Numerous technical publications have stated that lightning is responsible for approximately 65% of all of the non-scheduled outages occurring on transmission lines, thus creating many issues for power supply utilities.

Power supply utilities themselves have verified the load losses due to voltage sags on their systems from transitory outages caused by lightning activity and in some regions they have found serious permanent damage caused to the system itself due to these transitory disturbances occurring on important lines.

The effect of these transitory disturbances on transmission lines can also be more critical in areas with high ground resistivity when associated with high lightning activity.

Although it is a fact that most of the non-scheduled outages are transitory in nature, with a fault time shorter than 1 minute, in many cases this is still deemed, by power supply utilities and their customers, to be unacceptable. This loss of supply is critical for all modern industries now so reliant on sophisticated electronic equipment and especially production processes sensitive to momentary disturbances on the system.

In order to reduce the number of non-scheduled outages in electrical systems, power companies and industrial consumers have been studying and promoting improvements to transmission lines thereby increasing their reliability.

There are different methods to improve transmission lines performance due to lightning:

a) Increase the dry arcing distance from the insulators strings.
b) Install shield wires on lines without shield wires.
c) Improve the shield wire performance.
d) Improve the grounding system performance of surges by improving the tower footing resistance.
e) Installation of transmission line arresters to counteract the effects of lightning or switching activity

In most cases line arresters (TLA), electrically connected in parallel with the insulator string, have been considered as the most effective method currently applied to improve transmission line performance especially when associated with improvements to the grounding system and usually presents the best benefit versus cost relationship in reducing flashovers of the insulator string due to excessive voltages.

Data Sheet

TLA

  Transmission Line Surge Arresters up to 230 kV

Standard

  IEC 60099-4 for ZnO Surge Arresters.
  Vibration Test - CEMIG.

Key Features

  HV arrester suspended from a transmission line giving enhanced transmission line performance.
  Increasing system line voltage on standard insulated transmission lines.

Utility

  Utilities are required by demand to increase availability and reliability of transmission systems. Therefore eliminating operational high cost outages and mandoratory penalties is high on the agenda.

Benefits of TLA Installations

  Minimising circuit breaker operation with possible system outage resulting from back flashover on the transmission line.
  Switching overvoltages are absorbed over the length of the line reducing the severity of surge at the substation.
  Transmission systems can be operated even where sub-soil gives poor tower footing resistance.
  Eliminating interrupted supply for power supply for sensitive industrial processes.
  Installing Transmission Line Arresters on a standard 3 phase voltage system along the line, at calculated intervals, allows for optimun performance of the TLA, to give an increased system line voltage. Therefore eliminating the need to increase the standard insulation level required on conventional system upgrade.