Transmission lines carry electrical power and their characteristics make them conditional to ongoing checks and inspections. Power transmission lines are made up of towers and they run hundreds of kilometers through vastly different geographies and climates.
This characteristic exposes transmission lines to numerous external factors, such as corrosive agents, ice, wind and ultraviolet radiation, which damage their structures, components and parts. It is therefore essential for lines to undergo the regular maintenance that can extend their useful life by 30 (typical) to 50 years.
However, before the actual maintenance takes place, engineers must first draw up a diagnostic assessment. They have two ways to do this. The traditional method consists of setting up a schedule of periodic visits to the line. This means getting a team of two to three people, usually electrical technicians and mechanics, to the foot of the tower.
The second way to inspect a line involves the use of technology, a method that does not necessitate taking the line out of service. Technicians make use of infrared and ultraviolet light cameras and ultrasound detectors to obtain data locally or remotely. In the latter case, the information travels via cellular systems to a control center.
Transmission line maintenance types:
there are two types of maintenance carried out in transmission line,
- cold line maintenance
- Hot line maintenance
Cold line maintenance
In the cold line method the maintenance is carried out by availing outage on the line. The works of replacement of defective insulator strings, tightening loose nuts and bolts of the joints, cold line Insulator washing etc. and defects noticed in the thorough line patrolling are rectified, however since there is interruption in the line, there is huge revenue loss and customer’s dissatisfaction, which are the main disadvantages of cold line maintenance. Therefore hot line (live line) maintenance is highly preferable and adopted where ever possible.
Live line maintenance
hot line technique advantages
- No outage, so no interruption to consumers.
No revenue loss.
Problem is attended immediately, loose nut-bolts can be tightened by hot line technique and breakdown is avoided. Hence no interruption Emergency outage is avoided.
Contaminated disc insulators can be cleaned by hot line washing, so flashover of disc insulators resulting in to break-down can be avoided.
Punctured insulator can be detected with hot stick attached to punctured insulator detecting instrument either by Electric field measurement method or by Voltage measurement method. The punctured insulator can be replaced in live line
Hot spots noticed during thermos graphic scanning can be attended by hot stick method or by bare hand technique as preventive maintenance.
Defective jumper can be relieved from the danger of breakdown by providing parallel jumper and emergency is avoided
Very less man-power and very less time is required as compared to cold line method.
Live line maintenance by hot stick method In hot stick method the works are carried out by using hot line tools.
Bare hand technique for system maintenance It is based on faraday’s principle. Therefore, when a lineman is shielded in Faraday’s cage wearing Conductive Suit and it gets bonded to an energized conductor, he can work on the conductor and associated hard ware without shock or discomfort.