Transmission-line protection for disturbance-free system operation
Both large, small public and private utility owners of transmission systems face a sharpened competitive situation which demands increased availability and reliability of the systems. Consumers have become more demanding as their processes are dependent on constant and reliable energy supply of good quality.In many countries, it has also been increasingly difficult to obtain permission to build new lines of normal dimensions. Hence, new lines under construction may mostly be “compact-insulation“ lines. This, in turn, requires optimal control of overvoltages caused by lightning or switching events. Surge arresters installed along the line or at a few selected critical towers, in this case, may be an attractive solution or a complement to other means.
Improvement in the reliability and availability of a transmission system can be obtained in one or more of the following ways:
- Duplication of the system (more than one line)
This is a very expensive method and often impractical
- Increased insulation withstand
It can be both expensive and create other problems such as the need for increased insulation of station equipment.
- Improved footing impedance
Often difficult and expensive, specially in hilly terrain.
- Shield wires
If the provision was not in the original tower design, it can be expensive to retrofit such shielding. It helps eliminate a large number of interruptions but it is not enough to obtain the now-demanded degree of reliability
- Protection with surge arresters
Protection of line insulation by surge arresters connected in parallel with them at selected towers. In this application usually the term line arresters is used.