Africa’s electricity infrastructure is entering a period of significant expansion.
New solar farms, wind projects, hydropower stations, industrial developments, cross-border transmission lines, substations, and distribution networks are being built or upgraded across different parts of the continent. At the same time, existing grids are being asked to carry more power and connect areas that previously had limited electricity access.
Renewable energy is an important part of this expansion, but adding generation capacity is only the beginning.
A solar plant can produce electricity, but that electricity still has to be collected, stepped up to a suitable voltage, transmitted through the network, integrated with existing substations, and eventually delivered to industrial facilities, commercial loads, communities, and other users.
This is where the power transformer remains fundamental.
As renewable generation becomes a larger part of Africa’s electricity mix, the role of the power transformer does not become smaller. In many projects, transformer requirements actually become more varied because the network has to connect new generation sources, existing substations, expanding transmission systems, and growing distribution loads at the same time.
For HONLE, these projects are not simply about supplying a power transformer with the required MVA rating. Voltage level, generation type, grid structure, loading pattern, installation environment, future expansion, and the position of the transformer within the network all influence how the equipment should be configured.
Renewable Generation Is Only One Part of Grid Expansion
When a new renewable energy project is announced, installed generation capacity often receives most of the attention.
From the electrical system perspective, however, that generation only becomes useful when the electricity can be transported to where it is needed.
A utility-scale renewable project may follow a power path such as:
Solar or Wind Generation → Collection System → Step-Up Power Transformer → Transmission Network → Grid Substation → Distribution Network → Industrial, Commercial and Residential Loads
Each stage performs a different electrical function.
The transformer connects several of these stages by changing voltage levels and allowing large amounts of electricity to be transmitted more efficiently.
Generation Voltage Is Different from Transmission Voltage
Solar inverters and wind turbine systems do not normally deliver electricity directly at the voltage used by a regional transmission network.
Power from individual generating units is first collected at a suitable voltage. A step-up power transformer then raises that voltage so electricity can be transmitted with lower current for the same power level, helping reduce conductor losses and making long-distance transmission more practical.
At the receiving end, transformers are again required.
Substation power transformers reduce transmission voltage to the levels required by regional distribution systems, industrial networks, or downstream substations.
Renewable energy may change where electricity is generated, but it does not remove the need to coordinate voltage levels throughout the power system.
New Generation Can Require New Network Capacity
Renewable resources are not always located close to major load centers.
Strong solar resources may be found far from cities or industrial areas. Large wind projects may be developed in locations with limited existing transmission capacity. Hydropower stations may also be located considerable distances from the areas where most electricity is consumed.
Building the generating plant alone may therefore be insufficient.
The wider project can involve new transmission lines, additional substations, higher transformer capacity, expansion of existing substations, upgraded switchgear and protection systems, and new distribution connections.
For this reason, growth in renewable generation and growth in power transformer demand are often closely connected.
Why Renewable Projects Often Require Additional Power Transformer Capacity
A power grid is designed around expected generation, load, power flow, voltage levels, system impedance, and fault conditions.
When significant new generation is connected, some of these conditions change.
Existing Transformers May Not Have Enough Capacity
A substation originally designed around a certain level of power flow may not have sufficient transformer capacity for a major new solar, wind, or hydropower project.
If additional generation is connected to the same network, the resulting transformer loading and power flow still have to remain within the limits of the existing equipment and wider substation.
Expansion can therefore involve installing another transformer unit, replacing an existing unit with a higher-capacity power transformer, or modifying the overall substation arrangement.
This is one reason transformer planning should consider both present requirements and realistic future development rather than focusing only on the immediate project.
New Projects Can Change Power Flow
Many conventional distribution networks were originally developed around electricity moving mainly in one direction:
Grid Substation → Distribution Network → Load
Renewable generation introduces power at additional points in the system.
A large solar project connected to a regional network, for example, may inject power into an area that previously received most of its electricity from another part of the grid.
Depending on generation and demand at a particular time, this can change how heavily individual transformers and transmission paths are loaded.
The transformer therefore has to be considered as part of the actual future power-flow arrangement, not simply according to the way the network operated before the renewable project was connected.
Industrial Growth Adds Another Layer
Renewable energy is not the only reason electricity infrastructure is expanding across African markets.
Mining, mineral processing, manufacturing, water treatment, transportation, data infrastructure, commercial development, and urban growth can all create additional electricity demand.
In some areas, new generation and industrial development are happening together.
A solar plant may be developed to support an industrial zone, while an expanding mine may require its own substation, new transmission connection, and additional power transformer capacity.
Transformer infrastructure can therefore support both sides of the system: bringing new generation into the grid and delivering additional electricity to growing loads.
How Renewable Energy Changes Power Transformer Operating Conditions
Renewable generation does not change the basic role of a power transformer, but it can change how the power transformer is loaded and the electrical conditions it needs to handle.
Understanding those operating conditions is important when determining capacity, voltage ratio, impedance, cooling, tap-changing requirements, insulation, and the surrounding protection arrangement.
Renewable Generation Is Variable
Solar generation changes throughout the day and is influenced by irradiance and weather conditions.
Wind generation also varies according to available wind.
Transformers connected directly to renewable generation can therefore experience loading patterns that differ from those supplying relatively stable industrial loads.
A solar step-up transformer, for example, may carry very little generation-related load during the night and operate much closer to its expected daytime loading during periods of strong solar production.
Transformer selection should therefore consider more than the maximum installed generation capacity.
The expected loading profile, operating hours, temperature conditions, overload expectations, and planned future expansion can all influence the final transformer design.
Power May Flow in Different Directions
As utility-scale and distributed renewable generation become more common, some parts of the grid may experience bidirectional power flow.
A network that historically imported electricity from an upstream substation may export power during periods when local renewable generation exceeds local demand.
The transformer itself can operate with power flowing in either direction, provided its design and system conditions are suitable. However, the wider project still needs to consider protection coordination, voltage regulation, metering, tap control, and the expected operating mode of the network.
This is particularly important when an existing substation is being adapted for a connection that was not anticipated when the original system was designed.
Power Electronics Become More Common
Solar inverters, wind converters, battery energy storage systems, variable frequency drives, and many modern industrial loads rely on power electronic switching.
These technologies provide valuable control over generation and loads, but they also change the electrical characteristics of the network.
Harmonics, switching characteristics, power factor behavior, and reactive power control may therefore need to be considered when specifying a power transformer for a system containing a large amount of power-electronic equipment.
This does not mean every solar or wind project automatically creates a serious harmonic problem.
The actual effect depends on the inverter or converter design, filtering, system impedance, network strength, operating conditions, and the combination of other connected equipment.
For transformer selection, the important point is to understand the electrical environment rather than assuming that every renewable project behaves in the same way.
Voltage Conditions Can Become More Complex
Renewable generation can also influence voltage regulation, particularly in geographically large networks or grids with relatively weak interconnections.
The effect depends on factors such as generation capacity, transmission distance, network strength, reactive power control, transformer capacity, load distribution, and substation arrangement.
A power transformer cannot solve every voltage or grid-stability issue by itself.
However, transformer ratio, impedance, tap range, on-load or off-circuit tap-changing arrangement, and coordination with the surrounding system all form part of the final voltage-control strategy.
Step-Up Power Transformers Connect Renewable Generation to the Grid
For utility-scale renewable energy projects, the step-up power transformer is one of the main links between the generating plant and the wider electricity network.
The required configuration depends heavily on the generation technology, collection voltage, plant capacity, and point of interconnection.
Solar Power Plants
A large solar plant normally contains multiple inverter units or inverter stations.
Their output is collected through the plant’s medium-voltage network before being transformed to the voltage required at the grid connection point.
Depending on the project, voltage transformation may take place in more than one stage.
A simplified arrangement can be represented as:
PV Modules → Inverter → MV Collection System → Step-Up Power Transformer → Transmission Grid
The required transformer voltage ratio depends on the inverter output arrangement, collection system, substation design, and local grid.
Some projects operate through medium-voltage networks, while larger solar plants connected to regional transmission systems may require transformers associated with voltage levels such as 35kV, 66kV, 110kV, or other project-specific grid voltages.
The correct solution is therefore determined by the actual connection scheme rather than by the fact that the generation source is solar.
Wind Power Projects
Wind farms follow a similar overall principle.
Electricity from individual turbines is collected through a medium-voltage system and then transferred through step-up transformers before entering the transmission network.
Transformer capacity needs to reflect the installed generating capacity, expected production profile, connection voltage, loading conditions, and the layout of the wind farm and grid substation.
The distance between generation areas and transmission infrastructure may also influence how the electrical system is arranged.
Hydropower and Other Generation
Hydropower remains important in many African electricity systems.
Its generating characteristics differ substantially from solar and wind, but hydropower stations still depend on generator step-up transformers and substation equipment to connect generation to transmission networks.
The generation source can change, but voltage coordination between the generating plant and the transmission system remains necessary.
The same principle applies to conventional generation and hybrid projects that combine renewable energy with battery storage or other sources.
Substation Power Transformers Become More Important as Transmission Networks Expand
Renewable generation cannot be considered separately from transmission infrastructure.
When countries strengthen national grids, connect previously isolated regions, or increase cross-border electricity exchange, substations become the points where different voltage levels and transmission routes come together.
Power transformers sit at the center of these substations.
Transmission Expansion Creates New Transformation Points
A new transmission line normally connects substations rather than delivering power directly to end users.
At these substations, power transformers may be required to connect different grid voltage levels, step power down for regional distribution, supply industrial networks, support new generation connections, or increase the capacity of an existing grid node.
As transmission networks become more interconnected, both the number of transformation points and the capacity required at important substations can increase.
Existing Substations May Need Expansion
Grid development does not always require construction of a completely new substation.
In many cases, existing infrastructure is expanded.
A substation that initially operates with one or two transformers may later require additional capacity because of growing local demand, new renewable generation, additional transmission circuits, industrial development, or a new regional interconnection.
Adding another power transformer may allow capacity to increase while retaining part of the existing substation infrastructure.
Whether this is practical depends on available space, busbar capacity, switchgear ratings, protection systems, short-circuit levels, foundations, connection arrangement, and the condition of the surrounding equipment.
The new transformer also has to be electrically compatible with the system it is joining.
Redundancy Can Become More Important
As a substation supplies more users or supports a larger portion of the network, the consequences of taking one transformer out of service can become more significant.
Utilities and project owners may therefore consider arrangements that allow maintenance, equipment outages, or certain fault conditions to be managed without completely interrupting supply.
The required level of redundancy varies from project to project.
It can be particularly important for substations supplying cities, large industrial areas, mining operations, water infrastructure, hospitals, transport systems, data facilities, or other loads where prolonged outages have substantial consequences.
Distribution Transformers Remain Essential to Electrification
Large transmission lines and high-voltage substations often receive the most attention because of their size, but electricity ultimately has to reach the load.
This means distribution transformers remain essential even as high-voltage transmission capacity expands.
Transmission infrastructure can move large quantities of power between regions. Substation power transformers can then reduce the voltage for regional networks. Further transformation is still required before electricity reaches the voltage used by communities, commercial buildings, factories, farms, schools, hospitals, water systems, telecommunications facilities, and smaller industrial sites.
Africa’s grid expansion can therefore create transformer demand at several voltage levels.
It is not simply a market for large 110kV power transformers.
A complete network may require high-voltage power transformers, medium-voltage substation transformers, and large numbers of distribution transformers working together.
Rural and Remote Networks Have Different Priorities
A transformer supplying a remote distribution network can operate under very different conditions from one installed in a large urban substation.
Load density may be lower, feeder distances may be longer, maintenance access may be more difficult, and exposure to the surrounding environment may be greater.
In some areas, reliability and ease of maintenance may carry more weight because replacement equipment or service personnel cannot reach the installation quickly.
The appropriate transformer configuration therefore depends on the actual application rather than applying the same design approach to every location.
Existing Grids and New Renewable Projects Must Work Together
An important feature of Africa’s ongoing energy transition is that many renewable projects are not being connected to completely new electrical systems.
New generation frequently has to work with existing transmission and distribution infrastructure.
That infrastructure may include equipment installed at different times, designed for different capacity levels, and operating under different technical conditions.
Connecting new renewable generation to an existing system can therefore be more complex than simply designing the generating plant itself.
Existing Voltage Levels Shape the Project
A renewable plant cannot select its final grid connection voltage independently of the surrounding network.
The available transmission or distribution system determines the practical point of connection.
Transformer ratios therefore have to match the voltage levels actually used at that point in the grid.
The same applies when an existing substation is expanded.
A new power transformer has to operate with the existing busbars, switchgear, protection equipment, system frequency, insulation requirements, and voltage arrangement.
For parallel operation with existing transformers, additional technical conditions also need to be checked carefully.
Transformer Capacity Must Be Considered Together with Network Capacity
A grid may have the appropriate transmission voltage but insufficient transformer capacity at a particular substation.
In this situation, connecting new generation may require transformer expansion before the network can make effective use of the additional power.
The opposite can also occur.
A region may have sufficient generation and transformer capacity while the transmission network is unable to move enough electricity toward another major load center.
This is why generation, transformers, substations, and transmission lines need to be considered as parts of the same electrical system.
Increasing capacity in one part of the network does not automatically remove bottlenecks elsewhere.
Protection Coordination May Need to Be Reviewed
Connecting significant new generation can change fault-current contributions and power-flow conditions within a network.
Protection settings and equipment coordination may therefore need to be reviewed when a major generation source is added.
Transformer impedance also influences system fault current.
For this reason, a new or replacement power transformer should not be selected only according to rated voltage and MVA capacity.
The way it interacts with the rest of the substation also matters.
Future Development Should Be Considered Realistically
Power infrastructure normally has a much longer operating life than many types of industrial equipment.
A transformer installed today may remain in service while the surrounding grid changes considerably.
If a region is expected to add more renewable generation, industrial loads, distribution connections, or transmission capacity, the transformer arrangement should take that realistic development path into account.
This does not mean installing the largest transformer possible.
Oversizing also affects investment, no-load losses, operating efficiency, infrastructure requirements, and project economics.
A more practical approach is to match the current system properly while considering how additional capacity could be introduced later if the network continues to grow.
Environmental Conditions Influence Transformer Design Across Africa
Africa does not represent one single transformer operating environment.
Installation conditions in a coastal region can be very different from those in a desert, tropical area, high-altitude region, mining site, or heavily industrialized zone.
For projects across African markets, site conditions therefore need to be considered together with the electrical specification.
High Ambient Temperature
Higher ambient temperature reduces the thermal margin available during transformer operation.
Cooling arrangement, radiator design, oil temperature, winding temperature rise, expected loading, and local ambient conditions should therefore be considered together.
For heavily loaded substations, these factors become especially important because thermal performance affects both allowable loading and long-term insulation aging.
Dust and Sand
Outdoor substations in dry regions may be exposed to substantial dust and sand.
Bushings, external insulation, radiators, control cabinets, sealing arrangements, and maintenance requirements should reflect the installation environment.
Dust accumulation can also affect cooling surfaces and external insulation performance if operating and maintenance conditions are not considered during the design stage.
Humidity and Coastal Conditions
High humidity, salt contamination, and corrosive coastal environments can influence external insulation, enclosures, fittings, coatings, and overall corrosion protection.
A transformer intended for a coastal installation may therefore require different surface-treatment and insulation considerations from equipment installed in a dry inland area.
Altitude
At higher elevations, reduced air density can affect cooling and external insulation performance.
Transformer design may therefore require adjustment when installation altitude exceeds the conditions assumed by the applicable standard or normal rating basis.
These environmental considerations are not unique to renewable energy projects.
However, they become particularly relevant when new substations and transmission networks are being developed in areas that previously had limited large-scale electrical infrastructure.
HONLE Power Transformers for Grid Expansion and Renewable Energy Projects
The growth of renewable energy across Africa does not reduce the importance of conventional transformer infrastructure.
Instead, it creates more points where generation, transmission systems, substations, industrial networks, and distribution grids need to operate together.
At HONLE, we manufacture power transformers and distribution transformers for utility networks, renewable energy projects, industrial systems, substations, mining applications, and other electrical infrastructure.
Different projects naturally require different transformer configurations.
A utility-scale solar plant may require a step-up power transformer between its medium-voltage collection system and a higher-voltage grid.
A transmission expansion project may require large oil-immersed power transformers for new or upgraded substations.
A mining or industrial project may combine a dedicated substation with its own transformer capacity.
Urban and rural electrification projects can require distribution transformers across many different points in the network.
For these applications, transformer selection needs to reflect the actual electrical system and site conditions. We can configure a transformer around system voltage, rated capacity, frequency, impedance, cooling arrangement, temperature-rise requirements, tap range, insulation level, altitude, ambient temperature, accessories, protection requirements, and the standards or project specifications that apply.
The objective is not simply to place another transformer into the network.
A power transformer has to operate correctly as part of the electrical system around it.
As African grids expand and more renewable generation is connected, that system is becoming larger, more interconnected, and more varied.
Solar, wind, hydropower, battery energy storage, conventional generation, industrial loads, transmission lines, substations, and distribution networks will increasingly operate together.
The technologies used to generate electricity will continue to develop, but electricity still has to move from generation to load and between different voltage levels.
Power transformers will therefore remain one of the fundamental building blocks supporting Africa’s expanding electricity infrastructure.
FAQ
Why are power transformers important for renewable energy projects in Africa?
Renewable generation frequently operates at a different voltage from the transmission network. Power transformers raise the voltage for efficient transmission and later reduce it at substations for distribution and use. New renewable projects can therefore create demand for both generation step-up transformers and additional substation transformer capacity.
What type of transformer is commonly used for utility-scale solar projects?
Large solar projects commonly use step-up transformers between the plant’s medium-voltage collection network and the grid connection voltage. The final transformer configuration depends on inverter output, collection voltage, project capacity, grid voltage, substation arrangement, and local connection requirements.
Can renewable energy cause reverse power flow through a transformer?
Yes. When generation connected downstream of a transformer exceeds local demand, power can flow toward another part of the network. Whether and how frequently this occurs depends on the system configuration. Transformer operation, protection, metering, tap control, and other surrounding equipment should therefore reflect the expected power-flow conditions.
Are 35kV and 110kV power transformers suitable for renewable energy projects?
They can be, depending on the grid connection. 35kV may be used in medium-voltage collection systems or regional networks, while larger projects may connect through 66kV, 110kV, or other transmission voltages. The appropriate transformer voltage is determined by the actual project and local grid rather than by the renewable generation technology alone.
Does Africa’s grid expansion only create demand for large power transformers?
No. Grid expansion requires transformers across several voltage levels. Large power transformers are used in transmission systems and major substations, while medium-voltage and distribution transformers are required to bring electricity closer to industrial, commercial, infrastructure, and residential loads.
What information is useful when specifying a power transformer for an African grid or renewable project?
Useful information includes the system voltage, required capacity, frequency, transformer application, expected load profile, installation environment, ambient temperature, altitude, cooling requirements, tap range, impedance requirements, applicable standards, and surrounding substation configuration. These details allow us to match the transformer design more closely to the actual electrical system and operating conditions.