Earthing Transformer
Earthing Transformer – Technical SpecificationsAn earthing transformer is a special type of transformer used to provide a grounding (neutral) point for a three-phase power system where the neutral is otherwise not available. It ensures system stability, limits transient overvoltages during ground faults, and allows protective devices to operate correctly.
General Information|
Parameter
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Specification
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Type
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Zig-Zag (Zigzag-connected), Wye-Delta (Yd)
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Purpose
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Provide a neutral point and ground fault current path
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Voltage Class
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3.3 kV to 66 kV (common ranges: 11 kV, 22 kV, 33 kV)
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Frequency
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50 Hz / 60 Hz
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Rated Continuous Current
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As per system design (e.g., 100 A – 2000 A)
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Short-Time Current Rating
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Typically, 10–40 kA for 1–3 seconds
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Insulation Medium
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Oil-Immersed (Standard), Dry-Type (on request)
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Cooling Type
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ONAN / ONAF
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Vector Group
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Zn0 (Zigzag with grounded neutral), YNd1 (optional)
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Mounting
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Indoor or Outdoor
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Standard Compliance
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IS 2026, IS 5553, IEC 60076, IEEE C57.32
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Electrical Characteristics|
Feature
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Details
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|---|---|
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Impedance
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Designed to limit ground fault current
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Neutral Grounding
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Solid / Resistance / Reactance grounding possible
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Time Duration
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Short-circuit withstand: 1s, 2s, or as per design
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Thermal Class
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A or B (Oil), F or H (Dry)
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Insulation Level (BIL)
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According to system voltage and impulse withstand requirements
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Protection & Monitoring|
Protection Device
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Function
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|---|---|
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Neutral Grounding Resistor
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Limits fault current in resistance-grounded systems
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Buchholz Relay
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Detects internal gas faults (oil type)
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Temperature Sensors
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Monitor core/winding temperature
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Surge Arresters
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Protect against lightning/switching surges
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Applications- Generator and transformer grounding
- Isolated or delta-connected systems requiring artificial neutral
- Renewable energy systems (wind/solar farms)
- Power distribution and industrial substations
- Railway traction systems
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