REVIEW
ON THE 10 YEARS OPERATION OF GEHEYAN HYDROPOWER PLANT ON QINGJIANG RIVER
Liu
Zhaohui
Hubei Qingjiang Hydroelectric Development Co., Ltd
Hubei Yichang 443000
Abstract
This paper firstly briefed the basic info of Geheyan
Hydropower Plant. After summarizing the ten years operation of the plant, the paper
mainly analyzed the power generation equipment and water utilization by
theoretical and mathematical methods. It described the equipment reliability
and utilization rate, fault rate and features, water utilization, assimilation
on imported equipment, present advantages, achievements and existed problems
under the fact that the plant is not only for power generation, but also with
many auxiliary functions such as strong and frequent peak and frequency as well
as voltage regulations; the paper also proposed related measures to enhance
management on operation and maintenance, improve load factor, reduce operation
time at low load and dynamic standby capacity, carry out combined dispatching
among cascade projects to improve water utilization rate, take out the
compensation advantage among hydropower groups as well as more effectively
maintain the safety of power grid, so as to improve the reasonability and
reliability in operation, maximize the economic benefit and to improve the
overall operation level.
Key words:
Geheyan Hydropower Plant Operation
Review Exploitation and Improvement
Qingjiang Geheyan Hydropower Plant is
established on November 16, 1992. It has been 10 years since the commissioning
of its first unit on June 4, 1993, this paper is to review major aspects of its
operation in the past 10 years.
1. Basic info of Geheyan Hydropower
Plant on Qingjiang River
Qingjiang Geheyan Water Control
Project is located in the middle of the cascade development in the mainstream
of Qingjiang River. The project started to construct in January 1987 and passed
the final acceptance in April 1998. Annual average runoff at the dam site 12.7
billion m3, NPL 200m, dead level 160m, total reservoir capacity 3.4
billion m3, live capacity 2.2 billion m3. The power plant
is installed with 4X300MW turbine-generating units, annual output 3.04 TWh, firm
output 187 MW, rated head 103m, minimum head 80.7m. 4 sets of turbine, 2 sets
of generator, the governor and exciter for the 4 units, 4 sets of main
transformer as well as SF6 high voltage GIS and SCADA system are
imported and are of international advanced level in the period from the end of 80’s
to the beginning of 90’s. The first unit is commissioned on June 4, 1993 and
all 4 units are put into operation on November 26, 1994. Since the
commissioning of the first unit, the plant has been operated for 39.34
unit-years up to the end of December 2003 with accumulated power output of 24.88
billion kWh. The power plant has passed the severe test during the extra huge
flood in 1998, and the acceptance of “first class power plant” by the State
Power Corporation in November of the same year.
2. Reliability on equipment operation
2.1 During the operation of Geheyan
Hydropower Plant in the past 10 years, the whole plant has been operated for 147799
hours in an average of 3757h/unit-year. The reliability of equipment in
operation is generally sound.
With highly attached concern and
adequate measures on the import, assimilation and application of main equipment
as well as imported equipment. People with profound knowledge and rich
experiences are assigned to attend design liaison meeting, factory supervision
and acceptance test with insisting on technical specifications and standards, strictly
quality control, which makes the above equipment satisfactory with the design,
technical, quality standards and contract stipulations. Before putting the
equipment into operation, necessary personnel training is conducted in advance
so as to get familiar with the structure, performance as well as operation
requirement of the equipment, and to establish rules and regulations for
production management. People also assigned to take part into installation and
commissioning test so as to further get familiar with the structure and process
of the equipment, and to accept the installation with strict requirement. When
the equipment is put into operation, with strict management, rule and
regulations, careful operation and well-conducted patrol and inspection and
maintenance, main equipment and major auxiliary equipment is maintained on
reliable operation. Within the dispatching time, the plant has maintained 100%
of success rate in the frequent startup/shutdown (1.53 time/unit-day in
average), and 100% of availability for main equipment. Domestic auxiliary
equipment and common system could also meet the requirement of automatic
response through related technical reformation and innovation. Various indices
on the main and auxiliary equipments, relay protection, security automation and
control system are all reached and maintained at the standard of “first class
hydropower plant”. Now it is working hard toward the objective of “unmanned
operation”.
2.2 There are also occurred with a
certain number of faults in its power generating system at Geheyan Hydropower
Plant in the past 10 years. Based on actual records, within the dispatching
time, the annual average fault in all 4 units as well as their system is 7.73
times, dispersing coefficient 0.55, while for the fault rate (fault times in
hour) of each unit in various years, there is a big difference above one scale
level, and there is also shown without any trend and is largely dispersed. To
have a better expression and understanding, the fault time in every 90 days
within the dispatching time is shown in Table 1 and Fig. 1.
Table
1: Fault times converted into equivalent time within the dispatching time
|
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
|
|
Times |
||||||||||||
|
Unit |
||||||||||||
|
1F |
2.2 |
2.35 |
1 |
0.25 |
0 |
0.52 |
0 |
0.28 |
0.79 |
0.5 |
0.8 |
|
|
2F |
|
2 |
0 |
0.25 |
0.51 |
0.25 |
0.26 |
0.25 |
|
0.27 |
0.51 |
|
|
3F |
|
0.26 |
1 |
2.07 |
0.76 |
0.5 |
0 |
0.25 |
0.26 |
0.5 |
0 |
|
|
4F |
|
0 |
0.78 |
0.74 |
0.78 |
0 |
0.26 |
0.27 |
0.58 |
0.77 |
0.26 |
Above calculated dispersing coefficient,
difference on annual fault rate as well as the unit fault curve show that the
fault is highly random, which is consistent with the analysis result on fault
events. Random factors mainly come from human factors and the changeable
operation condition on equipment in meeting the demand of frequent
startup/shutdown for strong peak and frequency regulation. Human factors
include direct behavior, incomplete and rough rule and regulations as well as
rough implementation and incomplete understanding on these rules and
regulations, shortcomings on perceiving the technology of equipment as well as
deficiency in equipment maintenance and repairing. Through periodic
organization of learning and education on loving the job and the equipment as
well as technical trainings in combining the content of actual technology,
skill and process to improve people’s comprehensive diathesis, well conduct
fault analysis, operation analysis, perceive the principle of equipment,
perfect and strict implement rules and regulation, cultivate employee’s
affinity, ability and capability, is an effective way and long-term mechanism
to reduce unfavorable random human factors.
Fig.
1: Fault curve converted into equivalent time within the dispatching time
The fault curve of units didn’t show
any trends following the increase in operation years. The lower section in the
middle is due to enhanced technical reformation and maintenance, which
eliminated the initial defects such as oil leak on guide bearings and current
transformers as well as mal-connection, bad contact in secondary circuits, as
well as the improving performance resulted from reformations on technical water
supply and plant power supply system. The raising tail is mainly the result
from the variance of secondary components after 7~8 years of use, such as
photoelectric isolating, electrical and hydraulic converter in governor and RTD.
In the past ten years, the percentage of forced stoppage and abnormal operation
due to their fault has accounted for more than 30%.
Turbine cavitation is slight, the
cavitation in the first unit is shown on increasing, but generally within the
performance guarantee of the manufacturer.
2.3 The dam has passed the acceptance
and the first round of safety inspection. During the “Flood control in 1998”, the
level at dam has reached 203.94 m high, which is close to ten thousands year
flood check level 204.59 m, while the downstream level is about 20m lower than
designed value under such a flood level, all discharge gates are closed, the
water thrust has increased 15% on the dam and 50% on the discharge gate, technical
indices such as displacement are all within the design scope under such a worse
condition, created the condition to avoid flood diversion in the Jinjiang river
section of the Yangtze River, which has fully confirmed by the former premier
and related departments with obvious social and economic benefits. The practice
proved that Geheyan dam is a normal dam.
2.4 Well conduct repairing and
reformation on power generating and distribution equipments
The repairing and reformation on
Geheyan Hydropower Plant in the past ten years is adequate and effective. Integrated
repairing system is adopted in the guiding principle of transferring from
restoring repairing to performance improving repairing together with active
exploration on diagnosis-based repairing. Except the implementing of related
specifications and process standards during the repairing, self-prepared ISO9002
quality assurance system and repairing responsibility system are also
implemented and is ready to carry out quality supervision system on repairing, so
as to meet the periodic requirement through equipment repairing and repairing.
In the past ten years, the plant has
totally conducted 52 unit-times of repairs, each unit has conducted one
overhaul, and the generator has met the reliability index of overhaul once in
every 8 years specified by the manufacturer. Balanced arrangement in small
repair is conform to the actual situation and has ensured the health level of
equipment. The annual average repair is 1.22 time/unit-year, which is less than
the 2 time/unit-year specified in “Specification for Repairing and Repair in
Power Plant” (industrial specification). The average duration for minor repair
is 10.5 days/unit-time.
In the arrangement of repairing, the
first repair after commissioning shall be arranged as complete as possible to
eliminate outstanding issues from installation, the fixing of leaks, loosing,
mal~ connection, bad contact in secondary circuits resulted from trial
operation, check the performance and parameters in secondary equipment, gap
measurement and adjustment, cleaning powders produced in the grinding period as
well as the filtering out of impurity from the unit and governor oil are all necessary.
After about 7~8 years operation, attention shall be paid to secondary
components such as photoelectric isolating, electrical hydraulic converter and RTD,
especially the calibration and replacement of micro electronic components and
devices.
Equipment maintenance is carried out
by the power plant. The principles of “frequent, detail, strict and real” are
insisted on all the times to eliminate defects and abnormities timely so as to
ensure health operation.
In the past ten years, large amount
of fund has been invested to the systematic and upgrade on the technical water
supply system, plant power supply system, relay protection, automation system,
computer control system, oil emission of generator, maintenance and leaking
water drainage, high and low pressure air compressors and the dam safety
supervision system, which improved the safety and reliability, enhanced
performance, expanded function and ensured the health level of equipment with
obvious benefit.
To sum up the above, the fault rate
in Geheyan Hydropower Plant is quite low, except there are two faults happened
in the 500KV SF6 GIS in July 1995 and August 1996 respectively, no other fault
has happened with impact to the operation performance of main equipment, auxiliary
equipment and system are safe and reliable, the dam is maintained at normal and
the plant is of high automation level. The equipment reliability in Geheyan
Hydropower Plant is of a health and sound level.
3. Technical indices and peak and
frequency regulation
In order to meet the requirement of
peak and frequency regulation of the grid and to gain more seasonal energy, full
consideration is made in the design, the capacity of the plant is about 30%
higher than plants with similar hydrological conditions. Design annual utilization
is 2530h, just 35%~59% of other similar plants in the Central China Power
Network. The operation in the past ten years shows that the standby capacity as
well as the idle capacity in valley time and dynamic standby capacity for peak
and frequency adjustment are too big, load rate, utilization rate and output
factor are quite low, annual average utilization is only 1967h, 22% lower than
the design value, but the equipment availability is maintained at a high level;
annual
average equivalent availability 95.1%, which is 105% of the rated availability;
annual average available hour 8340h, operation hour 3757h, which is 45% of
available hours and 191% of utilization hour, standby hour is 122% of the
operation hour. See detail in Table 2 and Fig. 2
below.
Table 2:
|
Year |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2001 |
2002 |
2003 |
|
Availability (%) |
96 |
95 |
96.1 |
94.6 |
95.8 |
96.6 |
96.7 |
94.3 |
91.2 |
95.2 |
94.8 |
|
Output factor (%) |
68.2 |
44.9 |
62.9 |
73 |
66.5 |
59.7 |
51.2 |
48.5 |
45 |
58 |
52.9 |
|
Utilization rate (%) |
63 |
23.9 |
25.5 |
28.9 |
21.4 |
24.8 |
20 |
23.8 |
16 |
24.8 |
24.9 |
|
Load rate (%) |
45 |
15.9 |
24.6 |
28 |
20.6 |
24 |
20 |
24.7 |
16 |
23.9 |
24.2 |
The above operation indices shows
that these low technical indices in load rate, utilization rate and output
factor are poor for the economic indices as the basic operation expenses such
as operation, maintenance, repairing and reformation are defined by the
installation capacity; In the frequent peak and frequency regulations, it is
often to see several units with small load, small load in high head and high
load in low head. All of these have increased the water and equipment
consumptions. Secondly, there is a large space between availability and other
three technical indices, which has left a big margin for future improvement on
operation benefit and economic performance in one hand, on the other hand, due
to the high level of automation, sound equipment reliability and large peak and
frequency regulation capability of Geheyan Hydropower Plant in the past ten
years, especially after the commissioning of AGC, it is very swift and handy
for dispatching, and has become an ideal peak and frequency regulation power
plant in Central China Power Network.
According to dispatching regulation
of Central China Power Network, the order of main frequency regulation plants
is Dangjiangkou Hydropower Plant, Dongjiang Hydropower Plant, Geheyan
Hydropower Plant and Wuqiangxi Hydropower Plant, when Dangjiangkou Hydropower
Plant is unable to take frequency regulation, Geheyan Hydropower Plant and
Wuqiangxi Hydropower Plant will jointly act as main frequency regulation plants
after Dongjiang Hydropower Plant. Since the commissioning of AGC, the mode of
frequency regulation specified by the grid on Geheyan Hydropower Plant is to
trace the frequency in each level specified by the grid in the step of 50MW. Such a manner of frequency regulation is
effective to ensure qualified grid frequency, but it is over frequent
regulation for units participated into the regulation.
Fig. 2: 
Peak and frequency adjustment. As an
auxiliary function of a plant mainly for power generation, the portion of this
part in Geheyan Hydropower Plant is very high. The plant has played an active
function in maintaining the stability and safety of the grid in past ten years,
and taken strong peak regulation task. The plant is generally participated in
the peak regulation in three-section system, the adjusting margin is from 0~1200MW.
The annual average peak regulation capacity is 744.0MW, and 883MW in flood
season, the energy loss due to peak regulation is about 250 GWh. Annual average
peak regulation capacity in dry season is 673MW. In a specific time on July 13,
2001, upstream level is of better level above 178m, the load of unit 1, 2, 3 is
11MW, 13MW and 33MW respectively, as the grid frequency is not high, it is
adjusted to 65MW, 191MW and 65MW respectively,
one hour later, the output increased again, with 264 MWh of more power is
generated just in one hour, directly economic benefit RMB 95 thousands. In the
5 years from 1999~2003, the operation hour with light load around 3~70MW per
unit has reached 2700h; almost everyday has 2~3 units operated with light load
at the same time. By optimizing units with load below 70MW into one or two, at
least RMB 18 millions more income can be generated every year based on
calculation. The above cases are quite often to see in actual operation, but
there is also a problem in avoiding of rough zone. Due to the need of peak
regulation, although the unit is operated under design head range, it is often
with unreasonable output, poor operation condition and high water consumption; all
of these have reduced the profitability of the plant. Due to peak regulation,
units in Geheyan nee to frequently startup and shutdown; the average
startup/shudown per day in the past ten years within dispatching time is 1.53
time/unit-day; the startup/shudown in 1997 is 2598 unit- times, 1.86 time/unit-day
in average.
Frequent startup/shutdown and
adjustment have brought many unfavorable impacts to the safe and stable
operation of equipment as well as economic benefit; all of these need to be
taken by the plant. The water mass in the passage of turbine is of both
vibrator and the carrier of dynamic load, its frequent conversion in frequent
frequently startup and shutdown will become very complicate n\and unstable, hence
strong vibration, eddy vibration, surge, low frequency vibration, strike
vibration, even resonance are all somehow existed due to pulsation, cavitations
and so on. The blade of three turbine runners has produced 20 cracks in a total
length of 2597mm, the longest penetrating crack is 300mm long and 80~100mm deep,
the discharge cone of unit 2 was once washed away, there are also leak in the
servomotors and so on. In addition to design and manufacture factors, all of
these are related to operation conditions, and with unfavorable impact to the
life of equipment and the increasing in maintenance and repairing cost. For the
imported SF6 GIS, the manufacturer’s performance guarantee specified
that repair is required for breaking current above 400KA, and investigation
inspection shall be made to the live contact after every 3000~4000 times of
open/close cycle. Based on this specification and the annual average
startup/shutdown times of units in Geheyan plant, investigation inspection
shall be made in every 7 years even without the breaking of short circuit
current. Since it is of investigation inspection, it shall be participated or
done by manufacturer; this will surely increase the direct production cost, as
the participation of foreign supplier is often quite expensive.
In the past ten years, Geheyan
Hydropower Plant has taken strong peak and frequency regulation tasks in the
grid with fruitful achievement and active function in maintaining the stability
and safety of the grid; it will continue to take such a function in the future.
Geheyan Hydropower Plant as a plant mainly for power generation taking big
portion of auxiliary function is obvious different with other hydropower plants,
frequent startup/shutdown and adjustment for peak and frequency regulation
makes its operation condition complicate and changeable with poor stability; low
output factor increased equipment consumption and fault; huge losses in energy
due to peak regulation; increased water consumption rate; not so ideal in total
power generation. All of these issues have reduced the profitability of the
plant, increased its production cost. The plant is currently implemented with
the power and price based on cost and interest repayment, those unfavorable
impacts brought by the above auxiliary function are not compensated. Approaches
to solve or improve the issues are: Firstly, to well carry out scientific
dispatching to find out reasonable combination to reduce water consumption,
abandoning water and to generate more power; improve output factor, reduce or
avoid operation under unreasonable operation condition, including combined
dispatching among these three cascade projects on the mainstream of Qingjiang
River to fully take compensation function of hydropower group and to maximize
economic benefit; before the commissioning of the upstream Shuibuya project, in
view of the past and current situation, if the operation can be carried out
under the following conditions, about 400 GWh more energy can be produced in
normal year, and the standby capacity and peak regulation capacity can also
ensured at the same level.
(1) Whole
plant operation hour: 2800~3000 h;
(2) Limit
on load and operation hour for units in each head range of the reservoir as
follow;
|
Reservoir level (m) |
166~175 |
175~180 |
180 above |
|
Single unit load (MW) |
200~220 |
240~250 |
260~300 |
|
Operation hour (%) |
25 |
20 |
55 |
(3) Through
optimized dispatching to have output factor at 79~85%;
(4) To
reduce the operation hour of single unit load at 80MW and below as much as possible,
and to transfer load into one unit when two and more units are operated with
load 150MW and below, and to avoid the rough zone;
(5) Energy
loss due to peak regulation while abandoning water to be controlled about 100
GWh.
Secondly, to create reasonable
competitive environment in the reformation, implement contesting operation, best
price for best quality, peak regulation price and capacity compensation, and to
combine dynamic benefit with capacity benefit. With certain reward to auxiliary
functions is quite reasonable, generating enterprise will always try to avoid
free service and negative benefit if only with consideration to benefit.
4. Hydrology and power generation
Qingjiang River is of a creek type
river. The annual average runoff in the past ten years is 12.95 billion m3,
accounting for 95.3% of the historic average. It is good in rainfall. The
maximum runoff in the past ten years reached 17.6 billion m3 (1998)
and the minimum runoff is only 6.7 billion m3 (2001), the runoff in
other years is around 10 billion m3. The highest level has reached 203.94
m high in 1998, which is close to ten thousands year flood check level 204.59 m,
the minimum high level is occurred in 1995 at 180.4m. The project is designed
without irrigation function, based on the calculation, designed annual power
output will account for 93% of the total runoff under rated head; the portion
of power generation in water consumption is quite high, therefore highly
attention shall be paid to optimize dispatching, flood control and to take full
use of the limited water resources on Qingjiang River to generate more quality
power so as to improve the economic benefit of hydropower.
Due to the need of flood control, it
is not possible to use all water for power generation. About 80% of water has
been used for power generation in past ten years, the utilization rate is lower
than design, the average water consumption for power generation exceeded 4m3/kwh,
the average power generation in the ten years is only about 83% of the design
output, only 1996 has achieved the design output. The above situation on runoff,
water for power generation, power output, water consumption rate are largely
related to optimized power dispatching and the careful planning in large scaled
production. Attach more attention on spring flood, strict control on the main
flood, hold tightly the Autumn flood, repeat use on reservoir capacity, well
manage the storage are effective principles for safety operation and benefit
increasing. For instance the two scientific dispatching and reasonable
arrangement in June and July 2003 obtained about 690 million m3 of
water for power generation, increased more than 170 GWh in power generation
with direct economic benefit more than RMB 60 million. The runoff
and water consumption for power generation between June 1993 and the end of
2003 is shown below in Fig. 3.
Fig. 3. Historic
runoff and water consumption for power generation Unit: 100 million m3
For the limited water resources in
Qingjiang River, improper dispatching on it would impact both the benefit of
power generation and the peak and frequency regulation function due to the
consumption of water without power produced. When the upstream Shuibuya project
is commissioned, the lower level limit at Geheyan reservoir will be 180m, the
firm output will be increased to 287 MW, the annual power output can be about 3.3
TWh at Geheyan Hydropower Plant through combined operation among cascade
projects provided that the average output of single unit at Geheyan Hydropower
Plant can be maintained above 280MW, average utilization 2750~2850 h.
5. Safety operation at Geheyan
Hydropower Plant
Safety is a frequent talk and
important topic. The safety of power plant is related with many aspects, safety
operation is an important job in power plant. In the past ten years, the plant
always kept safety as an important daily work with strict management, strict
examination, strict rule and regulations to strength the safety consciousness
of all employees. No matter it is good or not, the principle of human-oriented
shall be insisted all the time in analysis and disposal. There have been some
ordinal accidents occurred in the past, but no big accident listed in the
“Specification for Accident Investigation”, the situation in safety is
generally sound.
Power generation, transmission and
distribution and consumer in the power system is an integrated whole with
organic contacts, they are mutual related. In considering the safety in power
generation is not only the safety of the plant itself, but also the safety of
the other two as unsafe power generation will somehow threat the safety of the
grid and hence the safety of customer. In the same way, any unsafe in one
aspect will somehow threat the safety of the rest two, and everybody is
responsible. Moreover, accident in power system is also well known due to its
swift, wide spreads and huge damage. The large area power shutdown accident
occurred in New York, USA and part of Canada on August 4, 2003 is a powerful
proof. It is a necessity and must for power generation, transmission and
distribution and consumer to be integrated into a cooperative whole so as to
bring new contribution to the power industry of China.