Xfmer Status Detection - GE 845 Instruction Manual

SYSTEM
Xfmer Status
Detection
4–100
The 845 relay can be set to detect the status of the protected transformer when energized
or de-energized. The detection of the transformer energized/de-energized status is set to
produce operands, which can be used for transformer monitoring applications, and to
trigger an LED (operand set by the factory to trigger LED "Transformer De-Energized"). The
transformer status is detected based on measured voltage, or breaker status, which can be
supervised by a current above the programmed minimum level.
Detection by breaker status
When the 'b' auxiliary contacts from all switching devices (which can be used to energize
the transformer) are assigned to the
indicate de-energization. When Current Supervision is enabled, any current exceeding the
minimum energization current indicates energization.
Detection by voltage
When energization sensing by voltage is enabled, any voltage drops below the minimum
energization voltage indicates de-energization. However, if Current Supervision is enabled,
any of the winding currents that exceed the minimum energization current shows that the
transformer is being energized.
Current Supervision
The Current Supervision is set to support the decision for the Transformer Energized or De-
Energized status. If all winding currents drop below the minimum transformer magnetizing
current after transformer de-energization, this will be added to the decision from the
selected sensing method (Opened Breakers, or Voltage), and will indicate de-energization.
Any current exceeding the minimum energization current will indicate energization.
ALL BREAKERS OPEN setpoints, closed contacts
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS