15MVA Cogeneration Power Plant Project in Zambia

Project Location: Industrial area surrounding Copperbelt Province, Zambia 

Power Plant Type: 15MVA Medium-Sized Cogeneration Power Plant (CHP)

Core Equipment: 1 x 15MVA 11/34.5kV On-Load Tap Changer; 2 x 4000kVA 11/0.415kV Off-Load Tap Changers; 1 x 2500kVA 11/0.433kV On-Load Tap Changer; 1 x 62.5kVA Grounding Transformer (all all copper-winding oil-immersed)

Contract Amount: RMB 4 million

Project Status: Delivered, equipment installation and commissioning completed, stable grid connection

 

Project Background

 

This project is located in an industrial cluster in Copperbelt Province or Central Province, Zambia, and is invested and constructed by a large local agricultural processing group. The group owns its own oil mill, feed mill, and is responsible for supplying power to the surrounding communities. The existing municipal power capacity is insufficient and extremely unstable, frequently causing production interruptions due to sudden voltage drops. Therefore, the group decided to construct a medium-sized combined heat and power (CHP) power plant, utilizing biomass (such as bagasse and sawdust) or natural gas as fuel to achieve self-consumption and surplus power grid connection.

 

Core Project Requirements:

 

The generator output voltage (typically 11kV) must be stepped up to 34.5kV and connected to the national power grid.

Simultaneously, reliable power distribution must be provided for multiple low-voltage electrical devices within the plant area (11kV/0.415kV, 11kV/0.433kV).

The grounding protection system must meet the requirements of the Zambian Electricity Corporation (ZESCO).

The equipment must operate stably for extended periods in Zambia's high-temperature (40℃+ during the dry season) and dusty environment.

 

TSTY Solution: Complete Customized Solution

Upon receiving the inquiry, TSTY dispatched technical engineers to Zambia for on-site investigation, working with the client's electrical team to analyze load characteristics, grid connection parameters, and environmental data. The final delivery was a complete oil-immersed transformer solution covering all scenarios from power generation to voltage step-up, power distribution, and grounding.

 

1. All-copper windings, resistant to high temperatures and overloads

 

All transformer windings use 99.97% electrolytic copper, with a conductivity ≥100% IACS.

Compared to aluminum windings, copper has 60% higher thermal conductivity, resulting in lower temperature rise in high-temperature environments.

Short-circuit withstand capacity is designed with a 1.5 times margin according to national standards to cope with sudden short circuits in the power grid.

 

2. Enhanced heat dissipation structure, adaptable to environments above 40℃

 

The height of the corrugated oil tank heat sink is increased by 20%, and the heat dissipation area is 35% larger than the standard model.

The top oil temperature limit is set at 58K (oil temperature ≤98℃ at an ambient temperature of 40℃), higher than the industry standard of 55K.

A forced air cooling auxiliary system is optional, automatically starting during high-temperature seasons.

 

3. Wide-range on-load tap changer for stable grid voltage

 

The 15MVA main transformer and 2500kVA auxiliary transformer utilize on-load tap changers with a 17-level tap changer range (±8×1.25%).

Voltage regulation accuracy reaches 0.625%/level, dynamically tracking grid changes without shutdown.

Equipped with an automatic voltage regulator (AVR), requiring no manual intervention.

 

4. Grounding transformer with comprehensive protection system

 

The 62.5kVA zigzag grounding transformer leads out the 11kV neutral point and grounds it through a small resistor.

Limits single-phase ground fault current to within 200A, protecting the generator stator core.

Simultaneously provides measurement signals for zero-sequence protection, enabling rapid fault clearing.