Most people may be familiar with “Electricity Generating Authority of Thailand (EGAT)” as the largest power producer in Thailand. However, some may not know that EGAT undertakes another major duty; a transmission of electricity generated by EGAT’s power plants and of electricity purchased from other power producers through EGAT’s power system networks covering the whole country with pressure levels at 500 kV, 230 kV, 115 kV and 69 kVs to Metropolitan Electricity Authority, Provincial Electricity Authority and other direct customers. Moreover, EGAT also distributes power to electricity authorities of neighbouring countries including Lao People’s Democratic Republic (Lao PDR) and Malaysia.

         Continuing transmission system development plans are required to standardize power system stability and liability, to serve higher demand on power in all parts of the country as well as to efficiently connecting domestic and overseas power plants to EGAT’s electricity system. Power transmission system development plans comprise additional construction of power transmission system and improvement or change of equipment to maintain continuity of power transmission.



         Normally power cable life span is approximately 40 years in average while equipment in high-voltage electricity station can be used for around 25 years. In case of breakdown or out - of - order, they would be repaired and maintained. However, at the end of their life spans, power cable and equipment will become deteriorated, which causes risks to electricity system including more maintenance works and costs. Moreover, some equipment versions may be outdated, so they have to be improved or replaced accordingly. Subsequently, power transmission system development throughout the country was originated from these reasons. EGAT has divided the projects into 5 categories as follows:

         Transmission system development Projects to accommodate increasing demand for power consumption

         These projects are operated with aims to meet the increasing demand for power consumption from existing industrial sector, private sector and general users as well as continuing applications for power usage. There are projects under construction such as transmission system development in Bangkok and perimeter and provincial transmission system expansions. In the future, there will be more projects to accommodate power consumption in special economic zones as well.


         Transmission system development projects to reinforce power security

         EGAT has gradually operated transmission system development projects to reinforce power security throughout regions in the country, to ensure continuity and sufficiency of power supply and to increase capability of transmission system to connect to renewable power plants in accordance with the Government policy. In the future, there will be a submarine cable system development project operated to Ko Samui District, Surat Thani Province as well.


         Transmission system improvement and expansion projects

         These projects are operated with aims to improve and replace transmission system equipment that has been used for a long time at substations, transmission system and control buildings in high voltage substations or add more equipment to ensure stability of power supply. There are projects under construction that are mainly high voltage substations and high voltage cables throughout the country.


         Transmission system development projects to accommodate connection to new power plants

         These projects are operated with aims to connect power system to new plants owned by EGAT and private power producers including power purchase system from foreign countries. The projects comprise transmission system for power purchase form independent power producers, transmission system expansions to accommodate power purchase form cogeneration systems of small power producers as specified in power purchase regulations B.E. 2553, transmission system for power purchase form Nam Ngum 3 and Nam Theun 1 Hydro power plants, transmission system development at areas in Loei, Nong Bua Lamphu and Khon Kaen for power purchase from Lao PDR, and transmission system development at areas in Ubon Ratchathani, Yasothon and Amnat Charoen for power purchase from Lao PDR.


         Transmission system development projects for grid to grid interconnection.

         These projects are operated with aim to have power systems of Thailand and neighbouring countries connected as grid to grid. The projects are taken at existing grid-connected points and potential areas that are expected to have grid-connected points constructed or expanded in the future to accommodate ASEAN Power Grid development.

         Currently, EGAT and Lao Holding State Enterprise (LHSE) exchange power (import/export) through 5 grid-connected points with pressure at 115 kV, which are located along Thailand - Lao PDR border areas (Nong Khai - Vientiane / Bueng Kan - Pakxan / Nakhon Phanom - Thakhek / Mukdahan 2 - Pak Bo / Sirinthon - Bang Yor). EGAT and Tenaga Nasional Berhad (TNB) of Malaysia also exchange power through grid-connected point with pressure of 300 kV HVDC.

         Similar to blood vessels, the overhead high voltage cables on gigantic steel towers or high voltage transmission towers which are towered along the way from north to south, transmit electric power to everywhere for everyone in Thailand. EGAT promises that EGAT shall always look after and maintain these blood vessels, so that they could work perfectly to ensure happiness of Thai forever.