Transformer protection

Transformer protection is essential for maintaining a reliable onboard power supply. Transformers must be protected to avoid damage and downtime while avoiding false trips (such as inrush current during energization).

Key transformer protection functions include:

  • ANSI 51       overcurrent protection
  • ANSI 49       thermal overload protection
  • ANSI 50       instantaneous overcurrent protection
  • ANSI 50G     ground overcurrent protection
  • ANSI 87N     restricted earth fault
  • Inrush detection of magnetization inrush current
  • ANSI 87       differential protection for 2 and 3 winding transformers

For transformer differential protection, there are two different options:

  • SYMAP®BC – 3-winding differential protection
  • SYMAP®T – 2-winding differential protection