U.S. patent application number 12/857988 was filed with the patent office on 2011-02-24 for turbine protection device.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Ichiro Hiraga, Yosuke HIRAKAWA, Mitsuru Sudo, Tsugutomo Teranishi.
Application Number | 20110041503 12/857988 |
Document ID | / |
Family ID | 43604183 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110041503 |
Kind Code |
A1 |
HIRAKAWA; Yosuke ; et
al. |
February 24, 2011 |
Turbine Protection Device
Abstract
An object of the present invention is to provide a turbine
protection device which can interrupt backflow from a deaerator to
a turbine completely even if a check valve provided between the
deaerator and the turbine can not interrupt the steam flow between
the deaerator and the turbine completely. In order to achieve the
above object, a control unit sends commands to a shutdown valve
device so as to close the shutdown valve device when a differential
pressure resulted from subtracting a pressure of a extraction steam
from a pressure within the deaerator becomes greater than or equal
to a first predetermined value. As a result, the backflow from the
deaerator to the turbine is interrupted by a stop valve of the
shutdown valve device.
Inventors: |
HIRAKAWA; Yosuke; (Hitachi,
JP) ; Sudo; Mitsuru; (Hitachi, JP) ; Hiraga;
Ichiro; (Hitachinaka, JP) ; Teranishi; Tsugutomo;
(Hitachiota, JP) |
Correspondence
Address: |
CROWELL & MORING LLP;INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Hitachi, Ltd.
Tokyo
JP
|
Family ID: |
43604183 |
Appl. No.: |
12/857988 |
Filed: |
August 17, 2010 |
Current U.S.
Class: |
60/646 ;
60/657 |
Current CPC
Class: |
F01D 21/14 20130101;
F01K 7/34 20130101; F01K 13/02 20130101; F01K 7/345 20130101; F01D
21/20 20130101; F22D 1/28 20130101 |
Class at
Publication: |
60/646 ;
60/657 |
International
Class: |
F01D 21/14 20060101
F01D021/14 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2009 |
JP |
2009-189423 |
Claims
1. A turbine protection device provided in a steam turbine system,
the steam turbine system comprising: a turbine driven by steam
generated in a boiler; a condenser to condense the steam exhausted
from the turbine into a condensate; a deaerator to store the
condensate which is preheated by being heated and deaerated; an
inlet pipe to take the extraction steam for heating and deaerating
into the deaerator; and a check valve provided in the inlet pipe,
comprising: pressure gauge to measure pressure of the extraction
steam and pressure within the deaerator; a shutdown valve device
provided in the inlet pipe; and control unit to control the
shutdown valve device using commands based on the pressure of the
extraction steam and the pressure within the deaerator, wherein the
shutdown valve device is opened and closed by the commands from the
control unit, and when the shutdown valve device is closed, the
shutdown valve device interrupts the steam flow from the deaerator
to the turbine.
2. The turbine protection device according to claim 1, wherein the
control unit sends commands to the shutdown valve device so as to
close the shutdown valve device when a differential pressure
resulted from subtracting the pressure of the extraction steam from
the pressure within the deaerator becomes greater than or equal to
a first predetermined value which is set in advance, and sends
commands to the shutdown valve device so as to open the shutdown
valve device when the differential pressure becomes greater than or
equal to a second predetermined value which is set in advance.
3. The turbine protection device according to claim 1, wherein the
control unit sends commands to the shutdown valve device so as to
close the shutdown valve device when a first predetermined time has
elapsed on condition that a differential pressure resulted from
subtracting the pressure of the extraction steam from the pressure
within the deaerator is greater than or equal to a first
predetermined value which is set in advance after the differential
pressure becomes greater than or equal to the first predetermined
value, and sends commands to the shutdown valve device so as to
open the shutdown valve device when a second predetermined time has
elapsed on condition that the differential pressure is less than or
equal to a second predetermined value which is set in advance after
the differential pressure becomes less than or equal to the second
predetermined value.
4. A method for controlling a steam turbine system, the steam
turbine system comprising: a turbine driven by steam generated in a
boiler; a condenser to condense the steam exhausted from the
turbine into a condensate; a deaerator to store the condensate
which is prepared by being heated and deaerated; an inlet pipe to
take the extraction steam for heating and deaerating into the
deaerator; and a check valve provided in the inlet pipe, comprising
the steps of: measuring a pressure of the extraction steam and a
pressure within the deaerator; opening and closing a shutdown valve
device provided in the inlet pipe based on a differential pressure
between a pressure of the extraction steam and a pressure within
the deaerator; and interrupting the steam flow from the deaerator
to the turbine by closing the shutdown valve device.
5. The method according to claim 4, wherein further comprising the
steps of: sending commands to the shutdown valve device so as to
close the shutdown valve device when a differential pressure
resulted from subtracting the pressure of the extraction steam from
the pressure within the deaerator becomes greater than or equal to
a first predetermined value which is set in advance, and sending
commands to the shutdown valve device so as to open the shutdown
valve device when the differential pressure becomes greater than or
equal to a second predetermined value which is set in advance.
6. The method according to claim 4, wherein further comprising the
steps of: sending commands to the shutdown valve device so as to
close the shutdown valve device when a first predetermined time has
elapsed on condition that a differential pressure resulted from
subtracting the pressure of the extraction steam from the pressure
within the deaerator is greater than or equal to a first
predetermined value which is set in advance after the differential
pressure becomes equal to or greater than or equal to the first
predetermined value, and sending commands to the shutdown valve
device so as to open the shutdown valve device when a second
predetermined time has elapsed on condition that the differential
pressure is less than or equal to a second predetermined value
which is set in advance after the differential pressure becomes
less than or equal to the second predetermined value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims benefit of the filing date of
Japanese Patent Application No. 2009-189423 filed on Aug. 18, 2009
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a turbine protection device
to protect a turbine of a steam turbine system.
[0004] 2. Description of Related Art
[0005] For example, a steam turbine system of an electric-power
generating steam turbine plant is provided with a deaerator to
store a condensate which is preheated by heating condensate
exhausted from a condenser using a extraction steam from a turbine
so as to deaerate gases such as oxygen, etc.
[0006] Also, during normal operation of the steam turbine system, a
pressure within the deaerator (a deaerator pressure) is decreased
from a pressure of the extraction steam (an extraction pressure)
due to a pressure loss of a path through which the extraction steam
passes from the turbine to the deaerator, thereby the deaerator
pressure is balanced at a lower pressure than the extraction
pressure.
[0007] However, when the extraction pressure is decreased quickly
associated with a quick decay in the turbine load at the time of an
occurrence of a turbine trip, or an interruption of a load, etc, a
decompression speed of the extraction pressure exceeds that of the
deaerator pressure, and a balance between the deaerator pressure
and extraction pressure may break down. That is, the deaerator
pressure may become greater than or equal to the extraction
pressure.
[0008] Also, during normal operation of the steam turbine system,
when the turbine load decays, the extraction pressure is decreased
depending on the decay rate. At this moment, the higher a decay
rate of the load of the turbine, the higher the decompression speed
of the extraction pressure.
[0009] On the other hand, regarding the deaerator having large
capacity, the more condensate stored within the deaerator, the
larger a heat capacity of the deaerator. Also, it will be difficult
to decrease deaerator temperature. As a result, it will be also
difficult to decrease the deaerator pressure.
[0010] Therefore, in the case where the capacity of the deaerator
is large, when the decay rate of the load of the steam turbine
system is high and the decompression speed of the extraction
pressure is high, the decompression speed of the extraction
pressure deaerator pressure may become lower than the decompression
speed, the balance between the deaerator pressure and extraction
pressure may break down, and the deaerator pressure may become
higher than or equal to the extraction pressure.
[0011] When the balance between the deaerator pressure and
extraction pressure breaks down and the deaerator pressure becomes
higher than the extraction pressure, a low-temperature steam flows
from the deaerator to the turbine and a water induction is
generated.
[0012] Hereinafter, a flow of steam from the deaerator to the
turbine is defined as a backflow.
[0013] If the water induction is generated in the turbine, casing
and rotor of the turbine at high temperature are cooled suddenly by
the low-temperature steam, and then the casing and rotor will be
deformed. Also, a contact between a rotational body such as the
rotor and a stationary body such as the casing, or an abnormal
vibration occurs, will result in turbine damage. With those
scenario, it is necessary to suppress generation of the water
induction. For this reason, it is necessary to prevent backflow
from the deaerator to the turbine.
[0014] Therefore, a check valve is conventionally provided between
the turbine and the deaerator so as to prevent the backflow from
the deaerator to the turbine.
[0015] Further, a shutdown valve device is provided so as to
interrupt the steam flow between the turbine and the deaerator.
[0016] For example, JP 11-148310 A discloses a technique for a
water induction protection device which is provided with a shutdown
valve (a shutdown valve device) to interrupt steam flow between a
feedwater heater and a turbine in a steam turbine system, and
prevents water induction occurrence when the water level of
feedwater heater is increased abnormally.
[0017] According to JP 11-148310 A, for example, if the water level
of a feedwater is increased by water leakage from a pipe inside the
feedwater heater, the shutdown valve will interrupt the steam flow
between the turbine and the feedwater heater so as to prevent water
induction occurrence.
[0018] If the technique disclosed in JP 11-148310 A is applied to
the deaerator, it is possible to prevent water induction occurrence
caused by increase in the water level within the deaerator.
[0019] By providing the check valve and shutdown valve device
between the deaerator and the turbine, it is possible to prevent
water induction occurrence caused by water level increase in the
deaerator and the backflow from the deaerator to the turbine.
SUMMARY OF THE INVENTION
[0020] However, because the check valve is instantaneously closed
so as to prevent the backflow from the deaerator to the turbine
when the deaerator pressure is greater than or equal to the
extraction pressure, for example, the check valve is
instantaneously closed when the extraction pressure decays quickly
(e.g., when the turbine trip occurs). Therefore, if the check valve
is opened and closed frequently, a component such as a valve disc
may be deformed by an impact at the time of closing the check
valve, and the backflow from the deaerator to the turbine may not
be interrupted completely.
[0021] Therefore, an object of the present invention is to provide
a turbine protection device which can interrupt the backflow from
the deaerator to the turbine completely even if the check valve
provided between the deaerator and the turbine can not interrupt
the steam flow completely.
[0022] In order to achieve the above object, the present invention
provides a turbine protection device comprising: a shutdown valve
device, in which the shutdown valve device is operated so as to
interrupt backflow from a deaerator to a turbine when a deaerator
pressure is greater than or equal to the extraction pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a block diagram showing an example of a steam
turbine system;
[0024] FIG. 2 is a graph showing a status in which an extraction
pressure and a deaerator pressure are decreased;
[0025] FIG. 3 is a flowchart showing a procedure by which a control
unit controls a shutdown valve device; and
[0026] FIG. 4 is a flowchart showing a procedure by which a control
unit having an internal timer controls the shutdown valve
device.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0027] Embodiments of the present invention will be explained in
detail, hereinafter, with reference to FIGS. 1-4.
[0028] In a steam turbine system 1 as shown in FIG. 1, the steam
generated in the boiler 13 rotates a high-pressure turbine 14, and
is taken into a reheater 13a of the boiler 13. The steam reheated
by the reheater 13a rotates a middle-pressure turbine 15 and a
low-pressure turbine 16, and is taken into a condenser 18 to be
condensed into a condensate.
[0029] In addition, for example, a generator 17 is connected to the
low-pressure turbine 16 as a load.
[0030] The condensate generated by condensing the steam in the
condenser 18 is pressurized by a condensate pump 19, heated by a
low-pressure heater 4 (e.g., using the extraction steam from the
low-pressure turbine 16), fed to the deaerator 5, heated using the
extraction steam from the middle-pressure turbine 15 (or the
low-pressure turbine 16) so as to deaerate gases, and stored in the
deaerator 5.
[0031] Then, the condensate stored in the deaerator 5 is
pressurized by a feed pump 6, heated in a high-pressure heater 7
(e.g., using the extraction steam from the high-pressure turbine 14
or the middle-pressure turbine 15), and taken into the boiler
13.
[0032] The high-pressure turbine 14, the middle-pressure turbine
15, and the low-pressure turbine 16, hereinafter, are referred as
turbine 2 in a mass.
[0033] The turbine 2 is connected to the deaerator 5 via an
extraction steam inlet pipe 3 (inlet pipe), and the extraction
steam from the turbine 2 passes through the extraction steam inlet
pipe 3 so as to be taken into the deaerator 5 as the extraction
steam for heating and deaerating.
[0034] Two check valves 3a are connected to the extraction steam
inlet pipe 3 in series, and a flow direction of the steam in the
extraction steam inlet pipe 3 is limited from the turbine 2 to the
deaerator 5.
[0035] The extraction steam inlet pipe 3 is connected to any one or
more of the high-pressure turbine 14, the middle-pressure turbine
15, or the low-pressure turbine 16.
[0036] Because the extraction steam from the turbine 2 is taken
into the deaerator 5 through the extraction steam inlet pipe 3, an
extraction pressure of the extraction steam from the turbine 2
(hereinafter, denoted by "P1 ") is decreased due to a pressure loss
caused by passing through the extraction steam inlet pipe 3.
[0037] Therefore, during normal operation of the steam turbine
system 1, the deaerator pressure (hereinafter, denoted by "P2")
becomes lower than the extraction pressure P1.
[0038] Also, during normal operation of the steam turbine system 1,
the deaerator pressure P2 is balanced at a pressure which is lower
than the extraction pressure P1 so as to prevent the backflow from
the deaerator 5 to the turbine 2.
[0039] Although the two check valves 3a are opened so as to allow
the steam to flow from the turbine 2 to the deaerator 5 when the
deaerator pressure P2 is less than the extraction pressure P1, the
two check valves 3a are instantaneously closed so as to interrupt
the backflow from the deaerator 5 to the turbine 2 when the
deaerator pressure P2 is greater than or equal to the extraction
pressure P1 when turbine trip occurs, etc.
[0040] Also, the extraction steam inlet pipe 3 is provided with a
shutdown valve device 12 between the two check valves 3a and the
deaerator 5. Shutdown valve device 12 includes a stop valve 12a to
interrupt the steam flow through the extraction steam inlet pipe 3,
and a valve driving unit 12b to open and close the stop valve 12a
rapidly.
[0041] The valve driving unit 12b drives the stop valve 12a so as
to close the extraction steam inlet pipe 3, to interrupt the
backflow from the deaerator 5 to the turbine 2, and to prevent
occurrence of a water induction, when water level within the
deaerator 5 measured by a water level gauge (not shown) becomes
greater than a predetermined value.
[0042] Also, the steam turbine system 1 according to this
embodiment includes a turbine extraction pressure gauge 9 to
measure the extraction pressure P1 of the extraction steam from the
turbine 2, deaerator pressure gauge 10 to measure the deaerator
pressure P2 of the deaerator 5, and a control unit 11 to control
the shutdown valve device 12 by sending commands to the valve
driving unit 12b.
[0043] For example, the turbine extraction pressure gauge 9 is
provided in proximity to a juncture between the turbine 2 and the
extraction steam inlet pipe 3, and measures the extraction pressure
P1 on condition that the pressure loss caused by the extraction
steam inlet pipe 3 does not occur.
[0044] The control unit 11 calculates the extraction pressure P1
based on a measured signal input from the turbine extraction
pressure gauge 9, and the deaerator pressure P2 based on a measured
signal input from the deaerator pressure gauge 10.
[0045] Also, the control unit 11 sends commands to the valve
driving unit 12b to drive the stop valve 12a to close the
extraction steam inlet pipe 3, when the deaerator pressure P2
becomes greater than or equal to the extraction pressure P1. Then,
the shutdown valve device 12 is closed.
[0046] Therefore, the stop valve 12a interrupts the backflow from
the deaerator 5 to the turbine 2.
[0047] After that, the deaerator pressure P2 is decreased. When the
deaerator pressure P2 becomes less than the extraction pressure P1,
the control unit 11 will send commands to the valve driving unit
12b to drive the stop valve 12a to open the extraction steam inlet
pipe 3. Then, the shutdown valve device 12 is opened.
[0048] The extraction steam from the turbine 2 passes through the
extraction steam inlet pipe 3 so as to be taken into the deaerator
5.
[0049] Also, in this embodiment, a turbine protection device 20
includes the turbine extraction pressure gauge 9, deaerator
pressure gauge 10, control unit 11, and shutdown valve device
12.
[0050] As shown in FIG. 2, in condition that the deaerator pressure
P2 (P2H) is lower than the extraction pressure P1 (P1H) slightly,
in the case where the steam turbine system 1 (see FIG. 1) is in
normal operation, for example, when an amount of electric-power
generation required for the generator 17 (see FIG. 1) is decreased
and the load of the turbine 2 decays, the extraction pressure P1 is
decompressed to P1L at the time t1 associated with a decay in the
load.
[0051] Also, the deaerator pressure P2 is decreased to P2L at the
time t2 associated with depression in the extraction pressure
P1.
[0052] However, for example, in the case where the capacity of the
deaerator 5 (see FIG. 1) is large and the decay rate of the load of
the turbine 2 (see FIG. 1) is high, when the decompression speed of
the extraction pressure P1 is higher than that of the deaerator
pressure P2, for example, the extraction pressure P1 is decreased
to the deaerator pressure P2 at the time t3. After that, the
deaerator pressure P2 is kept higher than the extraction pressure
P1 until the time t4 at which the deaerator pressure P2 is
decreased to P1L.
[0053] As described above, when the deaerator pressure P2 becomes
greater than or equal to the extraction pressure P1 (deaerator
pressure P2.gtoreq.extraction pressure P1), two check valves 3a
(see FIG. 1) are closed so as to prevent the backflow from the
deaerator 5 (see FIG. 1) to the turbine 2 (see FIG. 1).
[0054] However, for example, in the case where the valve discs of
two check valves 3a, etc., are deformed and the steam flow through
the extraction steam inlet pipe 3 (see FIG. 1) can not be
interrupted completely, the turbine 2 may be damaged by the
backflow from the deaerator 5 to the turbine 2.
[0055] For this reason, the control unit 11 according to this
embodiment (see FIG. 1) controls the shutdown valve device 12 so
that the shutdown valve device 12 (see FIG. 1) is closed from time
t5 at which a differential pressure .DELTA.P, which is resulted
from subtracting the extraction pressure P1 from the deaerator
pressure P2 when the steam turbine system 1 (see FIG. 1) is in
normal operation, becomes greater than or equal to the first
predetermined value (.DELTA.Pf1) which is set in advance till the
time t6 at which the differential pressure .DELTA.P becomes less
than a second predetermined value (.DELTA.Pf2) which is set in
advance.
[0056] Also, after the time t6 at which the differential pressure
.DELTA.P becomes less than or equal to the second predetermined
value .DELTA.Pf2, the control unit 11 controls the shutdown valve
device 12 to be closed.
[0057] When the differential pressure .DELTA.P becomes greater than
or equal to the first predetermined value .DELTA.Pf1 which is
resulted from subtracting the extraction pressure P1 from the
deaerator pressure P2, the control unit 11 will send commands to
the valve driving unit 12b (see FIG. 1) so that the stop valve 12a
(see FIG. 1) closes the extraction steam inlet pipe 3 so as to
close the shutdown valve device 12 (see FIG. 1).
[0058] And, when the differential pressure .DELTA.P becomes less
than or equal to the second predetermined value .DELTA.Pf2, the
control unit 11 will send commands to the valve driving unit 12b so
that the stop valve 12a opens the extraction steam inlet pipe 3 so
as to open the shutdown valve device 12.
[0059] In this way, the control unit 11 controls the shutdown valve
device 12 by sending commands based on the differential pressure
.DELTA.P between the deaerator pressure P2 and the extraction
pressure P1.
[0060] For example, considering measurement errors of the turbine
extraction pressure gauge 9 and deaerator pressure gauge 10, and
changes (microseisms) in the deaerator pressure P2 and extraction
pressure P1, etc., the first predetermined value .DELTA.Pf1 and
second predetermined value .DELTA.Pf2 are set to values as small as
possible. The first predetermined value .DELTA.Pf1 may differ from
or may be the same as the second predetermined value
.DELTA.Pf2.
[0061] Also, the first predetermined value .DELTA.Pf1 and second
predetermined value .DELTA.Pf2 may be "0".
[0062] In the case where the first predetermined value .DELTA.Pf1
is "0", the control unit 11 closes the shutdown valve device 12
(see FIG. 1) when the deaerator pressure P2 becomes greater than or
equal to the extraction pressure P1. In the case where the second
predetermined value .DELTA.Pf2 is "0", the control unit 11 opens
the shutdown valve device 12 (see FIG. 1) when the extraction
pressure P1 becomes greater than or equal to the deaerator pressure
P2.
[0063] In addition, the first predetermined value .DELTA.Pf1 and
second predetermined value .DELTA.Pf2 are set as differential
pressures resulted from subtracting the extraction pressure P1 from
the deaerator pressure P2. Therefore, in the case the extraction
pressure P1 is higher than the deaerator pressure P2, the first
predetermined value .DELTA.Pf1 and second predetermined value
.DELTA.Pf2 become negative values.
[0064] With reference to FIG. 3, a procedure by which the control
unit 11 controls the shutdown valve device 12 will be explained
(see FIGS. 1 and 2).
[0065] For example, this procedure is incorporated in a program
which the control unit 11 runs as a subroutine, and may be run by
the control unit 11 at intervals of 100 ms, etc.
[0066] When the procedure to control the shutdown valve device 12
starts, the control unit 11 calculates the extraction pressure P1
(step S1), and further calculates the deaerator pressure P2 (step
S2).
[0067] As described above, the control unit 11 can calculate the
extraction pressure P1 based on the measured signal input from the
turbine extraction pressure gauge 9, and can calculate the
deaerator pressure P2 based on the measured signal input from the
deaerator pressure gauge 10.
[0068] In this way, the control unit 11 calculates the extraction
pressure P1 and deaerator pressure P2 at every time the procedure
to control the shutdown valve device 12 is executed. Therefore, the
control unit 11 monitors the extraction pressure P1 and deaerator
pressure P2 at all times.
[0069] The control unit 11 calculates the differential pressure
.DELTA.P by subtracting the extraction pressure P1 from the
deaerator pressure P2 (step S3).
[0070] Also, when the calculated differential pressure .DELTA.P is
greater than or equal to the first predetermined value .DELTA.Pf1
(step S4.fwdarw.Yes), if the shutdown valve device 12 is opened
(step S5.fwdarw.Yes), the control unit 11 will send commands to the
valve driving unit 12b to drive the stop valve 12a to close the
shutdown valve device 12 (step S6), and the procedure to control
the shutdown valve device 12 is completed (RETURN). If the shutdown
valve device 12 is not opened (step S5.fwdarw.No), i.e., if the
shutdown valve device 12 is closed, the procedure to control the
shutdown valve device 12 is completed (RETURN).
[0071] On the other hand, when the calculated differential pressure
.DELTA.P is less than the first predetermined value .DELTA.Pf1
(step S4 .fwdarw.No), if the differential pressure .DELTA.P is
greater than the second predetermined value .DELTA.Pf2 (step
S7.fwdarw.No), the control unit 11 completes the procedure to
control the shutdown valve device 12 (RETURN).
[0072] Also, when the differential pressure .DELTA.P is less than
or equal to the second predetermined value .DELTA.Pf2 (step
S7.fwdarw.Yes), and if the shutdown valve device 12 is closed (step
S8.fwdarw.Yes), the control unit 11 will send commands to the valve
driving unit 12b to drive the stop valve 12a to open the shutdown
valve device 12 (step S9), and completes the procedure to control
the shutdown valve device 12 (RETURN). If the shutdown valve device
12 is not closed (step S8.fwdarw.No), i.e., if the shutdown valve
device 12 is open, the procedure to control the shutdown valve
device 12 is completed (RETURN).
[0073] The method by which the control unit 11 judges whether the
shutdown valve device 12 is opened or closed is not limited.
[0074] For example, the control unit 11 may includes a flag OP to
indicate whether the shutdown valve device 12 is opened or closed,
and the control unit 11 sets the flag OP to "0" in step S6 when the
shutdown valve device 12 is closed and sets the flag OP to "1" in
step S9 when the shutdown valve device 12 is opened.
[0075] The control unit 11 judges that the shutdown valve device 12
is opened if the flag OP is "1", and judges that the shutdown valve
device 12 is closed if the flag OP is "0".
[0076] Also, the shutdown valve device 12 may be provided with a
sensor (not shown) to detect whether the stop valve 12a closes or
opens the extraction steam inlet pipe 3. For example, if the sensor
(not shown) sends a detection signal to indicate whether the stop
valve 12a closes or opens the extraction steam inlet pipe 3 to the
control unit 11, the control unit 11 can detect whether the stop
valve 12a closes or opens the extraction steam inlet pipe 3 based
on the detection signal from the sensor (not shown). Also, the
control unit 11 can judge whether the shutdown valve device 12 is
opened or closed.
Modified Example
[0077] As described above, the control unit 11 of the steam turbine
system 1 according to this embodiment shown in FIG. 1 monitors the
extraction pressure P1 and deaerator pressure P2 at all times,
closes the shutdown valve device 12 when the differential pressure
.DELTA.P resulted from subtracting the extraction pressure P1 from
the deaerator pressure P2 becomes greater than or equal to the
first predetermined value .DELTA.Pf1, and opens the shutdown valve
device 12 when the differential pressure .DELTA.P becomes less than
or equal to the second predetermined value .DELTA.Pf2.
[0078] However, when the turbine extraction pressure gauge 9
measures the extraction pressure P1, the measured value can
slightly change. Likewise, the measured value of the deaerator
pressure gauge 10 can slightly change.
[0079] Therefore, the extraction pressure P1 and deaerator pressure
P2 calculated by the control unit 11 can also slightly change, and
further the differential pressure .DELTA.P resulted from
subtracting the extraction pressure P1 from the deaerator pressure
P2 can also slightly change.
[0080] If the differential pressure .DELTA.P changes across the
first predetermined value .DELTA.Pf1 and second predetermined value
.DELTA.Pf2, the control unit 11 will send commands to the valve
driving unit 12b to close the shutdown valve device 12 at every
time the differential pressure .DELTA.P becomes greater than or
equal to the first predetermined value .DELTA.Pf1, and will send
commands to the valve driving unit 12b to open the shutdown valve
device 12 at every time the differential pressure .DELTA.P becomes
less than or equal to the second predetermined value .DELTA.Pf2.
Therefore, the control unit 11 frequently sends commands to the
valve driving unit 12b to control the shutdown valve device 12, and
the shutdown valve device 12 is opened and closed frequently. As a
result, there arises a problem that the stop valve 12a and the
shutdown valve device 12 are degraded.
[0081] For this reason, in a modified example of the present
invention, for example, the control unit 11 may be provided with an
internal timer, and may close the shutdown valve device 12 when a
condition that the differential pressure .DELTA.P resulted from
subtracting the extraction pressure P1 from the deaerator pressure
P2 is greater than or equal to the first predetermined value
.DELTA.Pf1 continues for a predetermined time period.
[0082] Likewise, when a condition that the differential pressure
.DELTA.P resulted from subtracting the extraction pressure P1 from
the deaerator pressure P2 is less than or equal to the second
predetermined value .DELTA.Pf2 continues for a predetermined time
period, the control unit 11 may open the shutdown valve device
12.
[0083] With reference to FIG. 4, a procedure by which the control
unit 11 having the internal timer controls the shutdown valve
device 12 (see FIGS. 1 and 2).
[0084] Like the procedure shown in FIG. 3, this procedure is
incorporated in a program which the control unit 11 runs as a
subroutine, and may be run by the control unit 11 at intervals of
100 ms, etc.
[0085] In addition, the same reference numbers are used to denote
the same steps as those in FIG. 3, and their repeated explanations
will be omitted.
[0086] When the procedure to control the shutdown valve device 12
starts, the control unit 11 calculates the extraction pressure P1
(step S1), deaerator pressure P2 (step S2), and further calculates
the differential pressure .DELTA.P by subtracting the extraction
pressure P1 from the deaerator pressure P2 (step S3).
[0087] Also, when the calculated differential pressure .DELTA.P is
greater than or equal to the first predetermined value .DELTA.Pf1
(step S4.fwdarw.Yes), the control unit 11 stops measuring opening
valve waiting time (step S10), and if the shutdown valve device 12
is opened (step S5.fwdarw.Yes), the control unit 11 judges whether
a closing valve waiting time is being measured or not (step
S11).
[0088] The opening valve waiting time means waiting time during the
differential pressure .DELTA.P resulted from subtracting the
extraction pressure P1 from the deaerator pressure P2 becomes less
than or equal to the second predetermined value .DELTA.Pf2 and the
control unit 11 opens the shutdown valve device 12.
[0089] Also, the closing valve waiting time means waiting time
during the differential pressure .DELTA.P resulted from subtracting
the extraction pressure P1 from the deaerator pressure P2 becomes
greater than or equal to the first predetermined value .DELTA.Pf1
and the control unit 11 closes the shutdown valve device 12.
[0090] Also, if the closing valve waiting time is not being
measured (step S11.fwdarw.No), the control unit 11 starts measuring
the closing valve waiting time by the internal timer (step S12),
and the procedure to control the shutdown valve device 12 is
completed (RETURN).
[0091] Also, if the closing valve waiting time is being measured
(step S11.fwdarw.Yes), in the case where a predetermined time Tm1
(a first predetermined time) has elapsed since measuring the
closing valve waiting time started (step S13.fwdarw.Yes), the
control unit 11 closes the shutdown valve device 12 (step S6) and
completes the procedure to control the shutdown valve device 12
(RETURN), and in the case where the predetermined time Tm1 has not
elapsed (step S13.fwdarw.No), the control unit 11 completes the
procedure to control the shutdown valve device 12 (RETURN) without
closing the shutdown valve device 12.
[0092] Returning to step S5, if the shutdown valve device 12 is not
opened (step S5 .fwdarw.No), i.e., if the shutdown valve device 12
is closed, the control unit 11 completes the procedure to control
the shutdown valve device 12 (RETURN).
[0093] In step S13, for example, the predetermined time Tm1 to
determine whether the shutdown valve device 12 should be closed or
not may be determined as a time during which the control unit 11
can close the shutdown valve device 12 with the proper timing based
on an experiment, etc.
[0094] Returning to step S4, when the calculated differential
pressure .DELTA.P is less than the first predetermined value
.DELTA.Pf1 (step S4.fwdarw.No), the control unit 11 compares the
differential pressure .DELTA.P and the second predetermined value
.DELTA.Pf2 (step S7). Also, when the differential pressure .DELTA.P
is greater than the second predetermined value .DELTA.Pf2 (step
S7.fwdarw.No), the control unit 11 completes the procedure to
control the shutdown valve device 12 (RETURN).
[0095] Also, when the differential pressure .DELTA.P is less than
or equal to the second predetermined value .DELTA.Pf2 (step
S7.fwdarw.Yes), the control unit 11 stops the measuring the closing
valve waiting time (step S14). If the shutdown valve device 12 is
closed (step S8.fwdarw.Yes), the control unit 11 judges whether the
opening valve waiting time is being measured or not (step S15).
[0096] In addition, when the shutdown valve device 12 is not closed
(step S8.fwdarw.No), i.e., when the shutdown valve device 12 is
opened, the control unit 11 completes the procedure to control the
shutdown valve device 12 (RETURN).
[0097] Also, if the opening valve waiting time is not being
measured (step S15.fwdarw.No), the control unit 11 starts measuring
the opening valve waiting time by the internal timer (step S16),
and completes the procedure to control the shutdown valve device 12
(RETURN). Also, if the opening valve waiting time is being measured
(step S15.fwdarw.Yes), in the case where the predetermined time Tm2
(a second predetermined time) has elapsed since measuring the
opening valve waiting time started (step S17.fwdarw.Yes), the
control unit 11 closes the shutdown valve device 12 (step S9) and
completes the procedure to control the shutdown valve device 12
(RETURN), and in the case where the predetermined time Tm2 has not
elapsed (step S17.fwdarw.No), the control unit 11 completes the
procedure to control the shutdown valve device 12 (RETURN) without
opening the shutdown valve device 12.
[0098] In step S17, for example, the predetermined time Tm2 to
determine whether the shutdown valve device 12 should be opened or
not may be determined as a time during which the control unit 11
can open the shutdown valve device 12 with the proper timing based
on an experiment, etc., and may be the same as or differ from the
predetermined time Tm1 in step S13.
[0099] As shown in FIG. 4, in the modified example, when the
differential pressure .DELTA.P resulted from subtracting the
extraction pressure P1 from the deaerator pressure P2 is greater
than or equal to the first predetermined value .DELTA.Pf1, the
control unit 11 (see FIG. 1) starts measuring the closing valve
waiting time by the internal timer (step S12), and when the
predetermined time Tm1 has elapsed on condition that the
differential pressure .DELTA.P is greater than or equal to the
first predetermined value .DELTA.Pf1, the control unit 11 closes
the shutdown valve device 12 (see FIG. 1)(step S13). In this way,
after the differential pressure .DELTA.P resulted from subtracting
the extraction pressure P1 from the deaerator pressure P2 becomes
greater than or equal to the first predetermined value .DELTA.Pf1,
and when the predetermined time Tm1 (the first predetermined time)
has elapsed on condition that the differential pressure .DELTA.P is
greater than or equal to the first predetermined value .DELTA.Pf1,
the control unit 11 closes the shutdown valve device 12.
[0100] Also, when the differential pressure .DELTA.P resulted from
subtracting the extraction pressure P1 from the deaerator pressure
P2 is less than or equal to the second predetermined value
.DELTA.Pf2, the control unit 11 (see FIG. 1) starts measuring the
opening valve waiting time by the internal timer (step S16), and
when the predetermined time Tm2 has elapsed on condition that the
differential pressure .DELTA.P is less than or equal to the second
predetermined value .DELTA.Pf2, the control unit 11 opens the
shutdown valve device 12 (see FIG. 1)(step S17). In this way, after
the differential pressure .DELTA.P resulted from subtracting the
extraction pressure P1 from the deaerator pressure P2 becomes less
than or equal to the second predetermined value .DELTA.Pf2, and
when the predetermined time Tm2 (the second predetermined time) has
elapsed on condition that the differential pressure .DELTA.P is
less than or equal to the second predetermined value .DELTA.Pf2,
the control unit 11 will close the shutdown valve device 12.
[0101] Also, associated with changes in measured values of the
turbine extraction pressure gauge 9 and deaerator pressure gauge
10, in the case where the differential pressure .DELTA.P calculated
by the control unit 11 changes across the first predetermined value
.DELTA.Pf1 at intervals shorter than the predetermined time Tm1,
even if the differential pressure .DELTA.P is greater than or equal
to the first predetermined value .DELTA.Pf1, the control unit 11
does not close the shutdown valve device 12.
[0102] Likewise, even if differential pressure .DELTA.P is less
than or equal to the second predetermined value .DELTA.Pf2, the
control unit 11 does not open the shutdown valve device 12, in the
case where the differential pressure .DELTA.P calculated by the
control unit 11 changes across the second predetermined value
.DELTA.Pf2 at intervals shorter than the predetermined time
Tm2.
[0103] Therefore, the shutdown valve device 12 is prevented from
being operated frequently to suppress the problem that the shutdown
valve device 12 is degraded.
[0104] As described above, in the turbine protection device 20 of
the steam turbine system 1 according to this embodiment shown in
FIG. 1, the control unit 11 monitors the extraction pressure P1 and
deaerator pressure P2 at all times. When the differential pressure
.DELTA.P resulted from subtracting the extraction pressure P1 from
the deaerator pressure P2 is greater than or equal to the first
predetermined value .DELTA.Pf1, the control unit 11 closes the
shutdown valve device 12 to interrupt the backflow from the
deaerator 5 to the turbine 2 by the stop valve 12a.
[0105] When the deaerator pressure P2 becomes greater than or equal
to the extraction pressure P1, two check valves 3a are closed so as
to interrupt the backflow from the deaerator 5 to the turbine
2.
[0106] However, if the valve disc of two check valves 3a, etc. are
deformed and these two check valves 3a can not interrupt the steam
flow through the extraction steam inlet pipe 3 completely, the
turbine 2 may be damaged by the backflow from the deaerator 5 to
the turbine 2.
[0107] Even if two check valves 3a can not interrupt the steam flow
through the extraction steam inlet pipe 3 completely, the steam
turbine system 1 according to this embodiment can interrupt the
steam flow through the extraction steam inlet pipe 3 by the stop
valve 12a of the shutdown valve device 12, and can interrupt the
backflow from the deaerator 5 to the turbine 2 effectively.
[0108] Also, after the differential pressure .DELTA.P resulted from
subtracting the extraction pressure P1 from the deaerator pressure
P2 becomes greater than or equal to the first predetermined value
.DELTA.Pf1, and when the predetermined time Tm1 has elapsed, the
control unit 11 closes the shutdown valve device 12. After the
differential pressure .DELTA.P becomes less than or equal to the
second predetermined value .DELTA.Pf2, when the predetermined time
Tm2 has elapsed, the control unit 11 opens the shutdown valve
device 12.
[0109] In this way, the shutdown valve device 12 is prevented from
being operated frequently to suppress the problem that the shutdown
valve device 12 is degraded.
[0110] In addition, even if the deaerator pressure P2 becomes
greater than or equal to the extraction pressure P1 associated with
a quick decay in a load of the steam turbine system 1, the control
unit 11 can close the shutdown valve device 12, not only at the
time of normal operation of the steam turbine system 1 but also at
the time of an occurrence of a turbine trip, or an interruption of
a load, etc,. Therefore, even if two check valves 3a can not
interrupt the steam flow through the extraction steam inlet pipe 3
completely, the backflow from the deaerator 5 to the turbine 2 can
be interrupted completely, and the turbine 2 can be prevented from
being damaged.
[0111] Although the turbine protection device 20 is provided
between the deaerator 5 and the turbine 2 in this embodiment as
shown in FIG. 1, for example, the turbine protection device 20
according to this embodiment may be provided also between the
feedwater heater (not shown) and the turbine 2.
[0112] In this case, even if the pressure within the feedwater
heater becomes higher than the extraction pressure P1, the backflow
from the feedwater heater to the turbine 2 can be interrupted by
the stop valve 12a, and the turbine 2 can be prevented from being
damaged.
* * * * *