Oil-Immersed Distribution Transformer
Energy-efficient ONAN distribution transformers for utilities, commercial & industrial loads; robust thermal design with low losses.
Voltage
11/22/33 kV primary, 0.433 kV secondary (custom on request)
Cooling
ONAN (std), ONAF (higher ratings)
Vector Group
Dyn11 (std), others on request (Yyn0, Dyn5)
Impedance
as per IS 1180/IEC, site-specific
High-End Technical Details
- Core: CRGO M3/M4 grade with step-lap; optional amorphous core for ultra-low losses
- Windings: Electrolytic copper, transposed for low eddy losses; HV coil interleaved for impulse withstand
- Insulation: Thermally upgraded kraft + pressboard; oil-preserved in nitrogen cushion / conservator with breather
- Thermal Design: Optimized ducting, directed oil flow; hotspot within design limits at 50°C amb.
- Terminations: HV bushings per IS/IEC; LV cable lugs/bar; plug-in terminations on demand
- Monitoring: Oil temp indicator (OTI), winding temp indicator (WTI), magnetic oil gauge (MOG); PRV
Protection & Monitoring
- Buchholz relay (≥500 kVA with conservator)
- Pressure relief valve (PRV)
- Over-temp alarm/trip (WTI/OTI)
- LV/HV surge arresters
- Oil level alarm (MOG)
Standards / Type-Tests
- IS 1180 (Part-1)
- IS 2026 / IEC 60076
- IS 335 (oil)
- IS 3639 (tests)
Options / Accessories
- Hermetically sealed tank (no conservator)
- Copper/Aluminium variants
- HV Tap links ±5% in 2.5% steps
- OLTC (select ratings)
- Anti-theft locking hardware
Amorphous Core Distribution Transformer
Ultra-low no-load losses using amorphous metal cores; ideal for 24×7 feeders & green programs.
Efficiency
Star-rated / BEE compliant
Vector Group
Dyn11 typical
High-End Technical Details
- Core: Amorphous ribbon core with tightly clamped stacks; significantly reduced hysteresis losses
- Windings: Foil/strip LV for uniform current density; HV interleaved
- Tank & Oil: Corrugated wall tank (hermetically sealed) with nitrogen cushion; inhibited oil per IS 335
- Thermal: Loss-optimized design, lower temperature rise, extended life
Protection & Monitoring
- PRV
- Oil level indicator
- Temp alarms (OTI/WTI)
- Surge arresters
Standards / Type-Tests
- IS 1180
- IEC 60076
- Bureau of Energy Efficiency (Star rating)
Options / Accessories
- Pole/Plinth mounted kits
- HV Aerial bushing
- Smart meter ready CTs
Isolation Transformer (K-Rated Optional)
Galvanic isolation for sensitive loads—data centers, medical, drives; K-Factor for non-linear loads.
Voltage
LV/LV, MV/LV options
Insulation Class
Class F/H
K-Factor
K-4 / K-13 / K-20 as application
High-End Technical Details
- Electrostatic Shield: Multiple copper shields for common-mode noise attenuation
- Winding: Foil/strip with low leakage; impregnation for low audible noise
- Core: Low flux density for low inrush; CRGO/CRNGO
- Thermal: Natural/forced air cooling with temp sensors
Protection & Monitoring
- Over-temperature (PTC/RTD)
- Surge protection (optional)
Standards / Type-Tests
- IEC/IS 61558
- IEC 60076-11 (dry type variants)
Options / Accessories
- Harmonic-rated (K-factor)
- Faraday shielded
- Cast-resin variant
Earthing / Neutral Grounding Transformer (Zig-Zag)
Provides a reference neutral & limits earth-fault current using NGR; essential in MV systems with delta sources.
System Voltage
3.3 – 33 kV
Fault Current
50 – 1000 A (via NGR)
Duty
10 s / 30 s / continuous as specified
Connection
Zig-Zag (Zn0) with/without auxiliary winding
High-End Technical Details
- Core/Windings: Robust design to withstand short-time fault duty
- NGR: Stainless steel grid/resistor bank, IP23–IP54 enclosures
- Cooling: ONAN
- Terminations: Outdoor bushings / cable box
Protection & Monitoring
- Temp detectors
- NGR over-temp
- Ground fault relay interface
Standards / Type-Tests
- IEC 60076
- IEEE C62 (earthing practices)
Options / Accessories
- Aux winding for station service
- Outdoor canopy/kiosk
Power Transformer (OLTC)
Generator/step-up/step-down power transformers with on-load tap changer for voltage regulation, grid & industrial substations.
MVA Range
5 – 160 MVA (higher on request)
Voltage Levels
66/110/132/220 kV class & below
Tap Changer
OLTC ±10–16 steps
Impulse/BIL
As per system voltage & insulation level
High-End Technical Details
- Core: Built from low-loss CRGO; flux optimized with step-lap joints
- Windings: Continuously transposed conductor (CTC) for HV; disk/helix designs for short-circuit strength
- Insulation/Oil: High-grade mineral oil, cellulose insulation with drying/impregnation per QAP
- OLTC Gear: RTCC panel, AVR with line/drop comp; motor drive, position indicators
- Diagnostics: Tan-δ, SFRA, PD on request; dissolved gas analysis (DGA) provisions
Protection & Monitoring
- Buchholz relay
- PRV
- Oil/Winding temp alarms & trips
- Pressure/vacuum relief
- OLTC oil temp & interlocks
Standards / Type-Tests
- IEC 60076 series
- IS 2026
- IEC 60214 (OLTC)
Options / Accessories
- OLTC diverter supervision
- Online DGA monitor
- Bushing CTs
- OFWF coolers with redundancy
Autotransformer (HV/MV Intertie)
Efficient interconnection transformers for close voltage ratios; reduced footprint and losses vs two-winding designs.
Voltage
132/220/400 kV class interface
Vector
Auto-connected with tertiary (optional)
High-End Technical Details
- Design: Leakage flux control; tertiary for stabilization & harmonics
- Windings: CTC for main; foil/strip tertiary
- OLTC (opt): On HV series winding; AVR integrated
- Mechanicals: Core clamp rigidity, seismic provisions
Protection & Monitoring
- Buchholz
- PRV
- OTI/WTI
- OLTC interlocks (if fitted)
Options / Accessories
- Online monitoring
- Bushing CTs
- Spare cooler banks
Converter / Traction Duty Transformer (25 kV)
Designed for single-phase traction/convertor loads with unbalance & harmonics; reinforced thermal & mechanical strength.
System
25 kV single-phase (traction) / 12-pulse converters
K-Factor
High harmonic environment capable
High-End Technical Details
- Core/Flux: Controlled flux density for unbalance; noise constrained
- Windings: Interleaved/disc for harmonic currents; low eddy losses
- Terminations: HV bushings; LV bus-duct ready
- Thermal: Directed oil flow, hotspot within limits
Protection & Monitoring
- Buchholz
- PRV
- Temp alarms/trips
- Surge arresters
Standards / Type-Tests
- IEC 60076
- EN railway specs (as applicable)
Options / Accessories
- Neutral CTs
- Online temp/DGA monitoring
Dry-Type Transformer (VPI)
Vacuum Pressure Impregnated coils for indoor, fire-safe installations—malls, hospitals, basements.
High-End Technical Details
- Coils: VPI epoxy-varnish cycles for moisture resistance
- Core: CRGO/CRNGO with low losses
- Enclosure: IP23–IP54 (as required)
- Thermal: Embedded PT100/NTC for winding core
Protection & Monitoring
- Over-temp trips
- Space heaters (panel)
- Thermal relays
Options / Accessories
- Harmonic-rated
- K-factor
- In-panel MV/LV switchgear
Dry-Type Transformer (Cast-Resin)
Epoxy cast coils for very low partial discharge, high environmental immunity & minimal maintenance.
High-End Technical Details
- Coils: Vacuum cast epoxy with glass-fiber reinforcement
- Environment: Moisture/chemical resistance; coastal suitability
- Thermal Monitoring: PT100, digital controller with alarms
Protection & Monitoring
- Over-temp alarms/trips
- Restricted earth fault (panel)
Standards / Type-Tests
- IEC 60076-11
- IEC 60076-3 (insulation tests)
Options / Accessories
- IP31/IP41/IP54 enclosures
- Harmonic-rated design
Solar Inverter-Duty Transformer (IDT)
MV step-up transformers for PV plants; designed for high harmonic spectra & extended ambient with fan-cooling.
Range
1 MVA – 10 MVA (block)
Voltage
0.315/0.415 to 11/22/33 kV
Ambient
50–55°C site specific
Vector
Dyn11/YNd1 (as inverter topology)
High-End Technical Details
- Harmonics: Low eddy/hot-spot with foil/CTC combo
- Terminations: LV bus-duct/box; MV cable box/surge arresters
- Thermal/Noise: Kiosk integration; low dB for plant norms
Protection & Monitoring
- PRV
- Temp alarms
- Buchholz (as applicable)
Standards / Type-Tests
- IEC 60076
- IEC 60076-7 (loading guide)
Options / Accessories
- Kiosk with RMU
- Online temp logger
- IP55 outdoor
Furnace / Rectifier Duty Transformer
Designed for very high secondary currents, steep cyclic loads & harmonics—EAF, ladle, plating, rectifiers.
Secondary
Very low voltage / kA currents
Duty
Heavy cyclic (IEC duty classes)
High-End Technical Details
- Windings: Disc/helix with reinforced clamps; low eddy/hot-spot
- Tap System: OLTC/ULTC on primary for secondary control
- Rectifier Interface: 12/24-pulse, phase-shifting interphase
- Mechanicals: Short-circuit withstand, vibration control
Protection & Monitoring
- Buchholz
- PRV
- OTI/WTI
- Cooling failure alarms
Standards / Type-Tests
- IEC 60076
- IEC 61378 (convertor transformers)
Options / Accessories
- Online monitoring
- Spare cooler banks
- Oil filtering skid
