The Directorate is responsible for the operation and maintenance of all the existing Hydro Power Stations and the associated transmission system.

Generation
ZESCO produces most of its electric power from hydro-power stations which constitutes about 99.9% of its total production and the remaining 0.1% comes from Diesel Power Stations.

Kafue Gorge Power Stations
This is the largest Power Station in Zambia.  It is located on the Kafue River and its construction was completed in 1972.  The Station has an installed capacity of 900MW with 6 machines of 150mw each.  Two machines  feed one transformer consisting of three single-phase units.  There are therefore ten single-phase units including the spare unit.

Victoria Falls Power Station
he station is a run of river station located on the Zambezi River at Victoria Falls.  It has an installed capacity of 108MW and comprises three power stations in one. 

·          Station A was commissioned in 1936.  It has an installed capacity of 8MW consisting of 2 machines of 1MW each and another 2 of 3MW each. 

·          Station B was commissioned in 1968 and has an installed capacity of 60MW consisting of 6 machines of 10MW each. 

·          Station C was commissioned in 1968 and has an installed capacity of 40MW consisting of 4 machines of 10MW each. 

Small Hydro Power Stations  

There are four (4) small hydro stations with a combined capacity of 23.75MW.  These are Lusiwasi (12MW), Musonda Falls (5MW), Chishimba Falls (6MW) and Lunzua (750Kw).  Generally, the small hydros do not have sufficient water storage capacity to operate through the dry season. 
Kariba North Bank Power Station
The station is located on the north bank of Kariba Dam on the Zambezi River.  It has an installed capacity of 600MW with 4 machines of 150MW each.  Until recently, Kariba North Bank Power Company (KNBC) was under the Management control of ZESCO on behalf of the government.  Operationally, however, it is still under the control of ZESCO and its output is considered part of the national production. 

Main Reservoirs and Water Situation
The main reservoirs for Kariba North and Kafue Gorge Power Stations are Kariba Dam  and Itezhi-Tezhi Dam on the Zambezi and Kafue Rivers respectively.  Kariba Dam has long term storage capacity.  The water levels in the dams for the previous year are shown below. 

Water is the primary source of energy for production of hydro electricity.  Due to inadequate rainfall during the last rainy season, the water level in the Itezhi-Tezhi dam is low.  As a result of this, power generation has been reduced at Kafue Gorge. 

Surplus Capacity
The current ZESCO installed capacity (including that of KNBC) is about 1631MW as against the total demand of about 1200MW.  This gives a surplus capacity of 431MW some of which is exported within the region.  However, rehabilitation works on the generators at the main power stations have commenced under the World Bank funded Power Rehabilitation Project (PRP). 

At least two machines will be out of service for rehabilitation works at Kafue Gorge and Kariba North at all times for the next three (3) years, thereby reducing the surplus capacity to 131MW.  This means a greatly reduced level of export during this period.  Therefore whenever an extra machine is taken out of service for various reasons, it  is necessary to import power in order to meet the national demand. 

The Role of Zambezi River Authority (ZRA) 

The Zambezi River System and associated Kariba Dam and Lake are managed by ZRA.  They are responsible for yearly allocation of water usage to ZESCO and ZESA for Zimbabwe.  It is also responsible for operation and maintaining the Kariba Dam. 

Transmission System 
The transmission system has a total of 4,638 km of transmission lines spread as follows:  2,008 km of 330kV lines, 348 km of 220kv, 85 km of 132kV, 704 km of 88kV, and 2,823 km of 66kV lines (of which 2,180 km are under ZESCO’s Distribution and Supply Directorate).  The total transformer installed capacity is about 3,000MVA. 

It serves as a national grid to transport power from the generating stations and other systems to the Distribution Bulk supply points throughout the country and also to the Copperbelt Energy Corporation and Export points.

The transmission system is currently undergoing refurbishment under PRP. 

System Coordination and Cont rol 
The National Control Centre coordinates all the operations in the system which includes transmission switchings, generation, dispatch and exports.  The Control Centre uses a SCADA (Supervisory, Control and Data Acquisition) system which was commissioned in June, 1996.  The SCADA system covers 24 transmission stations which includes four (4) Power Stations and twenty (20) Substations. 

Southern African Power Pool (SAPP) & Stem 
ZESCO is a member of SAPP which falls under SADC.  There are twelve (12) member utilities of SAPP, whose objectives are to coordinate the planning and operation of member systems and to promote energy trading among members in the region.  For example, during the 2001/2002 period, ZESCO exported 1,590GWh of energy mainly to ESKOM of South Africa, and wheeled 265GWh to ESKOM and ZESA (Zimbabwe) from SNEL (Congo DR).

The Short Term Energy Market (STEM) for electricity trade in the region was recently established by the SAPP as a prelude to the eventual establishment of a spot market.  ZESCO and KNBC have recently commenced joint trading of surplus energy in the STEM.