10KV overhead cable transmission line common faults are 7 kinds
1 Single-phase grounding fault
Single-phase grounding is the most common fault in the power distribution system, mostly occurring in wet and rainy weather. Single-phase grounding not only affects the normal power supply of users, but also Hunan Sunshine Electronics School maintenance experts believe that: it may produce overvoltage, burn equipment, and even cause an inter-phase short circuit and expand the accident.
When a phase (such as the A-phase) is not fully grounded, that is, through high resistance or arc grounding, when the voltage of the faulty phase is reduced, the voltage of the non-faulty phase rises, greater than the phase voltage, but not up to the line voltage; if the A phase is fully grounded, the voltage of the faulty phase drops to zero, the voltage of the non-faulty phase rises to the line voltage. Find and deal with single-phase ground fault, should be ready to take safety measures to ensure personal safety. When the equipment is grounding, the indoor human body shall not be close to the fault point within 4 m, outdoor shall not be close to the fault point within 8 m, into the above range of staff must wear insulated boots, wear insulated gloves, use special tools.
2 Short circuit fault
Two points in the line with different potentials are shorted by the conductor, or the insulation between them is broken, failing the line can not work properly, known as a short-circuit fault. According to the different cases, short circuit fault is divided into a metallic short circuit, non-metallic short circuit; single-phase short circuit, and multi-phase short circuit.
3 metallic short circuits and non-metallic short circuit
Two metal conductors of different potentials, directly connected or shorted by the metal conductor, are known as a metallic short circuit. Metallic short circuit, the short circuit point resistance is zero, thus the short circuit current is very large; if the two points of different potentials are not directly connected, but after a certain resistance is connected, it is called a non-metallic short circuit. Non-metallic short circuit, the short circuit point resistance is not zero, so the short circuit current is not as large as the metallic short circuit, but the duration of Hunan Sunshine Electronics School maintenance experts think: maybe very long, in some cases, it’s more dangerous.
4 Inter-phase short circuit
Two-phase phase lines shorted to each other, are known as a two-phase short-circuit fault. Three-phase lines shorted to each other, are known as a three-phase short-circuit fault.
5 broken circuit fault
The broken circuit is the most common fault, the most basic form of expression is the circuit does not work. In some cases, the break will also cause overvoltage, the arc generated by the breaking point also Hunan Sunshine Electronics School maintenance experts believe that: may lead to electrical fires and explosive accidents.
6 breakpoint arc fault
Breaks, especially those seemingly broken non-break points, in the moment of disconnection will often produce arcing, or high temperature in the breaking point, the arc, and high temperature in the power line Hunan Sunshine Electronics School maintenance experts think: may lead to a fire.
7 three-phase circuits in the break fault
In the three-phase circuit, if a phase break fault occurs, one of the Hunan Sunshine Electronics School maintenance experts believes that: perhaps the motor is burned out due to the lack of phase operation. secondly, the three-phase circuit is asymmetrical, the voltage of each phase changes, so that the phase voltage rises, causing accidents.
So what are the causes of these 7 kinds of faults in 10KV overhead cable transmission lines?
1 single-phase grounding fault causes
Single-phase ground fault occurs in wet, rainy weather, is due to tree barriers, distribution lines on the insulator single-phase breakdown, wire joints overload burned off or oxidation corrosion off, single-phase disconnection, and many other factors caused.
2 Short circuit fault causes
3 External damage
In 2005, Zhengzhou distribution network faults accounted for 30% of external damage, mainly by vehicles hitting the poles, ultra-high cars hanging off the wire, rainy weather, tree line contradictions stand out, hitching on the line of foreign objects (such as high winds scraped to the line with aluminum foil of plastic paper, high-rise construction sites of waste wire, audiotape, colored strips, kites, etc.), the tower of the tower material gold theft caused by the inverted pole (tower) and so on.
4 lightning strike
With the increase in overhead insulated lines of the two networks, more and more lightning accidents, due to the urban distribution lines around most of the high-rise buildings, and most of the high-rise buildings are equipped with lightning protection facilities, so the urban distribution lines are not affected by lightning strikes. But the agricultural network lines are spread all over the fields, hills, and slopes, becoming the highest point of the whole surrounding, once lightning strikes, it becomes the channel of lightning current. Overhead insulated lines suffer more lightning accidents than overhead bare lines, lightning damage is more serious. Insulated overhead line lightning accidents are the more serious main reason: one is the structure of the insulated line, insulated wire using semiconductor shielding and cross-linked polyethylene as the insulation layer, which uses semiconductor materials with one-way conductive properties, in the thundercloud discharge of atmospheric overvoltage, it is easy in the conductor of the insulated wire, resulting in induced overvoltage, and it is difficult to release along the insulated wire skin; second is the insulated wire suffered Lightning strikes after the electromagnetic mechanism is special, resulting in more lightning strikes break line. Overhead bare wire lightning strikes, causing flashover accidents, is in the electromagnetic force of the frequency continuity, the arc will move along the wire (conductor), the arc moves in the release of energy, and the frequency continuity burned wire or damage insulators before the circuit breaker action trips to cut off the arc, and overhead insulated wire insulation layer to prevent the arc in its surface movement, the charge is concentrated in the breakdown point discharge, in the circuit breaker action before burning the wire. Because the lightning voltage is very high, and the current is instantly very large, the distribution line between the phase distance and insulation performance simply can not withstand, so cause the line phase arc to short circuit or ground insulation breakdown, resulting in a grounding phase short circuit.
5 bird damage
Birds fall on the line, nesting interphase short circuit, which mostly occurs in the line of the T-connector, corner pole, isolation switch installation, because these parts of the contact line are dense, the interphase distance can meet the requirements of the safety distance of 30 cm, but the margin of a safety distance is not enough, birds in the drop or take off when the wings spread, it is easy to interphase short circuit, and a contact line is also a good place for birds to nest, nesting branches, wire, etc., often cause an inter-phase short circuit.
6 line, equipment itself cause
The arc sag of the wire is too large, in the event of a windy wire swing, easy to cause a short circuit. In addition, the line, equipment running for a long time, and insulation performance decline, will also cause the occurrence of short-circuit fault.
Second, 2 short-circuit faults causes
2.1 External damage
Vehicles hit the pole, ultra-high cars hanging wire, trees, and other foreign objects such as broken wires caused by the break.
2.2 Lightning strike
Insulated lines in open areas are prone to lightning strikes and cause breakage faults, from the accident scene, most of the breakage fault points occur in the insulation support point within 500 mm, or the tension and expenditure lap.
2.3 Line, the equipment itself causes
Poor contact at the conductor joints or overload burned fallen fuse, Zhengzhou area distribution transformers are using fallen fuse for protection, sometimes due to high load current or poor contact, and burned contacts; there are manufacturing quality problems, the operator pulling together improper force too hard, and caused the fallen fuse porcelain body broken.
Third, the kV overhead line common fault preventive measures
1 single-phase grounding fault preventive measures
Timely pruning of tree line contradicts prominent place of trees.
Take lightning protection measures to reduce the single-phase grounding fault caused by lightning strikes. In addition, to reduce the surface of the insulator and porcelain skirt due to the accumulation of dirt, or poor manufacturing quality in the rainy damp, and flashover discharge, resulting in grounding faults occur, the line construction (transformation) must choose qualified, good quality insulators, and voltage test before installation, to ensure the quality of installation.
During the peak load period, the use of an infrared thermometer, measuring the temperature of the wire joints, once the temperature is found to be abnormal, is immediately processed to avoid high temperature fused wire.
2 short circuit fault prevention measures
3 prevent external damage measures
To reduce vehicle collision tower accidents, try to relocate the tower, can not relocate the tower can be hung on the tower of the reflective paint sign, to attract the attention of the vehicle driver.
Take to set up prominent warning signs, issue leaflets, and other ways to strengthen publicity and education, to prevent the occurrence of short-circuit faults caused by kites, colored strips, etc.
Strengthen the contact with the municipal gardening department, timely pruning of trees affecting the safety of operation.
Strive to get the local public security, security department cooperation, the development of effective measures, and specific prevention programs to strengthen the fight against theft of 10 kV line tower material and gold and other power facilities.
Run the department to regularly inspect the 10 kV line tower foundation, cable foundation, and unauthorized buildings, the hollowing of the tower foundation, cable foundation for timely maintenance, the existence of defects in the equipment for timely processing and maintenance, unauthorized buildings to clean up and rectify.
4 lightning strike prevention measures
In the open 10 kV overhead line, take the installation of a metal oxide lightning arrester and other lightning protection measures. Lightning arrester installation density control in 200 ~ 360 m or so, the specific should be based on environmental factors and operating experience. In addition, you can also choose a phase, two-phase, three-phase, top-phase, side-phase, or each phase of the wrong pole installation arrester on each base pole. Thus to meet the requirements of safety and economic operation.
In the line construction (transformation) must choose qualified, good quality insulators, and in the installation before the voltage test to ensure the quality of installation.
Check and rectify the grounding device. Regularly check and measure the grounding on the 10 kV line.
Conclusion
10 kV overhead lines are directly linked to the majority of users, branch lines are many and complex, especially the agricultural network lines, long power supply radius, and all radial power supply lines. After the city network in recent years, agricultural network transformation, line accident resistance has been significantly improved, but 10 kV overhead line faults still occur from time to time. Detailed understanding of overhead transmission line fault causes and the corresponding preventive measures to improve the safe operation of 10 kV overhead lines and improve power supply reliability.