Abstract: The advantages of common overhead bare conductors insulated overhead conductors distinct from its application in the 10kV distribution network, while the proposed overhead insulated wire should be chosen from planning and design, material selection, construction techniques and other aspects of mine Note that some of the problems.
Keywords: distribution network; overhead insulated wire; application; issues
1 advantage different from the ordinary bare overhead conductors
1.Good insulation properties
Since overhead insulated conductor insulation than a layer, with a more bare wires superior insulation performance can be reduced from the phase line, to reduce the insulation requirements for line support member, with increasing the number of stem loop line, foreign objects can be prevented due to phase short circuit.
1.2 small degree of corrosion
Overhead insulated wire more than a layer of plastic skin, than the bare wire small extent by the oxidation corrosion, improve the life of the line.
1.3 simplified Tower Structure
Line tower structure can be simplified, or even laying along the wall, which saves wiring materials, but also beautify the city streets.
1.4-depth load center
Facilitating load center depth high pressure, low-pressure line to reduce the power supply radius, improve the quality of the voltage.
1.5 conducive to urban greening
Trim amount in favor of urban construction and landscaping work will reduce the line of trees.
1.6 narrow line corridor
Save space occupied by overhead lines, overhead lines to facilitate the passage through the narrow, line corridor reduced, as compared with bare overhead line can be reduced many corridors.
1.7 Maintenance Cycle
Due to improve the technical condition of the line, reducing the maintenance workload, extending the maintenance cycle, reducing maintenance and power outages due time.
Application 2 overhead insulated wire
2.1 is suitable for densely populated downtown areas
Densely populated, bustling street area, use the overhead insulated wire can increase the safety factor.
2.2 line corridor is suitable for small places
In line construction, the sometimes-depth load center, often have to pass through a narrow channel, while the average overhead bare wire can not meet the requirements, so use insulated overhead conductors will solve this problem.
2.3 places suitable for growing trees fast
Now, more and more importance to urban greening the city, but if the trees grow fast line, the line does not meet the safety distance, is bound to affect the operation and safety of the line, so we choose to resolve conflicts overhead insulated wire and green lines, reducing line Ground Fault.
2.4 more places for salt contamination
In coastal areas, more salt spray, line corrosion aging faster, use insulated overhead conductors, because of the layer of organic material wrapped, can slow down the aging lines, extend the service life.
2.5 places suitable for balloon ribbons every now and then
Some local celebrations often, metallic balloons, ribbons every now and then, often causing short circuit accident, affecting the normal power supply, so use overhead insulated wire can reduce accidents.
2.6 typhoon season to reduce the chance of line trip
Typhoon season, due to the wind action, and white wires often collide, causing phase short-circuit trip, the choice of an insulated wire can reduce the overhead line trip probability.
3 issues should be noted
When using overhead insulated wires, due to lack of experience, often in accordance with the technical requirements of the general overhead bare wire to implement, causing irreparable damage and even accidents.
3.Question 1 planning and design
1) Planning insulated overhead lines should be coordinated with the general plan of the city, without regional distribution network planning, wire section 20a should be determined by the electrical load Development Plan.
2) insulated overhead line span of not more than 50m, Strain segment length of not more than 1km.Insulated overhead lines between lines a distance not less than 0.4m, the insulating holder using compact erection of not less than 0.25m.
3) If aluminum or aluminum alloy core insulated wire, the minimum section is designed to 150mm2 main trunk, branch lines 50mm2.
4) in contact on both sides of the switch, mycobacteria, Tension rods and joints may be provided with a power point on the ground working Reverse power line branching point lead; when the working power line is working grounding point insulating cover installed.
5) connected to terminal portions of the insulated wire fuses, surge arresters, transformers, should be insulated sealed.
6) insulated wire switching device should be installed in the following regions: a long branch or trunk line ①; ② ring power supply network; ③ tube distinguished boundary.
The device connecting portion of the insulated wire to be provided with a dedicated insulating cover.
3.Selection of material issue 2
1) overhead insulated conductors shall comply with GB14049, in accordance with insulated wires required to select its associated supporting materials, if you choose properly, will seriously affect the performance overhead insulated conductors of safety, accelerated aging and aluminum wire insulation of the wire oxidation corrosion.
2) Insulator shall comply GB1000 using Insulator, fittings and the insulating member shall meet the following requirements.(1) Laying single insulating distribution lines.Insulator straight needle bar should be used (Example: P-15M) or a bar Insulator (Example: ZS-10/4); Tension rod should adopt a suspension Insulator (Example: X-4.5) and a butterfly Insulator (Example: E-10), or composed of two suspension Insulator Insulator string and Clamp (NXJ series).(2) laying compact insulating distribution lines.Clamp hanger rod should be linear (XGU series); Tension rod-bearing strand Clamp employed, using insulated wire and an insulating pull rod Clamp; span should be used in the insulating holder.
3.Question 3 construction technology
1) set up overhead insulated wire should be selected in dry weather, to avoid the construction in greater humidity weather Actinomyces.
2) Construction of use before and after the discharge line insulation resistance meter 2500V megger shake test wire, the insulation resistance is determined whether the target, whether the lesion insulating layer.
3) When the discharge line, the insulated wire can not be on the ground, tower, cross arm, drag porcelain or other objects, to prevent damage to the insulating layer.
4) 10 and the insulating layer above the depth of damage when the insulating layer in the thickness of the insulation repair.Available adhesive insulating tape is wound between the insulating adhesive tape on a loop bandwidth pressure take 1/2 the thickness of the insulating Buxiu self-adhesive tape should be greater than the depth of the insulating layer damage, and not less than two; the insulating shield will also be good insulating layer cover the damaged portion, and the opening portion is sealed with an insulating adhesive tape is wound.Within a span, a single insulated wire damage repair insulating layer not more than three.
5) When the insulated wire core damage, if the cross section is not more than 17 damage conductive portion of the cross section, bonding lines can be repaired, the wiring length should exceed the damaged portion, each end is wound over a length not less than 100mm damaged portion.If the cross section of the damaged section within the conductive portion 6, the depth of damage in a single strand of a diameter of 1/3, used in partially wound injury with a single strand of metal, winding length should exceed the respective end portions injury 30mm.When one core injury following conditions should sawing reclosing:
In the same cross-section area of more than 17 damage the conductive portions of the core cross-section, an off steel core.
6) does not allow the connection of insulated wire wound should be dedicated clip, splicing tube connection; must be insulated after the insulated wire connection; ends of all insulated wires, connectors have insulation jacket, without wires, connectors nudity, prevent water; insulated wire connections must be shielded.
7) connected to the load-bearing joint pressure method using pliers, hydraulically construction, mounted at a joint insulating sheath, the insulating sheath diameter should generally be treated as a portion of a connecting pipe.2 ~ 5.0 times.
8) non-exposed portion of load-bearing joint shall be insulated, insulation shields install special.
9) When the tight line should not be too insulated wire traction, use nets or wire grip surface contact, and wound with a plastic or rubber bag insulating line card to prevent insulating layer damage.
Fixing the linear rod 10) of the insulated wire using a needle or bar Insulator Insulator, using two Tension rod and suspension Insulator Clamp Insulator suspension or an intermediate pressure and a butterfly Insulator.
11) a secondary side of the isolation transformer in the line and the line should be set to power ground work site, work power should be installed at the ground point a ground power dedicated fittings for suspending the ground line.
3.4 Lightning Protection issues
Currently, most of the erection of overhead insulated conductors not take lightning protection measures, resulting in lightning overhead insulated wire break accidents have occurred.
3.4.1 reason for disconnection
When lightning strikes the insulated wire, the insulating layer insulated wire to form a barrier to the arc movement of lightning, resulting in slower moving speed of the arc, arc is concentrated in the frequency breaking point of the insulating layer.When lightning damage the insulation of the insulated wire, which generates the arc current causes a short circuit between phases.Since blowing easier than bare wire arc portion is fixed, lightning occurs after the insulated wire.In addition, Insulator on the line will also occur due to lightning flashover or burst, causing the fuse wire and other accidents.
3.4.2 lightning protection measures
1) mounted in a respective lightning conductor insulated overhead conductors above; Insulator on line using a needle, struts Composite Insulator (Example: FP-1-0 / 2.5 or FZS-0/5).
2) re-mined areas, the line intervals of about 150m to install a set of arresters (Example: Y5WS-12.4/50).
3) should be grounded pole reinforced concrete residential, irons should be grounded, grounding resistance should not exceed 30Ω.
4) insulated overhead distribution lines with the lines of force of which bearing the load-bearing lines should be grounded, grounding resistance should not exceed 30Ω.
4 Conclusion
Overhead insulated wire is different from the general advantages of overhead bare wire, making it more and more obvious value, using insulated overhead conductors replace the ordinary overhead bare wire will become more common.However, since the selection and use of construction techniques overhead insulated conductors different from the ordinary overhead bare wire, and if you choose to use properly, will not only affect the quality of the project and operation management, will accelerate the oxidation reaction insulated wire insulation aging rate and aluminum wire, leave a lot of accidents.
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Source: Best Koki grid