable or after the cable is faulty and repaired, the cable must also have a connector, that is, an intermediate connector. Usually a considerable part of cable faults are joint faults, and their performance properties are different, but usually multi-phase-to-earth leakage high-resistance faults are in the majority.
1.2 Cable faults are classified by fault time 1. Operation faults. Operation failure refers to the failure of the protector to act and suddenly stop the power supply due to insulation breakdown or wire burnout of the cable during operation. Such faults are usually single-phase or multi-phase-to-earth leakage faults.
2. Test failure. Test failure refers to the failure of insulation breakdown or poor insulation in the preventive test, and the power supply can only be restored after maintenance. 1.3 Cable faults are classified according to fault responsibility 1. Personnel negligence.
Improper cable selection, wrong three-head structure design, improper operation, poor maintenance, etc. 2. Equipment defects. Cable manufacturing defects, cable three-head accessories material defects, the use of old equipment leftover defects, improper installation methods or poor construction technology and other reasons for the three-head quality defects.
3. Natural disasters. Lightning strike, flooding, typhoon attack, bird damage, insect damage, debris flow, ground subsidence, earthquake, celestial body fall, etc. 4. Normal aging.
Generally, the insulation of the cable is aging for more than 30 years, the outdoor head is soaked in moisture for more than 20 years, and the high-end of the vertically laid oil-paper cable is dry for more than 20 years. 5. External damage, corrosion, user negligence and trial of new products and new technologies, etc. 1.4 Cable faults are classified according to the nature of the fault 1. Short-circuit (grounding) type: a penetrating fault occurs in the insulation of one-phase or several-phase conductors of the cable to the ground or between the conductors.
According to the size of the short-circuit (grounding) resistance, there are high resistance, low resistance and metallic short-circuit (grounding) faults. 2. Disconnection type: The fault of one-phase or several-phase conductors of the cable is discontinuous. 3. Flashover type: The cable insulation breaks down instantaneously under a certain voltage, but the breakdown channel is randomly closed and the insulation recovers quickly.
4. Compound type: The cable fault has more than two fault characteristics.
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