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Customer Success Story

Bang Saphan

Increased power transmission capacity over AC intertie by improved transient stability by means of SVC

 Static var compensator (SVC) supplied by Hitachi Energy was commissioned in 1994 in the Bang Saphan 230 kV substation of the Electricity Generating Authority of Thailand (EGAT).


The SVC, rated at 50 Mvar inductive to 300 Mvar capacitive at 230 kV, was installed on a turnkey basis. 

The power system in Thailand is undergoing strong expansion. Increased generating capacity in different parts of the system increases the power transfer demands on the transmission system and on transfer of power over long distances. 

A weak part of the bulk system is a tie-line linking the load centre around Bangkok with a major generation area further to the south by means of a double-circuit 230 kV line and a double-circuit 115 kV line. The length of this inter connection is about 700 km, and the SVC at Bang Saphan is located approximately half-way in between.

Transient stability is a limiting factor for power transmission of this interconnection. The purpose of the SVC is consequently to increase the transient stability, thereby increasing the power transmission capability of the system by a considerable amount.

Main data
System SVC
Commissioning year 1994
Controlled voltage 230 kV
Dynamic range 50 Mvar inductive to 300 Mvar capacitive
Control system Three-phase voltage control by means of a voltage regulator.
Regulator functions include POD, strategy selection and gain supervision/optimisation. 
Thyristor valve Water-cooled three-phase valves with magnetic firing.

Bang Saphan: Increased power transmission capacity over AC intertie by improved transient stability by means of SVC