Underground Transmission Line Link between Bangkapi and Chidlom Terminal Stations

Project Name: Underground Transmission Line Link between Bangkapi and Chidlom Terminal Stations

Company Name: ATT Consultants Co, Ltd. (ATT)

Associated Firm: 

(a) Tokyo Electric Power Services Co., Ltd. (TEPSCO), Japan

(b) Electricit   de France (EDF), France

(c) TEAM Consulting Engineering and Management Co., Ltd. (TEAM), Thailand

Project Location: Bangkok Metropolitan Area, Thailand

Project Owner: Metropolitan Electricity Authority (MEA)

Type of Services: Feasibility Study, Conceptual Design, Tender Document, Construction Supervision (2002-2009)

Sector/Capacity: Energy/Two circuit of 230 kV Power Cable, 2x600 MVA

Project Cost: Approximate 5,000 million THB

Narrative of Project : The Chidlom Terminal Station is one of the key power station of MEA.  It situates in the heart of Bangkok Metropolitan area.  The station is equipped with 230 kV and 69 kV Gas Insulated Switchgear (GIS), and 3x250 MVA, 230/69 kV transformers, for over twenty years ago.  This station has been supplied by 230 kV transmission line, two (2) circuits from Bangkapi Terminal Station of Electricity Generating Authority of Thailand (EGAT) with about 7 km distance. 

The transmission lines are power cable oil-filled type, directly buried along the current right-of-way of the eastern railroad (Bangkok-Aranyaprathet) and the two other streets.  Since the transmission lines which are power cable type had been in service for a long time and have undergone to series of repair and maintenance, mainly due to oil leakage.  These are falling in poor and unreliable conditions for supply a huge power to Chidlom Terminal Station.  It is, therefore, needed to be changed, then a feasibility study had been made by the MEA.


The MEA’s study report had concluded that the new power cable transmission line route Bangkapi-Chidlom Terminal Station should be replaced and will be installed in a tunnel with 2.62 m inside diameter.  The tunnel route will be (now during construction as illustrated pictures) changed to run mainly beneath of the San Sab canal as below.

Highlight : Generally, the construction of a 230 kV transmission line, overhead type will require a right-of-way (ROW) width of 40 meters.  The R.O.W. 40 meters width of land between Bangkapi-Chidlom will be appropriated, if transmission line by overhead type is selected.  This directly impacts seriously to the environment. It is so MEA had selected the construction method to underground by tunnel type instead.

The tunnel is designed to accommodate high voltage power cable, 2,500 mm2 PPL oil-filled, two (2) circuits of 230 kV about 7 km of length.  It is approximately 30 m in depth and 2.62 m inside diameter.  The drilling for tunnel construction has used shield tunneling.  There are 10 shafts with varies distance 370-1,050 m apart.  The project is also to design a cooling plant building with water cooling pipes along the power cables that to reduce heat dissipation.