Transformer protection

Hitachi Energy's protection solutions are designed to ensure safe and reliable operation of the transformer and auto-transformer feeders for distribution, sub-transmission, and transmission systems. 

Protection solutions for transformers are designed to accommodate different busbar arrangements across all voltage levels and for high-voltage autotransformers. The solutions are intended for the following types of configuration:

1. Two- and three-winding transformers in different configurations
2. Autotransformers, with or without loaded tertiary winding

The protection functions are split between two groups of hardware (group 1 and group 2) to ensure good reliability. Different protection functions can be allocated to either of the groups, but typical arrangements are as follows:

Group 1 protection unit, basic version

• Biased differential protection for transformers / autotransformers
• Current- and thermal-overload protection
• Voltage protection
• Overexcitation
• Disturbance recorder

• High-impedance/low-impedance restricted earth-fault (REF) protection on the primary and/or secondary winding for transformers
• Per-phase high-impedance protection (for autotransformers)
• Non-directional overcurrent protection
• Tertiary earth-fault protection
• Disturbance recorder
• Busbar and breaker-failure protection schemes (decentralized) can be accommodated in transformer protection solutions.