General
Application
Environmental
Standards
The oil-filled hermetically sealed distribution transformer features a Hermetically sealed design that effectively prevents moisture intrusion and oxidation, safeguarding electrical performance in harsh environments. ensures silent operation and complies with fire safety standards. Corrugated tank walls accommodate thermal expansion, eliminating the need for a conservator and reducing external components. This design delivers consistent performance under varying load and climate conditions while minimizing the risk of internal contamination.
Hermetically sealed transformers are ideal for critical infrastructure, offering excellent corrosion resistance and ensuring stable operation across a variety of environmental conditions. Their compact, sealed design and quiet operation make them well-suited for applications such as residential areas, subway systems, and renewable energy installations. For users, this translates to extended insulation life, simplified installation, reduced maintenance frequency, and a lower risk of unplanned outages.
Application:outdoor installation.
Ambient temperature: -50°C to +40°C
Relative humidity: ≤90% (at 25°C); ambient air RH <93%.
Altitude: ≤ 1000m above sea level.
Max wind speed: ≤35 m/s.
Seismic withstand: Horizontal ≤0.3 g; Vertical ≤0.15 g.
Special conditions: Custom-built solutions available for project-specific requirements.
Ambient temperature: -50°C to +40°C
Relative humidity: ≤90% (at 25°C); ambient air RH <93%.
Altitude: ≤ 1000m above sea level.
Max wind speed: ≤35 m/s.
Seismic withstand: Horizontal ≤0.3 g; Vertical ≤0.15 g.
Special conditions: Custom-built solutions available for project-specific requirements.
1.IEC 60076 (International Electrotechnical Commission) – General requirements for power transformers.
2.IEC Standard for Liquid-Immersed Distribution Transformers – Covers design, testing, and performance criteria.
3.EN 50588 (European Standard) – Specifics for medium-power transformers.
4.Oil Quality: Mineral or biodegradable oil must meet IEC 60296 for dielectric strength and oxidation stability.
2.IEC Standard for Liquid-Immersed Distribution Transformers – Covers design, testing, and performance criteria.
3.EN 50588 (European Standard) – Specifics for medium-power transformers.
4.Oil Quality: Mineral or biodegradable oil must meet IEC 60296 for dielectric strength and oxidation stability.
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Transformer Features
Hermetically sealed distribution transformers offer compact, efficient, and safe performance with flexible design, minimal maintenance, reduced labor, and high reliability for diverse, space-constrained applications.
Flexible Design - Well-matched to a Range of Applications.
Engineered with customizable winding configurations, voltage taps, and kVA ratings to precisely match diverse grid requirements across industrial facilities, renewable energy systems, and urban distribution networks for optimal operational performance.
Space Saving – Effective, Flexible Layout
Compact three-phase design with minimized external dimensions enables installation in constrained substations or commercial buildings while maintaining full power capacity, reducing civil works costs and maximizing facility space utilization.
Laborsaving – Reduction of Manpower
Factory-assembled hermetic sealing eliminates on-site oil processing and reduces commissioning steps, requiring only 30-50% of the workforce needed for conventional transformers during both installation and maintenance operations.
Energy Saving – Reduced Operating Costs
Premium-grade amorphous steel core combined with precision-wound copper windings achieves >98% efficiency meeting Ecodesign TIER 3 standards, delivering substantial cost savings throughout the transformer's 30-year service life.
High Reliability – Long-term, Trouble-free Operation
Complete oxygen-free, moisture-proof encapsulation prevents insulating oil degradation and preserves dielectric strength across extreme temperature variations (-40°C to +50°C) for decades of uninterrupted service under demanding load conditions.
Safe Design – Ensures Operator’s Safety
Rugged steel tank with pressure relief system and integrated oil level monitoring complies with EN 50464-1 safety standards, ensuring personnel protection and environmental containment during faults or overload situations.
Minimal Maintenance – Reduced Maintenance Costs
Hermetic construction completely eliminates need for breather replacement or periodic oil purification, with recommended maintenance limited to biennial thermographic inspections and terminal checks under normal operating conditions.
Why Choose Kerun Intelec
Choose us for precision-engineered transformers—superior efficiency, global certifications, 24/7 support, and tailored solutions. Trusted durability, energy-saving innovation, ensuring optimal performance and longevity worldwide.
Fast Lead Times
Our made-to-order production timelines are highly competitive and as low as 8 weeks from order to delivery.
Design Conformance
We maintain rigorous oversight to ensure every transformer adheres precisely to your exact specifications.
Comprehensive Warranty
We stand behind the longevity and reliability of our products with a robust warranty that covers both materials and workmanship.
Competitive Pricing
We deliver exceptional value so you receive top-tier, reliable, high-quality products without the premium price tag
Exceptional Quality
We implement strict quality control measures at every stage of production to ensure our products meet or exceed industry standards.
Dedicated Support
Our support team is always at your service.Offering expert guidance from initial inquiry through post-installation support.
Standard Feature
HV&LV&Neutral bushings
Tap changer
Oil level gauge
Oil Thermometer indicator
Pressure relief device
Gas relay
Oil sample valve
Oil drain valve
Transformer breather
Earthing terminals
Lifting lugs
Rating plate
Optional Features
DIN/EN/ANSI bushings
Off-Circuit/On-load Tap changer
Copper/aluminum windings
Dial type thermometer with two contacts
DGPT2 / RIS / DMCR control device
Pressure – vacuum gauge
Pressure relief valve with contacts
Winding Temperature Indicator
LV/HV Cable boxes / Common cable box
Protection CT
Bidirectional rollers
Design Drawings
Detailed Hermetically Sealed Distribution Transformer drawings provide clear dimensions, interface data, and layouts, simplifying engineering coordination and installation.
30kV-300kVA-Hermetically-Sealed-Distribution-Transformer
10kV-630kVA-Hermetically-Sealed-Distribution-Transformer
10kV-2000kVA-Hermetically-Sealed-Distribution-Transformer
Tap Changer
Accessories Include
Hermetically Sealed Tank
Radiators
Tank Cover
Sealing Gaskets
Active Part
HV Bushings
LV Bushings
Neutral Bushing
Terminal Connectors
Busbars
Off-Circuit Tap Changer
Pressure Relief Valve
Pressure-Vacuum Gauge
Surge Arrester
Earthing Terminal
Oil Level Gauge
Oil Temperature Indicator
Winding Temperature Indicator
Oil Filling Plug /Valve
Lifting Lugs
Nameplate
Transformer Oil
About Construction
High-quality Hermetically sealed oil-immersed transformer accessories ensure enhanced safety, minimal maintenance, and extended lifespan in demanding conditions.
01
Tanks
02
Core
03
Coils
04
Active Part
05
Radiator
06
Bushings
07
Tap Changer
08
Oil Level Gauge
09
Contact Thermometer Meter
10
Pressure Relief Valve
11
Grounding Terminals
12
Nameplate
13
Wheel
14
Gas Relay
15
Oil Sample Valve
Tanks
Constructed from premium carbon steel, the tank is precision-robotically welded and vacuum-tested to ensure hermetic integrity. Surface treatments are tailored to site conditions—optional hot-dip galvanizing or a zinc-rich primer plus polyurethane system delivers up to 3 000-hour salt-spray resistance. Rated for –40 °C to +120 °C, the design supports custom dimensions without sacrificing rigidity, enabling compact footprints, lower installation costs, and long-term corrosion protection in coastal or industrial environments.
Surface protection: Optional hot-dip galvanizing or coating systems
Dimensions/structure: Customized special configurations supported.
Core
Built from high-permeability grain-oriented silicon steel, the core is processed on servo-controlled, vision-guided cutting lines for high precision, ultra-low length/angle error, and minimal burrs. Automated dot-stacking delivers orderly step-lap alignment and controlled air gaps, reducing no-load loss and noise. Custom options: amorphous metal, lamination thickness, flux density, clamping scheme, varnish/grounding configuration, and geometry optimized for 50/60 Hz efficiency and footprint targets.
Material options: Available in grain-oriented silicon steel or amorphous alloy.
Dimension customization: Custom sizes and lamination thicknesses available.
Coils
Hermetically sealed coils are available in electrolytic copper or aluminum, with foil or CTC windings and closed-loop tension control for dimensional stability. Insulation systems are customizable—from cellulose papers to Nomex pressboards—for higher thermal endurance and capacity. Radial/axial cooling ducts and optimized oil flow limit hotspots. Options cover conductor cross-section, tap geometry, and dielectric grading to meet IEC 60076 performance targets.
HV/LV Winding materials:Cu/Al wire.LV also available in Cu/Al foil.
Insulation materials: optional DMD, Nomex®, or Weidmann.
Transformer Active Part
Active part is engineered for minimal core and load losses, low vibration and Noise, and controlled flux density and current distribution across phases. PD-screened insulation stacks and graded clearances deliver high dielectric strength and verified lightning-impulse withstand. Rigid non-magnetic clamping frames with pre-compression maintain coil geometry under fault forces, stabilizing impedance and extending service life in demanding duty cycles.
Low losses, reduced vibration and noise, with uniform flux distribution.
High dielectric strength, impulse withstand; rigid clamping preserves coil geometry.
Radiator
The radiator in hermetically sealed transformers delivers superior thermal management through precision-engineered design. Utilizing robotic welding technology , it achieves consistent weld seams (≥3mm thickness) for enhanced structural integrity and leak resistance. Neatly aligned arrays optimize airflow, improve heat transfer, and reduce vibration. Standard interfaces simplify fan mounting and maintenance, enabling interchangeability and consistent performance under transport shocks and thermal cycling.
Precision design ensures superior thermal management.
Increased weld thickness improves integrity and leak resistance.
Bushings
Porcelain bushings use vitrified high-alumina ceramic with steel flanges and precision-machined gasket grooves for hermetic sealing. Voltage ratings are configurable from 6–36 kV in DIN, EN, and ANSI outlines, with selectable conductor palm/angle and terminal orientation. Shock- and cantilever-tested designs resist impact and vibration, while interchangeable bolt patterns and sealing interfaces simplify installation, reduce leak risk, and ensure low-maintenance
Voltage range: HV bushings available from 6–36 kV.
Type options: DIN, EN, or ANSI configurations available.
Tap Changer
Tap changers employ silver-plated copper contacts, arc-resistant diverter parts, nitrided shafts, stainless hardware, and oil-compatible FKM seals for durability in sealed oil. Select DETC (off-circuit) or OLTC (on-load) configurations. Customizable tap ranges (±2.5% to ±10%), 5–33 positions, manual or motor drives, mechanical interlocks, position encoders, and SCADA-ready status contacts deliver precise ratio control, low heating, and extended maintenance intervals.
Type selection: DETC (off-circuit) or OLTC (on-load) available.
Tap ranges ：(±2.5% to ±10%), 5–33 positions available.
Oil Level Gauge
Oil level solutions include tubular gauges with integrated pressure relief and alternative magnetic-float or sight-glass indicators. Corrosion-resistant housings, windows, and oil-compatible elastomers support hermetic service. Options include alarm contacts, 4–20 mA or Modbus transmitters, vertical mounting, and cold-climate heaters. Clear indication and overpressure venting enhance safety, enable remote monitoring, reduce maintenance, and maintain long-term reliability in demanding environments.
Tubular oil level gauge integrates pressure relief for safer operation.
Temperature Resilience Operates from -60°C to +105°C with silicone oil.
Contact thermometer meter
Contact thermometer with two adjustable setpoint contacts monitors transformer top-oil from 0–100 °C, enabling staged alarm/trip aligned with permissible temperature rise. Bimetal and capillary-based designs provide stable indication for hermetic or conservator tanks. Adjustable switching differential supports reliable pump control and fewer nuisance trips during load swings.
Two adjustable contacts match permissible transformer temperature rise.
Hermetic Moisture BarrierSealed gasket prevents humidity ingress.
Pressure Relief Valve
Hermetically sealed oil-immersed transformer pressure relief valve opens at 12–15 psi to avert tank rupture, then reseats to limit oil loss and moisture ingress. A calibrated spring and splash-guarded, directional outlet enable safe venting and operator protection. reduced gasket stress, fewer maintenance interventions, and longer asset life during internal faults, short-circuits, or thermal transients across varying load conditions worldwide.
Opens at 12–15 psi, prevents rupture, reseats quickly.
Hermetic Moisture Barrier Sealed gasket prevents humidity ingress.
Grounding
Grounding in hermetically sealed transformers ensures zero floating voltage on non-energized components (e.g., tank, core), eliminating arc discharge risks and operator electrocution hazards . By establishing equipotential bonding，it prevents step/contact voltages during faults, critical for outdoor installations exposed to environmental contaminants .
Single-point core grounding eliminates floating potential differences entirely.
Adheres to IEEE and IEC grounding practices standards.
Nameplate
The nameplate for hermetically sealed oil-immersed transformers is made from laser-etched stainless steel or anodized aluminum, providing UV-, chemical-, and weather-resistant, indelible markings. It consolidates essential data—kVA, voltages, frequency, vector group, cooling/temperature rise, impedance, BIL, serial number, weights, and oil volume—for correct selection, installation, and maintenance.
ECustomizable nameplate materials with multiple language options.
Data fields configured per customer requirements and standards.
wheel
Wheel assemblies for hermetically sealed oil-immersed transformers enable safe, bidirectional movement during installation and maintenance. Typical designs use bi-directional flat rollers or wheeled carts and integrate towing holes for controlled repositioning. Options include rail-gauge rollers to suit project specs and base frames allowing pipe rollers. reduced handling risk, bay alignment, less crane time, aligning with IEC accessory requirements.
Wheel materials selectable: cast steel, ductile iron, polyurethane.
Meets IEC 60076-22-7 accessory requirements for compliance globally.
Gas relay
Hermetically sealed oil-immersed transformer gas relays offer precise early detection of internal faults via gas accumulation or oil flow. Airtight integration prevents false triggers from external contaminants. Enhances operational safety with rapid response, minimizing downtime risks in critical power systems.
Integrates with hermetic enclosures without compromising seal integrity.
Distinguishes minor gassing from rapid pressure surges accurately.
Oil sample valve
Hermetically sealed oil sample valves for oil - immersed transformers have a tight seal, halting moisture and contaminants. They allow for convenient in - service sampling, ensuring accurate oil condition assessment. Their robust build ensures long - term reliability, reducing maintenance and safeguarding transformer performance.
Tight sealing prevents moisture ingress and particulate contamination.
Enables convenient in-service oil sampling without planned outages.
About Oil-Filled
Choose Mineral Oil, Silicone Fluid, or Envirotemp FR3—balancing fire safety, biodegradability, thermal headroom, and lifecycle cost for site-specific reliability needs
Mineral Oil
Low Transformer Cost
Preventative maintenance
Good Dielectric Performance
Potentialhigher installation cost
Low Maintenance Cost
Vaults required for indoor installations per NEC® due to low fire
Good heat dissipation
<30% biodegradability
Good cold climate performance
Silicone Fluid
Low heat release
Non-biodegradable
Reduced smoke
Not suitable for use with internal Bay-O-Net fuses
Low flame
Transformer cost
Self extinguishing
Disposal cost
Good dielectric performance
Viton gaskets required
Low toxicity
Retrofil applications
Moderate viscosity
High transformer cost
High stability
High moisture absorption
Envirotemp FR3
High fire point—360 °C
Transformer cost (lower than silicone fluid)
High flash point—330 °C
Pour point (–15 °C to–25 °C) transformer energized with full load with top oil temperature at –50 °C with no problems—no crystals formed at –68°C
Compatible with mineral oil
Allows transformers to be designed to operate at 10°C higher average winding rise (75°C) without reducing normal transformer insulation life
Excellent dielectric performance
Excellent switching medium
Greater than 99% biodegradable
Excellent cold weather performance
Greater tolerance to moisture, dramatically extending insulation life
About Testing
Each hermetically sealed distribution transformer is tested to verify electrical performance, insulation strength, sealing reliability, and safe operation before delivery.
Routine Tests
Type Tests
Special Tests
Winding resistance
Voltage ratio & polarity / phase displacement
No-load loss & no-load current
Load loss & short-circuit impedance
Applied AC withstand voltage test
Induced AC withstand voltage test
Insulation resistance / polarization index
Oil tests (dielectric strength, moisture, acidity)
Tank tightness / leak test (pressure or vacuum)
Functional checks (tap position, gauges/alarms if fitted)
Temperature rise test
Lightning impulse withstand test
Short-circuit withstand test
Sound level measurement
Partial discharge measurement
Zero-sequence impedance
Capacitance & dissipation factor (tan δ)
Frequency response analysis (SFRA)
Dielectric response (FDS/PDC)
Stray losses / harmonic loss verification
Oil dissolved gas analysis (DGA) baseline
Vacuum/pressure tank mechanical test (enhanced)
Coating / corrosion protection verification
All transformers undergo strict testing based on the latest ieee and iec standards, with detailed reports ensuring traceability. this guarantees each unit meets the highest standards of quality, safety, and performance.
Package & Delivery
We provide tailor-made packaging solutions for Hermetically Sealed Distribution Transformer ensure secure and efficient delivery, protecting critical components during transit.
Wooden / Steel Skid with Sealing Film
Wooden pallets deliver a customizable design, easy handling, and a cost-effective solution for secure and efficient transport of goods.
Wooden / Steel Frame
Combining moisture-resistant sealing film and sturdy wooden pallets, this packaging solution ensures optimal protection against environmental hazards (humidity, dust, and Scratches) during transit.
Wooden Crate
Shield shipments securely with durable sealing film and reinforced wooden frames—ensuring weatherproof, shock-resistant protection for safe global transit. Premium safeguarding guaranteed.
Container Shipment
Sturdy wooden boxes ensure robust protection for shipments—weatherproof, shock-resistant, and customizable. Ideal for fragile or heavy cargo, delivering reliability across global logistics.
Transportation & Delivery
With a range of customizable options, these solutions adapt to diverse logistical and storage requirements, offering flexibility and reliability.
Review key FAQ before purchasing a Hermetically Sealed Distribution Transformer, covering lead time, grid standard customization,certified components, factory testing, installation support, and long-term reliable operation.
What Is The Lead Time For A Hermetically Sealed Distribution Transformer?
The typical lead time for a Hermetically Sealed Distribution Transformer is 4 to 8 weeks, depending on rated capacity, voltage class,
winding material, sealed tank structure, corrugated fin configuration, accessories, factory testing, drawing approval, and transportation requirements.
winding material, sealed tank structure, corrugated fin configuration, accessories, factory testing, drawing approval, and transportation requirements.
Can The Transformer Be Customized For Different Grid Standards?
The transformer can be customized according to IEC, IEEE/ANSI, EN, or local utility standards. Project-required certificates, test reports, CE,KEMA,KERI or
related documents, and third-party inspection reports can be provided where applicable.
related documents, and third-party inspection reports can be provided where applicable.
What Customization Options Are Available For A Hermetically Sealed Distribution Transformer?
Customization options include winding material, insulation system, fully sealed tank, corrugated fins, pressure relief valve, oil temperature indicator,bushing type, transformer oil, tap changer, protection devices, monitoring accessories, enclosure coating, and anti-corrosion treatment.
What Tests Are Performed Before Delivery?
Routine tests include winding resistance, voltage ratio, vector group, impedance, load loss, no-load loss, insulation resistance, applied voltage, inducedvoltage, leak test, and oil tests. Type and special tests can be arranged as required, and third-party witnessed FAT.
Do You Support Installation And Commissioning?
Installation and commissioning support can be provided by documents, remote guidance, video support, or on-site engineers. Support includes
foundation guidance, accessory assembly, wiring checks, grounding inspection, protection verification, pre-energization inspection, and commissioning coordination.
foundation guidance, accessory assembly, wiring checks, grounding inspection, protection verification, pre-energization inspection, and commissioning coordination.
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Kerun Intelec
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