1. ABNORMALITY REPORT -2023
Page 1 of 7
CPSU/Elect./M-103/10/2023
Date: 23.06.2023
Sub: Abnormality report for TG-1 tripped on Under frequency and GT unloaded
to FSNL (Reverse power relay operated) on 15.06.2023.
Date& Time of Event: On 15/06/23 at 17:04:08 hrs.
Effect on Plant: Maximum demand reached to 47.092 MVA (Contract demand
30.0 MVA).
Description of events:
Before event, TG-1 was running @ at 11.0 MW (APR mode), GT was running
@ 25.0 MW (PS mode), import was @15.0 MW. Total plant load was @
51.0MW. TG-2 and Boiler-4 were under shutdown. Boiler-1,2 & 3 were
running.
MRS 11 KV Bus-B Incomer feeder circuit breaker tripped on "HV CB Open"
contact sensed by REC 670 relay falsely.
Hence, at 17:04:13:342 hrs. TG-1 isolated from grid (CCB open contact)
came as per scheme and APR to AFR change over took place successfully.
However, continuous hunting was observed in frequency and load; hence TG
manual lift control command given to 50% by process group.
TG-1 Turbine tripped on under frequency stage-2 at 17:06:15:615 hrs.
At 17:06:26:51 TG1 generator circuit breaker & field circuit breaker tripped
on Under voltage stage 2.
MRS Bus-B became dead hence CPP 11 KV INC-1 tipped on u/v at
17:06:28:494 and Auto change over took place in CPP 11 KV swgr
successfully..
No any change over took place in downstream of swgrs of CPP and CPSU.
At 17:06:27.055, TK Fan-1 & 3 tripped on overload. Process tried to increase
load on GT to maintain import but GT load was continuously on decreasing
trend and at 17:10:32:064 GT tripped on reverse power stage-1 (FSNL) due
to TKE fan 1 & 3 tripped on O/L as per logic. Active power at time of tripping
registered : 2.05MW, Reactive power : 1.56 MVAR.
2. ABNORMALITY REPORT -2023
Page 2 of 7
At 17:18:34:052 GT synchronized after clearance from process.
At 18:15:54:563 TG#1 synchronized after clearance from process.
TG-1 & GT GPR Relay events:
Time Duration Event Setting
17:04:13:342 00:00:00.000
TG-1 isolated from
Grid_ON.
17:05:52:607 00:01:39.265 81-1 Picked up_ ON
17:05:53:753 00:01:40.411 81-1 Picked up_ Off
17:06:02:766 00:01:49.424 81-1 Picked up_ ON 48 HZ & 1 Sec.
17:06:04:828 00:01:51.486 81-2 Picked up_ ON
17:06:14:826 00:02:01.484 81-2 Trip_ ON 47.5 HZ &10Sec
17:06:15:615 00:02:02.273 86T Trip_ ON
17:06:21:791 00:02:08.449
27-1 Under voltage
V < picked up_ ON
87.3 % V
17:06:22:046 00:02:08.704
24-1 v/f> warning
stage_ ON
V/F -1.10 & 10
sec.
17:06:22:691 00:02:09.349
27-1 Under voltage
V < trip_ ON
17:06:23:052 00:02:09.710
27-2 Under voltage
V << Picked up_ ON
17:06:24.000
BFP-1 Tripped on
process from DCS
17:06:26:051 00:02:12.709
27-2 Under voltage
V << Trip_ ON
83.6 % & 3.09
sec.
17:06:26:051 00:02:12.709
27-2 Under voltage
V << Trip_ ON
83.6 % & 3.09
sec.
17:06:26:078 00:02:12.736 86 U1U2 optd_ ON
17:06:26:145 00:02:12.803
TG1_FLCB&EXCON_
OFF
17:06:26:190 00:02:12.848
TG1_52G1 Close_
OFF
17:06:27:055 00:02:13.713
TK fan-3 trip on
over load
GT DCS Event
3. ABNORMALITY REPORT -2023
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17:06:27:055 00:02:13.658
TK fan-1 trip on
over load
GT DCS Event
17:06:28:494
00:02:15.152 11kV IC-1 Tripped
on 27-1& BC Closed
53% @1000ms
17:10:22:066 00:06:08.724
GT_Reverse power
picked_up_ON
17:10:32:064 00:06:18.722
GT_Reverse power
trip_ON
-1.5% @ 10 secs
17:10:32:065 00:06:18.723
GT_86 G1 trip
relay_optd_ON
17:10:32:068 00:06:18.726
GT_86 G2 trip
relay_optd_ON
17:10:32:151 00:06:18.809 GT_52G1 Open_ON
17:12:02:000
00:07:48.658
TK fan#2 started
and clearance given
for Sync.
GT DCS Event
17:14:16:962 00:10:03.620
TG-1 isolated from
Grid_OFF.
17:18:34:052 00:14:20.710 GT_52G1 Close_ON GT Syncronised
17:40:14:231
00:36:00.889 11kV IC-1 MCO & BC
OFF
18:15:54:563 01:11:41.221
TG-1 _52G1
Close_ON
TG-1
Syncronised
Analysis:
TG#1 came on AFR as per CCB open contact received from MRS as per
scheme. Hunting in frequency was observed and subsequently Turbine
tripped on 86T relay actuated from 81-2 (47.5 HZ &10Sec). Further
Generator CB & Field CB tripped on 27-2 (83.6 % & 3 sec.)
Since MRS Bus –B was isolated from MT-02 and TG#1was the only
generation source available, after tripping of TG1 MRS Bus B got dead and
11kV I/C-1 of CPP that is from MRS Bus B got tripped on under voltage (27-
1, 53% @1000ms). A/C/O taken place successfully as per scheme.
During frequency hunting, running TK Fan-1 & Fan-3 tripped on overload.
Both motors were on MRS Bus –B on which TG#1 was connected. Hence,
motors were tripped during frequency hunting. Due to unavailability of TK-
4. ABNORMALITY REPORT -2023
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1/ 2 & 3 GT unload command given after 15 sec by MARK-VI as per logic.
Auto start command of standby TK-2 was after 60secs from running fan trip,
as per logic in MARK VI.
Refer Annexures for Trend view.
Remedial action:
System worked as per scheme.
QEHSEn (ISO 14001, 45001, 9001 & 50001) related impact:
Nil
Sr. EE(AAS)
Through:
SM(PLP)------->SM(BGS) ------->CM(KKB) ------->AGM(RPT)
BFP-1 tripped from DCS on process at 17:06:16.591 as per event list from REM620.
