Afghanistan is a Landlocked South Asian Country Surrounded by Pakistan in the east and south, Turkmenistan, Uzbekistan and Tajikistan in the north and Iran in the west. Faryab is a border province in northern Afghanistan, where electrification was planned when Russian technology and engineering were available in the mid-1980s.
A 110-kV transmission interconnector with Turkmenistan, some 132 km (82 miles) long, was planned by the Afghanistan Electricity Department for importing 35 MW of peak load power to provide electrification to several villages surrounding Fiazabad, Jumabazar and Myamana. Although the construction work on this project was well underway, political unrest and a war prevented completion of the circuit.
However, since 2001, various countries have been extending assistance for the rehabilitation and reconstruction of the infrastructure in Afghanistan. India was one of the countries invited by the Ministry of Water and Power for the Transitional Islamic State of Afghanistan (MWP; Kabul, Afghanistan) to provide assistance in the development of the transmission system and distribution network in northern Afghanistan.
Following a formal request from Afghan's MWP to India's Ministry of External Affairs, the Water and Power Consultancy Services (India) Ltd. (WAPCOS), the government of India's premier consultancy, was entrusted with the contract for the supply of materials, engineering supervision and technical assistance linked to the provision of electricity supplies to households, agriculture, commercial and industrial development in Faryab Province.
The Turkmenistan interconnector is a 110-kV single-circuit transmission line from the Andhkey to Myamana substations supplying two 110/20-kV substations, Faizabad and Jumabazar, which were constructed on route. This section of the 110-kV network was designed to provide reliable service, safety during operation and maintenance, operational flexibility and easy maintenance.
The equipment for each switchyard was designed to withstand certain atmospheric conditions:
|Temperature||47.5°C (max) and -10°C (min)|
|Relative humidity||50% (max) and 10% (min)|
|Annual snow||15-mm (0.59-inch) radial thickness of ice|
|Seismic condition||As per Indian standard IS 1893|
|Altitude above mean sea level||1000 m to 1500 m (3280 ft to 4921 ft)|
The electrical design for the substation plant and the 110-kV and lower-voltage systems are generally based on the Indian Standard (IS) codes of practice or the IEC/IEEE standards. For the switchyard:
|110 kV||20 kV|
|Basic insulation level||550 kVp||125 kVp|
|Power-frequency voltage||230 kVp||50 kVp|
|Fault level (short-circuit current capacity)||25 kA for 1 sec||18 kA for 1 sec|
For auxiliary power requirements, each substation is equipped with two 100-kVA 20/0.415-kV transformers, with a standby 50-kVA diesel generator set to supply the auxiliaries in the event of an emergency, according to the following system parameters:
|110 kV||20 kV|
|Highest system voltage||123 kV||22 kV|
|Frequency||50 Hz||50 Hz|
|Design fault level||25 kA for 1 sec||18 kA for 3 sec|
The low-voltage distribution network is designed to operate at 415/240 V, with a permissible variation of ±10% at a frequency of 50 Hz ±5%. The combined variation of voltage and frequency is limited to ±10%.
SUBSTATION DESIGN STANDARDS
The design of the 110-kV switchyard is based on a main and transfer bus scheme (a bus coupler being installed for on-load circuit switching), which provides flexibility for equipment maintenance. For the 20-kV system, a single bus-bar scheme is installed with a sectionaliser with indoor switching control panels.
The 110-kV bus bars comprise aluminum conductors with steel reinforcement (ACSR) and are designed to withstand 25 kA for 1 second, and the tinned-copper flat bus bars in the 20-kV indoor switchboard are designed to withstand 18 kA for 1 second. Post insulators are used for the bus-bar support insulators having sufficient cantilever strength to withstand the combined action of electromagnetic forces under 3-phase short-circuit conditions, static weight and forces generated by wind pressure.
The three 110/20-kV substations are each equipped with two transformers: Faizabad with two 10-MVA units, Jumabazar with two 4-MVA units and Myamana with two 16-MVA units.
The design of the switchyard earthing systems is in accordance with IS 3043 and IEEE 80, and comprises a grid of buried mild-steel earth rods. The surfaces of the switchyards are covered by a 150-mm (6-inch) layer of crushed stone/gravel to improve the surface resistivity value. All earth conductors are laid at a depth of 600 mm (2 ft), with the joints being welded and taped. To determine the cross-section of the earth conductor, a fault level of 25 kA for 1 second was used while, for calculation of the step and touch potentials, the grid for 1 second was used after due allowance for the appropriate current division factor as specified in IEEE 80.
The lightning-protection design is based on the Razevig method of shielded zone and IS 2309. The protection of the switchyards is provided by 7/3.15-mm (7/0.124-inch) galvanized-steel shield wire that is connected to all the switchyard towers. Lightning arresters are used to protect all outdoor equipment in the switchyards from the effects of indirect lightning strokes, traveling waves and surges.
CONTRACT AND PROCUREMENT OF MATERIALS
The scope of the contract included the supply of all materials for the three 110/20-kV substations — Faizabad, Jumabazar and Myamana — and for one additional bay at the existing 110/20-kV Andhkey Substation. This US$3 million contract was awarded to M/s Angelique International Ltd., an Indian company.
Also included were materials to complete the construction of the 110-kV transmission line and the 20-kV distribution lines. M/s KEC International Ltd., an Indian manufacturer and turnkey contractor, was awarded the $2.7 million contract.
The final procurement was the supply and installation of 64 20/0.4-kV pole-mounted and indoor distribution substations. A $1.55 million contract was awarded to M/s Angelique International Ltd.
The supply of materials was subject to a one-year contract commencing in January 2004, but the logistics associated with this major project were complex. Materials were routed through different Indian ports and the Iranian port at Bander Abbas to the Afghanistan-Iran border at Islam Quala. The delivery of materials and equipment to the job site from Islam Quala was then completed by road a distance of more than 2800 km (1740 miles). This transit route covered 1300 km (808 miles) in Iran followed by 1500 km (932 miles) through Kabul in Afghanistan.
The construction of the 110-kV single-circuit transmission line, which was started in 1985, was designed to be supported by concrete produced by a manufacturing unit at Phul-e-Khumri in Afghanistan. Single-pole supports with double-pole supports at each angle position were erected, with the average span length being some 150 m (492 ft).
In 1985, almost 1700 concrete poles were erected for the planned 110-kV interconnector, but no conductor stringing was undertaken. Therefore, WAPCOS had to confirm that the strength of the 22-m to 25-m (72-ft to 82-ft) concrete poles was sufficient and that the structures remained vertical. Similar tests were conducted on sample crossarms at a designated Indian testing station. An additional 100 poles had to be erected to complete the line on a route that included several narrow river crossings.
The conductors used for the 110-kV single-circuit transmission line are 150-mm2 aluminium/25-mm2 steel ACSR supported by galvanised steel crossarms. The conductor stringing was undertaken by the Afghanistan Electricity Department with its own funding, supported by technical assistance by the WAPCOS engineering staff.
The 110/20-kV Myamana and Jumabazar substations were both commissioned in December 2006, and the 110/20-kV Faizabad Substation was commissioned in March 2007, followed by the commissioning of the 110-kV interconnector in July 2007.
Construction work on the 20-kV distribution network to supply the rural communities being undertaken by the Afghanistan Electricity Department is still in progress. The 20-kV distribution network is designed with dual construction to support the local 400-V, 3-phase network. This final stage of the electrification scheme includes the installation of 20 630-kVA and 12 400-kVA 20/0.4-kV ground-mounted indoor substations, 12 250-kVA and 20 160-kVA 20/0.4-kV pole-mounted substations.
This project required solutions to overcome many difficult issues that, in addition to the distances involved in moving materials and equipment to the job site, required the construction of transmission lines and substations in Afghanistan's deserted terrain in temperatures often exceeding 45°C (113°F). In spite of all these problems, the main contract was completed with only slight overrun on the specified time schedule.
Inder Singh was awarded a BE degree from Birla Institute & Technology and a post-graduate diploma in industrial engineering at the IIT, Delhi, and is now the general manager (electrical) of WAPCOS Ltd., where he has worked since 1993. Singh gained extensive experience in the operation and maintenance of thermal power plants in India, Libya and Zimbabwe while employed by the Central Electricity Authority and the Electricity Supply Commission (Libya).
D.V.S.N. Raju received a B.Sc. degree from the Regional Institute of Technology Jamshedpur, Ranchi University, and joined WAPCOS Ltd. 15 years ago, following appointments with Balaji Gears (Pvt.) 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 hydropower plants. He currently serves as additional chief engineer and is responsible for the management of extra-high-voltage and high-voltage transmission line projects in Bhutan, Afghanistan and Zimbabwe.
Hillol Biswas has a BE degree and for the past seven years he has held the post of senior engineer at WAPCOS Ltd., working mainly in the field of transmission lines. During his 14-year career, Biswas has experience working in India, Bhutan, Afghanistan and Sudan, among other places. He is a member of the Institution of Engineers, India and CIGRÉ.
Viren Dutt Sharma was awarded a B.Tech degree from Kuruskhetra University and has worked as a senior engineer for WAPCOS for seven years on extra-high-voltage substation design. Sharma has considerable experience having worked in India, Bhutan, Afghanistan, Zimbabwe and Japan, and is a member of the Institution of Engineers, India.