Page 38 - Energize September 2021 HR

TECHNICAL

Externally gapped line arresters:

Smart solution for stable power supply

Information from Toshiba

Metal-oxide surge arresters with external series gaps improve the reliability of transmission systems
and help eliminate lightning damage to transmission line equipment, as well as slight power
interruptions after trip-outs caused by lightning.
n

he integrated external series gap eliminates the need for
countermeasures against switching overvoltage or the
Tdeterioration of ZnO disks. This means that transmission line
arresters can be compact and lightweight, significantly easing the
installation and/or maintenance of the arresters.

Transmission line arrester with external series gap
Our modern, sophisticated society demands a stable and highly
reliable power supply. Lightning strikes on power transmission lines
cause very slight power interruptions which may seriously damage
IT equipment. Incorporating a design with lightning protection is
crucial for ensuring a stable power supply. The transmission line
Figure 1: Event comparison between “without EGLA” and “with EGLA”
arrester is the optimal method of lightning protection.
Toshiba offers a smart lightning protection solution, a
transmission line arrester with an external series gap, otherwise
known as an Externally Gapped Line Arrester (EGLA). EGLAs help to
eliminate lightning damage to transmission line equipment and the
slight power interruptions which occur after trip-outs. EGLAs also
protect insulator assemblies from flashovers caused by lightning. All
in all, the installation of an EGLA will definitely improve transmission
system reliability.

The Toshiba EGLA features
● Compact and lightweight design thanks to the superior
performance of ZnO disks, resulting in easy installation of the EGLA
● No deterioration of ZnO disks and no need to disconnect devices
because of series gaps, that means a maintenance free EGLA
● No violent scattering or burning ensuring public safety
● Successful re-closing, even in the failure of the arrester, improves
transmission system reliability
● Long term performance based on advanced silicone technologies
EGLA or gapless line arrester?
One of the countermeasures would appear to be installing full size
arresters specified with IEC or ANSI classification. However, the use
of an EGLA is a much smarter solution to protect the transmission
line from lightning.
Transmission systems are usually designed to withstand
internal surges such as switching surges and power frequency
overvoltage. Consequently, it may be practical to design the
arrester unit to handle lightning, but not switching surges and
power frequency over-voltages by ensuring it is equipped with Figure 2: EGLA installed on a powerline

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