LIGHTNING PROTECTION SYSTEM IMPROVEMENT ON EXTRA HIGH VOLTAGE 500 KV TRANSMISSION LINES IN INDONESIA USING EXTENDED MAST TERMINAL


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I. INTRODUCTION
Lightning overvoltage that happened at electric power
system could be caused by two kinds of lightning strikes, which
are indirect and direct strikes. Cases of direct strikes on
transmission lines, lighting can strike at phase conductor, tower
and ground wire. While indirect strikes is strike to the ground
which reside near by transmission lines.
Lightning direct strikes cause more problems in Extra High
Voltage Transmission lines. Strikes at phase conductor may
result flashover at insulator, and strikes at transmission tower or
ground wire may result back flashover. Both have potency to
bother the lines performance in transmitting electric power; in
this case will be read as phase to the ground problem generating
the opening of Circuit Breaker at the end of transmission lines.
Other effects of flashover are quality degradation of insulator
and broken insulator (glass type) which is needed to perform
replacement of insulator.



II. 500 KV EHV LINES PAITON KEDIRI
LIGHTNING DATA
Before the installation of Extended Mast Terminal at 500
kV EHV lines Paiton Kediri, Lightning Data analysis was
done to determine the regions in path of EHV lines that have
high density of lightning strikes. This lightning data also
very useful to predict lightning cycle that happened in area
of around EHV lines so that care to lightning strikes at the
lines can be concentrated at the time of high lightning
strikes frequency.
Center of obsevation for the lightning data is - 7.75023 S
, 112.8069 E. This coordinate is used as reference to derive
lightning data from Jaringan Deteksi Petir Nasional
(JADPEN) which using Lightning Position and Tracking
System (LPATS) technology. The border of the data window
is West : 111.9025 E, East : 113.7114 E, north : 7.4789 S,
and South : 8.0216 S. Lightning data was taken from
January 1st 1996 till December 31st 2000.



VI. CONCLUSION
Lightning Protection System using Extended Mast Terminal
is a new innovation compared to the conventional protection
used used at transmission lines which is ground wire. Lightning
strike on Extended Mast Terminal will prevent lightning current
parameter “read” the towers parameters. The lightning current
will only flow inside double shielded down conductor cable
which has very low inductance value (0.0037 microHenry) and
it will reduce the tower voltages due to the steepness of the
lightning current and reduce also the voltage stress accros the
insulators and prevent back flashover.
Installation of Extended Mast Terminal at tower 353 on 500
kV EHV lines Paiton-Kediri prevent back flashover that lead to
the insualtors damages. No broken insulators were found after
installing the EMT on tower 353 since early 2007.
Lightning strikes data collected during period of 2007-2008
indicate that the installation of EMT have protected the tower
from lightning direct strikes. Lightning current data which have
been collected shows that 8 data took place at transition season
on month March, April and May.