Typical Voltage Combinations

Note: Rated capacity, voltage ratio, impedance, insulation level, tap range, vector group and cooling system can be fully customized according to the customer's grid requirements and project technical specifications.

The 110kV / 115kV Power Transformer can be fully customized according to the electrical, environmental, installation and transportation requirements of different utility, EPC, industrial and renewable energy projects.

1. Electrical Parameter Customization

• Rated Capacity: 10–240 MVA or customized

• Primary Voltage: 110kV / 115kV

• Secondary Voltage: 6.3kV / 10kV / 10.5kV / 11kV / 13.8kV / 33kV / 34.5kV

• Three-Winding Configuration: Available

• Frequency: 50Hz / 60Hz

• Phase: Three-phase

• Rated Current: According to transformer capacity and voltage

• Short-Circuit Impedance: Customized

• No-Load Loss: Optimized according to efficiency requirements

• Load Loss: Customized according to project requirements

• Vector Group: Dyn11 / YNd11 / YNd1 / customized

• Neutral Connection: Neutral brought out / grounded / customized

2. Tap Changer Options

The transformer can be equipped with different voltage regulation solutions.

On-Load Tap Changer (OLTC)

• Automatic voltage regulation

• Manual / automatic control

• Remote control capability

• Multiple tap positions

• Typical range: ±8 × 1.25% or ±10 × 1.25%

• Customized tap range available

Off-Circuit Tap Changer

• Suitable for applications where voltage adjustment is not required under load

• Simple and economical configuration

3. Cooling System Customization

Different cooling systems can be selected according to transformer capacity and load profile.

Optional cooling components include:

• High-efficiency radiators

• Cooling fans

• Oil pumps

• Automatic fan control

• Oil flow indicators

• Cooling system control cabinet

• Standby cooling equipment

4. Insulation Level Customization

The insulation system can be designed according to the required system voltage, grounding method and insulation coordination.

Customization may include:

• Power-frequency withstand voltage

• Lightning impulse withstand level

• Switching impulse withstand level where applicable

• External insulation clearance

• Creepage distance

• Neutral insulation level

• Bushing insulation level

• Internal insulation structure

For 110kV/115kV applications, insulation coordination should be confirmed according to the applicable standard and project specification.

5. Winding Customization

The winding system can be customized according to load current, short-circuit requirements and project conditions.

Available options include:

• Copper winding

• Aluminum winding

• Disc winding

• Continuous disc winding

• Helical winding

• Interleaved winding

• Optimized axial and radial insulation

• Enhanced short-circuit mechanical strength

The winding structure can be engineered to improve:

• Short-circuit withstand capability

• Voltage distribution

• Thermal performance

• Insulation reliability

• Long-term operating stability

6. Core Customization

The magnetic core can be optimized according to loss, noise and efficiency requirements.

Options include:

• High-grade grain-oriented silicon steel

• Step-lap core construction

• Low-loss core design

• Optimized magnetic flux density

• Noise-reduction design

• Core grounding arrangement

The core design can be optimized to reduce no-load loss, excitation current and operating noise.

7. Tank & Mechanical Design

The transformer tank can be customized according to installation and transportation conditions.

Options include:

• Conservator tank

• Sealed tank

• Corrugated tank where applicable

• Detachable radiators

• Stainless-steel components

• Customized bushing positions

• Cable box

• Lifting lugs

• Jacking pads

• Grounding terminals

• Inspection covers

• Manholes

• Oil filling and draining connections

The tank structure can be designed to withstand vacuum treatment, internal pressure and transportation loads.

8. Bushing Configuration

Different bushing solutions can be selected according to system voltage and installation requirements.

Available options:

• Porcelain bushings

• Composite bushings

• Condenser bushings

• Oil-impregnated paper (OIP) bushings

• Resin-impregnated paper (RIP) bushings

Bushing arrangement can be customized for:

• HV terminals

• MV terminals

• LV terminals

• Neutral terminal

• CT integration

9. Protection & Monitoring Options

The transformer can be equipped with a comprehensive protection and monitoring system.

Protection Devices

• Buchholz relay

• Pressure relief device

• Sudden pressure relay

• Oil level protection

• Over-temperature protection

• Winding temperature protection

• OLTC protection

• Cooling failure alarm

Monitoring Devices

• Oil temperature indicator

• Winding temperature indicator

• Magnetic oil level gauge

• Online dissolved gas analysis (DGA)

• Moisture monitoring

• Bushing monitoring

• Partial discharge monitoring

• Fiber-optic temperature monitoring

• Transformer condition monitoring system

10. Control System Customization

The control system can be configured according to the customer's substation automation requirements.

Options include:

• Local control cabinet

• Remote control

• Automatic voltage regulation

• OLTC control

• Cooling system automatic control

• Alarm and trip circuits

• Digital temperature display

• RS485 communication

• Modbus communication

• IEC 61850 integration where specified

• SCADA interface

11. Environmental Customization

The transformer can be designed for different operating environments.

Available adaptations include:

• High-temperature environments

• Low-temperature environments

• High-altitude installations

• High-humidity environments

• Coastal environments

• Salt-fog environments

• Dusty environments

• Desert environments

• Mining environments

• Industrial pollution areas

Additional protection may include:

• Enhanced anti-corrosion coating

• Stainless-steel components

• Special sealing systems

• Increased creepage distance

• Special transformer oil

• High-temperature insulation materials

12. Transformer Oil Options

Different insulating media can be selected according to project requirements.

• Mineral transformer oil

• Natural ester fluid

• Synthetic ester fluid

• Low-flammability insulating fluid

Oil specifications can be selected according to applicable IEC, ASTM, GB or customer standards.

13. Three-Winding Transformer

For complex substation applications, a three-winding 110kV/115kV transformer can be supplied.

Typical configurations include:

• 110 / 33 / 11 kV

• 110 / 33 / 13.8 kV

• 115 / 34.5 / 13.8 kV

• Other customized combinations

Three-winding transformers can reduce equipment footprint and provide flexible power distribution between different voltage levels.

14. Renewable Energy Customization

For solar and wind power projects, the transformer can be customized for:

• Solar power plants

• Wind farms

• Battery energy storage systems

• Hybrid renewable energy plants

• Grid-connected renewable projects

Customization can include:

• Renewable-energy-specific voltage ratios

• OLTC

• High harmonic withstand capability

• Optimized loss performance

• Grid interconnection requirements

• Special cooling configuration

• SCADA communication

• Online monitoring

15. Transportation & Installation Customization

For large 110kV/115kV transformers, transportation dimensions can be considered during engineering.

Available solutions include:

• Detachable radiators

• Removable bushings

• Transport oil filling

• Nitrogen-filled transportation

• Separate accessory shipment

• Customized lifting points

• Jacking points

• Transportation brackets

• Shock monitoring

• Customized foundation interface

The manufacturer can provide GA drawings, transportation dimensions, weight data, center-of-gravity information and foundation drawings for EPC project planning.

16. Testing Customization

In addition to routine factory tests, additional tests can be arranged according to project requirements:

• Temperature-rise test

• Lightning impulse test

• Switching impulse test

• Partial discharge test

• Frequency response analysis (FRA)

• Capacitance and tan delta

• Zero-sequence impedance test

• Sound level test

• Short-circuit withstand test

• Transformer oil analysis

• Insulation resistance test

• Special customer-witnessed tests

17. Standards Customization

The transformer can be designed and tested according to:

IEC 60076
IEEE / ANSI
GB / DL
ASTM
Customer-specific utility standards

For international EPC projects, the complete technical design can be matched to the purchaser's Data Sheet, Technical Specification, Single-Line Diagram (SLD) and Grid Code.

Project-Based Customization

For a 110kV / 115kV transformer project, customers can provide the following information:

Capacity → Voltage Ratio → Frequency → Vector Group → Impedance → Tap Range → OLTC → Cooling → Insulation Level → Environmental Conditions → Protection → Monitoring → Applicable Standard

Zisheng can then prepare a project-specific technical proposal, transformer datasheet, GA drawing and quotation based on the customer's requirements.

The 110kV / 115kV Power Transformer is a large and heavy electrical equipment product. Its packing and transportation require careful engineering to protect the transformer against moisture, vibration, impact, corrosion and mechanical damage throughout inland transportation, port handling and international sea shipment.

Zisheng provides customized packing and shipping solutions according to transformer size, transport weight, destination, shipping method and project requirements.

1. Pre-Shipment Preparation

Before packing, every transformer undergoes a comprehensive pre-shipment inspection.

Typical procedures include:

• Final appearance inspection

• Nameplate verification

• Factory test report confirmation

• Bushing inspection

• Oil leakage inspection

• Sealing inspection

• Valve inspection

• Radiator inspection

• Cooling system inspection

• OLTC inspection

• Protection device inspection

• Terminal inspection

• Grounding inspection

• Accessory inventory

• Packing list verification

All detachable components are identified and recorded before shipment to facilitate installation at the project site.

2. Transportation Configuration

Depending on transformer capacity and transportation conditions, the transformer can be shipped in different configurations.

Option A — Complete Transformer Shipment

Suitable for relatively compact units.

The transformer is shipped with major components assembled, while selected accessories are packed separately.

Option B — Main Tank + Accessories

For large transformers, components such as:

• Radiators

• Bushings

• Conservator

• Cooling fans

• Control cabinet

• OLTC accessories

can be removed and packed separately.

This reduces the overall transport dimensions and facilitates handling.

Option C — Nitrogen-Filled Transportation

For large oil-immersed transformers, the transformer body can be transported under a controlled dry nitrogen atmosphere after draining the required amount of oil.

This helps protect the internal insulation system from:

• Moisture

• Oxygen

• Contamination

A pressure monitoring arrangement can be provided during transportation where required.

Option D — Oil-Filled Transportation

For selected transformer designs and transportation conditions, the main tank can be transported with insulating oil according to the agreed transportation specification.

The appropriate method depends on:

• Transformer size

• Transport distance

• Shipping route

• Transportation regulations

• Customer requirements

3. Transformer Main Body Protection

The main transformer body receives special protection before shipment.

Surface Protection

The painted steel surfaces are inspected and protected against:

• Scratches

• Impact

• Salt spray

• Moisture

• Corrosion

Exposed machined surfaces and connection points can receive temporary anti-corrosion protection.

Sealing Protection

All relevant openings are properly sealed to prevent:

• Rainwater penetration

• Dust contamination

• Moisture ingress

• Foreign material entering the transformer

4. Bushing Packing

High-voltage bushings are sensitive components and require dedicated packaging.

Depending on the design, bushings can be:

• Installed on the transformer

• Removed for transportation

• Packed separately

Separate bushings are normally protected with:

• Shock-resistant internal supports

• Moisture-resistant wrapping

• Protective end covers

• Reinforced wooden crates

• Identification labels

Special care is taken to prevent impact or bending forces during loading and unloading.

5. Radiator Packing

Radiators can be removed from the main transformer body for large units.

Before shipment:

1. Radiators are inspected.

2. Connection openings are sealed.

3. Internal cleanliness is checked.

4. External surfaces are protected.

5. Radiators are securely fixed to prevent movement.

Radiators can be packed individually or bundled according to their dimensions and shipping method.

6. Conservator Tank Packing

The conservator tank and associated accessories can be shipped separately.

Typical protection includes:

• Internal cleanliness inspection

• Sealing of connection ports

• Anti-corrosion protection

• Protective wrapping

• Reinforced wooden or steel support

• Identification marking

The conservator components are clearly labeled for convenient installation at the destination.

7. Control Cabinet Packing

The control cabinet is packed separately when required.

Protection includes:

• Moisture-proof packaging

• Dust protection

• Shock protection

• Corner protection

• Reinforced wooden case

• Cable terminal protection

Control cabinets are kept dry during storage and transportation.

8. OLTC Packing

For transformers equipped with an On-Load Tap Changer (OLTC), the OLTC components and drive mechanism are carefully protected.

Depending on the OLTC design:

• OLTC can remain installed on the transformer

• Motor drive mechanism can be packed separately

• Control components can be shipped separately

All components are identified according to the installation drawings and wiring diagrams.

9. Transformer Oil Transportation

The transportation method for transformer oil depends on transformer capacity and project requirements.

Oil Filled

The transformer is transported with insulating oil.

Partially Drained

A specified oil level is maintained during transportation.

Oil Drained + Nitrogen Filled

The transformer is drained and filled with dry nitrogen to protect the internal insulation system.

If the transformer is shipped under nitrogen, the nitrogen pressure should be monitored throughout transportation and storage.

Additional oil can be shipped separately in:

• Steel drums

• Oil tanks

• ISO tanks

• Customer-specified containers

10. Moisture Protection

Moisture protection is particularly important for oil-immersed high-voltage transformers because the insulation system must remain dry and clean.

Protection measures may include:

• Sealed openings

• Moisture-proof film

• Desiccant

• Dry nitrogen

• Sealed control cabinets

• Waterproof covers

• Moisture indicators

• Temporary anti-corrosion protection

For long-distance ocean transportation, additional waterproof protection can be applied according to the shipping environment.

11. Export Seaworthy Packing

For international projects, Zisheng can provide export seaworthy packing suitable for:

• Sea freight

• Container transportation

• Breakbulk shipping

• Heavy-lift vessels

• Project cargo transportation

Packing materials may include:

• Heavy-duty plastic film

• Waterproof membrane

• Moisture barrier

• Reinforced wooden cases

• Steel frames

• Shock-absorbing materials

• Protective covers

The packaging method is selected according to the actual transportation route.

12. Heavy Cargo Transportation

110kV/115kV transformers can have significant dimensions and weight.

Before shipment, transportation information can be provided, including:

• Total weight

• Transport weight

• Overall dimensions

• Center of gravity

• Lifting points

• Jacking points

• Loading points

• Securing points

• Transportation drawings

For oversized transformers, transportation may involve:

Factory → Heavy Truck → Port → Heavy-Lift Vessel / Breakbulk Vessel → Destination Port → Special Transport Vehicle → Project Site

Transportation engineering can be coordinated with the customer's EPC contractor or logistics company.

13. Container & Breakbulk Shipping

Container Shipping

Suitable for accessories and components within container dimensions.

Typical separately shipped items include:

• Bushings

• Radiators

• Control cabinets

• Cooling fans

• Conservator

• OLTC components

• Transformer accessories

Breakbulk / Project Cargo

For large 110kV/115kV transformers exceeding standard container dimensions, breakbulk or project cargo transportation may be more suitable.

This allows the transformer main body to be transported as heavy-lift cargo.

14. Loading & Securing

Professional loading procedures are used to minimize transportation risks.

The transformer and accessories are secured using suitable:

• Steel brackets

• Chains

• Tie-down systems

• Wooden supports

• Shock-absorbing materials

• Anti-slip materials

The securing method is designed to reduce movement caused by:

• Sudden braking

• Road vibration

• Ship movement

• Crane handling

• Port loading and unloading

15. Shock & Vibration Protection

High-voltage transformer components are protected against excessive mechanical shock.

Special attention is given to:

• Bushings

• Radiators

• Control cabinets

• OLTC mechanisms

• Instrumentation

• Internal active parts

For high-value projects, shock and tilt indicators can be installed to record abnormal transportation events.

16. Shipping Marks

Each package is clearly marked with relevant shipping information.

Typical markings include:

PRODUCT NAME

TRANSFORMER MODEL

SERIAL NUMBER

PACKAGE NUMBER

GROSS WEIGHT

NET WEIGHT

DIMENSIONS

CENTER OF GRAVITY

LIFTING POINT

THIS SIDE UP

KEEP DRY

FRAGILE

DO NOT STACK

Customized shipping marks can be provided according to the customer's logistics requirements.

17. Shipping Documents

The shipment can be supplied with complete export documentation.

Typical documents include:

• Commercial Invoice

• Packing List

• Bill of Lading

• Certificate of Origin

• Factory Test Report

• Routine Test Report

• Quality Certificate

• Product Certificate

• Technical Specification

• Installation Manual

• Operation Manual

• General Arrangement Drawing

• Foundation Drawing

• Wiring Diagram

• Nameplate Drawing

• Accessory List

• Transportation Drawing

• Insurance documents where required

Additional documents can be prepared according to the EPC contract or destination-country requirements.

18. Installation at Destination

For large transformer projects, installation support documents can be provided to assist the customer's site team.

Typical installation procedures include:

1. Unloading and positioning

2. Inspection after transportation

3. Installation of radiators

4. Installation of bushings

5. Installation of conservator

6. Installation of cooling equipment

7. OLTC connection

8. Control cabinet installation

9. Vacuum treatment where required

10. Transformer oil filling

11. Oil filtration

12. Electrical testing

13. Protection system testing

14. Commissioning

15. Energization

The exact procedure must follow the manufacturer's installation manual and project-specific requirements.

19. Long-Term Storage

If the transformer cannot be installed immediately after arrival, suitable storage conditions should be maintained.

Recommended storage measures include:

• Keep equipment in a dry environment

• Prevent rainwater accumulation

• Maintain required nitrogen pressure where applicable

• Protect bushings from moisture

• Keep control cabinets sealed

• Periodically inspect package integrity

• Check oil or nitrogen condition

• Monitor moisture indicators

• Protect accessories from corrosion

Long-term storage requirements should be confirmed according to the actual transportation configuration.

20. Global Delivery Support

Zisheng can coordinate packing and shipping requirements for international utility, EPC, industrial, mining and renewable energy projects.

Shipping Support

Factory Inspection → Final Testing → Packing → Loading → Port Transportation → Export Customs → Ocean Freight → Destination Port → Project Site

For each project, the packing and shipping method can be customized according to:

• Transformer capacity

• Transformer dimensions

• Total transport weight

• Destination country

• Port conditions

• Shipping route

• Incoterms

• Customer installation requirements

Custom export packing and project cargo transportation solutions are available for 110kV and 115kV power transformers.

The 110kV / 115kV Power Transformer is subjected to comprehensive manufacturer testing before shipment to verify its electrical performance, insulation integrity, mechanical strength, protection functions and overall manufacturing quality.

Testing is performed according to the applicable IEC 60076, IEEE/ANSI, GB standards and customer-approved technical specifications. For utility and EPC projects, additional type and special tests can be arranged according to the purchase specification.

1. Factory Testing Overview

Manufacturer testing generally includes:

Routine Tests

Performed on each transformer before delivery.

Type Tests

Performed to verify the design performance of a transformer type.

Special Tests

Performed when required by the purchaser, utility, EPC contractor or project specification.

For a 110kV/115kV transformer, the factory testing program can be expanded according to the required insulation level, capacity, grid requirements and contractual technical specification.

2. Visual & Mechanical Inspection

Before electrical testing, the completed transformer undergoes a detailed mechanical inspection.

The inspection includes:

• Overall transformer dimensions

• Tank construction

• Paint and surface condition

• Radiator installation

• Bushing installation

• Conservator installation

• Valve arrangement

• Grounding terminals

• Lifting lugs

• Jacking points

• Nameplate information

• Cable connections

• Control cabinet

• Cooling system

• OLTC mechanism

• Oil level indicators

• Temperature indicators

• Pressure relief devices

The inspection verifies that the manufactured transformer conforms to the approved General Arrangement (GA) Drawing and technical specification.

3. Winding Resistance Test

The resistance of each transformer winding is measured to verify:

• Winding conductor integrity

• Internal connections

• Soldered/jointed connections

• Tap changer contacts

• Phase consistency

Measurements are normally performed on all phases and tap positions as required.

The measured values are compared with the manufacturer's design calculations and applicable acceptance criteria.

4. Voltage Ratio Test

The transformation ratio is measured between the high-voltage and low-/medium-voltage windings.

The test verifies:

• Correct winding ratio

• Correct tap positions

• Correct winding connections

• Correct phase relationship

• OLTC operation

All applicable tap positions can be checked for transformers equipped with an OLTC.

5. Vector Group & Phase Displacement Test

The phase relationship between HV, MV and LV windings is verified.

The test confirms:

• Correct vector group

• Correct winding polarity

• Correct phase sequence

• Correct phase displacement

Typical configurations may include:

Dyn11

YNd11

YNd1

or a project-specific vector group.

6. No-Load Loss & No-Load Current Test

The transformer is energized at rated frequency and voltage without external load.

The manufacturer measures:

• No-load loss

• No-load current

• Excitation current

This test evaluates the magnetic performance of the transformer core.

The results are compared with the guaranteed values specified in the transformer technical datasheet.

7. Short-Circuit Impedance & Load Loss Test

The transformer is tested to determine:

• Short-circuit impedance

• Load loss

• Winding losses

The test provides important information about transformer efficiency and impedance characteristics.

The results are evaluated against the guaranteed values and applicable standards.

For utility transformers, the specified impedance is particularly important because it affects:

• Fault current

• Voltage regulation

• Parallel operation

• System stability

8. Applied Voltage Test

The applied-voltage test verifies the insulation between:

• HV winding and ground

• MV/LV winding and ground

• Other winding insulation systems

A specified power-frequency test voltage is applied for the required duration.

The purpose is to verify that the main insulation system can withstand the specified electrical stress without breakdown or abnormal discharge.

9. Induced Voltage Test

The induced-voltage test evaluates the insulation between turns, layers and winding sections.

The transformer is energized at an increased frequency and appropriate voltage level according to the applicable test procedure.

The test helps verify:

• Inter-turn insulation

• Inter-layer insulation

• Longitudinal insulation

• Winding insulation integrity

10. Lightning Impulse Test

For 110kV/115kV transformers, lightning impulse testing is an important part of high-voltage insulation verification when required by the applicable standard or project specification.

The test simulates transient overvoltages caused by lightning and verifies the transformer's ability to withstand the specified impulse stress.

Testing may include:

• Full-wave lightning impulse

• Chopped-wave impulse where specified

• HV terminal testing

• Neutral terminal testing where applicable

The applicable impulse withstand level is determined by the specified insulation coordination.

11. Switching Impulse Test

For applicable high-voltage transformer designs, switching impulse testing can be performed according to the required insulation level and project specification.

The test simulates transient overvoltages associated with:

• Circuit breaker operation

• Line energization

• Fault clearing

• Switching operations

This is particularly relevant to high-voltage transmission and substation applications.

12. Partial Discharge Test

Partial discharge (PD) testing can be performed to assess the quality of the transformer insulation system.

The test can detect localized electrical discharges caused by defects such as:

• Voids

• Contamination

• Poor insulation interfaces

• Localized electric-field concentration

• Manufacturing defects

For high-voltage transformers, PD testing can provide additional confidence in the long-term reliability of the insulation system.

The acceptance level is determined according to the applicable standard and project specification.

13. Temperature-Rise Test

A temperature-rise test can be performed as a type test or special test.

The test verifies the thermal performance of the transformer under specified loading conditions.

Measurements can include:

• Top oil temperature rise

• Average winding temperature rise

• Hot-spot temperature where applicable

• Cooling system performance

The results verify that the transformer operates within the specified temperature limits.

14. Short-Circuit Withstand Test

For major utility and EPC projects, a short-circuit withstand test may be specified.

The test verifies the transformer's ability to withstand the:

• Electromagnetic forces

• Mechanical stress

• Thermal stress

generated during external short-circuit conditions.

The test evaluates the mechanical integrity of:

• HV windings

• MV/LV windings

• Clamping structures

• Axial supports

• Radial supports

• Internal connections

This is especially important for large-capacity 110kV/115kV transformers.

15. Frequency Response Analysis — FRA

Frequency Response Analysis can be performed before shipment to establish a reference fingerprint of the transformer.

The FRA results can later be compared with measurements taken after:

• Transportation

• Installation

• Major fault events

• Maintenance

Changes in the response may indicate possible movement or deformation of internal active parts.

FRA is particularly useful for large transformers that will undergo long-distance transportation.

16. Capacitance & Tan Delta Test

Capacitance and dielectric dissipation factor (tan delta) measurements can be performed on:

• Transformer windings

• Bushings

• Insulation system

The test helps evaluate insulation condition and detect abnormalities such as:

• Moisture

• Contamination

• Aging

• Insulation deterioration

17. Transformer Oil Testing

Transformer insulating oil is tested before filling and/or after final filling according to project requirements.

Typical parameters include:

• Breakdown voltage

• Water content

• Acidity

• Dielectric dissipation factor

• Resistivity

• Interfacial tension

• Appearance

• Dissolved gas analysis where specified

The oil test confirms that the insulating medium meets the specified quality requirements.

18. Bushing Testing

High-voltage bushings are inspected and tested according to the applicable requirements.

Testing may include:

• Capacitance measurement

• Tan delta measurement

• Insulation resistance

• Dielectric tests

• Visual inspection

• Terminal inspection

For condenser bushings, capacitance and dielectric loss measurements are particularly important.

19. OLTC Testing

For transformers equipped with an On-Load Tap Changer, the complete tap-changing system is tested.

The manufacturer verifies:

• All tap positions

• Tap position indication

• Motor drive operation

• Electrical interlocks

• Manual operation

• Remote operation

• Limit switches

• Control circuit

• Emergency stop

• Tap position feedback

The OLTC operation is checked repeatedly to ensure smooth and reliable switching.

20. Cooling System Testing

The cooling system is tested before shipment.

Testing includes:

• Cooling fan operation

• Oil pump operation

• Automatic start/stop

• Temperature control

• Alarm functions

• Standby cooling function

• Control cabinet operation

• Fan rotation direction

• Pump operation

• Electrical interlocks

For ONAF, OFAF or ODAF transformers, the cooling system is verified under the specified control logic.

21. Protection Device Testing

The protection system can include:

Buchholz Relay

Tested for:

• Gas alarm

• Oil surge trip

• Contact operation

Pressure Relief Device

Checked for:

• Mechanical operation

• Alarm/trip contacts

• Pressure relief function

Oil Level Indicator

Verified for:

• Normal level indication

• Low-level alarm

• Contact operation

Temperature Indicators

Checked for:

• Temperature indication

• Alarm

• Trip

• Cooling control

22. Control Cabinet Testing

The transformer control cabinet is tested before delivery.

Testing includes:

• Wiring inspection

• Terminal verification

• Insulation resistance

• Control circuit operation

• Alarm circuits

• Trip circuits

• Cooling control

• OLTC control

• Local/remote switching

• Interlock functions

• Communication interface where applicable

The wiring is checked against the approved electrical drawings.

23. Leak & Pressure Testing

The transformer tank and associated oil systems undergo leakage inspection.

Testing may include:

• Tank leakage test

• Vacuum tightness test

• Pressure test

• Radiator leakage test

• Valve inspection

• Bushing connection inspection

The purpose is to ensure that the transformer can maintain its required oil and sealing conditions during long-term operation.

24. Noise Level Test

A noise test can be conducted when required.

The test evaluates the acoustic performance of the transformer during operation.

Noise can be affected by:

• Core flux density

• Core construction

• Cooling fans

• Oil pumps

• Tank structure

For projects located near residential, commercial or environmentally sensitive areas, a specific maximum sound level can be included in the technical specification.

25. Final Factory Acceptance Test — FAT

For major EPC and utility projects, customers can participate in a Factory Acceptance Test (FAT).

The FAT may include:

Document Review → Visual Inspection → Routine Tests → Protection Test → OLTC Test → Cooling Test → Special Tests → Test Report Review → Final Acceptance

Customer representatives can witness selected tests according to the approved Inspection & Test Plan (ITP).

26. Test Documentation

After testing, the manufacturer can provide a complete testing dossier.

Typical documents include:

• Routine Test Report

• Type Test Report

• Special Test Report

• Factory Acceptance Test Report

• Transformer Oil Test Report

• Calibration Certificates

• Material Certificates

• Inspection Records

• Dimensional Inspection Report

• Protection Test Records

• OLTC Test Records

• Cooling System Test Records

• Quality Certificate

• Final Inspection Report

The test documentation can be submitted for customer, EPC contractor, consultant or utility approval.

Manufacturer Testing Process

Manufacturing → Internal Inspection → Mechanical Inspection → Routine Electrical Tests → Dielectric Tests → Protection Tests → Special Tests → FAT → Final Inspection → Packing & Shipping

Key Quality Commitment

100% Factory Tested Before Delivery

IEC 60076 Compliant Testing

Customer Witness Testing Available

Complete Test Documentation

FAT Support for EPC & Utility Projects

Project-Specific Inspection & Test Plan (ITP)