Hello,
We have eight 2000 vintage frame 7EA with DLN1 and MarkV control system and EX2000 exciter.
When we came onsite this morning, 7 of the 8 units were displaying the following alarms (these are from our Unit 6);
Description - Variable Name
Voter mismatch, <R> SSDIFF1 - T6.D_3449_C
Voter mismatch, <R> SSDIFF1 - T6.D_3450_C
Voter mismatch, <S> SSDIFF1 - T6.D_3690_C
Voter mismatch, <S> SSDIFF1 - T6.D_3691_C
Voter mismatch, <T> SSDIFF1 - T6.D_3931_C
Voter mismatch, <T> SSDIFF1 - T6.D_3932_C
Voter mismatch, <R> L52B_SEL - T6.D_1834_C
Voter mismatch, <S> L52B_SEL - T6.D_2330_C
Voter mismatch, <T> L52B_SEL - T6.D_2826_C
Affected Units
Demand Display of SSDIFF1(phase) shows value toggling sporadically between 1800deg and 0deg.
Prevote Data display of SSDIFF1(phase) shows value toggling sporadically between 1800deg and 0deg.
The cores do not change states simultaneously, resulting in the mismatch alarms.
Demand Display of SSDIFF1(slip) shows value toggling sporadically between 128% and 0%.
Prevote Data display of SSDIFF1(slip) shows value toggling sporadically between 128% and 0%.
The cores do not change states simultaneously, resulting in the mismatch alarms.
Demand Display of L52B_ALM shows value toggling sporadically between 1 and 0.
Prevote Data display of L52B_SEL shows value toggling sporadically between 1 and 0.
The cores do not change states simultaneously, resulting in the mismatch alarms.
Unaffected Unit
Demand Display of SSDIFF1(phase) shows stable value of 1800deg.
Prevote Data display of SSDIFF1(phase) shows stable value of 1800deg.
Demand Display of SSDIFF1(slip) shows stable value of 128%.
Prevote Data display of SSDIFF1(slip) shows shows stable value of 128%.
Demand Display of L52B_ALM has a stable 0.
Prevote Data display L52B_ALM has a stable 0.
We ran all 8 units the night before, but shutdown in the same manner as we always do.
The alarms were not present for ~1 hour after the shutdown.
Today, I rebooted <R>, <S>, <T>, <C>, <X>, <Y>, <Z> cores, as well as the HMI (which restarts the project) on one of the affected units.
Afterwards, it was still behaving the same.
What could cause this?
What risk does this pose?
Can this interfere with unit synchronization?
Will the condition(s) clear up once we generate again?
We have eight 2000 vintage frame 7EA with DLN1 and MarkV control system and EX2000 exciter.
When we came onsite this morning, 7 of the 8 units were displaying the following alarms (these are from our Unit 6);
Description - Variable Name
Voter mismatch, <R> SSDIFF1 - T6.D_3449_C
Voter mismatch, <R> SSDIFF1 - T6.D_3450_C
Voter mismatch, <S> SSDIFF1 - T6.D_3690_C
Voter mismatch, <S> SSDIFF1 - T6.D_3691_C
Voter mismatch, <T> SSDIFF1 - T6.D_3931_C
Voter mismatch, <T> SSDIFF1 - T6.D_3932_C
Voter mismatch, <R> L52B_SEL - T6.D_1834_C
Voter mismatch, <S> L52B_SEL - T6.D_2330_C
Voter mismatch, <T> L52B_SEL - T6.D_2826_C
Affected Units
Demand Display of SSDIFF1(phase) shows value toggling sporadically between 1800deg and 0deg.
Prevote Data display of SSDIFF1(phase) shows value toggling sporadically between 1800deg and 0deg.
The cores do not change states simultaneously, resulting in the mismatch alarms.
Demand Display of SSDIFF1(slip) shows value toggling sporadically between 128% and 0%.
Prevote Data display of SSDIFF1(slip) shows value toggling sporadically between 128% and 0%.
The cores do not change states simultaneously, resulting in the mismatch alarms.
Demand Display of L52B_ALM shows value toggling sporadically between 1 and 0.
Prevote Data display of L52B_SEL shows value toggling sporadically between 1 and 0.
The cores do not change states simultaneously, resulting in the mismatch alarms.
Unaffected Unit
Demand Display of SSDIFF1(phase) shows stable value of 1800deg.
Prevote Data display of SSDIFF1(phase) shows stable value of 1800deg.
Demand Display of SSDIFF1(slip) shows stable value of 128%.
Prevote Data display of SSDIFF1(slip) shows shows stable value of 128%.
Demand Display of L52B_ALM has a stable 0.
Prevote Data display L52B_ALM has a stable 0.
We ran all 8 units the night before, but shutdown in the same manner as we always do.
The alarms were not present for ~1 hour after the shutdown.
Today, I rebooted <R>, <S>, <T>, <C>, <X>, <Y>, <Z> cores, as well as the HMI (which restarts the project) on one of the affected units.
Afterwards, it was still behaving the same.
What could cause this?
What risk does this pose?
Can this interfere with unit synchronization?
Will the condition(s) clear up once we generate again?