Technical Details – Distribution Transformer
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Distribution Transformer – Technical Specifications
Distribution transformers are vital components in the electrical grid, used to step down high-voltage electricity from transmission lines to lower voltages suitable for commercial, industrial, and residential use. They are designed for high efficiency, safety, and long service life under varying load conditions.
General Specifications
|
Feature
|
Details
|
|---|---|
|
Rated Capacity
|
25 kVA to 2500 kVA
|
|
Primary Voltage (HV)
|
11 kV / 22 kV / 33 kV
|
|
Secondary Voltage (LV)
|
433 V (3-phase) / 230 V (1-phase)
|
|
Frequency
|
50 Hz (standard)
|
|
Phase Configuration
|
1-Phase / 3-Phase
|
|
Cooling Type
|
ONAN (Oil Natural Air Natural)
|
|
Mounting
|
Pole-Mounted / Pad-Mounted / Foundation Mounted
|
|
Insulation Class
|
Class A (Oil-immersed), F or H (Dry-type)
|
|
Standard Compliance
|
IS 1180 (Part 1), IS 2026, IEC 60076
|
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Electrical Characteristics
|
Parameter
|
Typical Range
|
|---|---|
|
Efficiency
|
≥ 98.5%
|
|
Impedance
|
4% – 6.25%
|
|
Vector Group
|
Dyn11 (most common), Dyn1, Yyn0
|
|
Tapping Range
|
±10% upto -20% × 2.5% (Off-circuit tap changer)
|
|
Losses
|
As per IS1180 efficiency levels & BEE Star, Levels 1, 2, 3, 4, 5)
|
|
Dielectric Strength
|
As per BIL standards for relevant voltage class
|
|
Temperature Rise
|
≤ 35°C (oil), ≤ 45°C (winding)
|
Protection & Monitoring Features
|
Feature
|
Function
|
|---|---|
|
HT Fuse / Drop-out Fuse
|
Overcurrent protection on high-voltage side
|
|
LV MCCB / MCB
|
Overcurrent/short-circuit protection on low-voltage side
|
|
Breather with Silica Gel
|
Moisture control in conservator tank
|
|
Oil Level Indicator
|
Visual indication of oil level
|
|
Pressure Relief Valve
|
Releases excess pressure during internal faults
|
|
Earthing Terminals
|
Ensures safe fault current dissipation
|
Applications
- Utility distribution networks
- Commercial and residential buildings
- Rural and urban electrification
- Industrial and agricultural installations
- Solar and renewable energy output connection
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