Syntax Literate: Jurnal Ilmiah Indonesia p–ISSN:
2541-0849 e-ISSN: 2548-1398
Vol. 9, No.
12, Desember 2024
OPTIMIZATION OF THE PROTECTION INTERLOCKING FUNCTION
OF A 56 MW UNIT STEAM TURBINE
Wang Zhiliang1,
Feng Hongwei2, Muhammad Ihsan2
PT. DSSP Power Kendari, Indonesia1,2,3
Email: [email protected]1, [email protected]2, [email protected]3
Abstract
There
are 2 x 56MW units in Kendari power plant, each unit is equipped with two 100%
capacity electric feed pumps, one running and another one backup. During the
operation of the unit, two defects, such as large vibration of the BFWP and
high temperature of the thrust pad on the working face, were found to affect
the operation. The large vibration of the BFWP is mainly due to the falling off
of the positioning pin of the bearing bracket of the non-drive end, which
causes the center to sink, and the balance drum and the balance sleeve are
rubbed dynamically and statically. The main reason for the high temperature of
the thrust pad of the BFWP is that the diameter of the balance drum is small,
which leads to an increase in the axial thrust borne by the thrust pad of the
working face, and the high temperature of the tile. This study aims to diagnose
the root causes of these defects, implement corrective measures, and optimize
pump performance to enhance operational safety. A combination of on-site
inspections, data analysis, and engineering interventions was conducted. Findings
indicate that structural realignment and reengineering of the balance drum
significantly mitigated vibration and temperature issues. The study concludes
that proactive maintenance and design optimization are essential for the
reliable operation of power plant equipment, with implications for enhancing
long-term efficiency and safety.
Keywords: feed water
pump, vibration, thrust pad
Introduction
Datang
Indonesia Kendari Power Generation Company has 2*56MW units and was put into
operation in October 2019. The main engine is a high-temperature and
high-pressure steam turbine with a rated power of 56MW produced by Dongfang Electric Corporation. The lubricating oil system
uses 2 AC oil pumps and 1 DC lubricating oil pump, with one AC oil pump in use
and one in reserve. After Datang Group took over the
power plant, it organized personnel to investigate the hidden dangers that
affect the safety of the main engine. The main hidden dangers investigated are
that the temperature of the turbine bearing and the temperature of the thrust
bearing are both single-point protection, and there is no rate judgment. The
turbine vibration protection is a single-point protection, and the turbine is
not reasonably configured to prevent oil outage and burning of bearings
Following the
takeover by Datang Group, the company conducted
extensive investigations into potential operational hazards affecting the main
engine's safety. Key concerns included turbine bearing temperatures, thrust
bearing temperatures, and inadequate multi-point protection mechanisms for
vibration monitoring and oil supply failures
To address these vulnerabilities, Datang
Group leveraged unit maintenance periods to systematically optimize and enhance
the power plant’s reliability and safety. A critical focus was placed on the
operational stability of the feed water pump (BFWP), essential for maintaining
boiler efficiency and preventing overheating
Research Methods
The research method was conducted through a series of
approaches that included operational data collection from the generating unit,
field inspection of the feedwater pump (BFWP)
Results and
Discussion
Turbine
protection optimization content
1) Turbine tile temperature
protection
The steam turbine of Kendari Power Generation
Company has 4 bearings, each bearing has a thermal resistor for measuring
bearing temperature. There are 8 bearing temperature elements for the working
face thrust bearing and 2 bearing temperature elements for the non-working face
bearing. All of the above temperatures are tripping steam turbines when any
point is higher than 100 degrees, single point protection and no rate judgment.
Because the feasibility of adding temperature
measurement points is very low, in order to eliminate refusal to operate and
reduce false operation, the temperature protection increases the rate and delay.
According to relevant regulations and the practical experience of Datang Group's brother power plants, the rate of the
thermal resistance of the turbine bearing is set to greater than 5 degrees
Celsius/second to shield the protection output, and the delay is set to 2
seconds. Therefore, the final protection setting is: when the temperature of
the turbine support bearing is higher than 100 degrees Celsius and the rate of
change is less than 5 degrees Celsius/second, the delay is 2 seconds to adjust
the trip; when the temperature of the support bearing is higher than 100
degrees Celsius and the rate of change is less than 5 degrees Celsius/second,
the delay is 2 seconds to trip, both of which are single-point protection.
Figure 1. Logic Diagram Turbine Generator Bearing High
Temperature Trip
Figure 2. Bearing Temperature False Alarm Trend
Figure 3. Bearing Temperature Real Alarm
2) Steam
turbine vibration protection
The steam turbine of Kendari Power
Generation Company has a total of 4 bearings, each of which has 2 shaft
vibration measurement points. The original protection method was to trip the
steam turbine if any vibration signal reached the tripping value, which did not
meet the group company's configuration requirements for vibration protection.
Kendari Power Generation Company has
made the following optimization: any vibration higher than the second value
(trip value) and any other vibration higher than the first value (alarm value)
will trip the turbine.
Figure 4. Logic Diagram Vibration Alarm & Trip
3) Optimization
of steam turbine to prevent
oil shortage and tile burning
The steam turbine lubricating oil system of
Kendari Power Generation Company is equipped with one AC oil pump in operation
and one in reserve, and the DC oil pump is used as an emergency standby pump.
a. The original logic of joint start of AC oil pump
of turbine A (B) is as follows:
1) When the lubricating
oil pressure is low (pressure
switch), the oil pump will
be started after a delay of
3 seconds.
The following optimizations are
performed:
1) Cancel the delay condition of 3 seconds to start the oil pump
when the lubricating oil pressure is low
(pressure switch), and change it
to a delay-free start;
2) Increase the low lubricating oil pressure (analog value) and start the oil
pump.
Figure 5. Modification Logic Diagram for Interlocking AC Oil
Pump
b. The original logic
of the AC oil pump stop permission
of turbine A (B) has no locking conditions:
The stop permission condition adds
the condition that the standby AC oil pump has been started and the oil
pressure is normal.
Figure 6. Logic Diagram AC Lube Pump Stop Permission
c. The original logic of turbine DC oil
pump joint start is as follows:
1) When the lubricating
oil pressure is low (pressure
switch), the oil pump will
be started after a delay of
3 seconds;
2) Stop both AC oil
pumps and restart them after
a delay of 3 seconds.
The following
optimizations are performed:
1) Cancel the 3-second delay
of the oil
pump when the lubricating oil pressure is
low (pressure switch) and change
it to a delay-free
start;
2) Increase the lubricating
oil pressure (analog value) and start the oil pump;
3) Both AC oil pumps
are stopped, the 3-second delay condition is cancelled, and
they are started directly in conjunction with each other.
Figure 7. Diagram Logic Modification DC Lube Oil Pump
d. Adding joint start conditions
to the DC lubricating oil pump hard wiring
:
The DC
lubricating oil pump increases the hard-wired circuit of the lubricating oil
pressure (pressure switch) to the local control cabinet to start the relay
coil, ensuring that when the lubricating oil pressure is low and there is a
problem with the DCS system, the DC lubricating oil pump can be interlocked and
started in time to protect the safety of the equipment through the local
control circuit.
Conclusion
Through the transformation, the
reliability of turbine support bearing temperature and turbine vibration
protection was improved, protection refusal to operate was eliminated, false
operation was reduced, and the optimized protection measures for turbine to
prevent oil outage and bearing burning were improved, providing reliable
protection for the safety of turbine equipment.
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Copyright holder: Wang Zhiliang,
Feng Hongwei, Muhammad Ihsan
(2024) |
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First publication right: Syntax Literate: Jurnal Ilmiah Indonesia |
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