Analysis of the reasons for accessories heating and processing in transmission line

In the long-term transmission line operation and maintenance process, the heat of the line clip is the main defect of the line. Transmission line clamps are mainly equipment clamps, tension-resistant clamps, and trench clamps, etc. The following is based on the field operation and maintenance, for the clamps class heat problem for in-depth analysis.

1. The main phenomenon

(1) line clip connection plate at the heat

(2) hydraulic type tension line clip, jumper equipment line clip pressure tube at the heat

(3) trench line clip heating

2. The main causes of defects

(1) crimping force is insufficient and has poor contact.

Fixtures, wires, etc. in operation due to thermal effects, and different metal expansion coefficients do not know, resulting in its expansion, shrinkage, coupled with the slow plastic deformation of metals under stress and other reasons, causing small displacement between the parts, fastening parts, crimp surface loosening; wire in vibration, wind deflection swing, electric field and many other effects, making the bolt of the wire clamp connection plate loose, the contact surface gaps.

(2) gold contact surface oxidation, corrosion.

Wires, fixtures exposed in the atmosphere running, long-term exposure to sun, rain, dust and chemically active gas erosion, contact surface corrosion in moisture, salt spray, mold and other media, the formation of non-conductive corrosion products, so that the surface resistance is increasing, especially aluminum wire, fixtures, its surface will form a hard layer of aluminum oxide film, for high resistance; when the lap surface for different metal materials, such as copper, Aluminum butt, due to its standard potential is different, its contact surface of moisture, oxides, etc. to form electrolyte, electrochemical corrosion occurs, more than ordinary oxidation damage, accelerate the contact surface oxidation, corrosion.

(3) The construction process is not up to standard.

Contact surface not polished, remove the oxide layer, the contact surface is not flat, residual debris, resulting in point contact; conductive paste is not evenly applied or too thick; joint bolts and holes do not match, etc., the bolt strength is not enough, not pad spring shims, flat pad, not using the diagonal tightening way tightening, tightening is not used torque wrench; wire and crimp tube is not cleaned, crimping force is not enough; old wire re- crimp, bolt tightening before the surface oxide film is not Clear clean; use of non-standard fixtures.

(4) improper design, the quality of the fixture.

Clips, wires and the flow rate does not match, improper choice of connector connection, clips and wires do not match; terminal block punching unreasonable.

(5) The actual operation of the overload.

Due to improper control of the tide, resulting in line current exceeds the design value, due to the current thermal effect, causing line clamps heat.

3. Processing methods and requirements

(1) deal with line clip bolt loosening choose to meet the standard, design requirements of the bolt and matching gasket; bolt should be tightened diagonally on the way, the torque needs to meet the requirements of the regulations.

(2) deal with contact surface problems

Minimize the broken lead point of the wire. When dealing with the contact surface of the joint, first use files, wire brushes, etc. to file off the contact surface of the joint serious unevenness and burrs, remove the surface of the oxide film, so that the contact surface is smooth and clean, and then wipe the contact surface clean with cotton yarn dipped in alcohol or acetone, immediately apply 0.05-0.1mm thick conductive paste on the surface of the joint. Conductive paste selection of high-quality conductive paste, neutral performance, drip point of not less than 150 ℃, there is a certain viscosity and low contact resistance, etc., avoid the use of Vaseline. (Note: the best conductive paste selected in line with the national grid standard Q/GDW 634-2011, recommended the use of national network interconnection conductive paste)

(3) deal with the tension-resistant wire clips and jumper clips crimp at the heat

Line to the maintenance state for processing, replace the jumper, replace the tension-resistant clips. Process requirements for the national power industry, "transmission and substation engineering overhead conductors and ground hydraulic crimping process procedures" (DL/T 5285-2013).

(4) trench line clip heating

Line to the maintenance state to deal with the hot jumper and trench clamps removed and replaced with the Trantone wire clamps (C-type clamps).