Hot Line Maintenance of 400/220/132kv EHV Line
At present uninterrupted supply is required in all sectors like domestic, agriculture, industrial etc. For which the 100% reliability of the transmission as well as the distribution system comes in mind. But at the same time for healthiness of the system, periodical and sudden required maintenance is a must. It requires planned shut-downs and unplanned as well. But it reduces the reliability & continuity. Some times even it becomes almost impossible to give shut-down on transmission lines or substations for the most urgent . These lines are transporting huge quantum of power even interstate also. To avoid shut-downs as much as possible, the Hot Line Maintenance Technique or Live Line Technique, proves to be the best solution. It means working on a line while it energized, for inspecting or replacement if necessary, defective parts to avoid costly forced shut-downs or outages.
The earliest tools were manufactured in 1913 in Ohio, USA. They were home-made, crude and bulky. One by one a number of Hot-Line tools were introduced & developed over the years like electrical hook, hacksaw, saddles, clamps, clamp-sticks, wire-tongs and numerous hand tools. It is very useful when power circuits could not be easily de-energized while insulators, cross-arms, poles and other equipment were being replaced. It was realized that duplicate circuits for service purposes would be entirely too costly and that the rapid growth of electrical users would demand that electrical power be maintained without any interruption.
Initially Hot Line Work was restricted to lines up to 22kv but gradually it increased up to 500kv till 1957. In 1959, the new light weight epoxy glass handle for Hot Line Tools were introduced and by 1964 these were used in all EHV lines in USA and Canada including 735kv, almost eliminating the use of wooden tools for EHV.
Weight of Hot Line Tools is an important factor in hot line work. Because we have to do an operation with maintaining a safe clearance of about 4.5m to 8m for which we use 6m to 10m hot line sticks, so that the weight of tools must be as less as possible. Therefore considerable attention was given to making the tools lighter, stronger and safer.
Live Line Maintenance:
Hot line work can be classified into three as follows:
1. HOT STICK METHOD:
In this method the person will be at ground potential working with Hot Sticks(tools) keeping safe clearance from the line. 2. BARE HAND METHOD:
Here the person will be working at line potential keeping safe clearance from the ground. For this insulated suits made of 25% microscopic stainless steel and 75% Nomex, will be provided. 3. COMBINATION:
This method is a combination of above two methods.
Ropes pay an important role in any Hot Line Operation. By it heavy load be taken on it , in the operation. So its 100% reliability is a must, otherwise a big fatal accident can take place which could be avoided only by using stronger at perfect in strength as well as insulation is concerned. For which Synthetic fiber rope may be better. They are of three types as follows: ← Poly Dacron,
← Poly Propylene and
It is white in color having good strength when dry. It is good for sliding or when friction is more. It is mechanically strong and durable. Its dielectric strength is 110kv/feet.
|Size (in Inches) |Working Load |Breaking Load (in Pounds) | |3/8” |20% of Breaking Load |2650 | |½” |20% of Breaking Load |4800 | |5/8” |20% of Breaking Load |6700 |...
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