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1. POWER HOLDING COMPANY OF NIGERIA PLC
NATIONAL CONTROL
CENTRE
OSOGBO
GENERATION
AND
TRANSMISSION
GRID OPERATIONS
2007
(ANNUAL TECHNICAL REPORT)
ISSUED BY:
GENERAL MANAGER (S/O)
NATIONAL CONTROL CENTRE
OSOGBO
FEBRUARY, 2008.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
2. TABLE OF CONTENTS
PAGES
INTRODUCTION 1
1.0 GRID OPERATIONS IN 2007 1
1.1 Hydrology and Lake Operation. 1
1.2 Thermal Generation 9
1.3 Generation Ordering and Load Dispatching 19
1.4 Frequency Control 19
1.5 Voltage Control 19
1.6 Outage Planning 22
1.7 Energy Production 29
2.0 CONSTRAINTS TO GRID OPERATIONS 41
2.1 Constraints to Grid vis-a-vis System Communication 41
2.2 Generation Constraints 49
2.3 Transmission Constraints 49
3.0 REINFORCEMENT AND REHABILITATION OF
NATIONAL GRID 62
4.0 SYSTEM DISTURBANCES 66
4.1 Transmission System faults 66
4.2 Generation System faults 66
5.0 ACCIDENTS AND MISHAPS 66
6.0 CONCLUSIONS AND RECOMMENDATIONS 67
7.0 APPENDICES 71
(i)
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
3. NO. LIST OF TABLES PAGE
1A. HYDROLOGICAL SUMMARY 3
1B COMP. AVE.INFLOW AND TURB.DISCH. 6
2 AVERAGE MONTHLY MW AVAILABILITY 12
3 SUMMARY OF GENERATION CAPABILITIES OF PHCN POWER 20
STATIONS AS OPERATED IN 2007
4. PHCN POWER SYSTEM FREQUENCY 27
5A. 2007 OUTAGES STATISTICAL SUMMARY 330KV LINE 29
5B. 2006 OUTAGES STATISTICAL SUMMARY 330KV LINE 29
6A. 2007 OUTAGES STATISTICAL SUMMARY 132KV LINE 30
6B. 2006 OUTAGES STATISTICAL SUMMARY 132KV LINE 30
7. ENERGY GENERATED (MWH) 38
8. HYDRO & THERMAL ENERGY GENERATED(MWH) 39
9. ENERGY GENERATION & POWER CONSUMPTION RECORDS 43
10. MONTHLY ENERGY BALANCE SUMMARY 46
11 ENERGY AVAILABLE FOR SALES PLUS DISTRIBUTION LOSSES
IN EACH REGION (MW) 47
12 TOTAL GAS CONSUMED 48
13 COST OF GAS (NAIRA) AGAINST ENERGY GENERATED 2007 49
14 OPERATING FUEL COST (NAIRA/KWh) 50
15 MONTHLY MAXIMUM DEMAND/GENERATION ANALYSIS (MWH) 84
16 SYSTEM GENERATION PEAK LOAD (FORECAST & ACTUAL) 85
17 SUMMARY OF OCCURRENCE MAXIMUM PEAK LOAD 86
18 SUMMARY OF SYSTEM DISTUBANCES 107
19A SUMMARY OF SYSTEM DISTUBANCES OF INTEGRATED GRID 108
19B SUMMARY OF GRID COLLAPSES 109
19C SUMMARY OF SYSTEM DISTURBANCES OF INTEGRATED GRID OPERATIONS 110
(ii)
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
4. NO. CHARTS PAGE
1. KAINJI AVERAGE MONTHLY TOTAL DISCHARGE AND INFLOW 4
2. KAINJI HYDROGRAPH 4
3. JEBBA AVERAGE MONTHLY TOTAL DISCHARGE AND INFLOW 8
4. JEBBA HYDROGRAPH 8
5. SHIRORO AVERAGE MONTHLY TOTAL DISCHARGE AND INFLOW 9
6. SHIRORO HYDROGRAPH 9
7. 2007 AVERAGE MONTHLY MW AVAILABILITY 14
8. POWER STATIONS AVAILABILITY FACTOR 14
9 POWER STATIONS AVERAGE MW AVAILABILITY 21
10 POWER STATIONS INSTALLED CAPACITY 21
11 ANNUAL ENERGY GENERATED. 25
12 SIMULTANEOUS NATIONAL PEAK DEMAND (MW) 25
13 330KV FORCED OUTAGES (2006 & 2007) 32
14 132KV FORCED OUTAGES (2006 & 2007) 32
15 COMBINED 2006 & 2007 330KV OUTAGES. 33
16 COMBINED 2006 & 2007 132KV OUTAGES. 33
17 330KV PLANNED, URGENT AND EMERGENCY OUTAGES 34
18 132KV PLANNED,URGENT & EMERGENCY OUTAGES 34
19 PERCENTAGE ENERGY USED IN POWER STATIONS 40
20 HYDRO, THERMAL AND TOTAL ENERGY GENERATED 40
21 ENERGY GENERATED IN HYDRO POWER STATIONS 42
22 ENERGY GENERATED IN MAJOR THERMAL POWER STATIONS 42
23 AVAILABLE ENERGY FOR SALES 44
24 TOTAL MONTHLY ENERGY AVAILABLE FOR SALE 44
25 TRANSMISSION REGIONS: MONTHLY ENERGY AVAILABLE FOR SALE 51
(iii)
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
5. NO. CHARTS PAGE
26 REGIONAL ENERGY AVAILABLE FOR SALE 51
27 MAJOR THERMAL STATIONS FUEL COST 52
28 MONTHLY UNIT PROD. COST (NAIRA/UNIT) 53
29 STATIONS AVE. PROD. COSTS (NAIRA/UNIT) 54
30 MONTHLY PEAK DEMAND FORECAST AND ACTUAL GENERATION 87
31 WEEKLY PEAK GENERATION 87
32 KAINJI G.S. USABLE GEN. CAP. SPECTOGRAPH PLOT AVAILABLE 88
33 JEBBA G.S. USABLE GEN. CAP. SPECTOGRAPH PLOT AVAILABLE 88
34 SHIRORO P.S. USABLE GEN. CAP. SPECTOGRAPH 89
35 EGBIN P.S. USABLE GEN. CAP. SPECTOGRAPH 89
36 DELTA P.S. USABLE GEN. CAP. SPECTOGRAPH 90
37 AFAM P.S. USABLE GEN. CAP. SPECTOGRAPH 90
38 SAPELE P.S. USABLE GEN. CAP. SPECTOGRAPH 91
39 OMOTOSHO P.S. USABLE GEN. CAP. SPECTOGRAPH 91
40 AES P.S. USABLE GEN. CAP. SPECTOGRAPH 92
41 OKPAI P.S. USABLE GEN. CAP. SPECTOGRAPH 92
42 GEREGU G.S. USABLE GEN. CAP. SPECTOGRAPH 93
43 OMOTOSHO G.S. USABLE GEN. CAP. SPECTOGRAPH 93
44 OMOKU P.S. USABLE GEN. CAP. SPECTOGRAPH 94
45 AJAOKUTA P.S. USABLE GEN. CAP. SPECTOGRAPH 94
46 OLORUNSOGO P.S. USABLE GEN. CAP. SPECTOGRAPH 95
47 DAILY TOTAL GRID GEN. AVAILABILITY STATUS 95
48 GRAPHICAL REPRESENTATION OF SYSTEM COLLAPSE (DAYS) 111
49 GRAPHICAL REPRESENTATION OF SYSTEM COLLAPSE (MONTHS) 111
50 SUMMARY OF SYSTEM DISTURBANCES 2007 112
51 LOAD LOSS DUE TO SYSTEM DISTURBANCES 112
(iv)
Generation and Transmission Grid Operations-2006-National Control Centre, Osogbo
6. lNTRODUCTION
T
his Technical Report, an annual publication of Power Holding Company Nigeria Plc
(PHCN), covered the National Generation and Transmission Grid Operations in 2007. It
was collated from NCC electronics data bank. Among the major headings elaborated on
were:
• 1.0 Grid Operations in 2007.
• 2.0 Constraints to Grid Operations in 2007.
• 3.0 Reinforcements to the National Grid in 2007.
• 4.0 System Disturbances, Accidents and Mishaps in 2007.
• 5.0 Accidents and Mishaps
• 6.0 Conclusions and Recommendations.
Grid Operations in 2007 was compared with the preceding year 2006 and the previous
years through tables and graphs.
Also presented are detailed analyses of plant and equipment outages, energy generated,
transmitted and available to the distribution network.
Depicted also are supplementary charts, graphs and other significant details that aid
comprehension of the report.
1.0 GRID OPERATIONS IN 2007
The plant average availability at Kainji Power Station in 2007 was 524.1MW. This was
115.3MW higher than 2006 figure of 408.8MW.
Jebba’s plant availability ranged between 578.4MW and 559.1MW in 2007 with average
availability of 572.3MW. This was greater than 2006 average availability of 554.2MW
by 4.9MW.
At Shiroro Power Station plant availability throughout the year was little less than 2006.
The availability varied between 600MW and 444.4MW in 2007. It stood at an average of
524.8MW. This was just 5.1MW lower than 2006 figure of 529.9MW.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
7. 1.1 HYDROLOGY AND LAKE OPERATIONS
1.1.1. Kainji Lake
The average computed inflow of the 2006/2007 black flood yield into the Kainji Lake
was higher than the average forecast inflow by 8.98%.
When the black flood inflow was compared with the figures of immediate past five years
the 2006/2007 black flood was higher than the 2005/2006 by 14.6%, higher than
2004/2005 by 34.54%, lower than 2003/2004 by 14.78%, higher than 2002/2003 by
22.21%, lower that 2001/2002 by 9.4%.
The fairly, good flood yield, brought the head water elevation to 141.69 meters
corresponding to a volume of 11.95 billion cubic metres of water at the beginning of the
hydro year, January 1st 2007.
The black flood peaked on 8th December 2006, with a value of 1724 cubic metres per
second (m3/sec).
This was (2.78%) higher than the peak daily computed black flood inflow of 2005/2006.
At the Joint Operations/Generation Planning meeting held in Jebba Hydroelectric
Business Unit on the 7th - 8th March 2007, the planned turbine discharges and the
expected inflow into the Kainji Lake from the months of March through August were as
in the Table1B. The importance of the meeting was to agree on the draw down
trajectory.
The forecast inflow between January and June 2007 was 26.85% lower than the actual
computed inflow. It was noted that the actual turbine discharge during the period fell
short by (1.24%) of the planned discharge, in spite of the fairly robust inflow. This was a
result of fall in Kainji MW availability.
Also during this period while the Kainji MW was low and Jebba MW availability was
higher, hence the amount of inflow into the Jebba Lake was not good enough to keep the
head water elevation high for efficient Power Generation. It became necessary to engage
on controlled spillage, to sustain Jebba Operations. Between January and April a total
average volume of water spilled was 1405.56 cubic metres per second.
The difference of 641.66 m3/sec between the average computed total station discharge of
1213.61 m3/sec and the average total computed inflow rate of 571.95 m3/sec resulted in
the drawing down of the Lake to an elevation of 130.44 metres by June 28, 2007.
This corresponded to a storage balance of 1.38 billion cubic metres of water. This
volume was 0.37 billion cubic metres lower than the lowest volume attained on July 24,
2006. It was observed that, the volume attained in 2007 was the lowest ever since the
inception of the Kainji Lake Operations 1968.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
2
9. KAINJI AVE.MONTHLY TOT. DISCHARGE & INFLOW
JANUARY-DECEMBER 2007, CHART 1 (SEE TABLE 1)
2800
2400
FLOW IN CUBIC METRES/SEC
2000
1600
1200
800
400
0
JAN. FEB. MAR. APR. MAY. JUN. JUL. AUG. SEP. OCT. NOV. DEC.
MONTHS
DISCHARGE INFLOW
KAINJI HYDROGRAPH
1994-2007 CHART 2
144
142
HEAD WATER ELEVATION IN METRES
140
138
136
134
132
130
JAN. FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
MONTHS
2007ACTUAL 2006ACTUAL 2005ACTUAL 2004ACTUAL 2003ACTUAL
2002ACTUAL 2001ACTUAL 2000ACTUAL 1999ACTUAL 1998ACTUAL
1997ACTUAL 1996ACTUAL 1995 ACTUAL 1994 ACTUAL
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
4
10. The fast draw down was as a result of National demand as the gas supply to the Thermal
Power Stations was unstable. To maintain supply during the nationwide elections and
subsequent inaugurations, all available water was used to generate power.
At the Joint Operations/Generation Planning meeting held in Shiroro Hydro Electric
PLC, between 5th and 6th September 2007, the impoundment program from September
2007 – February 2008 for the white flood and subsequent black flood was agreed on.
Normally, it was convenient to fill the Kainji Lake to an elevation of 140.06 metres
corresponding to a volume of 10 billion cubic metres of water by the end of the white
flood usually October ending.
Records showed that the actual average computed inflow was slightly higher than
forecast inflow by 0.76%. The average actual turbine discharge during the white flood
was (17.65%) lower than the planned turbine discharge, because Kainji 1G6 which was
expected to be on the grid in September was surprisingly unavailable.
The peak of the computed white flood occurred on 1st September 2007, with a magnitude
of 4660 m3/sec. That magnitude was 1.75% higher than the peak value of 4580 m3/sec of
the previous year which occurred on September 8, 2006.
All the available units in Kainji Power station were kept running to avoid spillage. It has
to be mentioned that, if the Kainji Lake was not drawn down to the lowest elevation ever,
spillage was would have been inevitable.
At that period, spillage in Kainji would have been undesirable for Jebba Lake whose head
water elevation was above 102.5 metres already.
By the end October 2007, the Kainji Lake head water elevation was 140.04 metres,
corresponding to almost 10.00 billion cubic metres as planned.
Before the end of October, Jebba Lake head water was observed to have to be reduced
drastically, because Kainji turbine discharge was not high enough as the lateral inflow
into the Jebba Lake has dropped significantly.
By October 30, 2007, the Jebba Lake head water elevation had dropped to 99.9 metres.
For 13 days, from 1st – 13th November 2007, controlled spillage was embarked on Kainji
spillway gate. An average of 192.50 m3/sec was spilled, to boost Jebba Lake.
The head water elevation of the Kainji Lake was at 139.24 metres, corresponding to 9.08
billion cubic metres by the month of December 31st, 2007. This volume was lower
(31.61%) than the volume obtained by the same time 2006.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
5
12. Overall Kainji MW availability was better (28.2%) than the figure of the previous year
(see chart 1&2)
1.1.2 Jebba Lake
At the beginning of the hydro year, 1st January 2007, the head water elevation at Jebba
lake was at 100.96 metres, corresponding to 3.2875 billion cubic metres. This was
slightly higher (0.23%) than the storage balance of 3.28 billion cubic metres of water
recorded at the beginning of 2006 hydro year.
Appreciable lateral inflow into the Jebba Lake started on 25th August 2007, with a value
of 1223 m3/sec. It peaked on 28th August 2007 with a value of 1813 m3/sec and ebbed
out after the second week of October. The peak value was higher (39.68%) than the peak
lateral inflow recorded on September 17th, 2006.
During the year, the minimum head water recorded, was 99.02 metres which occurred on
June 26th, 2007.
The maximum station turbine discharge of 2266 m3/sec occurred on September 10, 2007,
and the maximum computed inflow of 2876 m3/sec occurred on August 28, 2007.
When the head water elevation was 102.73 metres on September 9th, 2007, the six units
were run for 24 hours for almost 12 days.
Due to unstable gas supply to the Thermal Power Plants, great demand was on the hydro
plants. This head water elevation (102.73metres) corresponded to a storage balance of
3.803 billion cubic metres (see chart 3 &4)
From Table 2, Jebba MW availability was higher than the previous year by 3.27%. Even
though Kainji MW availability improved this year, it was evident from Table 1A the
monthly average turbine discharge which was the primary source of inflows into Jebba
Lake was always lower than Jebba turbine discharge because of its MW availability. For
this reason the head water elevation in Jebba lake was always drawn down early in the
year.
By the end of the year, December 31st 2007, the head water elevation in Jebba was
102.74 metres, corresponding to 3.805 billion cubic metres of water. This was 15.65%
higher than the headwater of the Lake at the same period 2006.
1.1.3 Shiroro Lake
At the beginning of the hydro year, January 1st 2007, the reservoir head water elevation
was 376.29 metres corresponding to a storage balance of 4.2678 billion cubic metres of
water. This volume was lower (6.68%) than the storage balance at the same time 2006.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
7
13. JEBBA AVE. MONTHLY TOTAL DISCHARGE & INFLOW
JANUARY-DECEMBER 2007, CHART 3 (SEE TABLE 1)
2500
2000
FLOW IN CUBIC METRES/SEC
1500
1000
500
0
JAN. FEB. MAR. APR. MAY. JUN. JUL. AUG. SEP. OCT. NOV. DEC.
MONTHS
DISCHARGE INFLOW
JEBBA HYDROGRAPH
1994-2007 CHART 4
103.5
103
HEAD WATER ELEVATION IN METRES
102.5
102
101.5
101
100.5
100
99.5
JAN. FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
MONTHS
2007ACTUAL 2006ACTUAL 2005ACTUAL 2004ACTUAL
2003ACTUAL 2002ACTUAL 2001ACTUAL 2000ACTUAL
1999ACTUAL 1998ACTUAL 1997ACTUAL 1996ACTUAL
1995 ACTUAL 1994 ACTUAL
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
8
14. SHIRORO AV. MONTHLY TOT. DISCHARGE & INFLOW
JANUARY-DECEMBER 2007 CHART 5 (SEE TABLE 1 ).
1300
1200
1100
1000
FLOW IN CUBIC METRES/SEC
900
800
700
600
500
400
300
200
100
0
JAN. FEB. MAR. APR. MAY. JUN. JUL. AUG. SEP. OCT. NOV. DEC.
MONTHS
DISCHARGE INFLOW
SHIRORO HYDROGRAPH
1994-2007, CHART 6
385
380
HEAD WATER ELEVATION IN METRES
375
370
365
360
355
JAN. FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
MONTHS
2007ACTUAL 2006 ACTUAL 2005 ACTUAL 2004 ACTUAL 2003ACTUAL
2002ACTUAL 2001ACTUAL 2000ACTUAL 1999ACTUAL 1998ACTUAL
1997ACTUAL 1996ACTUAL 1995ACTUAL 1994ACTUAL
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
9
15. The draw down plan of the Shiroro Lake between March and August 2007 was agreed
upon at the Joint Operations/Generation Planning meeting held in Jebba Hydroelectric
Business Unit on the 7th & 8th March 2007, as displayed in table 1B.
The actual computed inflow during the period was higher than the forecast inflow by
19.97%. Total station turbine discharge exceeded the total computed by 1079.89 m3/sec.
This resulted in drawing down the lake to an elevation 358.41 metres by July 13, 2007.
The unstable gas supply from the Nigerian Gas Company forced the Operation to draw
down the lake to that all time low head water elevation. This elevation was lower the
previous year minimum elevation of 359.65 metres on July 15, 2006 by 0.1427 billion
cubic metres.
The pattern of flood yield into the Shiroro Lake this year can be described as sporadic.
The flood peaked in August and substantial inflow was for short duration about three
weeks precisely. The peak value of computed inflow recorded was 3175 m3/sec on
August 28, 2007. The forecast inflow was 794 m3/sec, while the actual computed inflow
was 1048.87 m3/sec. Hope rose that definitely the Lake will be filled during the flood
season.
After the first twelve days in September the inflow ebbed out. The hope was suddenly
dashed.
Usually, it was planned to fill the lake within the first two weeks in October every year,
but the disappointing inflow yield of September, torpedoed the plan.
Maximum head water elevation attained during the flood was 379.37 metres on
September 30, 2007.
When it became obvious that the lake could not be filled, water regulation started. The
head water elevation improved 379.49 metres corresponding to 4.987 billion cubic metres
on October 12, 2007.
Since appreciable inflows were not expected into the Shiroro Lake, plans were drawn out,
in order to manage the available water resource from October 2007 till mid-July 2008.
Overall Shiroro MW availability throughout 2007, dropped slightly by 0.97%, when
compared with 2006 figure.
By December 31st 2007, the head water elevation stood at 373.68 metres corresponding
to a storage balance of 3.7188 billion cubic metres. This balance was 14.76% lower than
the storage balance at the same time 2006. (See chart 5&6).
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
10
16. 1.2. THERMAL GENERATION
1.20. GENERATION AVAILABILITY
In table 2, the average Power(MW) availability was depicted. Analysis of the year’s
thermal availability was conducted employing the popular relevant statistical measures.
Thermal plant average availability was 2535.0MW in 2007. Of this figure 699.5MW
(27.59%) was contributed by the 3 Independent Power Producers (IPP). The thermal
availability was 60.99% of aggregate of Hydro and thermal availability of 4156.2MW in
2007. It surpassed 2006 figure of 2396.4MW by 138.6MW.
1.21 SAPELE G. S.
Sapele ST1 generated from January to 23rd May, when it was on forced outage.
Restored back on 26th, the unit remained synchronized to the grid till 6th September when
it tripped on high vibration.
Between 13th September and 25th October the unit was available. It then went through a 3
week outage to clear serious oil leakage on the generator. Tripped on 20th November on
supper heater very high temperature the unit was restored by November ending and
generated through out December, 2007.
Sapele ST2 which had been on outage since September, 2002 due to high bearing
problem was restored to the grid in August, 2007. It tripped on turbine high vibration on
6th August. After a week of outage the unit was available till 31st August when it was
forced out of the grid for a week due to restricted earth fault. It generated throughout
September until it tripped during the system disturbance early October.
From 30th October to the 2nd week of November, the unit was available. It then tripped on
control oil pressure and remained unavailable throughout December, 2007.
Sapele ST3 was unavailable since 28th May, 2006 due to faulty generator transformers.
By 31st December, 2007, the unit was still unavailable.
Sapele ST4 was forced out of the grid due to high winding temperature fault since the
third quarters of 1994. It was still unavailable by 31st December, 2007.
Sapele ST5 has been on outage since 2nd March, 1986 when its unit transformer and
associated switchgear got burnt. The unit was unavailable by December, 31st 2007.
Sapele ST6 tripped following System disturbance on the 29th September, 2005. The
ensuing fire outbreak in the station destroyed the governor control cable.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
11
18. The unit was restored on the 3rd week of September, 2006. By November, 2006 it
developed bearing vibration trouble. It was virtually out of service in 2007 due to crack
on the turbine blade and high vibration.
1.22 AFAM P. S.
Afam GT1 was out of service since last quarter of 1993. It remained out of service by
December, 2007.
Afam GT2 - scrapped.
Afam GT3 out of service since February 1990 on damaged exciter and generator bearing
problem, still maintained its enoperatable state by December, 2007.
Afam GT4 was unavailable due to rotor balancing and labyrinth seal problem since 1998.
Afam GT5 was on outage due to excessive oil leakage from the generator between
January and the third week of February. It ran for only a week and was then shut down
due to smoke on the exciter.
Tied in the first week of August, it rolled generation into the grid till 28th September,
2007. It was on bars for 9 days before it tripped as a result of system disturbance.
Having generated the last week of September, the unit tripped again on turbine main lube
oil low pressure. By 31st December, 2007, the unit was still out of service.
Afam GT6 was unavailable throughout the year with the exception of the first five days
of January, having developed high turbine inlet temperature.
Afam GT7 was unavailable in the year on burnt generator breaker and control cable
faults.
Afam GT8 had been on outage since 3rd April, 1988 on damaged turbine and turbine
blade failure.
GT9’s major overhaul was suspended in the last quarter of 1995 and still on breakdown
outage since.
GT10 supposed to be on rehabilitation since 2002 was still unavailable by December, 31st
2007.
GT11 was out of service in September 1997 due to the fatal fire outbreak at Afam P.S.
though it was restored to service 2 weeks after, it sooned tripped on oil drain high
temperature and still out by 31st December, 2007.
Afam GT12 was shutdown in August 1998 due to compressor blade failure. It was still
out of service at the expiration of 2007.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
13
19. 2007 AVE. MONTHLY MW AVAILABILITY
JANUARY-DECEMBER 2007 CHART 7(SEE TABLE2)
2500
2000
MONTHLY AVAILABILITY
1500
1000
500
0
J F M A M J J A S O N D
MONTHS
KAINJI JEBBA SHIRORO SAP.TOT AFAM EGBIN
DELTA IJORA CALABAR AES OKPAI AJAOKU
THMAL PHCN THMAL IPP HYDRO TOT GRAND TOT OMOKU
POWER STATIONS AVAILABILITY FACTOR
JANUARY-DECEMBER 2007, CHART 8(SEE TABLE 3)
1.20
AVAILABILITY FACTOR
1.00
0.80
0.60
0.40
0.20
0.00
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Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
14
20. Afam GT13 had been on outage due to turbine failure since February 1997. By the end
of 2007, the unit was still unavailable.
Afam GT14 which had been on outage due to compressor blade failure since April 1992
was on outage by December, 2007.
Afam GT15 had been out of service since 1995 and required major overhaul to come
back on stream.
Afam GT16 which had compressor blades failure in 1992 was still unavailable by 31st
December, 2007.
Afam GT17 was out of service on ignition failure from January to October 21, 2007. It
came back on stream briefly and was later shutdown for reliability test. By November,
when the reliability test was over, it only generated for 2 days following which it was
shutdown due to bearing oil leakage. It was still on outage by December, 2007.
GT18 was shutdown from January to 15th October to clear the accumulated condensates
on the gas pipeline. It generated in the 2nd weekend, shutdown thereafter on low gas
pressure. Returned to the grid in early November, the unit tripped a week after on low
gas pressure. Attempts to restore it failed as condensate problems surfaced. By 31st
December, 2007, the unit was out of service.
GT19 was out of service on high air intake differential pressure. The unit was
synchronized to the grid a week after. Between 14th and 23rd January, it went out of
service on dirty air inlet filters. From 8th April to end of June, the unit was available.
Out for a week on underfrequency, the unit was available thereafter till the expiration of
2007.
GT20 generated into the grid in the first 14 days of January. It was then shutdown due to
dirty air inlet filters till 16th March. On 25th March, it shutdown again due to air intake
filter leakages.
The unit was available then till the end of 2007 except the third week of June when it
tripped on high inlet temperature.
Afam average plant availability was 166.9 MW in January 2007. The first half annual
peak of 232.6 MW was attained February.
In the second half of the year, the peak average demand was 295.2 MW, recorded in
December. The year’s average MW availability was 228.1MW. It was 147.8MW
(189%) greater than 2006 figure of 80.30 MW.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
15
21. 1.23 DELTA P.S.
Delta GT1 & GT2 had been scrapped.
Delta GT3, 4 & 5 were out of service due to non-availability of the 81MVA 11/132kV
transformer since January 2006 and remained unavailable by the end of 2007.
Delta GT6 was generally available in 2007. It only went out on a week outage on
excitation fault.
Delta GT7 was available from January to mid May when it was on a week outage. It ran
thereafter till the 3rd week in July when it was on forced outage for a week. By the 2nd
week of November, the unit developed compressor bleed valve trouble and was still
unavailable by 31st December, 2007.
Delta GT8 was in service from January to 17th April. It developed serious oil leakage
from reduction gear for a week and run till the 2nd week of September when it shutdown
due to faulty generator bleed valve position trouble. It thereafter generated in the 3rd and
4th week of October but tripped in early November. It was thereafter synchronized to the
grid till the end of December, 2007.
Delta GT9 was generally available through out the year except the outage to seal the oil
leakage on its unit transformer between 7th and 18th February, 2007.
Delta GT10 was available from January to 7th February. It then went on outage to seal
the oil leakage on the unit transformer. Returned to the grid by 18th February, the unit ran
till the 1st week in September when it tripped on excitation trouble. After a week outage
the unit remained on the grid till 31st December, 2007.
Delta GT11 was on the grid from January to 7th February when it was shutdown on
planned outage to seal oil leakage on its unit transformer. Restored to the grid on 18th
February, the generating unit was available till the end of 2007.
Delta GT12 was available through out the year except the planned outage on the 3rd week
of July, 2007.
Delta GT13 was available in the year 2007 except the 3rd week in July when it was on
planned outage and the last week of December when the unit was shutdown due to
abnormal bearing problem.
Delta GT14 was on the grid from January to the 3rd week of July when it was on planned
outage. It then generated till mid October when it tripped on exhaust over temperature.
By 31st December, 2007, the unit was still unavailable.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
16
22. Delta GT15 was available from January to March 2007. It developed starting problem
and remained out of service by 31st December, 2007.
Delta GT16 was still undergoing rehabilitation in 2007.
Delta GT17 was out of service from January to 31st July 2007. It ran for 13 days in
August. Thereafter, it was shutdown due to fire in the turbine accessory.
Delta GT18 was available throughout 2007 except the last 3 weeks of August when it
was on outage due to high exhaust temperature.
Delta GT19 had been on outage since April 1998 on combustion trouble. Rehabilitation
was still in been awaited by 31st December, 2007.
Delta GT20 generated into the grid from January to 19th February 2007, when it
developed hydrogen gas leakage. By February 28 the unit was tied to the grid. It tripped
again by 1st April on faulty crank motor. Synchronized back on 14th April, the unit
generated till 18th May when it tripped on ignition problem. The unit was then available
from mid June till 31st December, 2007.
Delta monthly average availability was 474.5 MW in January 2007. That was the mid
year peak generation. In the second half of the year, the peak demand was 381.7 MW
recorded in October, 2007.
The Station’s annual average availability was 338.8MW. It was 31.21% lower than
2006 value of 492.5 MW.
1.24. EGBIN P.S.
Egbin ST1 was available from January to April 2007. It was shutdown from 1st to 17th
May for condenser cleaning. The unit was then available till the last week of July when it
tripped on control system failure. By the third week of September the unit was out for
inspection.
Restored to the grid by the 2nd week of November, the unit generated for a week. It was
thence available till 31st December, 2007 except a week of outage to clear its control
valve problem.
Egbin ST2 was available throughout the year except a week outage each in April and
June 2007.
Egbin ST3 was on the grid from January to the tail end of January when it developed
boiler problem. By 31st December, 2007 the unit was still unavailable
Egbin ST4 generated from January to the first week in March, 2007. It then went on
planned outage till 21st March. It was shutdown for condenser cleaning in the third week
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
17
23. of June and went on planted outage in the last week of August. It was thereafter available
till 31st December, 2007.
Egbin ST5 was available from January to 20th March when it went on outage due to
generator breaker fault. It remained on bars thence.
Egbin ST6 which tripped on 13th March, 2006 on furnace distortion remained unavailable
by 31st December, 2007.
Egbin plant generation availability was 997.4 MW in January, 2007. That was the peak
availability for the 1st half of the year (January to June). In the second half of the year,
the peak plant generation availability of 814.0 MW was attained in September. Annual
average generation availability was 735.5 MW. It fell short of 2006 value of 1005.5 MW
by 26.80%.
1.25 IJORA P.S.
Ijora GT4 was awaiting commissioning throughout the year 2007.
GT5 which had been on breakdown outage due to exhaust plenum fault since the third
week of March, 2006 was still unavailable by 31st December, 2007
1.26 CALABAR P.S.
Calabar EE1 was unavailable since the 2nd week of March, 2002 on burnt bearing. By
31st December, 2007 the unit was still unavailable.
Calabar EE2 has been out of service due to abnormal noise since 31st March, 2005. It
was still unavailable by 31 December, 2007
GM2’s starting problem that commenced in June 2004, continued throughout 2007.
1.27 AES – INDEPENDENT POWER PRODUCERS (IPP)
AES Barge 202 was tied to the grid from January to December 2007, safe a week outage
in the last week of January and the 2nd week of April when it was shutdown due to the
Nigeria Gas Company (NGC) pigging work.
Barge 203 ran from January to 9th March. It then tripped on high bearing vibration. Tied
back in the 1st week of April, it generated for only 3 days after which it was shutdown
due to condensate problem. From early May to the 3rd week of July, it was unavailable
due to bearing, it failure and lube oil leakage.
The unit was synchronized to the grid from 4th week in July to 31st December, 2007.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
18
24. Barge 204 was on the grid between January and 5th April when it was shutdown due to
condensate problem. It was tied back on 12th April and ran till 22nd May when it tripped
on high frequency. Between June and December 2007, the unit went on outage thrice
viz: 1st to 8th September on maintenance outage; third week of September due to water
leakage from cooling water pump and 26th October to the first week of November due to
rotating pump problem.
AES 205 barge went on outage six times in 2007. Between 22nd and 9th February it was
shutdown to reposition its circuit. From 1st to 22nd March it was unavailable on diesel
main starting problem. In second week of April, it was shutdown due to condensate
problem.
From the first week in September to 19th October, a major combustion inspection was
carried out on the unit. By 31st December 2007, the unit was still available and
synchronized to the grid.
Barge 207 ran from January to 5th February. It was on planned outage thence till the tail
end of February. On the 2nd week of April it had starting problem. Synchronized on 18th
April, it ran till 8th May when it was shutdown 7 weeks for compressor washing. It later
went on outage from 3rd July to the 2nd week of August on generator fault.
The unit was however available thereafter till 31st December, 2007.
Barge 208 generated in the first 3 weeks of January, tripped on turbine bearing high
vibration and remained out of service till 10th May. It generated thence till 31st December
except outage in June (15th – 13th); August (1st week maintenance) and November (1st
week due to serious water leakage.
Barge 209 was mostly available in 2007. It was shutdown only once in the third week of
March due to condensate problem.
Barge 210 was available from January to December, 2007 except a week outage in the 2nd
week of April due to condensate problem.
Barge 211 was on outage due to transformer fault. It ran till 2nd week in April when it
was shutdown due to condensate problem. From then till 31st December, 2007, the unit
produced energy into the grid.
1.28 OKPAI IPP
Okpai ST1 was synchronized to the grid from January to 10th April when it went on
outage due to steam leakages. Restored on 29th April, the unit was available till 31st
December except the first week of June when it tripped on fault and the third week of
December when it was shutdown for generator maintenance.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
19
25. TABLE 3. SUMMARY OF GENERATION CAPABILITIES OF PHCN POWER
STATIONS AS OPERATED IN THE YEAR 2007( JANUARY - DECEMBER )
AVAILABILIT AVERAGE
INSTALLED
POWER STATION Y FACTOR AVAILABILIT
CAPACITY (MW)
(MW) Y (MW)
KAINJI HYDRO 0.69 524.14 760.00
JEBBA HYDRO 0.99 572.28 578.40
SHIRORO 0.87 524.80 600.00
EGBIN STEAM 0.56 735.53 1320.00
AJAOKUTA 0.90 80.94 90.00
A.E.S (GAS) 0.81 219.96 270.00
SAPELE ST 0.11 114.59 1020.00
OKPAI GAS/ 0.88 393.88 450.00
AFAM (GAS) 0.37 228.11 623.00
DELTA (GAS) 0.38 338.80 882.00
GEREGU (GAS) 0.60 250.42 414.00
OMOKU GT 0.86 85.67 100.00
OMOTOSHO 0.23 76.79 335.00
OLORUNSOGO 0.03 10.29 335.00
TOTAL 0.53 4156.19 7777.40
DEFINITIONS:-
1. AVAILABILITY FACTOR = AVERAGE MW. AVAILABILITY
PI
2. PI = The sum of current site rating of
commissioned units installed in the
station for the year.
3. AVERAGE MW. AVAILABIL = This is a measure of average
usable MW capacity of each station
putting gas pressure constraints
and other external factors into
consideration.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
20
26. POWER STATIONS AVERAGE MW AVAILABILITY
JANUARY-DECEMBER 2007, CHART 9 (SEE TABLE 3)
800.00
700.00
AVERAGE MW AVAILABILITY (MW)
600.00
500.00
400.00
300.00
200.00
100.00
0.00
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Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
21
27. GT11 was available throughout the year except a five week outage between the 2nd week
of May and 3rd week of June (20th) when the unit was shutdown for overhaul.
GT12 was synchronized to the grid from January to 22nd March. It then went on
inspection and restored by the end of April 2007. The unit pooled power to the grid till
31st December except the last week of September 2007.
1.29. AJAOKUTA P.S.
Ajaokuta ST1 produced from January to 9th February when it was shutdown for routine
maintenance. It was restored by 17th February but tripped again by 12th March as the
H.P. side of the unit. The unit was then available for 10 weeks after which it tripped on
axial shifts problem in the 2nd week of June. It ran in the next 13 weeks and then tripped
due to System Disturbance. The unit generated into the grid in November and December
2007, except the last week of November when it was out due to low gas pressure.
ST2 was available in the first 3 weeks of January. After a week outage the unit stayed on
grid till the last week of May when it tripped on fault. In the next 13 weeks June to the
1st week in September, the unit generated into the grid following which it tripped and
remained out of service for 10 days. It barely ran for a week when it developed
hydrologic trouble.
From October to 31st December, 2007, the unit was unavailable.
1.30 OMOKU P.S.
Omoku GT1 was available throughout 2007 except 17th to 23rd January when the causes
of its tripping could not be ascertained and the last week in May when it was out of
service on reverse power problem.
Omoku GT2 was available through out 2007.
Omoku GT3 was available throughout 2007 with exception of the 2nd to 4th week of
January when it tripped on fault.
Omoku GT4 was unavailable from January to the 3rd week of March, It then generated till
the 1st week of May when it was shutdown on planned outage. Restored back by 5th June,
the unit was synchronized to the grid. It remained available until the last week of
September when it was on annual maintenance. The unit was still out-of-service by 31st
December, 2007.
1.31 OMOTOSHO P.S.
Commissioning of Omotosho GT1 commenced on 23rd June, 2007. 1st July, the unit
was shutdown for continuation of commissioning test. Tied back to the grid by the 3rd
week of July, GT1 generated till 6th August when it developed starting problem for about
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
22
28. a week. On 14th August it could not run due to low gas pressure that spanned 10 days.
The unit was however available from 24th August to 31st December, 2007.
Omotosho GT3 was commissioned in the first week of December. It tripped on D.C.
ground fault but was restored by the 2nd week and remained available by 31st December,
2007.
Omotosho GT6 commissioning and commenced in mid October. It generated till 21st
when it tripped due to system disturbance, restored back by the last week of October, it
generated thereafter till 31st December, 2007.
Omotosho GT7 was commissioned tied to the grid on 2nd September 2007. It generated
till 7th October when it tripped on fault. Tied back in the 2nd week of October, the unit
was synchronized to the grid up till 31st December, 2007.
Omotosho GT8 commenced generation by 15th August and was available till 31st
December, 2007.
1.32 GEREGU P. S.
GT1 was commissioned on 9th March 2007. It was shutdown by 18th March for checks.
Restored on 21st March, the unit ran till 26th June when it was shutdown for gas
restoration. Between 1st to 23rd July, the unit generated into the grid.
Thereafter it was on outage due to faulty natural gas unloading valve. From then the unit
was available except 10 days outage on mid September caused by low water pressure and
an 11 – day maintenance outage in early December. The unit was however
synchronously tied to grid by 31st December, 2007.
GT1 started production on 5th April, 2007. Its was on a 4 day outage for gas pipe
restoration on 26th June. From 1st July to August, the unit was tied to the grid.
For almost a month of September the unit was on outage due to vent fan oil leakage.
It generated on October and November but unavailable through out December on faulty
cooling system.
GT13 came on stream in early June. It was however shutdown in order to restore gas
pipe line. Between 7th to 25th July, the unit developed faulty fan motor. From 25th July to
28th September it generated into the grid.
It then went on a week outage to repair the generator transformer tap changer. The unit
was on the grid throughout December, 2007.
1.33 OLORUNSOGO P.S.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
23
29. Commissioning of the units commenced in December, 2007.
GT1’s commissioning commenced on 7th. It ran for the rest of December, 2007.
GT2’s commissioning began on 17th December, 2007. It was on the grid for the rest of
December, 2007.
GT3 was commissioned on 10th December, 2007. The unit was still generating by 31st
December, 2007.
GT5 was commissioned on 16th December. It generated for the remaining days of
December, 2007.
1.40 GENERATION ORDERING AND LOAD DISPATCH
An integrated grid was operated in 2007, pooling generation from Kainji, Jebba and
Shiroro Hydro Power Station and Egbin, Delta, Afam, Sapele, AES, Okpai, Omotosho,
Omoku and Olorunsogo thermal Stations.
Inadequate gas supply from the Nigerian Gas Company (NGC) and incessant low gas
pressure militated against full thermal capacity generation into the grid. Among the
affected Stations were: Egbin and AES which although capable of an average generation
of 955.0MW was frequently confined between 200 and 700 MW.
There was a time that the combined stations could only pooled less than 100 MW into the
grid. Likewise, Geregu, Omotosho and Olorunsogo output to the grid was often limited
by gas availability to about 30% of available capacity.
Since generation availability was grossly inadequate to meet the ever increasing load
demand, load shedding continued through out the year in order to maintain power
balance.
1.50 FREQUENCY CONTROL
Due to generation shortage, the grid was operated outside the frequency control policy of
50Hz + 0.40% i.e. 49.80Hz to 50.20Hz, resulting in frequency excursions outside the
operational limits.
Most of the gas turbines on the grid were operated on temperature control mode. Hence
they were often insensitive to vagaries of system frequency.
The automatic voltage regulator (AVRs) and governor system of Kainji, Kaplan units
(variable blades) were not functional. All the other machines in the system were
considered base load, except Jebba units that regulate occasionally.
Generation and Transmission Grid Operations-2007-National Control Centre, Osogbo
24
