1000kVA Cast Resin Transformer: Facility Integration
1000kVA cast resin transformer
is commonly used to step medium-voltage power down to the operating voltage required by factories, commercial buildings, data centers, hospitals, transportation facilities, and other large electrical loads.
However, choosing a 1000kVA nameplate rating is only one part of the project. Successful facility integration also depends on the voltage ratio, actual load profile, transformer room layout, ventilation, low-voltage current, cable or busbar arrangement, protection coordination, enclosure rating, temperature monitoring, and commissioning procedure.
A transformer may have the correct rated capacity but still experience overheating, excessive voltage drop, nuisance tripping, or shortened insulation life when these installation factors are not properly considered.
This guide explains how to integrate a 1000kVA cast resin transformer into an industrial or commercial facility and what information should be confirmed before placing an order.
What Is a 1000kVA Cast Resin Transformer?
A 1000kVA cast resin transformer is a three-phase dry-type transformer with a rated apparent power of 1,000 kilovolt-amperes. Its high-voltage windings are normally encapsulated in epoxy resin instead of being immersed in transformer oil.
This oil-free construction makes the transformer suitable for indoor installations where fire safety, low maintenance, cleanliness, and compact installation are important. It is commonly installed in manufacturing plants, commercial buildings, hospitals, data centers, transportation projects, renewable-energy facilities, mining sites, and large EV charging stations.
ZHONGSHAO supplies both
and other
for different voltage classes, operating environments, and project requirements.
Does 1000kVA Mean 1000kW?
No. A transformer is rated in kVA, while most facility loads are described in kW. The relationship between them depends on the load power factor:
kW = kVA × power factor
Load Power FactorApproximate Active Power at 1000kVA1.001,000kW0.95950kW0.90900kW0.85850kW0.80800kW
For example, an 800kW facility operating at a power factor of 0.90 requires approximately:
800kW ÷ 0.90 = 889kVA
A 1000kVA transformer would therefore operate at approximately 89% of its rated capacity under this condition. The remaining capacity may or may not be sufficient once motor starting, harmonic currents, ambient temperature, future expansion, and temporary peak loads are considered.
For a more detailed sizing method, read our guide on
.
Reference Specifications for 1000kVA Cast Resin Transformers
The ZHONGSHAO product catalog includes SCB10 1000kVA cast resin transformer configurations for 10kV, 20kV, and 35kV-class systems.
Reference ModelVoltage ClassImpedanceNo-Load LossLoad Loss at 120°CCatalog LwASCB10–1000/106–11kV class6%1,770W8,130W64dB(A)SCB10–1000/2020–22kV class6%2,070W9,785W64dB(A)SCB10–1000/3534.5–38.5kV class6%2,430W10,450W64dB(A)
The catalog also provides the following reference dimensions and weights:
Reference ModelIP00 DimensionsIP20 DimensionsIP00 WeightIP20 WeightSCB10–1000/101700 × 850 × 1550mm2350 × 1650 × 2000mm3,320kg3,820kgSCB10–1000/201800 × 1000 × 1850mm2350 × 1650 × 2000mm3,600kg4,100kgSCB10–1000/352100 × 1200 × 2100mm3000 × 1850 × 2500mm5,240kg5,930kg
Important:
These are catalog reference values rather than final construction dimensions. The actual transformer size, losses, weight, terminal arrangement, and enclosure dimensions may change according to the voltage ratio, winding material, efficiency series, tap range, impedance, cooling method, cable direction, enclosure design, and applicable project standard.
Civil construction and electrical-room planning should always be based on the final approved general arrangement drawing.
Calculate the Primary and Secondary Current
The rated line current of a three-phase transformer can be calculated using the following formula:
Current = kVA × 1000 ÷ (√3 × line voltage)
For a 1000kVA three-phase transformer, the approximate current at common system voltages is shown below.
System VoltageApproximate Rated Current6kV96.2A10kV57.7A11kV52.5A20kV28.9A35kV16.5A400V1,443A415V1,391A480V1,203A690V837A
These figures demonstrate why the low-voltage connection requires careful engineering. A 10kV/400V, 1000kVA transformer carries only about 57.7A on the high-voltage side but approximately 1,443A on the low-voltage side.
The low-voltage connection may therefore require a busduct, large copper busbars, or several parallel cables. The design must consider continuous current capacity, ambient temperature, cable grouping, voltage drop, short-circuit withstand, harmonic content, neutral current, terminal loading, and maintenance access.
More current calculation examples are available in our
.
Select the Correct Voltage Ratio and Vector Group
The transformer voltage ratio must match both the incoming utility supply and the facility distribution voltage. Common project configurations include 10kV/400V, 10.5kV/400V, 11kV/415V, 20kV/400V, 22kV/415V, 33kV/415V, and 35kV/400V.
The correct ratio cannot be selected from the transformer capacity alone. The buyer should confirm the utility nominal voltage, maximum and minimum system voltage, frequency, low-voltage equipment rating, and required tap range.
The vector group must also be specified. A configuration such as Dyn11 is commonly used in distribution applications, but the final choice depends on the grounding arrangement, neutral requirement, phase displacement, protection scheme, and local utility requirements.
Check Parallel-Operation Requirements
When the new 1000kVA transformer will operate in parallel with an existing transformer, the two units must be electrically compatible.
The rated voltage ratio, vector group, phase sequence, polarity, frequency, tap position, and percentage impedance should be reviewed before the order is placed. Differences in voltage ratio may create circulating current, while significant impedance differences may result in unequal load sharing.
Under these conditions, one transformer may become overloaded before the combined installation reaches its expected total capacity.
Plan the Transformer Room Around the Final Drawing
The transformer room must accommodate more than the basic transformer footprint. Space is also needed for high-voltage cable termination, low-voltage busbar connections, cooling airflow, inspection, cleaning, enclosure door movement, panel removal, and future transformer replacement.
For example, the catalog SCB10–1000/10 reference unit measures approximately 1700 × 850 × 1550mm in IP00 construction. The corresponding IP20 reference enclosure increases the dimensions to approximately 2350 × 1650 × 2000mm.
The enclosure therefore has a significant effect on room size. Higher protection ratings, acoustic treatments, bottom cable chambers, cooling fans, and custom terminal arrangements may increase the dimensions further.
The final general arrangement drawing should show the overall dimensions, mounting positions, roller distance, operating weight, lifting points, terminal positions, cable-entry direction, ventilation clearances, and enclosure door movement.
Verify Floor Loading and Access Routes
A 1000kVA cast resin transformer can weigh several tonnes. The SCB10–1000/10 catalog reference is approximately 3,320kg in IP00 construction and 3,820kg with the referenced IP20 enclosure.
The building engineer should verify the electrical-room floor capacity, concentrated loading at the mounting points, door width, corridor dimensions, elevator capacity, turning space, and the equipment required to move the transformer into its final position.
Checking only the average weight per square meter may be insufficient because most of the load is concentrated at the transformer base channels, rollers, or mounting points.
Design Adequate Transformer Room Ventilation
Cast resin transformers use air as the cooling medium. A poorly ventilated electrical room can trap heat and raise the winding temperature even when the transformer is operating below its rated capacity.
The ZHONGSHAO catalog lists the following losses for the SCB10–1000/10 reference model:
No-load loss: approximately 1.77kW
Load loss at the stated reference temperature: approximately 8.13kW
Approximate total loss at full load: 9.90kW
This means the transformer room may need to remove close to 10kW of heat from the transformer at full load. Heat generated by the switchgear, cables, busbars, cooling fans, and other electrical equipment must be added separately.
At partial load, an approximate transformer loss can be calculated using:
Total loss = no-load loss + load factor² × rated load loss
At a 75% load factor:
Total loss = 1.77 + 0.7⁵² × 8.13 ≈ 6.34kW
This result can be used as an initial reference for the ventilation or HVAC design. The final calculation should also consider the expected load cycle, room temperature, equipment arrangement, installation altitude, and local climate.
The
explains the importance of dissipating the heat generated by transformers and other substation equipment.
In a typical transformer room, cooler air should enter from a lower position while warm air exits through higher openings. The layout should prevent discharged hot air from returning to the transformer inlet, and the winding air passages must remain unobstructed.
Consider Ambient Temperature and Altitude
The ZHONGSHAO catalog provides reference operating conditions including an installation altitude of approximately 1,000m and a maximum ambient air temperature of 40°C.
Projects located above the reference altitude or in high-temperature environments may require a thermal review, derating, additional cooling, or a modified transformer design.
The manufacturer should be informed about the maximum ambient temperature, average daily temperature, altitude, humidity, dust concentration, corrosive gases, salt-spray exposure, and whether the transformer will be installed indoors or outdoors.
A standard 1000kVA rating should not automatically be assumed to remain unchanged under every environmental condition.
Natural-Air Cooling vs. Forced-Air Cooling
A cast resin transformer normally operates with natural-air cooling. Cross-flow fans may also be installed when additional airflow or temporary overload capacity is required.
Forced-air cooling can be useful for temporary peak loads, emergency load transfer, redundant transformer systems, facility expansion, or transformer rooms with high ambient temperatures.
However, cooling fans do not automatically increase every 1000kVA transformer to the same higher rating. The permitted fan-assisted capacity, maximum operating time, fan quantity, control temperature, and alarm logic must be confirmed by the manufacturer.
Where a facility depends on fan-assisted capacity, fan failure alarms and winding-temperature protection should be connected to the building management or supervisory control system.
Select the Appropriate Enclosure
An IP00 open transformer may be suitable inside a clean, secure, access-controlled electrical room. Other facilities may require an enclosure to reduce exposure to dust, moisture, dripping water, or accidental contact.
Common options include IP00 open construction, IP20 indoor enclosures, IP23 ventilated enclosures, powder-coated steel enclosures, stainless-steel enclosures, acoustic enclosures, and project-specific outdoor enclosures.
A higher enclosure protection rating is not automatically better. Restricting airflow may increase the internal temperature and require a larger enclosure, additional ventilation, or forced-air cooling.
The enclosure specification should balance personnel protection, environmental exposure, cooling performance, corrosion resistance, noise control, and maintenance access.
Coordinate Transformer Impedance and Fault Current
The ZHONGSHAO catalog lists 6% impedance for the referenced 1000kVA SCB10 models.
Transformer impedance affects the available short-circuit current, low-voltage breaker interrupting rating, busbar short-circuit withstand, voltage drop during motor starting, protection coordination, and parallel load sharing.
As a simplified estimate, a 1000kVA, 400V transformer has a rated secondary current of approximately 1,443A. With 6% impedance, the transformer-limited fault current at its terminals is approximately:
1,443A ÷ 0.06 ≈ 24kA
This is only a preliminary estimate. The final calculation must also consider the utility source impedance, transformer tolerances, cables, busduct, switchgear, and motor contribution.
The low-voltage switchboard should not be ordered until a qualified engineer has completed the short-circuit and protection-coordination study.
Plan for Harmonic and Nonlinear Loads
A transformer supplying conventional motors and lighting may experience a different thermal duty from one supplying UPS systems, variable frequency drives, rectifiers, data-center equipment, or DC fast chargers.
Nonlinear loads can produce harmonic currents that increase winding eddy-current losses, conductor heating, neutral current, busbar temperature, voltage distortion, and insulation stress.
For projects with significant nonlinear loads, provide the manufacturer with the expected harmonic spectrum, total harmonic current distortion, neutral loading, duty cycle, and electrostatic shielding requirements.
Depending on the application, the transformer may require larger conductors, additional thermal margin, an optimized winding design, or a dedicated harmonic-duty specification.
Facilities with major UPS and server loads can also read our article about
.
Check the Applicable Transformer Standards
The applicable transformer standard should be stated clearly in the purchase specification.
covers dry-type power transformers, while
provides general requirements for dry-type distribution and power transformers.
Projects intended for the United States should also review applicable federal efficiency requirements. The
provides information about energy-conservation standards and test procedures.
The selected standard may affect rated voltage, frequency, insulation levels, temperature rise, efficiency, losses, sound limits, routine tests, type tests, terminal arrangements, nameplate information, and technical documentation.
For a detailed comparison, see our guide to
.
Integrate Temperature Monitoring and Protection
ZHONGSHAO cast resin transformers can be supplied with winding-temperature sensors and a temperature controller. Depending on the selected configuration, the system may provide three-phase temperature display, automatic fan control, over-temperature alarms, trip contacts, and remote communication.
The complete protection system may include medium-voltage overcurrent protection, earth-fault protection, a low-voltage main circuit breaker, winding-temperature alarms, over-temperature tripping, fan failure alarms, surge protection, grounding, and ventilation interlocking.
Protection settings should be based on the transformer data, system fault study, cable ratings, downstream coordination requirements, and local electrical regulations.
Coordinate Cable Entry and Busbar Connections
The transformer manufacturer needs to know how the unit will connect to the surrounding switchgear and distribution equipment.
Possible arrangements include top- or bottom-entry high-voltage cables, side-entry low-voltage busduct, top-mounted low-voltage busbars, bottom cable connections, close-coupled switchgear, and separate neutral terminals.
For a 400V secondary current exceeding 1,400A, the busduct or cable system should not impose excessive mechanical force on the transformer terminals.
Flexible connections can help reduce the transfer of vibration, thermal expansion, and alignment tolerances between the transformer and the low-voltage switchboard.
Control Transformer Noise and Vibration
The catalog lists a reference LwA value of 64dB(A) for the 1000kVA models shown above. LwA is a sound-power value and should not be treated as the sound pressure measured at a specific distance inside the completed transformer room.
The actual perceived noise depends on the transformer core, supply voltage quality, load current, harmonic distortion, enclosure design, room reflections, ventilation fans, busbar vibration, and building structure.
For hospitals, offices, hotels, residential towers, and other noise-sensitive facilities, the required sound limit should be included in the purchase specification.
Possible noise-control measures include flexible busbar connections, anti-vibration pads, structural isolation, low-noise core designs, acoustic enclosures, and locating the transformer room away from occupied spaces.
Factory Acceptance Testing Before Shipment
The factory acceptance test scope should be agreed upon before production is completed. Typical checks include nameplate verification, approved drawing review, winding resistance, voltage ratio, vector group, insulation resistance, applied-voltage testing, induced-voltage testing, no-load loss, load loss, impedance voltage, temperature-controller operation, fan operation, alarm outputs, enclosure inspection, and packing inspection.
A partial-discharge test may also be included when required by the selected standard or purchase specification.
Measured results should be compared with the approved technical datasheet rather than with a generic catalog alone.
See our
for more information about witness points, test reports, and shipment approval.
Installation and Commissioning
Before Installation
After delivery, inspect the transformer and its packaging for transportation damage. Check the resin windings, fans, sensors, terminals, enclosure, and supplied accessories. The nameplate and test reports should match the approved order and transformer serial number.
The foundation, access route, lifting equipment, electrical room, and ventilation system should be ready before the transformer is moved into position.
During Installation
The transformer should be positioned and leveled according to the approved drawing. Rollers must be locked or the transformer secured to its foundation. Grounding connections, high-voltage cables, low-voltage busbars, neutral conductors, temperature sensors, fans, alarm contacts, and trip circuits should then be installed and checked.
Connections must be tightened according to the approved torque requirements, and cables or busbars should not impose excessive stress on the transformer terminals.
Before Energization
Before the transformer is energized, complete the visual inspection, insulation testing, grounding continuity test, ratio verification, vector-group confirmation, phase-sequence check, protection-relay testing, fan-control testing, and alarm simulation.
Electronic temperature-control devices should be isolated or handled according to the manufacturer’s instructions during insulation-resistance testing.
Initial Energization
The transformer is normally energized without load first. The commissioning team should observe the primary and secondary voltage, phase sequence, sound, vibration, smell, temperature indication, cooling-fan operation, and protection alarms.
The facility load can then be increased progressively while phase current, voltage, phase balance, winding temperature, and transformer room temperature are monitored.
Routine Maintenance
Cast resin transformers do not require transformer oil sampling, but they are not completely maintenance-free.
A practical maintenance program should include cleaning dust from winding air passages, inspecting resin surfaces for cracks or electrical tracking, checking grounding connections, verifying terminal tightness, testing fans and temperature alarms, inspecting room ventilation, and performing infrared thermography.
Operating current, temperature, noise, and ventilation conditions should be recorded regularly. Any unusual discoloration, smell, vibration, noise, or temperature rise should be investigated promptly.
The maintenance interval should reflect the operating environment. A clean commercial electrical room normally requires less frequent cleaning than a cement plant, mine, metal-processing facility, or coastal installation.
Information Required for a 1000kVA Transformer Quotation
To prepare an accurate quotation and technical proposal, the manufacturer first needs the basic electrical parameters, including the 1000kVA rated capacity, primary and secondary voltages, frequency, number of phases, vector group, tap range, and required impedance.
The buyer should also confirm the preferred winding material, efficiency or loss requirements, permitted temperature rise, and whether the transformer will use natural-air or forced-air cooling.
Installation conditions are equally important. Please provide details such as indoor or outdoor installation, enclosure protection rating, maximum ambient temperature, altitude, humidity, dust level, corrosive conditions, and any significant harmonic loads.
The quotation request should also state the required sound level, cable or busduct entry direction, temperature-monitoring functions, applicable IEC, IEEE, ANSI, or local standards, order quantity, and delivery destination.
A single-line diagram, facility load schedule, equipment layout, and existing switchgear drawings can help the engineering team confirm the transformer design and reduce technical clarification time.
Frequently Asked Questions
How many amps does a 1000kVA transformer produce?
A three-phase 1000kVA transformer produces approximately 1,443A at 400V, 1,391A at 415V, 1,203A at 480V, 57.7A at 10kV, and 52.5A at 11kV.
Is a 1000kVA transformer suitable for an 800kW facility?
It may be suitable, but the power factor must be considered. An 800kW load at a power factor of 0.80 equals 1,000kVA and leaves no spare transformer capacity. At a power factor of 0.90, the same load equals approximately 889kVA.
What are the dimensions of a 1000kVA cast resin transformer?
The ZHONGSHAO catalog lists the SCB10–1000/10 reference model at approximately 1700 × 850 × 1550mm in IP00 construction and 2350 × 1650 × 2000mm with the referenced IP20 enclosure. Final dimensions depend on the voltage, enclosure, winding material, terminal design, and accessories.
How much does a 1000kVA dry-type transformer weigh?
The catalog SCB10–1000/10 reference model weighs approximately 3,320kg in IP00 construction and 3,820kg with its referenced IP20 enclosure. The 20kV and 35kV configurations are generally heavier.
Does a 1000kVA cast resin transformer need a dedicated room?
It is normally installed in a dedicated or controlled electrical area with restricted access, adequate ventilation, appropriate electrical clearances, and sufficient maintenance space. Local building, fire, and electrical regulations determine the final room requirements.
Can a 1000kVA cast resin transformer be installed outdoors?
Yes. The transformer must be supplied with an enclosure and cooling design suitable for outdoor service. Rain, solar heating, condensation, dust, humidity, corrosion, salt spray, and ventilation should all be considered.
Does forced-air cooling increase transformer capacity?
Forced-air cooling may provide a manufacturer-approved increase in temporary or continuous loading capacity. The actual increased rating must be confirmed for the specific transformer design and should not be assumed from the base 1000kVA rating.
What is the typical impedance of a 1000kVA transformer?
The referenced ZHONGSHAO SCB10 1000kVA catalog models have 6% impedance. Other impedance values may be designed according to fault-current, motor-starting, voltage-drop, and parallel-operation requirements.
Final Thoughts
Integrating a 1000kVA cast resin transformer requires coordination between the transformer manufacturer, electrical engineer, switchgear supplier, busduct or cable supplier, civil contractor, and commissioning team.
The most important steps are to confirm the actual load demand, calculate the low-voltage current, obtain the final approved dimensions, remove transformer heat from the room, coordinate short-circuit protection, and confirm every mechanical and electrical interface before production.
When these factors are addressed during the design stage, a properly selected cast resin transformer can provide safe, stable, and low-maintenance power distribution for many years.
To obtain an order-specific transformer proposal, send your voltage information, load schedule, single-line diagram, installation environment, enclosure requirement, and connection arrangement through the ZHONGSHAO
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