JPS5838305A - 2-stage reheat turbine - Google Patents

Abstract

PURPOSE:To shorten a time which starts from a boiler ignition and ends to a turbine draft and to reduce a life consumption rate due to the thermal stress of the turbine, by a method wherein, by the aid of a bypass pipe, steam is charged to a reheater before a turbine draft. CONSTITUTION:An inlet side of a super heater 5 is connected to a first low-temperature reheat pipe 9 with a low-temperature superhigh-pressure turbine bypass valve 23, and a main steam pipe 6 to a first high-temperature reheat pipe 11 with a high-temperature superhigh-pressure turbine. The first low-temperature reheat pipe 9 is connected to a second low-temperature reheat pipe 14 with a low-temperature high-pressure turbine bypass valve 27, and the first high-temperature reheat pipe 11 to a second high-temperature reheat pipe 16 with a high- temperature high-pressure turbine bypass valve 29. Additionally, the second high- temperature reheat pipe 16 is connected to a condenser 19 with a low-pressure turbine bypass valve 31 and a temperature reducer 32. As noted above, a turbine can be cooled by supplying steam to a first reheat 10 and a second reheater 15, and this permits shortening of a time which starts from a boiler ignition and ends to a turbine draft.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for converting exhaust gas from, for example, an ultra-high pressure turbine into
The present invention relates to a two-stage reheat turbine in which exhaust gas is reheated by a reheater and supplied to a high-pressure turbine, and exhaust gas from the high-pressure turbine is reheated by a second reheater and supplied to an intermediate-pressure turbine.

FIG. 1 is a system diagram of a conventional two-stage reheat turbine, in which the steam turbines include an ultra-high pressure turbine 1, a high-pressure turbine 2,
The boiler is composed of an intermediate pressure turbine 3 and four low pressure turbines, and the steam superheated in the superheater 5 of the boiler passes through the main steam pipe 6, the main steam stop valve 7, and the steam control valve 8 before being sent to the ultra-high pressure turbine. It is vented before being vented, and after doing its work there, it is sent to the first reheater 10 through the first low-temperature reheating tube 9. The steam reheated in the first reheater 1o is transferred from the first high temperature reheat pipe 11 to the first reheat steam stop valve ball and the first intercept valve 13.
The steam is supplied to the high-pressure turbine 2 through the steam, and after performing work there, is sent to the second reheater 15 through the second low-temperature reheat pipe 14, and is further reheated in the second reheater 15. Pass through the second high temperature reheat pipe 16 #! The steam is sequentially supplied to the intermediate pressure turbine 3 and the low pressure turbine 4 through the second reheat steam valve 17 and the second intercept valve 18. The steam that has worked in the low pressure turbine 4 is sent to the condenser 19.

On the other hand, on the upstream side or downstream side of the superheater 5 of the boiler, a starting bypass pipe 2ja or ηb having a starting bypass valve 20 & or 20b and a desuperheater 21 is installed to
9 until the steam from the boiler reaches conditions suitable for turbine ventilation when starting the turbine.
The steam is led to the condensate @19 via the startup bypass pipe 22 & or 22bt.

By the way, in general, when the turbine ventilation conditions are the same, the time from boiler ignition to turbine ventilation becoming possible becomes shorter as the amount of boiler fuel input is larger.

However, in the above-mentioned conventional device, as mentioned above, steam does not flow into the first reheater 10 and the second reheater 15 before the turbine is vented. The amount of fuel input is limited in order to prevent overheating of the heater 15, and therefore the time from boiler ignition to turbine ventilation is also limited. Therefore, during intermediate load operation that involves frequent startups and shutdowns, it takes a long time to complete the startup, and if the turbine is ventilated before the optimal ventilation conditions to save time, the turbine There are problems such as an increase in the life consumption rate due to thermal stress.

1--H In view of these points, the present invention is designed to cool the first reheater and the second reheater by flowing steam even before the turbine is vented, and to improve the boiler ignition. It is an object of the present invention to provide a two-stage reheat turbine that can shorten the time from start to turbine ventilation and reduce the life consumption rate of the turbine due to thermal stress.

Another object of the present invention is to provide boiler F, CBfp
When transitioning to in-plant standalone operation, or when the load is interrupted, the steam in the superheater is transferred to the first reheater, the steam in the first reheater is transferred to the second reheater, and the steam in the second reheater is transferred to the second reheater. The superheater, the first reheater, the second
It is an object of the present invention to provide a two-stage reheat turbine which is capable of suppressing pressure rise in each reheater and suppressing disturbance to boiler control.

Still another object of the present invention is to provide a two-stage reheat turbine capable of preventing overheating of the ultra-high pressure turbine and the high-pressure turbine during extremely low flow rate operation at startup.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a system diagram of the two-stage reheat turbine of the present invention, in which superheated steam flowing out from the superheater 5 of the boiler flows into the ultra-high pressure turbine 1 through the main steam stop valve 7 and the steam control valve 8, where it flows into the ultra-high pressure turbine 1. work, then the first low temperature reheat tube 9″1Sl
- is sent to the first reheater 10 to be reheated, and further supplied to the high pressure turbine 2 via the first reheat steam stop valve 12 and the first intercept valve 13. The above high pressure turbine 2
The steam that has been supplied to and performed work there is sent to the second reheater 15 through the second low-temperature reheat pipe 14, and the reheated steam is transferred to the second reheater 15.
The steam is sequentially supplied to the intermediate pressure turbine 3 and the low pressure turbine 4 via the reheat steam stop valve 17 and the second intercept valve 18, and then sent to the condenser 19.

These configurations are exactly the same as the conventional two-stage reheat turbine, but in the present invention, the inlet side of the superheater 5 and! ! The main steam pipe 6 and the first high temperature reheat pipe 11 are connected to each other through a first bypass line 24 having a low temperature ultra-high pressure turbine bypass valve n, and the main steam pipe 6 and the first high temperature reheat pipe 11 are connected to each other through a first bypass line 24 having a low temperature ultra-high pressure turbine bypass valve n. They are connected to each other by a second bypass line 26 with a valve 6. Also,#! The first low-temperature reheat pipe 9 is connected to a third bypass pipe Z having a second low-temperature reheat pipe 14 and a low-temperature and high-pressure turbine bypass valve n, and the Kgl high-temperature reheat pipe 11 is connected to a third bypass pipe Z having a high-temperature and high-pressure turbine bypass valve n. The 5g2 high temperature reheat pipes 161C are connected by the 4 bypass pipes. Furthermore, the second high temperature reheat pipe 1
6 is connected to the condenser 19 by a low pressure turbine bypass valve 31 having a low pressure turbine bypass 'W' path.

On the other hand, an ultra-high-pressure turbine outlet check valve M1 is provided at the outlet of the ultra-high-pressure turbine 1 and the high-pressure turbine 2, respectively.

When the turbine bypass operation is performed at the time of startup of the turbine, Lfi=, the superheater 50 inlet flow rate false is determined by the control of the low temperature ultra-high pressure turbine bypass valve passage so that the flow rate C11 is the first
It branches to the low-temperature reheat pipe 9 side, and the remaining flow rate G is heated by the superheater 5 (see FIG. 3).

The flow rate G of steam output from the superheater 5V is controlled by the high temperature ultra-high pressure turbine bypass valve 5 so that the flow rate hu is increased to the first high temperature reheat pipe 11.
The remaining flow rate X is controlled by the steam control valve 8 and supplied to the ultra-high pressure turbine 1. The steam having a flow rate Ctt that has passed through the low-temperature ultra-high pressure turbine bypass valve 3 joins the steam flow rate X after doing work in the ultra-high pressure turbine 1 in the first low-temperature reheat pipe 9, and a part of the flow C1M is transferred to the low-temperature high-pressure turbine. The second low temperature reheat pipe 14 is designed to control the bypass valve n.
The remaining flow rate G flows into the first reheater 10 and is reheated.

The steam at the flow rate G that exits the first reheater 10 joins the steam that has passed through the high-temperature and ultra-high pressure turbine bypass valve 5 in the first high-temperature reheat pipe 11, and a part of the steam flow rate G is at the high-temperature and high-pressure turbine bypass valve. Steam flows into the second high-temperature reheat pipe 16 under the control of B, and the remaining flow rate y flows into the high-pressure turbine 2 under the control of the first intercept valve 13. The flow rate passes through the high-pressure turbine bypass valve n, and the steam merges with the flow rate G to become a flow rate G, which is reheated in the second reheater 15. It merges with llA'Ah** that has passed through B at the second high temperature reheating pipe 16, resulting in a flow rate of G4. On the other hand, of the flow rate G4 of the second high-temperature reheat pipe 16, the flow rate -c is discharged to the condenser 19 under the control of the low-pressure turbine bypass valve 31, and the remaining flow rate 2 is intermediated under the control of the second intercept valve 18. The flow rate 2 flows into the pressure turbine 3, and in the condenser 19, the flow rate 2 after performing work on the intermediate pressure turbine 3 and the low pressure turbine 4C and the flow rate hall that has passed through the low pressure turbine bypass valve 31 are combined.

- However), the high temperature and ultra high pressure turbine bypass valve 9 is connected to the main steam line pressure, the high temperature and high pressure turbine bypass valve 9 is connected to the first high temperature reheat line pressure, and the low pressure turbine bypass valve 31 is connected to the first high temperature reheat line pressure. 2 For high-temperature reheat twin pressure, it acts as a primary pressure adjustment valve that controls each pressure to a constant value during turbine bypass operation, and after turbine bypass operation is completed, it maintains a constant bias to the pressure corresponding to the load in the high load range. Acts as a primary pressure relief valve whose set value is the added pressure.

Figure 4 shows a high temperature ultra-high pressure turbine bypass valve 5, a high temperature high pressure turbine bypass valve B, and a low pressure turbine bypass valve 3.
1 shows the relationship between load and setting value in No. 1. In the figure, the horizontal axis shows the load, and the vertical axis shows the pressure, or the load at the completion of the turbine bypass operation, P.

The pressure corresponding to the beam, solid line 1. indicates a pressure line corresponding to the load, ΔP indicates a constant bias amount, and l' indicates a set value corresponding to the load.

Furthermore, the low temperature ultra-high pressure turbine bypass valve passage is a control valve that allows a flow rate determined as a function of the ultra high pressure turbine passing flow rate to flow, and the low temperature and high pressure turbine bypass valve γ allows a flow rate to flow determined as a function of the high pressure turbine passing flow rate 1. It is a control valve.

By the way, in Figure 3 it is clear that G, = G, :
Go here, CI! ”αx ao-(1), C1
M = βxa0 = < 2), then G+ = Go -C+ t = (1-α) xco-
(3) Stone = G, -x = (1-α) xGo-x
...(4) Gm = Cm5 ”7=βxGo +y
”・(5)h□=G4−G,=(1
-β)xco-y...(6)Q, jll
Iz+(:,,-(:,,==iz+αXG,-βXG
, ...(7)11,. xQ4-2wQ, -Z
”・(8) Furthermore, α is a function of the ultra-high pressure turbine passing amount X, and β is the high pressure turbine passing amount y.
As a function of α=αe x (1-x/alj) /Fu β* x (1-y/Go), then (1)! l C+m-α,X (G,-1)
・ C1U(2) ri C, -β@
× (GO-y) ... (2
(3) yo p G, = C0-αa x (Go
-X) ・(3')(4)yo') hl! =
(1−αe) X (Go −x) −(4
) (5) Machining Q, = β @ × (Gl+ -3')
+1 ...(5') (6) Machining -=(1-β
. ) × (Go -y) ... (6') From (7) G, =, +αo x (G, -x) - β × (Go
-y)... (7 However, in the state before turbine ventilation, zxQ
, since y=xo * ZHO (1 to (7')
And from equation (8), C11”α.XG0 C snow, =β.XG.

G, = (1-α.)XG0 h＋＊　　　　　　　-α.)X% G, = β. XGo bH=　　　　　-β.)　×q G, = (α.-β.)”XG.

b. xQ.

becomes. That is, the superheater inlet flow rate G0 is branched to the low-temperature ultra-high pressure turbine bypass valve path by the flow rate α, × false, and the remaining flow rate (1-α.) to the superheater 5 and high-temperature ultra-high pressure turbine bypass valve 5 is ＞Can ring. Low temperature ultra-high pressure turbine bypass valve flow rate α. XGo diverts the flow rate AX to the low temperature and high pressure turbine bypass valve n and the second reheater 15, and
The remaining flow rate flowing into the reheater 10 (α.-^) Go is the flow rate (1-α.) passing through the high-temperature ultra-high pressure turbine bypass valve δ.
Flow rate (1-β.)XGo flows to the high temperature and high pressure turbine bypass valve B by merging with the High temperature and high pressure turbine bypass valve flow rate (1-β.) XG0 is the second reheater flow rate β. XG
, and becomes the second high temperature reheat flow rate G0, and the flow rate G0 also flows through the low pressure turbine bypass valve 31 and is discharged to the condenser 19.

On the other hand, if the turbine is also ventilated and the aeration rate changes, that is, the ultra-high pressure turbine flow rate changes from xt to x'mx.
If it changes to +Δ bulk, then from (1') Δctt
”σ1! −CI! = −α.×ΔX(3′) From ΔG, =G′−G, ==α.×Δx(4′) From ΔhIt =h’ll −ha1=+ (1−α. )
×Δx(7) yo5 Δa, =CF−G, = (1
−α. ) x ΔX@In other words, with respect to the increase in the flow rate of the ultra-high pressure turbine ΔX, the low-temperature ultra-high pressure turbine bypass valve operates to decrease the flow rate by x ΔX, and the high-temperature ultra-high pressure turbine bypass valve 5 operates to increase the flow rate (t -Tun) It operates to reduce by XΔX. Therefore, the flow rate of the superheater 5 is α. ×ΔX increases, and the flow rate of the first reheating 1s10 also increases (
1-α. ) increases by Xaz. Similarly, high pressure turbine/
When the flow rate of 2 increases by Δy, the flow rate of the low temperature and high pressure turbine bypass valve 4 becomes β. The flow rate of the high-temperature and high-pressure turbine bypass valve is reduced by (1-β.)×Δy, and as a result, the flow rate of the first reheater 10 is A×
The second reheater flow rate also increases by Δy (1-β.)×Δ
Increase by y. Furthermore, when the intermediate pressure turbine flow rate increases by Δ2, the flow rate of the low pressure bottle bypass valve 31 increases by Δ2.
only decreases.

In neutralizing the turbine bypass operation, the superheater inlet flow rate G0 is constant, and when the turbine passing flow rate reaches G, the turbine bypass valve is fully closed and the turbine bypass operation is completed. In other words, the ultra-high pressure turbine flow rate is X=G0
Then, from (1') C,, =O (3') G, =G0 (4') Machining h+t=0 (7') G, ,, =G, -β. ×(Go −y
) Therefore, when the ultra-high-pressure turbine flow rate X reaches the flow rate G, the low-temperature ultra-high-pressure turbine bypass valve n and the high-temperature ultra-high pressure turbine bypass valve δ are fully closed, and as a result, the superheater 5 has a flow rate G0. The bypass operation of the ultra-high pressure turbine 1 is completed. At this time, the first reheater flow rate is Go-β. x (Gll-y), but if the high-pressure turbine flow rate y% flow rate G, K has been reached, then G, = G,
Therefore, the flow rate G0 also flows through the first reheater 10. Similarly, when the high pressure turbine flow rate y reaches the flow rate G,
The high temperature and high pressure turbine bypass valve 27 is fully closed, and as a result, the second reheater 1
5, the flow rate G0 will flow, and the bypass and operation of the high-pressure turbine 2 will be completed. Also, when the intermediate pressure turbine flow 1z is suitable for the flow rate GoKR, the low pressure turbine bypass valve flow rate is fully closed at -o, and the intermediate pressure turbine 3) is low pressure! , = g, y, 4ΩZeiper δ operation is completed 0 However, as the steam turbine becomes larger, the ultra-high pressure turbine 1
In both the high-pressure turbine 2, the tip diameter of the rotor blades increases, and windage loss due to rotational friction increases due to high horse speed.However, during turbine bypass operation, neither the first reheat line nor the second reheat line is in a vacuum. Because they are controlled by pressure, both the ultra-high-pressure turbine and the high-pressure turbine have high steam density, which contributes to an increase in windage loss.

Furthermore, when operating at an extremely low flow rate, such as during startup, the steam does almost no work, resulting in an ultra-high fertilization rate.Bottle exhaust temperature and high-pressure turbine exhaust temperature tend to rise. Therefore, when the turbine is started, the rotor blades tend to overheat due to wind loss due to rotational friction. Therefore, in order to prevent this, K should allow more steam to flow through the 4' ultra-high pressure turbine 1 and the high pressure turbine 2 trap, the intermediate pressure turbine 3, and the low pressure turbine 4. Since the intermediate-pressure turbine 3 and the low-pressure turbine 4 are at a vacuum or a low pressure close to vacuum, they are less likely to overheat than the ultra-high-pressure turbine 1 or the high-pressure turbine 2, so the flow rate may be relatively small.

For example, in the flow rate ratio z Q y Q z of the ultra-high pressure turbine flow rate Desirable from the point of view of prevention.

That is, in cases where the turbine is relatively small and the ultra-high pressure turbine 1 or high-pressure turbine 2 is relatively difficult to overheat, or in cases where long blades are adopted as the low-pressure turbine rotor blades and the low-pressure turbine 4 is relatively easy to overheat, etc. Select a value close to 1 for
Conversely, if the ultra-high pressure turbine 1 or the high-pressure turbine 2 is likely to overheat, X and y are selected to have values close to 4. It should be noted that if the value of X-work y is set to a value that is 4 times larger, the flow rate 2 of the low-pressure turbine 4 will be too small and overheating of the low-pressure turbine 4 will become a problem. In this way, the flow rate of each turbine can be controlled by the opening degree of each inno valve, and overheating of the turbine can also be prevented.

In addition, in the event of a system accident, when transitioning from so-called PCB, which rapidly cuts off most of the fuel in the boiler, to isolated operation within the plant, or when cutting off the load, the steam control valve 8 and the first intercept valve 13 By the sudden closing of the second intercept 5P18, the pressures of the main steam line, the first reheat steam line, and the second reheat steam line increase, which causes the high temperature ultra-high pressure turbine bypass valve 5 to increase. , the high temperature and high pressure turbine bypass valve passage and the low pressure turbine bypass valve 31 are suddenly closed. Further, the low-temperature ultra-high pressure turbine bypass valve section and the low-temperature high-pressure turbine bypass valve 27 are also abruptly closed when the ultra-high pressure turbine flow rate X and the high pressure turbine flow rate y become zero, respectively.

Therefore, the steam in the superheater can be rapidly discharged to the first reheater 10, the steam in the first reheater to the second reheater 15, and the steam in the second reheater to the condenser 19. It is possible to suppress the pressure rise in the main steam line, the first reheat steam line, and the second reheat steam line without causing any disturbance to the boiler, and the fuel cut-off speed of the boiler is also relatively small. , the impact on the boiler can be reduced.

FIG. 5 shows another embodiment of the present invention.
In the device shown in the figure, the upstream side of the ultra-high pressure turbine outlet check valve section and the upstream side of the high pressure turbine outlet check valve section are further connected to the condenser 19 via the first ventilator valve and the second ventilator valve, respectively. It is connected.

Therefore, immediately before the turbine is installed, both the first ventilator valve and the second ventilator valve γ are fully opened. Therefore, in this case, the inside of ultra-high-pressure turbine 1 and high-pressure turbine 2 are in vacuum, windage loss due to friction of the rotating parts is reduced, and both turbines have high-pressure steam flowing regardless of whether they are flowing or not. First, overheating of the turbine can be prevented. After the turbine is installed, the steam flow rate required for the turbine increases, so there is no need to create a vacuum inside the turbine, so both ventilator valves 37 are fully closed.No. 6II is a diagram showing still another embodiment of the present invention. The downstream steel of the main steam control valve 8 is connected to the condenser 19 via the first ventilator valve, and a bypass valve is provided in parallel after the ultra-high pressure turbine outlet reversal valve. The upstream side of the check valve is connected to the condenser 19 via the second ventilator valve 37.

However, in this case as well, until just before the turbine is added, the first
When the chiller valve A, the second ventilator valve 37, and the bypass valve are fully opened, the interior of the ultra-high pressure turbine 1 and high pressure turbine 2 becomes almost a vacuum state, reducing windage loss and overheating of the turbine as described above. Moreover, since relatively low-temperature steam flows back into the ultra-high pressure turbine 1 via the check valve, overheating of the turbine is further prevented.

In the above embodiment, the downstream side of the main steam control valve 8 is connected to the condenser, but as shown in FIG. 7, the downstream side of the first intercept valve 13 is connected to the second ventilator valve π.
Alternatively, as shown in FIG. 8, the downstream side of the main steam control valve 8 and the downstream side of the first intercept valve 13 can be connected to the first ventilator valve A, A bypass valve 39 may be connected to the condenser 19 via the ventilator valve r, and provided in parallel with the ultra-high pressure turbine outlet check valve and the high pressure turbine outlet check valve.

As explained above, in the present invention, the superheater inlet, the low-temperature first reheat pipe, the main steam pipe, the high-temperature first reheat pipe, and the low-temperature first reheat pipe
Since the reheat pipe and the low-temperature second reheat pipe, the high-temperature first reheat pipe and the high-temperature second reheat pipe, and the second high-temperature reheat pipe and the condenser are connected through the turbine bypass valve, during turbine bypass operation, , the steam can be cooled by flowing into the first reheater and the second reheater even before the turbine is vented, and the amount of fuel input from boiler ignition to turbine venting can be increased, and the steam temperature can be increased. rate can be increased. Therefore, the time required to reach the optimum temperature condition for turbine ventilation can be shortened, the time from boiler ignition to turbine ventilation can be shortened, and the startup time can be shortened. In addition, since the optimal turbine ventilation conditions can be established in a short time, there is no need to ventilate the turbine before the conditions are established, there is no thermal shock during turbine ventilation, and the life consumption rate due to thermal stress can be kept low. I can do it. In addition, since the ultra-high-pressure turbine and the high-pressure turbine are connected to the condenser via a valve at the inlet or outlet, it is possible to prevent overheating of both turbines before the turbine is installed. play.

[Brief explanation of drawings]

Fig. 1 is a system diagram of a conventional two-stage reheat turbine, Fig. 2 is a system diagram of a two-stage reheat turbine of the present invention, Fig. 3 is an explanatory diagram of steam flow in the turbine of the present invention, and Fig. 4 is a turbine diagram. Explanatory diagrams of pressure setting values for bypass valve loads, Figures 5 to 8
The figures are system diagrams showing other embodiments of the present invention. 1...Ultra high pressure turbine, 2...High pressure turbine, 3...
...Intermediate pressure turbine, 4...Low pressure turbine, 5...Superheater, 6...Main steam pipe, 10...First reheater, 15
...Second reheater, 19...Condenser, B...Low temperature ultra-high pressure turbine bypass valve, δ...High temperature ultra-high pressure turbine bypass valve, n...Low temperature high pressure turbine bypass valve, 4 ... High temperature and high pressure turbine bypass valve, 31 ... Low pressure turbine bypass valve, A ... First bay intulator valve, 37
...Second ventilator valve.

Claims (1)

[Claims] 1. A first bypass pipe having a low-temperature ultra-high pressure turbine bypass valve and connecting the superheater inlet of the boiler and a first low-temperature reheat pipe, and a high-temperature ultra-high pressure turbine bypass valve. , a second bypass line that connects the main steam pipe and the first high-temperature reheat pipe, and a third bypass line that has a low-temperature and high-pressure turbine bypass valve and connects the first low-temperature reheat pipe and the second low-temperature reheat pipe. a bypass conduit;
a fourth bypass pipe line having a high temperature and high pressure turbine bypass valve and connecting the first high temperature reheat pipe and the J12 high temperature reheat pipe;
A two-stage reheat turbine comprising a low-pressure turbine bypass valve and a desuperheater, and a low-pressure turbine bypass line connecting a second high-temperature reheat pipe and a condenser. 2. It has a low-temperature ultra-high pressure turbine bypass valve, and has a first bypass line that connects the superheater inlet of the boiler and the first low-temperature reheat pipe, and a high-temperature ultra-high pressure turbine bypass valve that connects the main steam pipe and the first bypass line. a second bypass pipe that connects the first high-temperature reheat pipe; a third bypass pipe that has a low-temperature and high-pressure turbine bypass valve and connects the first low-temperature reheat pipe and the second low-temperature reheat pipe;
a fourth bypass pipe line having a high temperature and high pressure turbine bypass valve and connecting the 1g1 high temperature reheat pipe and the second high temperature reheat pipe;
A low-pressure turbine bypass line is provided which has a low-pressure turbine bypass valve and a desuperheater and connects the second high-temperature reheat pipe and the condenser. A two-stage reheat turbine characterized in that the upstream sides of the stop valves are each connected to a condenser via a ventilator valve. 3. It has a low-temperature ultra-high pressure turbine bypass valve, and has a first bypass line that connects the superheater inlet of the boiler and the first low-temperature reheat pipe, and a high-temperature ultra-high pressure turbine bypass valve that connects the main steam pipe and the first a second bypass pipe that connects the first high-temperature reheat pipe; a third bypass pipe that has a low-temperature and high-pressure turbine bypass valve and connects the first low-temperature reheat pipe and the second low-temperature reheat pipe;
a fourth bypass line having a high temperature and high pressure turbine bypass valve and connecting the first high temperature reheat pipe and the second high temperature reheat pipe; and a fourth bypass line having a low pressure turbine bypass valve and a desuperheater and connecting the second high temperature reheat pipe and the second high temperature reheat pipe; A low-pressure turbine bypass pipe is provided to connect the condenser to the condenser, and the inlet part of at least one of the ultra-high pressure turbine and the high-pressure turbine is connected to the condenser via a pentilator valve. A two-stage reheat turbine characterized by having a bypass valve installed in parallel with a stop valve.