ABB RELION REX640 Technical Manual page 1414

Condition monitoring functions
enumerated monitored data indicates the effect of signal loss (quality faulty) on all
the four algorithms (i.e. Fueling Fault-Correlation, Fueling Fault-Voting, Excitation
Fault-Correlation and Excitation Fault-Voting).
Correlation algorithm:
The generator excitation system normally follows the droop characteristic. Hence,
the average generator phase-phase bus voltage (Uavg), derived from the three
phase input U3P, and local generator reactive power are compared to the set droop
curve. Deviation above/below this curve indicates over/under excitation condition.
The Correlation algorithm for excitation faults can be disabled through the setting
Disable Ext Crl . The droop curve is set through the settings U set point no load and
Voltage droop .
Table 1345
algorithm.
Table 1345: Correlation algorithm for identifying excitation faults
Type of fault
Over excitation
fault
Under excitation
fault
Voting algorithm:
As in Fueling fault detection block, the Voting algorithm for excitation faults is also
applied when at least 3 generators (including the local generator) are running in
parallel. Whenever necessary, the algorithm can be disabled through the setting
Disable Ext Voting .
Table 1346
algorithm.
Table 1346: Voting algorithm for identifying excitation faults
Type of fault
Over excitation
fault
Table continues on the next page
1414
shows the criteria for detecting excitation faults using Correlation
Fault detection criteria
Uavg > U set point no load - (( Voltage droop *0.01) *
Max Volts deviation
Q) +
U set point no load - (( Voltage droop * 0.01) *
Uavg <
Max Volts deviation
Q) -
shows the criteria for identifying excitation faults using Voting
Fault detection criteria
Number of generators in parallel with same gover-
nor mode >= 3
AND
MAX(Q1, Q2, ... Q8) – MIN(Q1, Q2 ... Q8) <
Vot
(Check to ensure that the network generators, ex-
cluding local generator, are operating with similar
load)
AND
Q > MAX(Q1, Q2 ... Q8) +
Max Q Dev
Max Q Dev Vot
1MRS759142 F
Output
activation
OV_EXCT_FLT
UN_EXCT_FLT
Output
activation
OV_EXCT_FLT
REX640
Technical Manual