Afghanistan is a landlocked South-Asian country surrounded by the neighbouring countries of Pakistan, Tajikistan, Turkmenistan, Uzbekistan and Iran. In the period following the recent conflicts in Afghanistan, various countries and international organizations embarked on several rehabilitation programmes, which included the construction of hydroelectric power plants and transmission system networks.

The Salma Dam hydroelectric power plant, which has a planned installed capacity of three 14-MW units, is located 162 km (101 miles) east of the town of Herat, 2 km (1.2 miles) downstream from Salma village and 9 km (5.6 miles) from the village of Chist-e-Sharif in Herat Province. Positioned on the Hari Rud River, this hydroelectric plant has a catchment area of 11,700 sq km (4,517 sq miles) and a storage capacity of 560 million cu m (732.5 million cu yd). The anticipated annual energy output is 86.6 GWh assuming 90% availability and 186.13 GWh assuming 75% availability.

The Indian Ministry of External Affairs awarded WAPCOS a contract to complete construction of the Salma Dam hydroelectric power plant and an associated 110-kV single-circuit transmission line from the power plant to Herat.

Optimum Circuit Voltage

Power system studies revealed a 110-kV single-circuit transmission line constructed with a delta configuration was the optimum circuit voltage to transmit 42 MW from Salma Dam to Herat. The transmission line was designed to maintain satisfactory voltage regulation with low line losses, without having to install a reactor at the receiving end to overcome no-load voltage rise.

The line spans 157 km (97.6 miles) through plains and moderate hilly terrain. The route from the power plant to the town of Obe, a distance of 49 km (30.5 miles), is through hilly terrain and from Obe to Herat, the remaining 108 km (67.1 miles), is through flat terrain. The entire circuit had to be able to withstand snow in the winter and extreme heat in the summer.

The climatic and isoceraunic conditions required the 110-kV transmission line to be strung with a Panther 30/7 ACSR phase conductor with each strand being 3 mm (0.118 inches) in diameter and a galvanized steel 7-strand ground wire with 3.35-mm (0.132-inch)-diameter strands. The towers were designed for a basic wind speed of 39 m/sec (128 ft/sec), in accordance with Indian Standard 802: 1991 and 1995. The towers also were designed with increased height to accommodate the hilly terrain and were subject to type testing at several Indian test stations, including the Central Power Research Institute (CPRI), Kalpataru Transmission Power Ltd. and Richardson & Cruddas Ltd.

Line Construction

The turnkey contract for transmission line construction was awarded to Jaguar Overseas Ltd., which had previously completed and commissioned a similar government of India contract in Laos. The terms and conditions of the original contract, valued at INR31.51 crores (US$7 million), with a completion date of within 27 months, were subsequently revised with the contract value increased to INR40 crores (US$8.8 million) and the time for completion increased to 36 months.

Construction of the line was challenging, because the main road from Salma to Herat is unpaved, and the 157-km (98-mile journey takes around six and a half hours. Daily journeys were absolutely essential to ensure progress and day-to-day coordination of work activities. The line passes several areas where the use of vehicles is impossible, so contractors used donkey carriage transport to access many tower positions.

The major line materials were supplied by companies based in India and China: steel towers from Transrail Structures Ltd.; line conductors from Smita Conductors Ltd.; ground-wire conductor from Bharat Wire Ropes Ltd.; insulator hardware from Asbesco Ltd.; and line insulators from Dalian Ceramic Technic Co. Ltd.

The transmission line construction contract is in advance of the commissioning of the Salma Dam hydroelectric power plant. The line was some 90% complete in December 2008, with the foundation of stubs cast and towers erected. The 14 km (8.7 miles) of conductor stringing that remained had to be deferred as a result of heavy snowfall, which temporarily halted line construction work. The line was completed in spring 2009.

A Step Forward

The commissioning of the Salma Dam-to-Herat 110-kV transmission line is a significant step forward in the program to rebuild infrastructure in war-torn Afghanistan. Although the generation capacity of the Salma Dam hydroelectric power plant is relatively small in terms of the installed capacity, this power source will substantially improve the living standards of the population of Herat Province.


O.P. Chibber (wapcos@yahoo.co.uk) is chief engineer at WAPCOS Ltd. He has a bachelor's degree in engineering and a P.G. diploma in system and computer programming from the Delhi Productivity Council. Chibber, who has worked for more than 27 years in India, Bhutan, Afghanistan, Zimbabwe and Japan, has international experience in hydro planning, transmission, distribution and power system studies.

D.V.S.N. Raju (dndraju@yahoo.co.in) serves as chief engineer at WAPCOS Ltd. and is responsible for the management of extra-high-voltage and high-voltage transmission line projects in Bhutan, Afghanistan, Zimbabwe and Laos. He received a bachelor's degree from the Regional Institute of Technology Jamshedpur, Ranchi University, and joined WAPCOS 16 years ago, following appointments with Balaji Gears Ltd., Hyderabad and the Central Electricity Authority. During his career at WAPCOS, Raju has held a series of appointments linked to design studies, specifications and contracts for hydroelectric power plants.

M. Manoj Kumar (manojkumar.07@gmail.com) joined WAPCOS Ltd. as a transmission and substation engineer some five years ago, after being awarded a B.Tech degree in electrical engineering and a M.Tech degree in power systems. With considerable work experience in India, Bhutan, Afghanistan and Laos, Kumar is a member of IEEE and a young Individual member of CIGRÉ in India.

Hillol Biswas (hillolbiswas@rediffmail.com) held the position of senior engineer for seven years at WAPCOS Ltd., working mainly in the field of overhead transmission lines. During his 15-year career, Biswas has gained experience working in India, Bhutan, Afghanistan and Sudan. He recently joined the consulting firm British Power International in the U.K.

Design Parameters
Parameter Value or Range
Maximum temperature Conductor 85°C (185°F)
Minimum temperature -36°C (-33°F)
Maximum ambient temperature 40°C (104°F)
Mean annual temperature 15°C (59°F)
Basic wind speed 39 m/sec (128 ft/sec)
Relative humidity Maximum 98%, minimum 5%
Maximum rainfall 1,826 mm ( 72 inches ) per annum
Rainy months December to February
Number of rainy days 100 per annum
Thunderstorm days 60 per annum
Altitude 1,000 m to 2,000 m (3,281 ft to 6,562 ft)
Seismic coefficients Horizontal 0.05 g; vertical 0.25 g
Maximum snow days per month 6
Maximum snow depth 609.6 mm (24 inches) per month
Ice radial thickness 15 mm (0.60 inches)
Design Features of the 110-kV Transmission Line
Voltage Highest system voltage 123 kV
Phase conductors 30/7/3-mm diameter Panther
(0.83-inch o.d.)
Rated current 427 A
Ground wire conductors 7/3.35-mm diameter galvanized steel
(0.4-inch o.d.)
Frequency 50 Hz
Neutral grounding Solid earthing
Basic insulation level (BIL) 550 kV peak
Power frequency withstand (wet) 460 kV rms
Short-circuit level 20 kA
Width of right of way 22 m ( 72 ft)
Circuit configuration Single-circuit delta
Basic span length 305 m (1,000 ft)
Number of towers 385 normal height
147 increased height
Phase Conductor Sags and Tensions
Wind pressure kg/m2 (psf) Temperature °C (°F) Radial Ice mm (inches) Sag m (ft) Tension kg (lb)
0 15 (59) 0 4.954 (16.3) 2,286 (5,040)
109 (22.3) 15 (59) 0 7.243 (24.2) 3,994 (8,805)
109 (22.3) -10 (14) 0 6.589 (21.6) 4,390 (9,678)
27 (5.5) -10 (14) 15 (0.6) 7.034 (23.1) 4,761 (10,494)
27 (5.5) -10 (14) 0 4.450 (14.6) 2,945 (6,493)
0 -36.3 (-33) 0 3.323 (10.9) 3,408 (7,513)
0 -36.3 (-33) 15 (0.6) 5.979 (19.6) 4,919 (10,845)
82 (16.8) -10 (14) 0 5.926 (19.4) 3,882 (8,558)
0 85 (185) 0 7.450 (24.4) 1,520 (3,351)

Companies mentioned:

Asbesco www.asbesco.in

Bharat Wire Ropes http://bharatwireropes.com

CPRI www.cpri.in

Dalian Ceramic www.dlpower.cn

Indian Ministry of External Affairs www.mea.gov.in

Jaguar Overseas www.jaguaroverseas.com

Kalpataru Power www.kalpatarupower.com

Richardson & Cruddas www.richardsoncruddas.com

Smita Conductors www.smitaconductors.com

Transrail Structures www.transrailltd.com

WAPCOS Ltd. wapcos.gov.in