Completing The Test - ABB REG650 Commissioning Manual

Section 6
Testing functionality
6.6.5.3
88
(
= +
DU U U
3 N
EQUATION2078 V1 EN
3. Read the value of BU (bias voltage: Beta ·U
below 1 for a non-faulted generator.
4. After synchronization of the generator the ratio DU/BU is checked for different
load levels of the generator. These different monitoring of load levels should be
the base for the setting of beta.
If the function is used with the option of neutral point measurement only the test
is performed by check of this voltage. The operate value should be above the
measured residual third-harmonic voltage in the neutral point at normal
operation (non-faulted generator).

Completing the test

Continue to test another function or end the testing by setting the parameter TestMode
to Off under Main menu/Tests/IED test mode/TESTMODE:1. If another function
is tested, then set the parameter Blocked to No under Main menu/Tests/Function test
modes/Voltage/STEFPHIZ(59THD)/STEFPHIZ:1 for the function, or for each
individual function in a chain, to be tested next. Remember to set the parameter
Blocked to Yes, for each individual function that has been tested.
Generator rotor winding and its associated dc supply electric circuit is typically fully
insulated from the earth. Therefore single connection of this circuit to earth will not
cause flow of any substantial current. However, if second earth-fault appears in this
circuit circumstances can be quit serious. Depending on the location of these two
faults such operating condition may cause:
• Partial or total generator loss of field
• Large dc current flow through rotor magnetic circuit
• Rotor vibration
• Rotor displacement sufficient to cause stator mechanical damage
Therefore practically all bigger generators have some dedicated protection which is
capable to detect the first earth-fault in the rotor circuit and then, depending on the
fault resistance, either just to give an alarm to the operating personnel or actually to
give stop command to the machine.
Rotor earth fault protection can be integrated in the IED among all
other protection functions typically required for generator protection.
Instruction 1MRG001910 gives an example of a testing procedure by
using COMBIFLEX injection unit RXTTE4.
) (
2
× +
cos(ANGLE) U
3T
1MRK 502 049-UEN A
)
2
×
sin(ANGLE)
3T
). The ratio DU/BU should be well
3N
Commissioning manual
(Equation 34)