There are two basic Live Line methodologies for High Voltage (HV) work, which in industry terminology are called ‘Hot-stick’ and ‘Bare-hand’ methods.
Using hot-stick methods, direct human contact with live components is avoided. Line workers use tools fastened to insulated fiberglass poles to carry out the work, and always keep themselves at a safe distance from the live components.
In contrast, when using bare-hand methods, the line worker is positioned in direct contact with the live components and is livened or raised to the electrical potential of the conductor being worked on. For transmission voltages in South Africa, this ranges from 110,000 volts (110kV) to 765 kV. This may sound chilling, but for well-trained live line mechanics it is all in a day’s work - much like the birds that land on power wires all the time and survive.
The same principal applies to bare-hand live line workers. The complex part of the job is getting the line mechanic on to and off the wires safely. Though this sounds simple in theory, in practice live line work is potentially very hazardous, and must be undertaken in a very methodical manner with highly trained workers in a carefully planned and controlled work environment. When accessing live conductors for bare-hand work, it is critical that the live line mechanic does not at any time bridge the gap between the live conductor and any earthed object (including the tower or pole that supports the conductor). There are several ways of achieving this:
- One way is to raise the live line mechanic from the ground or a part of the tower below the working position using live-line (insulating) rope attached to a body harness. To ensure that all parts of a bare-hand worker are raised to the same potential as the live conductor he/she is in contact with, the worker wears a special conductive suit complete with hood and conductive socks.
- The alternative method is to place the worker onto the working position by means of the helicopter. The worker, attached to an insulated fiberglass pole and lanyard, is suspended below the helicopter. To prevent inadvertent release from the helicopter, the complete system from the helicopter hook down to the body harness is duplicated. The process of transporting people, tools and hardware suspended below the helicopter is termed Aerial Live Work.
Safety and process: To ensure the safety of workers involved in Live Line work, a rigorous set of rules and guidelines have been developed, and made mandatory in South Africa under the Electricity Act 1995 in the form of the RSA Electrical Code of Practice for High Voltage Live Line Work.
In South Africa, Eskom (national power utility) also sets specific requirements for contractors to meet before granting them approval to undertake Live Line work on the national electricity grid. Both the Code of Practice and the Eskom Standards require contractors to have comprehensive management systems to control all aspects of Live Line work, including tool management, training of staff, weather conditions and their impact on the work, and the development and approval of work procedures. All work tasks must have a fully documented work procedure that has been trailed and proven before being approved for use on live assets..