Grounding Transformers [ZN (Zigzag), ZNyn, YNd(open), Ii0]

Grounding Transformers are designed to provide an artificial, neutral point for ungrounded three phase power systems.

During the line-to-ground faults, grounding transformers provide an easy path to ground faults, thus limit the fault currents and transient over-voltages.

Grounding transformers normally carry short-circuit ground current until the circuit breaker clears the fault. Therefore, they have short time ratings.

The kVA rating of a earthing transformer depends on the normal line-to-neutral voltage and the fault current value for a specified time, such as seconds to minutes.



Technical Specifications
Types Dry or oil-immersed [ZN (Zigzag), ZNyn, YNd(open), Ii0]
Voltage Up to 36 kV
Current Up to 3000 A*
Duty (seconds) 10 /30 / 60 or others
Cooling method



Frequency 50 Hz / 60 Hz
Installation Indoor / Outdoor
Ambient Temperature -30°C to 55°C*

IEC 60076-6

IEC 60076-1

Enclosure Options Transformer cabinets for any IP degrees with:

- CT

- VT

- Isolation switch

*Consult factory for higher values.






Test List
  • Visual & Dimensional Check
  • Measurement of Voltage Ratio
  • Measurement of Winding Resistance
  • Measurement of Zero Sequence Impedance
  • Measurement of No-Load Loss and Current
  • Measurement of Short-Circuit Impedance and Load Loss
  • Dielectric Tests
    • Separate Source AC Withstand Voltage Test
    • Induced AC Withstand Voltage Test
    • Lightning Impulse Test
  • Temperature Rise Test
  • Final Check

For special tests, please contact us.