Railway stations and metro systems depend on a wide range of electrical equipment long before a train enters the platform. Lighting, ventilation, escalators, elevators, platform screen doors, water pumps, fire protection systems, communication equipment, ticketing systems, control rooms, workshops, and other station facilities all require stable power distribution.
For these projects, selecting the right power transformer is not simply a matter of converting one voltage level to another. The transformer must fit the incoming network, station load profile, installation environment, redundancy strategy, protection system, and future expansion plan.
As a power transformer manufacturer, HONLE supports transformer solutions for infrastructure and transportation power distribution projects, including both dry-type and oil-immersed designs. In railway and metro projects, these transformers can serve station facilities, auxiliary equipment, equipment rooms, depots, and other building and infrastructure power distribution systems.
What Does a Power Transformer Do in a Railway Station or Metro System?
A railway or metro station normally receives electricity from an upstream utility network or dedicated distribution system. The incoming voltage then needs to be transformed and distributed to different categories of station equipment.
A power transformer can form an important part of this distribution chain by stepping voltage down to a level suitable for downstream switchgear and station loads.
Typical loads may include:
- Station lighting
- Ventilation and air-conditioning systems
- Escalators and elevators
- Drainage and sewage pumps
- Fire pumps and emergency systems
- Platform screen doors
- Automatic fare collection equipment
- Communication and monitoring systems
- Workshops and maintenance facilities
- Control and equipment rooms
- Commercial areas within large stations
These loads do not all operate in the same way.
An escalator motor, for example, creates different electrical conditions from lighting or communication equipment. Ventilation fans may operate continuously or vary according to passenger demand. Pumps can create relatively high starting currents, while electronic systems may introduce nonlinear loads and harmonics.
The power transformer therefore needs to be selected around the station’s actual electrical load profile rather than only the total connected load.
Station and Auxiliary Power Distribution Has Its Own Transformer Requirements
Within a railway or metro project, different parts of the electrical system can have very different transformer requirements.
For station buildings and auxiliary facilities, the transformer may supply low-voltage switchboards or other distribution equipment serving mechanical systems, lighting, pumps, escalators, control equipment, communication systems, and other station loads.
The required transformer configuration depends on where the equipment is installed and which loads it needs to support.
An indoor transformer room in an underground metro station, for example, has different environmental and space limitations from an outdoor distribution point at a railway depot. These differences influence whether a dry-type or oil-immersed power transformer is more suitable.
Dry-Type Power Transformers Are Often Suitable for Indoor Station Electrical Rooms
Railway and metro stations contain many enclosed electrical spaces. In these locations, a dry-type power transformer can be a practical solution.
Dry-type transformers use solid insulation and air cooling instead of transformer oil, making them suitable for many indoor power distribution environments.
HONLE’s transformer range includes SC(B) series three-phase dry-type distribution transformers that can be configured for different indoor distribution requirements.
Indoor installation is a major consideration
Metro stations frequently place electrical equipment inside dedicated equipment rooms because much of the infrastructure itself is underground or enclosed.
In this situation, engineers normally need to consider:
- Available installation space
- Ventilation
- Ambient temperature
- Fire protection requirements
- Transformer operating noise
- Access for inspection and maintenance
- Cable routing
- Clearance around electrical equipment
A dry-type power transformer can therefore integrate well into many station electrical-room layouts.
The final selection still needs to consider the actual room conditions. Ventilation and heat dissipation, in particular, should be checked carefully before transformer capacity and enclosure requirements are confirmed.
Heat generated inside underground stations cannot be ignored
Underground metro systems already contain substantial heat sources, including passengers, lighting, train movements, mechanical equipment, and ventilation systems.
Transformer losses add another heat source to the electrical room.
If the transformer room is poorly ventilated or operates at an elevated ambient temperature, transformer capacity and temperature-rise requirements should be reviewed during specification.
This becomes especially important for stations operating long daily service hours with limited shutdown periods.
Oil-Immersed Power Transformers Can Support Outdoor and Upstream Distribution
Not every transformer in a railway infrastructure project is located inside a station building.
Outdoor substations, depot areas, railway maintenance facilities, utility interfaces, and larger distribution points may be better suited to an oil-immersed power transformer.
Oil-immersed transformers use insulating oil for electrical insulation and heat dissipation and are widely used across utility, industrial, and infrastructure distribution systems.
HONLE manufactures oil-immersed transformer solutions for different distribution capacities and voltage requirements, including S11, S13, and other configurations, as well as power transformer solutions for higher-voltage systems.
The choice between dry-type and oil-immersed equipment should follow the actual installation conditions rather than capacity alone.
Installation location, network voltage, load level, protection arrangement, cooling requirements, maintenance conditions, and project standards all need to be considered together.
Railway Stations Have Highly Mixed Electrical Loads
One characteristic of station power distribution is the variety of loads operating within the same facility.
A metro station may combine motors, lighting, electronic systems, pumps, HVAC equipment, and sensitive control loads.
When requesting a power transformer, providing only the required kVA rating may therefore leave out important information.
Motor loads need to be considered separately
Large ventilation fans, pumps, escalators, and other rotating equipment can draw substantial current during startup.
Where several motors may start within a short period, the electrical design should consider:
- Starting current
- Permitted voltage drop
- Starting method
- Motor starting sequence
- Transformer impedance
- Downstream protection
- VFD or soft starter use
A transformer that appears adequate according to normal running load can still experience excessive voltage fluctuation if motor-starting conditions have not been considered.
For railway and metro projects with a high proportion of motor loads, this information should be provided when the power transformer manufacturer reviews the specification.
Nonlinear loads can affect transformer operation
Modern railway stations also contain increasing numbers of electronic loads.
Variable-frequency drives, UPS systems, LED lighting power supplies, automation systems, communication equipment, and other power electronics can introduce harmonics into the distribution network.
These conditions can influence transformer losses, temperature rise, and overall system performance.
Where nonlinear loads represent a significant part of the station demand, their characteristics should be included in the electrical design and transformer specification rather than treated as ordinary resistive loads.
Transformer Capacity Should Reflect Real Station Operation
Selecting a power transformer purely from connected load is rarely enough for a railway or metro project.
The engineering team needs to consider both the expected operating demand and the way different equipment operates throughout the day.
Station ventilation, for example, may run at different levels according to passenger volume. Escalators can operate continuously during service hours, while drainage pumps may operate intermittently. Emergency loads may remain idle during normal conditions but still need to be covered by the distribution strategy.
Transformer sizing should therefore consider:
- Maximum operating demand
- Simultaneous load
- Continuous motor loads
- Motor starting conditions
- Harmonic-producing equipment
- Emergency loads
- Future station expansion
- Required transformer loading margin
Excessive oversizing should also be avoided.
A much larger power transformer does not automatically create a better distribution system. It increases initial equipment cost and can lead to unnecessary no-load losses when actual demand remains much lower than the transformer rating.
The target should be sufficient operating margin without unnecessary oversizing.
Redundancy Can Be Important for Critical Station Loads
Loss of electrical power in a railway station can affect much more than passenger comfort.
Depending on the distribution architecture, an outage can influence ventilation, drainage, lighting, access systems, escalators, communications, monitoring, fire protection, and other essential equipment.
For critical systems, designers may therefore use two transformers or divided distribution sections rather than placing all station loads behind a single transformer.
Two transformers, for example, may normally serve separate load sections while allowing essential loads to be transferred when one transformer is unavailable.
The required arrangement should be defined clearly when transformers are specified.
Depending on the project, transformers may:
- Operate independently
- Supply separate bus sections
- Share loads
- Operate in parallel
- Provide standby capacity for each other
If parallel operation is required, transformer parameters such as rated voltage, vector group, impedance, tap position, and capacity need to be properly coordinated.
These requirements are much easier to address before manufacturing than after the equipment has arrived on site.
Transformer Impedance Influences Protection and Voltage Performance
Transformer impedance is another specification that directly affects the wider station distribution system.
It influences both voltage regulation and prospective short-circuit current.
Lower impedance can reduce voltage drop under load but may result in higher fault current. Higher impedance can help limit short-circuit current but may cause greater voltage variation under certain operating conditions.
For railway and metro distribution projects, transformer impedance should therefore be coordinated with:
- Short-circuit calculations
- Circuit breaker breaking capacity
- Busbar ratings
- Protection settings
- Motor starting performance
- Parallel transformer operation
The power transformer and downstream protection equipment need to be considered as parts of the same distribution system.
Providing system calculations, single-line diagrams, or specified impedance requirements at the quotation stage can help HONLE match the transformer more closely to the project design.
Underground Metro Environments Require Additional Attention
Metro stations can present environmental conditions that differ considerably from standard industrial buildings.
Electrical equipment may operate below ground for many years with restricted space and limited access.
Depending on the station, the transformer installation may need to account for humidity, dust, ventilation, condensation, ambient temperature, vibration, water ingress risk, and access for maintenance.
Humidity and condensation need to be considered
Underground spaces can be more sensitive to moisture and condensation than ordinary above-ground electrical rooms.
Transformer installation should therefore be coordinated with the room’s ventilation and environmental control design.
Insulation requirements, enclosure configuration, protective measures, and maintenance arrangements should reflect actual site conditions rather than assuming a clean, temperature-controlled indoor environment.
Restricted access can determine transformer dimensions
Large railway and metro projects are often designed around fixed equipment rooms, corridors, doors, shafts, and lifting routes.
The power transformer must be capable of reaching its final installation position.
Before transformer dimensions are finalized, the project team should check:
- Maximum transportation dimensions
- Door and corridor dimensions
- Lifting restrictions
- Equipment-room access
- Transformer weight
- Cable entry direction
- Required maintenance clearance
For underground metro projects, these physical restrictions can affect transformer design just as much as electrical parameters.
Discovering an access limitation after production can create significant installation problems on site.
Future Station Expansion Should Be Considered Before Ordering
Railway stations rarely remain electrically unchanged throughout their full operating life.
Passenger volume may increase. Additional escalators may be installed. Commercial areas can expand. HVAC systems may be upgraded, while new automation, communication, monitoring, security, or charging equipment may add further electrical demand.
A power transformer selected with no allowance for realistic expansion can eventually become a limitation within the station distribution system.
At the same time, future capacity should be based on actual project plans rather than arbitrary oversizing.
When discussing a railway or metro project with HONLE, customers can provide both the current expected demand and any planned future loads. This makes it easier to determine an appropriate capacity margin without selecting a transformer that is unnecessarily large from the beginning.
What Should Be Confirmed with a Power Transformer Manufacturer?
Railway and metro projects often involve detailed technical approval processes involving contractors, consultants, system integrators, utilities, or project owners.
Providing a complete specification early helps reduce repeated revisions during transformer selection and approval.
Important information normally includes:
- Rated capacity
- Primary voltage
- Secondary voltage
- Frequency
- Number of phases
- Vector group
- Transformer impedance
- Tap range and tap arrangement
- Cooling method
- Insulation requirements
- Temperature-rise requirements
- Indoor or outdoor installation
- Ambient temperature
- Altitude
- Required enclosure or protection level
- Cable or busbar connection arrangement
- Monitoring accessories
- Applicable standards
- Required tests
- Drawing and documentation requirements
Load information is also useful, particularly when the system includes large motors, VFDs, UPS equipment, or other nonlinear loads.
For projects with specific railway or metro requirements, these conditions can be included in the technical data sheet and confirmed with HONLE before production.
Testing and Documentation Matter for Infrastructure Projects
A power transformer supplied for transportation infrastructure normally passes through several technical review and approval stages before commissioning.
Transformer manufacturing capability is therefore only one part of the supply process.
Project teams may also require:
- Technical data sheets
- Outline and dimensional drawings
- Nameplate information
- Routine test reports
- Inspection arrangements
- Packing requirements
- Export documentation
- Installation information
Testing requirements should be agreed according to the applicable standard and project specification.
If the project requires witness testing, additional tests, or specific documentation formats, these requirements should be confirmed before the manufacturing schedule is finalized.
This helps keep transformer production, technical approval, inspection, and project delivery aligned.
HONLE Power Transformer Solutions for Railway and Metro Projects
Different parts of a railway or metro project can require different transformer configurations.
An indoor station electrical room may use a dry-type transformer, while an outdoor distribution facility, depot, maintenance area, or upstream power distribution point may be better suited to an oil-immersed power transformer.
HONLE supplies both dry-type and oil-immersed transformer solutions for different voltage levels, capacities, installation environments, and distribution requirements.
Rather than selecting a transformer only by model number, we can review customer drawings, single-line diagrams, technical data sheets, load information, installation conditions, and applicable project standards.
As a power transformer manufacturer, HONLE works with electrical contractors, railway equipment suppliers, infrastructure companies, distributors, and engineering teams during transformer specification and quotation.
For a railway station or metro distribution project, the most useful starting information is usually the incoming and outgoing voltage, required capacity, installation environment, major load characteristics, redundancy arrangement, and applicable technical standard.
With this information, the transformer can be configured around the actual power distribution system and installation conditions.
Reliable Station Power Starts with the Right Transformer Specification
Railway stations and metro systems combine many electrical loads that need stable and predictable power throughout long daily operating periods.
The right power transformer needs to support these loads while fitting the station’s distribution architecture, electrical room, protection system, environmental conditions, and future development.
Dry-type transformers can be suitable for many indoor station electrical rooms, while oil-immersed transformers can serve outdoor, upstream, depot, and other appropriate distribution applications.
The final selection depends on the project rather than a single standard transformer configuration.
For contractors and project teams sourcing transformers for railway stations, metro stations, depots, auxiliary substations, and related transportation infrastructure, HONLE can review the electrical specification and provide a power transformer solution matched to the project’s actual operating and installation requirements.
FAQ
What type of power transformer is commonly used inside a metro station?
Dry-type transformers are commonly considered for indoor station electrical rooms because they do not use transformer oil and can integrate well with building power distribution systems. The final selection still depends on voltage, capacity, ventilation, environmental conditions, and project requirements.
Can oil-immersed power transformers be used for railway projects?
Yes. Oil-immersed power transformers can be used in railway substations, outdoor distribution facilities, depots, maintenance facilities, and other suitable parts of the railway electrical network.
How should transformer capacity be calculated for a railway station?
Capacity should consider expected maximum demand, load simultaneity, motor loads, starting conditions, nonlinear loads, emergency requirements, redundancy strategy, and reasonable future expansion rather than simply adding all connected loads.
Can two transformers be used for redundancy in a metro station?
Yes. Critical distribution systems may use multiple transformers or divided bus sections to improve power continuity. If transformers are intended to operate in parallel or provide mutual backup, their electrical parameters need to be coordinated during system design.
What information should I send HONLE for a railway power transformer quotation?
Provide the required capacity, primary and secondary voltage, frequency, vector group, impedance, tap requirements, installation environment, cooling method, applicable standard, load information, and any project-specific testing or documentation requirements. A single-line diagram or transformer data sheet is especially helpful.
