ABB REG670 Commissioning Manual page 83

1MRK 502 073-UEN A
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Commissioning manual
Calibrating injection based 100% stator earth fault protection
• LV winding of a distribution transformer (DT) located at the stator neutral
point
• Open delta winding of a three-phase VT set located at generator terminals
• Open delta winding of a three-phase grounding transformer (GT) located at
generator terminals
Whatever injection alternative is used, the neutral point of the generator must be
accessible in order to connect the calibration resistance (step 2) and short circuit
(step 3) during the calibration.
Commissioning
The generator can be in several operating conditions, for example:
• Generator stand still
• Generator running up, not synchronized to the network (circuit breaker open)
• Generator normal operation (circuit breaker closed)
Other operating conditions can be identified.
If a particular stable operating condition of the generator requires a dedicated
reference impedance, it can be defined and saved by the Commissioning tab of
ICT.
Different operating conditions of the machine may require different reference
impedances. The first reference impedances is defined during the calibration.
Up to five reference impedances can be defined for the protection function
STTIPHIZ.
ICT also performs a verification between the new reference impedance(s) and
existing reference impedance(s), and warns the user if the resulting estimated
resistance difference could cause alarm or trip when one reference is shifted from
another during operation.
If more than one reference impedance is to be used, a logic must be configured to
detect such changes in the operating conditions that requires a change of reference
impedance. A logic can be based on the following conditions in order to select the
active reference impedance automatically:
1. Generator voltage < set value and generator circuit breaker open: Reference
impedance 1
2. Generator voltage > set value and generator circuit breaker open: Reference
impedance 2
3. Generator voltage > set value and generator circuit breaker closed: Reference
impedance 3
For more information see separate application note 1MRG005030 Application
example for injection based 100% Stator EF and Sensitive Rotor EF protection.
Section 7
77