Method and system for restarting lubricating oil system of steam turbine

Abstract

The invention provides a steam turbine lubricating oil system restarting method and system.The method comprises the steps that the pressure of a lubricating oil mother pipe is monitored in real time through three independent lubricating oil pressure sensors, and two-out-of-three judgment logic is adopted; a two-position mechanical latching relay and a lubricating oil low-voltage normally-closed contact are connected in series in a direct-current lubricating oil pump starting loop, and a direct-current pump is directly started when the pressure is abnormal; interlocking logic composed of a two-position relay, a controller state relay and a pressure signal relay is arranged on a starting loop of the auxiliary oil pump and the top shaft oil pump, and automatic starting is achieved when auxiliary power is recovered. The system comprises a pressure monitoring module, an emergency starting module, an automatic recovery module and a control processing module. Reliable restart of the lubricating oil system is achieved, and the running safety of the steam turbine is improved.

Description

Technical Field

[0001] This document relates to the technical field of steam turbine lubricating oil systems, and in particular to a method and system for restarting a steam turbine lubricating oil system. Background Art

[0002] During turbine operation, the lubricating oil system is crucial to the safety of the rotor. In existing technologies, when a plant-wide power outage or control system failure occurs, the lubricating oil pressure switch is typically interlocked to start the DC oil pump to maintain lubricating oil pressure and prevent bearing damage. Once plant power is restored or the control system returns to normal, the operator must manually start the auxiliary oil pump and, according to procedures, the top shaft oil pump. Once the system stabilizes, the DC lubricating oil pump can be manually stopped. However, existing technologies have the following drawbacks:

[0003] 1. Reliability issues of DC oil pumps:

[0004] Lubricating oil pressure switches are susceptible to pressure fluctuations or set point deviations, which may cause the DC oil pump to start incorrectly or fail to operate, threatening unit safety. Due to frequent operation, medium corrosion, or mechanical overload, the reliability of pressure switches decreases with operating time, increasing maintenance costs. After long-term operation, sensors may lose measurement accuracy due to aging, oil contamination, and other factors, affecting the accuracy of interlock control.

[0005] 2. Oil supply dependency after plant power is restored: After plant power or the control system is restored, manual intervention is still required to start the auxiliary oil pump and the top shaft oil pump. During the transition period, the system still relies on the DC oil pump for oil supply, resulting in continuous consumption of the DC power supply and affecting the availability of the emergency power supply. If the operator does not respond in time, the operating time of the DC oil pump may be extended, further increasing the burden on the DC system and even affecting the emergency power supply of other key equipment.

[0006] Therefore, given the problem that existing technologies are highly dependent on the control logic of DC oil pumps and require many manual intervention steps, and may not be able to optimally guarantee the supply of lubricating oil in emergency situations, a more reliable and automated solution is urgently needed. Summary of the Invention

[0007] According to an embodiment of the present invention, a method and system for restarting a steam turbine lubricating oil system are provided, aiming to solve the above-mentioned problem.

[0008] According to an embodiment of the present invention, a method for restarting a steam turbine lubricating oil system is provided, comprising:

[0009] Three independent lubricating oil pressure sensors monitor the lubricating oil main pipe pressure in real time, and a preset two-out-of-three judgment logic is used to determine whether the lubricating oil pressure is normal;

[0010] A two-position mechanical latching relay is connected in series to the starting circuit of the DC lubricating oil pump. The normally open contact of the two-position mechanical latching relay is connected in series with the normally closed contact of the lubricating oil low pressure. When the lubricating oil pressure is abnormal, the normally closed contact of the low pressure is closed, and the DC lubricating oil pump is directly started through the hard-wired circuit.

[0011] An interlocking logic consisting of a two-position relay, a controller status relay, and a pressure signal relay is set in the electrical starting circuit of the auxiliary oil pump and the jacking oil pump. When the factory power is restored, the auxiliary oil pump and the jacking oil pump are automatically started through the coordinated action of the interlocking relay group.

[0012] According to an embodiment of the present invention, a steam turbine lubricating oil system restarting system based on the above-mentioned steam turbine lubricating oil system restarting method is provided, characterized in that it includes:

[0013] The pressure monitoring module consists of three independently set lubricating oil pressure sensors, which are installed in different sections of the lubricating oil main pipe. They are used to collect lubricating oil pressure signals in real time and transmit the signals to the control processing module;

[0014] The emergency start module includes a two-position mechanical latching relay and a lubricating oil low-pressure normally closed contact. The two are connected in series and connected to the starting circuit of the DC oil pump. The coil of the two-position mechanical latching relay is connected to the set command output terminal of the controller, and the lubricating oil low-pressure normally closed contact is connected to the three-out-of-two logic output terminal of the lubricating oil pressure.

[0015] The automatic recovery module includes a two-position relay, a controller status relay, and a pressure signal relay. The normally open contacts of the three are connected in series and then connected to the starting circuits of the auxiliary oil pump and the top shaft oil pump. Among them, the coil of the two-position relay is connected to the set instruction output terminal of the controller; the coil of the controller status relay is connected to the heartbeat signal output terminal of the controller; and the coil of the pressure signal relay is connected to the three-out-of-two logic output terminal of the lubricating oil pressure.

[0016] Control processing module: used to execute three-out-of-two pressure judgment logic, and output double-position relay setting and reset instructions, controller status monitoring instructions and auxiliary oil pump jacking oil pump start instructions. Its hardware carrier is the controller of the turbine control system.

[0017] By adopting the embodiment of the present invention, a two-out-of-three judgment logic is used to monitor lubricating oil pressure, avoiding misjudgment of single sensor failure and ensuring the accuracy of pressure monitoring. The hard-wired start-up design of the DC lubricating oil pump allows for quick and direct start-up in the event of pressure anomalies, thereby improving the system's emergency response capabilities. Interlocking logic controls the automatic start-up of the auxiliary oil pump and the top shaft oil pump, enabling intelligent restart after the factory power is restored. The system's modules work together to ensure stable operation of the lubricating oil system, reduce the risk of turbine failure due to lubricating oil problems, and improve the reliability and safety of equipment operation. At the same time, the sequential control logic optimizes the system startup process and enhances the system's automation level. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a flow chart of a method for restarting a steam turbine lubricating oil system according to an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of monitoring lubricating oil pressure using a two-out-of-three judgment logic according to an embodiment of the present invention;

[0021] Figure 3 A DC lubricating oil pump relay startup logic diagram according to an embodiment of the present invention;

[0022] Figure 4 This is a logic diagram for starting the auxiliary lubricating oil pump / jacking oil pump relay according to an embodiment of the present invention;

[0023] Figure 5 is a schematic diagram of the normal logic of the controller according to an embodiment of the present invention;

[0024] Figure 6 Schematic diagram of the interface between the auxiliary lubricating oil pump and jacking oil pump start-up instructions and the MCC according to an embodiment of the present invention;

[0025] Figure markings: K1-lubricating oil main pipe pressure 1>MIN3 (40%) output relay; K2-lubricating oil main pipe pressure 2>MIN3 (40%) output relay; K3-lubricating oil main pipe pressure 3>MIN3 (40%) output relay; K4S-DC lubricating oil pump double position instruction output relay; K4R-DC lubricating oil pump double position reset instruction output relay; K5-double position relay (mechanical lock); K6-DC lubricating oil pump start instruction output relay; K7-DC lubricating oil pump stop instruction output relay; K8-lubricating oil pressure 3 out of 2>MIN3 (40%) output relay; K11-DC lubricating oil pump power supply normal output relay; K12-AC lubricating oil pump / top shaft oil pump double position relay; K13-controller working normally output relay; K14-lubricating oil pressure 3 out of 2>MIN3 (40%) output relay; K15-auxiliary lubricating oil pump start output relay; K15-top shaft oil pump start output relay; TCS-turbine control system. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this document.

[0027] Method Example

[0028] According to an embodiment of the present invention, a method for restarting a steam turbine lubricating oil system is provided. Figure 1 This is a flow chart of a method for restarting a steam turbine lubricating oil system according to an embodiment of the present invention. Figure 1 As shown, a method for restarting a steam turbine lubricating oil system according to an embodiment of the present invention includes:

[0029] S1. Real-time monitoring of lubricating oil main pipe pressure via three independent lubricating oil pressure sensors, and determination of whether the lubricating oil pressure is normal using a preset two-out-of-three judgment logic;

[0030] The three-out-of-two judgment logic is specifically: when the detection values ​​of at least two lubricating oil pressure sensors are lower than the preset threshold MIN3, it is determined that the lubricating oil pressure is abnormal. Figure 2 The diagram shows a schematic diagram of lubricating oil pressure monitoring using a 2-out-of-3 judgment logic according to an embodiment of the present invention. The MIN3 threshold is 40% of the rated oil pressure, and a 500ms delay judgment time is set.

[0031] S2. Connect a two-position mechanical latching relay in series with the starting circuit of the DC lubricating oil pump. The normally open contact of the two-position mechanical latching relay is connected in series with the normally closed contact of the lubricating oil low pressure. When the lubricating oil pressure is abnormal, the normally closed contact of the low pressure is closed, and the DC lubricating oil pump is directly started through the hard-wired circuit.

[0032] The two-position mechanical locking relay is set to keep its normally open contact closed by a sequential control instruction when the system is operating normally.

[0033] Figure 3 This is a logic diagram for starting a DC lubricating oil pump relay according to an embodiment of the present invention. The electrical connection method of the hard-wired circuit is as follows: the positive pole of the DC power supply is connected in sequence to the normally open contact of the two-position mechanical latching relay, the normally closed contact of the lubricating oil low voltage, and the coil of the DC oil pump starting relay, and then returns to the negative pole of the DC power supply to form a complete DC oil pump starting control circuit.

[0034] S3. An interlocking logic consisting of a two-position relay, a controller status relay, and a pressure signal relay is set in the electrical starting circuit of the auxiliary oil pump and the jacking oil pump. When the factory power is restored, the auxiliary oil pump and the jacking oil pump are automatically started through the coordinated action of the interlocking relay group.

[0035] The connection method of the interlock relay group is as follows: the coil of the double-position relay is controlled by the controller instruction; the coil of the controller status relay is connected to the controller heartbeat signal; the coil of the pressure signal relay is connected to the three-out-of-two signal of the lubricating oil pressure; the normally open contacts of the three are connected in series and then connected to the starting circuit of the auxiliary oil pump and the top shaft oil pump.

[0036] Figure 4 This is the auxiliary lubricating oil pump / top shaft oil pump relay starting logic diagram of an embodiment of the present invention. When the factory power is restored, the specific process of automatically starting the auxiliary oil pump and the top shaft oil pump through the coordinated action of the interlocking relay group is as follows: when the controller status relay detects that the controller heartbeat signal is normal and the lubricating oil pressure three-out-of-two signal meets the conditions, the normally open contacts of the interlocking relay group are closed, triggering the starting circuit of the auxiliary oil pump and the top shaft oil pump to be energized, thereby realizing automatic start.

[0037] A specific implementation process of the embodiment of the present invention is as follows:

[0038] After the controller is programmed with the lubricating oil sequence control logic, the startup steps include:

[0039] Start the exhaust fan, and the pre-selected exhaust fan starts and proceeds to the next step;

[0040] Start the two AC lubricating oil pumps at the same time. When the lubricating oil main pipe pressure is greater than 60%, proceed to the next step.

[0041] Start the AC lubricating oil pump, the DC lubricating oil pump software interlocks, sends the DC lubricating oil pump double-position relay setting instruction, and proceeds to the next step after receiving feedback;

[0042] Automatically stop a standby AC lubricating oil pump, send the auxiliary oil pump / top shaft oil pump double-position relay setting instruction, and proceed to the next step after receiving feedback, and the sequential control startup is completed.

[0043] The stopping steps include:

[0044] Release the software interlock of the AC lubricating oil pump and the DC lubricating oil pump, send a reset command for the DC lubricating oil pump two-position relay and the auxiliary oil pump / jacking oil pump two-position relay, stop the AC lubricating oil pump, and proceed to the next step after receiving feedback;

[0045] Stop the exhaust fan;

[0046] Sequential control stop is completed.

[0047] Monitor the status of the controller and program Figure 5 The controller shown works fine logic, as well as Figure 2 The logic shown is that two out of three lubricating oil pressures are higher than MIN3.

[0048] Hardware includes:

[0049] Install a double-position mechanical locking relay (K5) in the lubricating oil control cabinet and connect the pressure signal and start circuit according to the logic diagram.

[0050] Interlock relays (K12-K14) are added to the auxiliary oil pump and top shaft oil pump control circuits to achieve automatic switching.

[0051] Build the relay logic according to the diagram. The specific connection method is as follows Figure 3 、 Figure 4 、 Figure 5 and Figure 6 shown.

[0052] The controller's normal logic monitors the controller's operating status, ensuring that when the control system returns to normal, the interlock logic is triggered to automatically start the auxiliary oil pump and the jacking oil pump. The heartbeat signal is used to determine whether the controller is operating normally.

[0053] Figure 6 This is a schematic diagram of the interface between the auxiliary lubricating oil pump and top shaft oil pump start-up instructions and the MCC in an embodiment of the present invention. It shows the actual connection method between the relay logic and the motor control center (MCC), ensuring that the start-up instructions can be accurately transmitted to the auxiliary oil pump and top shaft oil pump to complete the automatic start-up process.

[0054] By adopting the embodiments of the present invention, the following beneficial effects are achieved:

[0055] Lubricating oil pressure is monitored using a two-out-of-three judgment logic to avoid misjudgment of single sensor failures and ensure accurate pressure monitoring. The DC lubricating oil pump's hard-wired start-up design allows for rapid and direct startup in the event of pressure anomalies, enhancing the system's emergency response capabilities. Interlocking logic automatically controls the start-up of the auxiliary and jacking oil pumps, enabling intelligent restart after plant power is restored. The system's modules collaborate to ensure stable operation of the lubricating oil system, reduce the risk of turbine failures due to lubricating oil problems, and improve equipment reliability and safety. Sequential control logic also optimizes the system startup process and enhances system automation.

[0056] System Example

[0057] According to an embodiment of the present invention, a steam turbine lubricating oil system restart system is provided. The steam turbine lubricating oil system restart system according to an embodiment of the present invention includes:

[0058] The pressure monitoring module consists of three independently set lubricating oil pressure sensors, which are installed in different sections of the lubricating oil main pipe. They are used to collect lubricating oil pressure signals in real time and transmit the signals to the control processing module;

[0059] The emergency start module includes a two-position mechanical latching relay and a lubricating oil low-pressure normally closed contact. The two are connected in series and connected to the starting circuit of the DC oil pump. The coil of the two-position mechanical latching relay is connected to the set command output terminal of the controller, and the lubricating oil low-pressure normally closed contact is connected to the three-out-of-two logic output terminal of the lubricating oil pressure.

[0060] The automatic recovery module includes a two-position relay, a controller status relay, and a pressure signal relay. The normally open contacts of the three are connected in series and then connected to the starting circuits of the auxiliary oil pump and the top shaft oil pump. Among them, the coil of the two-position relay is connected to the set instruction output terminal of the controller; the coil of the controller status relay is connected to the heartbeat signal output terminal of the controller; and the coil of the pressure signal relay is connected to the three-out-of-two logic output terminal of the lubricating oil pressure.

[0061] Control processing module: used to execute three-out-of-two pressure judgment logic, and output double-position relay setting and reset instructions, controller status monitoring instructions and auxiliary oil pump jacking oil pump start instructions. Its hardware carrier is the controller of the turbine control system.

[0062] The hard-wired circuit of the emergency start module is also connected in series with the normally open contact of the DC oil pump power normal relay. The coil of the DC oil pump power normal relay is connected to the 220VDC power circuit of the DC oil pump, and is used to close the start circuit when the DC power supply is normal.

[0063] The control processing module is also used to execute the sequential control logic of the lubricating oil system, including:

[0064] Start the exhaust fan and AC lubricating oil pump in sequence, and switch on and off the DC lubricating oil pump software interlock when the lubricating oil main pipe pressure is greater than 60% of the rated pressure;

[0065] Send the set and reset instructions for the two-position mechanical latching relay and the two-position relay. The set instruction is used to close the normally open contact of the two-position relay when the sequence control is started, and the reset instruction is used to restore the relay to its initial state when the system is operating normally.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for restarting a steam turbine lubricating oil system, characterized in that include: Three independent lubricating oil pressure sensors monitor the lubricating oil main pipe pressure in real time, and a preset two-out-of-three judgment logic is used to determine whether the lubricating oil pressure is normal; A two-position mechanical latching relay is connected in series to the starting circuit of the DC lubricating oil pump. The normally open contact of the two-position mechanical latching relay is connected in series with the normally closed contact of the lubricating oil low pressure. When the lubricating oil pressure is abnormal, the normally closed contact of the low pressure is closed, and the DC lubricating oil pump is directly started through the hard-wired circuit. An interlocking logic consisting of a two-position relay, a controller status relay, and a pressure signal relay is set in the electrical starting circuit of the auxiliary oil pump and the jacking oil pump. When the factory power is restored, the auxiliary oil pump and the jacking oil pump are automatically started through the coordinated action of the interlocking relay group.

2. The method according to claim 1, characterized in that The two-out-of-three judgment logic is specifically: when the detection values ​​of at least two lubricating oil pressure sensors are lower than the preset threshold MIN3, it is determined that the lubricating oil pressure is abnormal.

3. The method according to claim 1, characterized in that The MIN3 threshold is 40% of the rated oil pressure, and a delay judgment time of 500ms is set.

4. The method according to claim 1, wherein The two-position mechanical locking relay is set to keep its normally open contact closed by a sequential control instruction when the system is operating normally.

5. The method according to claim 1, wherein The connection method of the interlock relay group is as follows: the coil of the double-position relay is controlled by the controller instruction; the coil of the controller status relay is connected to the controller heartbeat signal; the coil of the pressure signal relay is connected to the three-out-of-two signal of the lubricating oil pressure; the normally open contacts of the three are connected in series and then connected to the starting circuit of the auxiliary oil pump and the top shaft oil pump.

6. The method according to claim 1, characterized in that The electrical connection method of the hard-wired circuit is as follows: the positive pole of the DC power supply is connected in sequence to the normally open contact of the double-position mechanical latching relay, the normally closed contact of the lubricating oil low voltage, and the coil of the DC oil pump starting relay, and then returns to the negative pole of the DC power supply to form a complete DC oil pump starting control circuit.

7. The method according to claim 1, characterized in that The specific process of automatically starting the auxiliary oil pump and the jacking oil pump through the coordinated action of the interlock relay group when the auxiliary power is restored is as follows: When the controller status relay detects that the controller heartbeat signal is normal and the lubricating oil pressure three-out-of-two signal meets the conditions, the normally open contacts of the interlock relay group are closed, triggering the auxiliary oil pump and top shaft oil pump starting circuit to energize, realizing automatic start.

8. A steam turbine lubricating oil system restarting system based on the steam turbine lubricating oil system restarting method according to any one of claims 1 to 7, characterized in that: include: The pressure monitoring module consists of three independently set lubricating oil pressure sensors, which are installed in different sections of the lubricating oil main pipe. They are used to collect lubricating oil pressure signals in real time and transmit the signals to the control processing module; The emergency start module includes a two-position mechanical latching relay and a lubricating oil low-pressure normally closed contact. The two are connected in series and connected to the starting circuit of the DC oil pump. The coil of the two-position mechanical latching relay is connected to the set command output terminal of the controller, and the lubricating oil low-pressure normally closed contact is connected to the three-out-of-two logic output terminal of the lubricating oil pressure. The automatic recovery module includes a two-position relay, a controller status relay, and a pressure signal relay. The normally open contacts of the three are connected in series and then connected to the starting circuits of the auxiliary oil pump and the top shaft oil pump. Among them, the coil of the two-position relay is connected to the set instruction output terminal of the controller; the coil of the controller status relay is connected to the heartbeat signal output terminal of the controller; and the coil of the pressure signal relay is connected to the three-out-of-two logic output terminal of the lubricating oil pressure. Control processing module: used to execute three-out-of-two pressure judgment logic, and output double-position relay setting and reset instructions, controller status monitoring instructions and auxiliary oil pump jacking oil pump start instructions. Its hardware carrier is the controller of the turbine control system.

9. The system according to claim 8, characterized in that The hard-wired circuit of the emergency start module is also connected in series with the normally open contact of the DC oil pump power normal relay. The coil of the DC oil pump power normal relay is connected to the 220VDC power circuit of the DC oil pump, and is used to close the start circuit when the DC power supply is normal.

10. The system according to claim 8, wherein: The control processing module is also used to execute the sequential control logic of the lubricating oil system, including: Start the exhaust fan and AC lubricating oil pump in sequence, and switch on and off the DC lubricating oil pump software interlock when the lubricating oil main pipe pressure is greater than 60% of the rated pressure; Send the set and reset instructions for the two-position mechanical latching relay and the two-position relay. The set instruction is used to close the normally open contact of the two-position relay when the sequence control is started, and the reset instruction is used to restore the relay to its initial state when the system is operating normally.

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