ABB RELION REX640 - Page 1414

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 shows the criteria for detecting excitation faults using Correlation
algorithm.
Table 1345: Correlation algorithm for identifying excitation faults
Type of fault Fault detection criteria
Output
activation
Over excitation
fault
Uavg > U set point no load - (( Voltage droop *0.01) *
Q) + Max Volts deviation
OV_EXCT_FLT
Under excitation
fault
Uavg < U set point no load - (( Voltage droop * 0.01) *
Q) - Max Volts deviation
UN_EXCT_FLT
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 shows the criteria for identifying excitation faults using Voting
algorithm.
Table 1346: Voting algorithm for identifying excitation faults
Type of fault Fault detection criteria
Output
activation
Over excitation
fault
Number of generators in parallel with same gover-
nor mode >= 3
AND
MAX(Q1, Q2, … Q8) – MIN(Q1, Q2 … Q8) < Max Q Dev
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 Vot
OV_EXCT_FLT
Table continues on the next page
Condition monitoring functions 1MRS759142 F
1414 REX640
Technical Manual