Gas turbine parallel steam side high-pressure bypass pressure control system and method

Abstract

The invention discloses a gas turbine parallel steam side high-pressure bypass pressure control system and method. The system comprises a non-module, a first switching module, an AND module, a second switching module, a multiplication module, a large selection module, a rate limiting module and a small selection module. The method comprises the steps that when a second parallel steam electric valve is fully opened to be '1' and a first parallel steam electric valve is fully opened to be '1', the output of a first switching module is 0.5, multiplication calculation is conducted on the output value of the front pressure of a second high-pressure parallel steam valve, and after numerical optimization of a large selection module, a rate limiting module and a small selection module is conducted, a bypass pressure set value is obtained. The problems that the effect of the steam merging process at the initial stage of unit starting is poor, and control over all parameters is unstable are solved, pressure and temperature are kept stable in the unit starting operation process, and safe and efficient operation of the unit is ensured.

Description

Technical Field

[0001] The invention belongs to the field of intelligent control of thermal power plants, and in particular relates to a control system and method for a high-pressure bypass pressure on the steam-combined side of a combustion engine. Background Art

[0002] The high-pressure bypass control in the process of gas turbine steam connection is realized through high-pressure, medium-pressure and low-pressure bypass systems. Especially in the "two-to-one" combined cycle unit, this control method helps to maintain the stability of pressure and temperature during startup, operation and shutdown, ensuring the safe and efficient operation of the unit. In practical applications, the pressure control of the high-pressure bypass also needs to consider the start-up and shutdown sequence of the unit. For the "two-to-one" unit, it will switch from one-to-one operation to two-to-one operation during startup, and vice versa during shutdown. These operations need to be completed with the help of the bypass system, and the bypass fast opening function needs to be guaranteed, especially under high load conditions. If the turbine protection action occurs, the bypass needs to be opened quickly to transfer the steam flow, and the pressure stability of the bypass system needs to be taken into account. However, because the operation of each system in the process of gas turbine steam connection is complex and the parameter fluctuations are large, the pressure control is very likely to rise or fall suddenly. Therefore, it is very important to stabilize the control of the high-pressure bypass pressure on the gas turbine steam connection side. Summary of the invention

[0003] The purpose of the present invention is to provide a high-pressure bypass pressure control system and method on the steam-connected side of a gas turbine, so as to solve the problems of poor steam connection effect and unstable control of various parameters in the initial stage of unit startup, maintain the stability of pressure and temperature during the startup and operation of the unit, and ensure the safe and efficient operation of the unit.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] The present invention provides a high-pressure bypass pressure control system for a gas turbine steam-side, comprising a negation module, a first switching module, an AND module, a second switching module, a multiplication module, a large selection module, a rate limiting module and a small selection module;

[0006] The output end of the non-module is connected to the input end of the AND module, the output end of the AND module is connected to the input end of the second switching module, the output end of the second switching module and the output end of the first switching module are both connected to the input end of the multiplication module, the output end of the multiplication module and the output end of the rate limiting module are both connected to the input end of the general election module, the output end of the general election module is connected to the input end of the rate limiting module, and the output end of the rate limiting module is connected to the input end of the small selection module.

[0007] A further improvement of the present invention is that the input end of the non-module is connected to a switch input signal of the fully open No. 2 parallel steam electric valve.

[0008] A further improvement of the present invention is that a switch quantity input signal of fully opening the No. 1 parallel steam electric valve is also connected to the input end of the module.

[0009] A further improvement of the present invention is that the input end of the second switching module is also connected to the analog value of the pressure before the No. 1 high-pressure steam-combining valve and the analog value of the pressure before the No. 2 high-pressure steam-combining valve.

[0010] A further improvement of the present invention is that the input end of the first switching module is connected to the switch input signal of the fully open No. 2 parallel steam electric valve, the analog input signal when the set value is 0.5, and the analog input signal when the set value is 0.

[0011] A further improvement of the present invention is that the input end of the small selection module is also connected to an analog input signal of a maximum pressure setting value, and the output end of the small selection module is connected to a high-pressure bypass pressure setting control value.

[0012] The present invention also provides a method for controlling the high-pressure bypass pressure on the steam-assisted side of a gas turbine. The method is based on the above-mentioned high-pressure bypass pressure control system on the steam-assisted side of a gas turbine, and comprises:

[0013] When the No. 2 steam-parallel electric valve is fully open to "1" and the No. 1 steam-parallel electric valve is fully open to "1", the output of the first switching module is 0.5, and it is multiplied by the output value of the pressure before the No. 2 high-pressure steam-parallel valve. After numerical optimization of the large selection module, the rate limiting module and the small selection module, the bypass pressure setting value is obtained.

[0014] A further improvement of the present invention is that it also includes:

[0015] When the No. 2 steam-parallel electric valve is fully open to "0" and the No. 1 steam-parallel electric valve is fully open to "1", the output of the first switching module is 0, and it is multiplied by the output value of the pressure before the No. 1 high-pressure steam-parallel valve. After numerical optimization of the large selection module, the rate limiting module and the small selection module, the bypass pressure setting value is obtained.

[0016] A further improvement of the present invention is that it also includes:

[0017] When the No. 2 steam-parallel electric valve is fully open to "1" and the No. 1 steam-parallel electric valve is fully open to "0", the output of the first switching module is 0.5, which is multiplied by the output value of the pressure before the No. 2 high-pressure steam-parallel valve. After numerical optimization of the large selection module, the rate limiting module and the small selection module, the bypass pressure setting value is obtained.

[0018] A further improvement of the present invention is that it also includes:

[0019] When the No. 2 steam parallel electric valve is fully opened to "0" and the No. 1 steam parallel electric valve is fully opened to "0", the bypass setting value will automatically follow the maximum pressure setting value to keep the pressure on both sides of the turbine equal.

[0020] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0021] The high-pressure bypass pressure control system on the steam-connected side of a gas turbine provided by the present invention adopts a control logic system to present the technical route of the present invention. The system can be deployed and developed in the industrial control systems of various manufacturers in power plants. The system includes four control modes, which effectively solves the problems of inaccurate control strategy judgment and incomplete system deployment modules in this field, realizes the application objectives of various functional modules, and presents the process flow and operation methods of the gas turbine steam-connected process to the operating personnel in a more complete manner, which can serve the on-site operating personnel in research and development and application.

[0022] The method for controlling the high-pressure bypass pressure on the steam-to-gas side of a gas turbine provided by the present invention adopts a method combining four control modes to ensure the stability of the high-pressure bypass pressure on the steam-to-gas side of the gas turbine, while taking into account the judgment of the current working state of the electric valve on the steam-to-gas side. Respectively: in mode one, the No. 1 steam-to-gas electric valve is fully open and the No. 2 steam-to-gas electric valve is fully open; in mode two, the No. 1 steam-to-gas electric valve is fully open and the No. 2 steam-to-gas electric valve is closed; in mode three, the No. 1 steam-to-gas electric valve is closed and the No. 2 steam-to-gas electric valve is opened; in mode four, the No. 1 steam-to-gas electric valve is closed and the No. 2 steam-to-gas electric valve is closed. Taking into full consideration the regularity of the bypass pressure under various working conditions, the methods of each mode can also be flexibly combined and matched, which is applicable to various types of gas turbines, ensuring the accuracy of the control of the present invention.

[0023] In summary, the high-pressure bypass pressure control system and method on the steam-connected side of a gas turbine described in the present invention solve the problems of poor steam-connected process in the initial stage of unit startup and unstable control of various parameters, maintain pressure and temperature stability during the startup and operation of the unit, and ensure safe and efficient operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a control principle diagram of a high-pressure bypass pressure control system on the steam side of a combustion engine.

[0025] Description of reference numerals:

[0026] 001 means the No. 2 steam-parallel electric valve is fully open, 002 means the No. 1 steam-parallel electric valve is fully open, 003 means the set value is 0.5, 004 means the set value is 0, 005 means the pressure before the No. 1 high-pressure steam-parallel valve, 006 means the pressure before the No. 2 high-pressure steam-parallel valve, 007 means the maximum pressure setting value, 008 means the non-module, 009 means the first switching module, 010 means the AND module, 011 means the second switching module, 012 means the multiplication module, 013 means the large selection module, 014 means the rate limiting module, 015 means the small selection module, and 016 means the high-pressure bypass pressure setting control value. DETAILED DESCRIPTION

[0027] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0028] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0029] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0032] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0033] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0034] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0035] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] Example 1

[0038] like Figure 1 As shown, the present embodiment provides a control system for the high-pressure bypass pressure of the steam-connected side of a gas turbine, comprising a non-module 008, a first switching module 009, an AND module 010, a second switching module 011, a multiplication module 012, a general election module 013, a rate limiting module 014 and a small selection module 015; the output end of the non-module 008 is connected to the input end of the AND module 010, the output end of the AND module 010 is connected to the input end of the second switching module 011, the output end of the second switching module 011 and the output end of the first switching module 009 are both connected to the input end of the multiplication module 012, the output end of the multiplication module 012 and the output end of the rate limiting module 014 are both connected to the input end of the general election module 013, the output end of the general election module 013 is connected to the input end of the rate limiting module 014, and the output end of the rate limiting module 014 is connected to the input end of the small selection module 015.

[0039] In this embodiment, the input end of the non-module 008 is connected to the switch input signal of the No. 2 parallel steam electric valve fully open 001.

[0040] In this embodiment, the input end of the module 010 is also connected to the switch input signal of the No. 1 parallel steam electric valve fully open 002.

[0041] In this embodiment, the input end of the second switching module 011 is also connected to the analog value of the pressure 005 before the No. 1 high-pressure steam-combining valve and the analog value of the pressure 006 before the No. 2 high-pressure steam-combining valve.

[0042] In this embodiment, the input end of the first switching module 009 is connected to the switch input signal 001 of the No. 2 parallel steam electric valve fully open, the analog input signal 003 when the setting value is 0.5, and the analog input signal 004 when the setting value is 0.

[0043] In this embodiment, the input end of the selection module 015 is also connected to the analog input signal of the maximum pressure setting value 007, and the output end of the small selection module 015 is connected to the high-pressure bypass pressure setting control value 016.

[0044] In this embodiment, a control logic system is used to present the technical route of the present invention. The system can be deployed and developed in the industrial control systems of various manufacturers in power plants. The system includes four control modes, which effectively solves the problems of inaccurate control strategy judgment and incomplete system deployment modules in this field, realizes the application goals of each functional module, and presents the process flow and operation methods of the gas turbine steam paralleling process to the operating personnel in a more complete way, which can serve the on-site operating personnel in research and development and application.

[0045] Example 2

[0046] like Figure 1 As shown, this embodiment provides a high-pressure bypass pressure control system for the steam-side of a gas turbine, comprising:

[0047] 1) Add the automatic control strategy of the bypass in the steam connection and steam removal process. When the steam connection or steam removal is manually operated, the bypass of the steam turbine can still be in the automatic state. The operator can efficiently complete the steam connection or steam removal of the unit by operating the steam connection electric valve, which reduces the time consumption of steam connection and steam removal.

[0048] 2) Figure 1 Schematic diagram of high-pressure bypass pressure control on the steam side of the gas turbine.

[0049] Specifically, it includes: No. 2 steam-parallel electric valve fully open 001, No. 1 steam-parallel electric valve fully open 002, set value is 0.5 003, set value is 0 004, No. 1 high-pressure steam-parallel valve front pressure 005, No. 2 high-pressure steam-parallel valve front pressure 006, maximum pressure setting value 007, non-module 008, first switching module 009, and module 010, second switching module 011, multiplication module 012, large selection module 013, rate limiting module 014, small selection module 015 and high-pressure bypass pressure setting control value 016.

[0050] Figure 1 The control strategy logic diagram includes: the switch input signal of the No. 2 steam parallel electric valve fully open 001 is connected to the input end of the non-module 008, the switch input signal of the No. 1 steam parallel electric valve fully open 002 and the output end of the non-module 008 are connected to the input end of the module 010. The output end of the module 010 is connected to the input end "S" of the second switching module 011, the analog input end of the No. 1 high-pressure steam parallel valve front pressure 005 is connected to the input end "PV1" of the second switching module 011, and the analog input end of the No. 2 high-pressure steam parallel valve front pressure 006 is connected to the input end "PV2" of the second switching module 011. The switch input signal of the No. 2 steam parallel electric valve fully open 001 is connected to the input end "S" of the first switching module 009, the analog input signal of 003 is connected to the input end "PV1" of the first switching module 009 when the setting value is 0.5, and the analog input signal of 004 ​​is connected to the input end "PV2" of the first switching module 009 when the setting value is 0. The output end of the second switching module 011 and the output end of the first switching module 009 are both connected to the input end of the multiplication module 012. The output end of the multiplication module 012 and the output end of the rate limiting module 014 are both connected to the input end of the general selection module 013, the output end of the general selection module 013 is connected to the input end of the rate limiting module 014, and the output end of the rate limiting module 014 and the analog input signal of the maximum pressure setting value 007 are both connected to the input end of the small selection module 015. The output end of the small selection module 015 is connected to the high-pressure bypass pressure setting control value 016.

[0051] Example 3

[0052] like Figure 1 As shown, this embodiment provides a method for controlling the high-pressure bypass pressure of a gas turbine steam-assisted side, comprising:

[0053] Control mode 1: When the No. 2 steam parallel electric valve is fully open 001 is "1" and the No. 1 steam parallel electric valve is fully open 002 is "1", the output of the first switching module 009 is 0.5, and it is multiplied by the output value of the No. 2 high-pressure steam parallel valve front pressure 006, and then the bypass pressure setting value is obtained through rate limiting, large selection mode and small selection mode numerical optimization. The bypass setting value can automatically follow the current operating pressure to keep the pressure on both sides of the turbine basically the same.

[0054] Control mode 2: When the No. 2 steam parallel electric valve is fully open 001 is "0" and the No. 1 steam parallel electric valve is fully open 002 is "1", the output of the first switching module 009 is 0, and it is multiplied by the output value of the No. 1 high-pressure parallel valve front pressure 005, and then the bypass pressure setting value is obtained through rate limiting, large selection mode and small selection mode numerical optimization. The bypass setting value can automatically follow the maximum pressure setting value 007 or the pressure value at the previous moment to keep the pressure on both sides of the turbine basically the same.

[0055] Control mode three: When the No. 2 steam parallel electric valve is fully open 001 is "1" and the No. 1 steam parallel electric valve is fully open 002 is "0", the output of the first switching module 009 is 0.5, and it is multiplied by the output value of the No. 2 high-pressure parallel valve front pressure 006, and then the bypass pressure setting value is obtained through rate limiting, large selection mode and small selection mode numerical optimization. The bypass setting value can automatically follow the maximum pressure setting value 007 or the pressure value at the previous moment to keep the pressure on both sides of the turbine basically the same.

[0056] Control mode 4: When the No. 2 steam parallel electric valve is fully opened 001 is "0" and the No. 1 steam parallel electric valve is fully opened 002 is "0", the bypass set value will automatically follow the maximum pressure set value 007 to keep the pressure on both sides of the turbine equal.

[0057] In this embodiment, a method combining four control modes is adopted to ensure the stability of the high-pressure bypass pressure on the steam side of the gas turbine, while taking into account the judgment of the current working state of the electric valve on the steam side. Respectively: Mode 1, the No. 1 steam electric valve is fully open and the No. 2 steam electric valve is fully open; Mode 2, the No. 1 steam electric valve is fully open and the No. 2 steam electric valve is closed; Mode 3, the No. 1 steam electric valve is closed and the No. 2 steam electric valve is opened; Mode 4, the No. 1 steam electric valve is closed and the No. 2 steam electric valve is closed. Taking into account the regularity of the bypass pressure under various working conditions, the methods of each mode can also be flexibly combined and matched, which is applicable to various types of gas turbines, ensuring the accuracy of the control of the present invention.

[0058] Example 4

[0059] The simulation shows that the No. 1 gas turbine is already running, and the operating parameters of the steam connection process after the No. 2 gas turbine is started. After the application of the present invention, the operating conditions of the unit pressure and temperature parameters are good, and the bypass control effect is stable.

[0060]

[0061] Example 5

[0062] The simulation shows that the No. 1 gas turbine is already running, and the No. 2 gas turbine is started. The operating parameters of the steam connection process are simulated. After the present invention is applied, the operating conditions of the temperature after the steam connection electric valve and the bypass valve opening parameters of the unit are good, and the bypass control effect is stable.

[0063]

[0064]

[0065] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0066] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A high-pressure bypass pressure control system for a gas turbine steam-assisted side, characterized in that: It includes a non-module (008), a first switching module (009), an AND module (010), a second switching module (011), a multiplication module (012), a general election module (013), a rate limiting module (014) and a small election module (015); The output end of the non-module (008) is connected to the input end of the AND module (010), the output end of the AND module (010) is connected to the input end of the second switching module (011), the output end of the second switching module (011) and the output end of the first switching module (009) are both connected to the input end of the multiplication module (012), the output end of the multiplication module (012) and the output end of the rate limiting module (014) are both connected to the input end of the general election module (013), the output end of the general election module (013) is connected to the input end of the rate limiting module (014), and the output end of the rate limiting module (014) is connected to the input end of the small selection module (015).

2. A gas turbine steam-side high-pressure bypass pressure control system according to claim 1, characterized in that: The input end of the non-module (008) is connected to the switch input signal of the No. 2 steam electric valve fully open (001).

3. A gas turbine steam-side high-pressure bypass pressure control system according to claim 2, characterized in that: The input end of the module (010) is also connected to a switch input signal of the No. 1 parallel steam electric valve fully open (002).

4. A gas turbine steam-side high-pressure bypass pressure control system according to claim 3, characterized in that: The input end of the second switching module (011) is also connected to the analog value of the pressure (005) before the No. 1 high-pressure steam valve and the analog value of the pressure (006) before the No. 2 high-pressure steam valve.

5. A gas turbine steam-side high-pressure bypass pressure control system according to claim 4, characterized in that: The input end of the first switching module (009) is connected to the switch input signal of the No. 2 parallel steam electric valve fully open (001), the analog input signal when the setting value is 0.5 (003), and the analog input signal when the setting value is 0 (004).

6. A gas turbine steam-side high-pressure bypass pressure control system according to claim 5, characterized in that: The input end of the small selection module (015) is also connected to the analog input signal of the maximum pressure setting value (007), and the output end of the small selection module (015) is connected to the high-pressure bypass pressure setting control value (016).

7. A method for controlling the high-pressure bypass pressure on the steam-assisted side of a gas turbine, characterized in that: The method is based on a high-pressure bypass pressure control system on the steam side of a gas turbine as described in claim 6, comprising: When the No. 2 steam-connecting electric valve is fully open (001) to "1" and the No. 1 steam-connecting electric valve is fully open (002) to "1", the output of the first switching module (009) is 0.5, and is multiplied by the output value of the pressure before the No. 2 high-pressure steam-connecting valve (006), and then the bypass pressure setting value is obtained through numerical optimization of the large selection module (013), the rate limiting module (014) and the small selection module (015).

8. A method for controlling high-pressure bypass pressure on the steam-assisted side of a gas turbine according to claim 7, characterized in that: Also includes: When the No. 2 steam-parallel electric valve is fully open (001) to "0" and the No. 1 steam-parallel electric valve is fully open (002) to "1", the output of the first switching module (009) is 0, and is multiplied by the output value of the pressure before the No. 1 high-pressure steam-parallel valve (005), and then the bypass pressure setting value is obtained through numerical optimization of the large selection module (013), the rate limiting module (014) and the small selection module (015).

9. A method for controlling high-pressure bypass pressure on the steam-assisted side of a gas turbine according to claim 8, characterized in that: Also includes: When the No. 2 steam-connecting electric valve is fully open (001) to "1" and the No. 1 steam-connecting electric valve is fully open (002) to "0", the output of the first switching module (009) is 0.5, which is multiplied by the output value of the pressure before the No. 2 high-pressure steam-connecting valve (006), and then the bypass pressure setting value is obtained through numerical optimization of the large selection module (013), the rate limiting module (014) and the small selection module (015).

10. A method for controlling high-pressure bypass pressure on the steam-assisted side of a gas turbine according to claim 9, characterized in that: Also includes: When the No. 2 steam parallel electric valve is fully open (001) to "0" and the No. 1 steam parallel electric valve is fully open (002) to "0", the bypass set value will automatically follow the maximum pressure set value (007) to keep the pressure on both sides of the turbine equal.

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