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.

RECENT HISTORY

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.

PROJECT DESIGN

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
Grounding	Solid	Solid

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.