U.S. patent application number 13/712212 was filed with the patent office on 2014-01-02 for protection device for turbine exhaust chamber and condenser and monitoring controller for turbine exhaust chamber and condenser.
The applicant listed for this patent is Toshitada Asanaka, Mamoru Fukui, Kouichi Kitaguchi, Takahiro Mori, Manabu Tateishi, Masayuki TOBO. Invention is credited to Toshitada Asanaka, Mamoru Fukui, Kouichi Kitaguchi, Takahiro Mori, Manabu Tateishi, Masayuki TOBO.
Application Number | 20140000260 13/712212 |
Document ID | / |
Family ID | 48924041 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140000260 |
Kind Code |
A1 |
TOBO; Masayuki ; et
al. |
January 2, 2014 |
PROTECTION DEVICE FOR TURBINE EXHAUST CHAMBER AND CONDENSER AND
MONITORING CONTROLLER FOR TURBINE EXHAUST CHAMBER AND CONDENSER
Abstract
There is provided a protection device for a turbine exhaust
chamber and a condenser, having, a condenser, a turbine exhaust
chamber casing covering the steam turbine and the condenser, an
atmosphere discharge disc for discharging atmosphere when a
pressure reaches a first predetermined value, a temperature
measuring unit for measuring a temperature in the turbine exhaust
chamber casing, a first setter for setting a second predetermined
value, an output unit for producing an external output, based on
the measured temperature and the second predetermined value, when a
pressure corresponding to the temperature becomes higher than or
equal to the second predetermined value related to pressure or when
the temperature becomes equal to or higher than the second
predetermined value related to temperature, and a releasing unit
for releasing the steam in the turbine exhaust chamber casing to an
exterior when the output unit produces the external output.
Inventors: |
TOBO; Masayuki;
(Kawasaki-Shi, JP) ; Kitaguchi; Kouichi;
(Yokohama-Shi, JP) ; Fukui; Mamoru; (Yokohama-Shi,
JP) ; Tateishi; Manabu; (Yokohama-Shi, JP) ;
Mori; Takahiro; (Yokohama-Shi, JP) ; Asanaka;
Toshitada; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOBO; Masayuki
Kitaguchi; Kouichi
Fukui; Mamoru
Tateishi; Manabu
Mori; Takahiro
Asanaka; Toshitada |
Kawasaki-Shi
Yokohama-Shi
Yokohama-Shi
Yokohama-Shi
Yokohama-Shi
Tokyo |
|
JP
JP
JP
JP
JP
JP |
|
|
Family ID: |
48924041 |
Appl. No.: |
13/712212 |
Filed: |
December 12, 2012 |
Current U.S.
Class: |
60/660 |
Current CPC
Class: |
F01B 25/00 20130101;
F05D 2270/09 20130101; F05D 2270/3032 20130101; F01D 25/30
20130101 |
Class at
Publication: |
60/660 |
International
Class: |
F01B 25/00 20060101
F01B025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2012 |
JP |
2012-21109 |
Claims
1. A protection device for a turbine exhaust chamber and a
condenser comprising: a condenser for cooling and condensing steam
exhausted from a steam turbine; a turbine exhaust chamber casing
integrally covering the steam turbine and the condenser; an
atmosphere discharge disc for discharging atmosphere when a
pressure in the turbine exhaust chamber casing reaches a first
predetermined value; a temperature measuring means for measuring a
temperature in the turbine exhaust chamber casing; a first setter
for setting a second predetermined value; an output means for
producing an external output, based on the temperature measured by
the temperature measuring means and the second predetermined value
set by the first setter, when a pressure corresponding to the
temperature becomes higher than or equal to the second
predetermined value related to pressure or when the temperature
becomes equal to or higher than the second predetermined value
related to temperature; and a releasing means for releasing the
steam in the turbine exhaust chamber casing to an exterior when the
output means produces the external output.
2. A protection device for a turbine exhaust chamber and a
condenser according to claim 1, wherein the output means includes a
converter to which the temperature measured by the temperature
measuring means is given and which converts the temperature into a
corresponding pressure and outputs the pressure, and a comparator
for comparing the pressure obtained by conversion by the converter
and the second predetermined value related to the pressure and set
in the first setter and producing an output when the pressure
becomes higher than or equal to the second predetermined value.
3. A protection device for a turbine exhaust chamber and a
condenser according to claim 2, wherein the second predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the second predetermined value related to
the temperature and set in the first setter is a lower value than
the first predetermined value.
4. A protection device for a turbine exhaust chamber and a
condenser according to claim 2, wherein the second predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the second predetermined value related to
the temperature and set in the first setter is positive pressure or
higher.
5. A protection device for a turbine exhaust chamber and a
condenser according to claim 1, wherein the output means includes a
comparator for comparing the temperature measured by the
temperature measuring means and the second predetermined value
related to temperature and set in the first setter and producing an
output when the temperature becomes higher than or equal to the
second predetermined value.
6. A protection device for a turbine exhaust chamber and a
condenser according to claim 5, wherein the second predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the second predetermined value related to
the temperature and set in the first setter is a lower value than
the first predetermined value.
7. A protection device for a turbine exhaust chamber and a
condenser according to claim 5, wherein the second predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the second predetermined value related to
the temperature and set in the first setter is positive pressure or
higher.
8. A protection device for a turbine exhaust chamber and a
condenser according to claim 1, wherein the second predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the second predetermined value related to
the temperature and set in the first setter is a lower value than
the first predetermined value.
9. A protection device for a turbine exhaust chamber and a
condenser according to claim 1, wherein the second predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the second predetermined value related to
the temperature and set in the first setter is positive pressure or
higher.
10. A protection device for a turbine exhaust chamber and a
condenser according to claim 1, wherein the releasing means is a
vacuum breaker valve provided to a pipe connecting an inside and an
outside of the condenser and driven by a direct-current power
supply.
11. A protection device for a turbine exhaust chamber and a
condenser according to claim 1 and further comprising: a second
setter for setting a third predetermined value; and an alarm means
for outputting an alarm, based on the temperature measured by the
temperature measuring means and the third predetermined value set
in the second setter, when the pressure corresponding to the
temperature becomes higher than or equal to the third predetermined
value related to pressure or when the temperature becomes higher
than or equal to the third predetermined value related to
temperature.
12. A monitoring controller for a turbine exhaust chamber and a
condenser comprising: a first setter for setting a first
predetermined value; and an output means for outputting an external
output, based on a measured temperature in a turbine exhaust
chamber casing integrally covering a condenser for cooling and
condensing steam exhausted from a steam turbine and the steam
turbine and the first predetermined value set by the first setter,
when a pressure corresponding to the temperature becomes higher
than or equal to the first predetermined value related to pressure
or when the temperature becomes higher than or equal to the first
predetermined value related to temperature.
13. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 12, wherein the output means includes
a converter to which the measured temperature in a turbine exhaust
chamber casing is given and which converts the temperature into a
corresponding pressure and outputs the pressure, and a comparator
for comparing the pressure obtained by conversion by the converter
and the first predetermined value related to the pressure and set
in the first setter and producing an output when the pressure
becomes higher than or equal to the first predetermined value.
14. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 13, wherein the first predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the first predetermined value related to
the temperature and set in the first setter is a lower value than
the first predetermined value.
15. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 13, wherein the first predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the first predetermined value related to
the temperature and set in the first setter is positive pressure or
higher.
16. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 12, wherein the output means includes
a comparator for comparing the measured temperature in a turbine
exhaust chamber casing and the first predetermined value related to
temperature and set in the first setter and producing an output
when the temperature becomes higher than or equal to the first
predetermined value.
17. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 16, wherein the first predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the first predetermined value related to
the temperature and set in the first setter is a lower value than
the first predetermined value.
18. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 12, wherein the first predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the first predetermined value related to
the temperature and set in the first setter is a lower value than
the first predetermined value.
19. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 12, wherein the first predetermined
value related to the pressure and set in the first setter or the
pressure corresponding to the first predetermined value related to
the temperature and set in the first setter is positive pressure or
higher.
20. A monitoring controller for a turbine exhaust chamber and a
condenser according to claim 12 and further comprising: a second
setter for setting a second predetermined value; and an alarm means
for outputting an alarm, based on the temperature measured by the
temperature measuring means and the second predetermined value set
in the second setter, when the pressure corresponding to the
temperature becomes higher than or equal to the second
predetermined value related to pressure or when the temperature
becomes higher than or equal to the second predetermined value
related to temperature.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims benefit of
priority under 35 USC 119 from the Japanese Patent Application No.
2012-021109, filed on Feb. 2, 2012, the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a protection device for
turbine exhaust chambers and a condenser and a monitoring
controller for the turbine exhaust chambers and the condenser.
[0004] Related Art
[0005] A power-generation plant having a steam turbine is provided
with a condenser for cooling and condensing exhaust steam of the
turbine. During operation of the plant, an inside of the condenser
is kept at a negative pressure.
[0006] Seawater for cooling the exhaust steam of the turbine is
supplied by a circulating water pump. However, the supply of the
cooling water by the circulating water pump may be stopped for some
reasons. As another reason for an insufficient flow rate of the
cooling water, a blackout accident in the plant, which is the loss
of all power supply in the power-generation plant, may occur, for
example. In this case, a cooling function and a condensing function
of the condenser are lost.
[0007] If such an accident occurs, a boiler and the steam turbine
come to an emergency stop. However, the boiler immediately after
the stop has residual heat. In order to release the residual heat,
steam and heat drain water flow into the condenser via a turbine
bypass valve, various drain valves, and the like.
[0008] However, since the cooling function and the condensing
function of the condenser have been lost, the steam does not
condense. As a result, pressures in the condenser and the turbine
exhaust chamber, which is a pressure vessel integral with the
condenser, gradually increase due to a steam pressure and
eventually turn from negative pressures into positive pressures,
i.e., pressures equal to or higher than the atmospheric pressure.
The positive pressures are not suitable conditions for the
condenser and the turbine exhaust chambers which are originally
designed to be used at the negative pressure.
[0009] Therefore, as a protection device for the condenser and the
turbine exhaust chambers, atmosphere discharge discs are used.
[0010] The atmosphere discharge discs are disposed at a ceiling
portion of the turbine exhaust chambers and form parts of the
turbine exhaust chambers. If the pressures in the turbine exhaust
chambers turn into the positive pressures and, more specifically,
if gauge pressures reaches the positive pressures of about 20 kPa
to 40 kPa, the atmosphere discharge discs rupture. In this manner,
the atmosphere discharge discs are designed to discharge the steam
in the condenser into the atmosphere.
[0011] In other words, the atmosphere discharge discs are provided
to prevent breakage of the important turbine exhaust chambers and
condenser by rupturing themselves.
[0012] In lines 36 to 41 in column 5 on page 3 of the
after-mentioned Patent Document 1 disclosing the prior-art
protection device, there is the following description:
[0013] "Many of currently-used steam turbines have structures
resistant to the negative pressure. Therefore, as in this prior
art, if the outside air is forced into the steam turbine for
cooling to build the positive pressure in the steam turbine,
unexpected breakage such as rupture of the atmosphere discharge
discs or the like occurs. [0014] Patent Document 1: Japanese
Examined Patent Publication (Kokoku) No. 3-4723
[0015] If the atmosphere discharge discs rupture, repair work of
them takes a few days, which forces the power-generation plant to
stop to thereby seriously affect society when demand for
electricity is critically high, for example.
[0016] Moreover, for an independent power producer (IPP) running a
power-generation plant under an electric power selling contract
with a power company for business, this is directly linked to a
large financial loss.
SUMMARY OF THE INVENTION
[0017] With the above circumstances in view, it is an object of the
present invention to provide a protection device for turbine
exhaust chambers and a condenser and a monitoring controller for
the turbine exhaust chambers and the condenser, which can prevent
breakage of the turbine exhaust chambers and the condenser without
requiring much time and cost for repair.
[0018] According to one aspect of the present invention, there is
provided a protection device for a turbine exhaust chamber and a
condenser comprising:
[0019] a condenser for cooling and condensing steam exhausted from
a steam turbine;
[0020] a turbine exhaust chamber casing integrally covering the
steam turbine and the condenser;
[0021] an atmosphere discharge disc for rupturing when a pressure
in the turbine exhaust chamber casing reaches a first predetermined
value;
[0022] a temperature measuring means for measuring a temperature in
the turbine exhaust chamber casing;
[0023] a first setter for setting a second predetermined value;
[0024] an output means for producing an external output, based on
the temperature measured by the temperature measuring means and the
second predetermined value set by the first setter, when a pressure
corresponding to the temperature becomes higher than or equal to
the second predetermined value related to pressure or when the
temperature becomes equal to or higher than the second
predetermined value related to temperature; and
[0025] a releasing means for releasing the steam in the turbine
exhaust chamber casing to an exterior when the output means
produces the external output.
[0026] According to one aspect of the present invention, there is
provided a monitoring controller for a turbine exhaust chamber and
a condenser comprising:
[0027] a first setter for setting a first predetermined value;
and
[0028] an output means for outputting an external output, based on
a measured temperature in a turbine exhaust chamber casing
integrally covering a condenser for cooling and condensing steam
exhausted from a steam turbine and the steam turbine and the first
predetermined value set by the first setter, when a pressure
corresponding to the temperature becomes higher than or equal to
the first predetermined value related to pressure or when the
temperature becomes higher than or equal to the first predetermined
value related to temperature.
[0029] With the protection device for the turbine exhaust chambers
and the condenser and the monitoring controller for the turbine
exhaust chambers and the condenser according to the invention, it
is possible to prevent the breakage of the turbine exhaust chambers
and the condenser without requiring much time and cost for the
repair.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a vertical sectional view of a structure of a
protection device for turbine exhaust chambers and a condenser
according to a first embodiment of the present invention;
[0031] FIG. 2 is a graph showing a relationship between a saturated
steam pressure and a saturated steam temperature;
[0032] FIG. 3 is a circuit diagram showing a configuration of a
monitoring controller provided to the protection device for the
turbine exhaust chambers and the condenser; and
[0033] FIG. 4 is a vertical sectional view showing a configuration
of a monitoring controller provided to a protection device for
turbine exhaust chambers and a condenser according to a second
embodiment of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0034] As described above, when the pressures in the turbine
exhaust chambers reach the positive pressures, the atmosphere
discharge discs rupture to discharge the steam in the condenser
into the atmosphere to thereby prevent breakage of the important
turbine exhaust chambers and the condenser. Such atmosphere
discharge discs serve the purpose by rupturing themselves.
Therefore, it is necessary to have the atmosphere discharge discs
as last protection means. However, if the positive pressures in the
turbine exhaust chambers can be sensed and the steam in the turbine
exhaust chambers can be released into the atmosphere before the
atmosphere discharge discs rupture, it is possible to avoid the
above-described nonproductive repair work.
[0035] An important point here is to measure a very low positive
pressure close to the atmospheric pressure with high accuracy.
[0036] In general, pressure is measured by using a pressure
transmitter, a pressure switch, or the like. However, if they are
used in an attempt to measure the very low positive pressure with
high accuracy, "the pressure transmitter and the pressure switch
measure a saturated pressure of an atmospheric temperature instead
of the pressures in the turbine exhaust chamber". This phenomenon
will be described below.
[0037] In general, to measure the pressure by using the pressure
transmitter, actual process, i.e., steam, water, oil, or the like
to be measured at a measure point is led to the pressure
transmitter through a capillary tube which is also called
instrumentation pipe and a pressure of the actual process is
measured.
[0038] Measurement of the pressure in the vicinity of the
atmosphere discharge discs by using such a pressure transmitter
will be discussed.
[0039] In the vicinity of each of the atmosphere discharge discs in
the turbine exhaust chambers, a basket chip, for example, for
taking in the stream as the actual process is disposed. The steam
in each of the turbine exhaust chambers comes into the basket chip
and is led out of the turbine exhaust chamber through the capillary
tube and sent to the pressure transmitter where the pressure of the
steam is measured.
[0040] The steam pressure at this time is affected by an
environmental temperature around the capillary tube outside the
turbine exhaust chamber, i.e., an atmospheric temperature. More
specifically, the pressure in the capillary tube is a saturated
pressure of the atmospheric temperature or a pressure close to the
saturated pressure due to an influence of the saturated
pressure.
[0041] As a result, the pressure transmitter measures the saturated
pressure of the atmospheric temperature outside the turbine exhaust
chambers or the pressure close to the saturated pressure instead of
the pressures in the turbine exhaust chambers. Such an
inconvenience occurs similarly when the pressure switch, which
measures the pressure by similarly leading the steam out of each of
the turbine exhaust chambers through the capillary tube, is
used.
[0042] This phenomenon can be ignored when the temperature and
pressure of the actual process are much higher than the atmospheric
temperature and pressure. However, it can not be ignored in the
measurement of the actual process at the pressure and temperature
close to the atmospheric pressure and reduces the measurement
accuracy.
[0043] In order to suppress such a phenomenon, measures such as a
heat insulator provided around the capillary tube may be taken.
With such measures, however, it is extremely difficult to
fundamentally improve the pressure measurement accuracy.
[0044] Therefore, in the embodiments of the invention, the
inventors have noted that the steam in each of the turbine exhaust
chambers is saturated steam and thought of measurement of the
temperature in each of the turbine exhaust chambers instead of the
measurement of the pressure. The measured temperature is converted
into the saturated pressure of the steam. It is detected that the
obtained pressure in each of the turbine exhaust chambers has
reached a predetermined positive pressure. The embodiments are
characterized in that the steam in the turbine exhaust chambers is
released into the atmosphere by actuating any releasing means
before the atmosphere discharge discs rupture.
[0045] The protection devices for the turbine exhaust chambers and
the condenser and the monitoring controllers for the turbine
exhaust chambers and the condenser according to the embodiments of
the invention will be described below with reference to the
drawings.
(1) First Embodiment
[0046] FIG. 1 illustrates a structure of a protection device for
turbine exhaust chambers and a condenser according to a first
embodiment of the invention. FIG. 1 illustrates sectional
structures of a low-pressure turbine rotor 104, an inner casing
105, a turbine exhaust chamber casing 106, and a condenser 107 in a
power-generation plant. The turbine exhaust chamber casing 106
integrally covers a turbine and the condenser 107 as a casing.
[0047] During operation of the power-generation plant, pressures in
turbine exhaust chambers 101a and 101b and the condenser 107
(hereafter referred to as internal pressures) are maintained at
negative pressures close to a vacuum. From exhaust of an
intermediate-pressure turbine (not shown), steam a flows into a
crossover pipe 108. This steam a is led into the inner casing 105
and drives the low-pressure turbine rotor 104 as driving steam
b.
[0048] Pressure of the driving steam b is reduced at every stage of
the low-pressure turbine rotor 104. Finally, the steam is exhausted
as exhaust steams c and d into the turbine exhaust chambers 101a
and 101b and the condenser 107, respectively. With cooling water
sent into the condenser 107 from a circulating water pump (not
shown), the exhaust steams c, d are condensed and collected in a
hot well 109 at a lower portion.
[0049] In this operating state, if the circulating water pump stops
due to some accident and supply of the cooling water stops or a
flow rate of the cooling water becomes insufficient, the exhaust
steams c, d are not condensed. As a result, the internal pressure
increases. If the internal pressure reaches a protection trip
value, the power-generation plant including the steam turbine and a
boiler comes to an emergency stop and inflow of the exhaust steams
c, d stop.
[0050] However, the boiler immediately after the stop has residual
heat. This heat flows into the condenser 107 in forms of bypass
steam e sent from a turbine bypass valve 110 and heat drain water f
sent from a drain valve 111. As a result, the internal pressure
gradually increases.
[0051] As described above, the steam in the turbine exhaust
chambers 101a and 101b is the saturated steam. Therefore, between
saturated steam pressure and saturated steam temperature, there is
such a relationship that the pressure increases as the temperature
increases as shown in FIG. 2.
[0052] The atmosphere discharge discs 100a and 100b rupture when
the internal pressure increases and turns from the negative
pressure into the positive pressure, e.g., when it reaches 129.51
kPaabs (abs stands for absolute pressure). In this way, the
saturated steam in the turbine exhaust chamber casing 106 is
released into the atmosphere. In the following description, the
pressure at which the atmosphere discharge discs 100a and 100b
rupture is defined as 129.51 kPaabs for the sake of
convenience.
[0053] A structure provided in the first embodiment in order to
release the saturated steam at a stage before the rupture pressure
of the atmosphere discharge discs 100a and 100b is reached will be
described.
[0054] A resistance temperature detector 102a measures an internal
temperature g in the vicinity of the atmosphere discharge disc 100a
and a resistance temperature detector 102b measures an internal
temperature h in the vicinity of the atmosphere discharge disc
100b, respectively, in the turbine exhaust chamber casing 106. The
measured temperatures g and h are input to a monitoring controller
201 through cables 112a and 112b, respectively.
[0055] FIG. 3 illustrates a configuration of an arithmetic section
circuit 202 provided in the monitoring controller 201 according to
the embodiment. The arithmetic section circuit 202 includes a high
value selector 203, a converter 204, a setter 205, a comparator
206, a setter 207, and a comparator 208. The converter 204 and the
comparator 206 form an output means for generating an output n.
[0056] The internal temperatures g and h measured by the resistance
temperature detectors 102a and 102b are input to the high value
selector 203. Higher one of the internal temperatures g and h is
output as a steam temperature j and input to the converter 204.
[0057] In the converter 204, a characteristic curve representing
the relationship between the saturated steam pressure and the
saturated steam temperature shown in FIG. 2 is set. Therefore, if
the steam temperature j is input to the converter 204, the
saturated pressure k corresponding to the steam temperature j is
obtained based on the characteristic curve and output. To put it
more concretely, the steam temperature j on a Y-axis is converted
into the saturated steam pressure k on an X-axis on the
characteristic curve shown in FIG. 2 and output.
[0058] The output saturated steam pressure k is input to the
comparators 206 and 208.
[0059] A predetermined set value m is set in the setter 205. The
saturated steam pressure k and the set value m are input to the
comparator 206 and compared to each other. While the saturated
steam temperature k is not higher than the set value m, the output
n of the comparator 206 is maintained in an OFF state. If the
saturated steam pressure k exceeds the set value m, the output n is
turned on. Operation of the comparator 208 will be described
later.
[0060] Here, as the set value m, the vacuum breaker valve opening
pressure of 105.09 kPaabs shown in FIG. 2 is set, for example. This
set value m is set at a value smaller than 129.51 kPaabs at which
the atmosphere discharge discs 100a and 100b rupture.
[0061] If the external output n from the comparator 206 is
generated, the external output n is produced from the monitoring
controller 201 shown in FIG. 1. This output is transmitted to a
driving motor 114 via a cable 113. By the driving motor 114
driving, the vacuum breaker valve 103 opens. As a result, the
saturated steam in the turbine exhaust chamber casing 106 is
released into the atmosphere through a pipe 115.
[0062] Here, if the external output n is produced from the
comparator 206, the vacuum breaker valve 103 is used as a releasing
means for releasing the steam in the turbine exhaust chamber casing
106 to an exterior. However, the releasing means is not limited to
the vacuum breaker valve, if it can operate as a means for
releasing the steam in the turbine exhaust chamber casing 106 to an
exterior in response to the output from the comparator.
[0063] The vacuum breaker valve 103 is a motor-operated valve which
is provided to the condenser 107 without exception. The vacuum
breaker valve 103 is for carrying out what is called vacuum break
which is opening of the inside of the condenser 107 into the
atmospheric state when the plant stops for a long period of
time.
[0064] This vacuum breaker valve 103 is disposed on the pipe 115
connecting the inside and the outside of the condenser 107 as
described above. While the negative pressure is maintained in the
condenser 107, the vacuum breaker valve 103 is closed. To carry out
the vacuum break, the vacuum breaker valve 103 is opened and the
air flows into the condenser 107.
[0065] In the first embodiment, on the other hand, the vacuum
breaker valve 103 is opened when the internal pressures in the
turbine exhaust chamber casing 106 and the condenser 107 reach the
predetermined positive pressure. In this way, the internal steam is
released into the atmosphere.
[0066] As described above, the internal pressure in the turbine
exhaust chamber casing 106 is retained by the saturated steam.
Therefore, by measuring the internal temperature, it is possible to
obtain the internal pressure by using the characteristic curve in
FIG. 3.
[0067] To measure the internal temperature, a thermocouple may be
used, for example, besides the above-described resistance
temperature detector. If the temperature is measured by using the
resistance temperature detector or the thermocouple, the capillary
tube, which is necessary in the measurement of the internal
pressure, is unnecessary. Therefore, it is possible to measure the
internal temperature with high accuracy to calculate the internal
pressure without being affected by the atmospheric temperature. In
the first embodiment, the resistance temperature detector, which is
generally considered to have higher measurement accuracy than the
thermocouple, is used.
[0068] As shown by the characteristic curve in FIG. 2, the
saturated temperature corresponding to 105.09 kPaabs, which is the
pressure preset as the set value m in the setter 205, is
101.degree. C. On the other hand, the saturated temperature
corresponding to 129.51 kPaabs, which is the pressure at which the
atmosphere discharge discs 100a and 100b rupture, is 107.degree. C.
By using the resistance temperature detectors 102a and 102b, it is
possible to reliably discriminate the temperature difference of
6.degree. C.
[0069] Therefore, the vacuum breaker valve 103 is opened when the
internal temperature of 101.degree. C. which is sufficiently lower
than the internal temperature 107.degree. C. corresponding to the
internal pressure at which the atmosphere discharge discs 100a and
100b rupture is detected. In this way, it is possible to protect
the turbine exhaust chamber casing 106 and the condenser 107.
[0070] Here, as a means for releasing the steam in the turbine
exhaust chamber casing 106 and the condenser 107, the vacuum
breaker valve 103 is used. As described above, the vacuum breaker
valve 103 is equipment provided to the condenser 107 without
exception. Therefore, it is unnecessary to additionally provide a
means for releasing the steam, which prevents an increase in
cost.
[0071] The vacuum breaker valve is normally provided as a
motor-operated valve which is driven by a direct-current (DC) power
supply to carry out a stop of turbine rotation as an emergency
measure.
[0072] In a blackout accident in the plant, an alternating-current
(AC) power supply is lost. However, the direct-current (DC) power
supply can always be secured even in an emergency. Therefore, by
using the vacuum breaker valve 103 which can be driven by the
direct-current (DC) power supply, it is possible to obtain the
reliable protection device.
[0073] If the vacuum breaker valve 103 is used as the steam
releasing means, there is an element to consider. When the
atmosphere discharge discs 100a and 100b rupture, large areas
rupture and, as a result, the internal steam is released at a
burst. On the other hand, when the steam is released by using the
vacuum breaker valve 103, the steam cannot be released at a burst
and it takes time for the steam to be released due to restriction
by dimensions of the pipe 115.
[0074] Of course opening of the vacuum breaker valve 103 has to be
started at a positive pressure lower than the positive pressure at
which the atmosphere discharge discs 100a and 100b rupture.
However, it is necessary to consider that reduction of the internal
pressure requires time when the steam is released by the vacuum
breaker valve 103.
[0075] Therefore, the opening of the vacuum breaker valve 103 is
preferably started at a very low positive pressure immediately
after the saturated pressure turns from the negative pressure into
the positive pressure. Therefore, in the first embodiment, the set
value m is 105.09 kPaabs. Such setting is possible because of
high-accuracy measurement by using the resistance temperature
detectors 102a and 102b.
[0076] According to the first embodiment, by opening the vacuum
breaker valve 103 immediately after the saturated pressure turns
from the negative pressure into the positive pressure, the residual
heat flowing into the turbine exhaust chamber casing 106 after that
escapes into the atmosphere. As a result, it is possible to prevent
increase of the internal pressure from the pressure at the time of
the valve opening.
[0077] Because the first embodiment has the structure for opening
the vacuum breaker valve 103 after the saturated pressure turns
from the negative pressure into the positive pressure, it may not
have the atmosphere discharge discs 100a and 100b. In this case, it
is possible to reduce manufacturing cost of the atmosphere
discharge discs and cost required for the repair.
[0078] However, depending on various forms of accidents of the
power-generation plant, the internal pressure does not necessarily
increase gradually and a possibility of abrupt increase cannot be
denied.
[0079] Considering all forms of accidents, it is preferable to
dispose the atmosphere discharge discs 100a and 100b so as to
further increase security.
[0080] As described above, preferably the set value m is set at the
very low positive pressure immediately after the saturated pressure
turns from the negative pressure into the positive pressure and the
vacuum breaker valve 103 is opened at this pressure. However, it is
also possible to allow more time by setting the set value m at a
negative pressure lower than the positive pressure and opening the
vacuum breaker valve 103 when the pressure is the negative
pressure.
[0081] However, if the vacuum breaker valve 103 is opened at the
negative pressure, the internal pressure increases toward the
atmospheric pressure at that instant.
[0082] A phenomenon which can occur at this time will be
considered. Seal steam is supplied to gland portions 116a and 116b
where the low-pressure turbine rotor 104 passes through the turbine
exhaust chamber casing 106 in order to seal clearances in the
passing-through portions.
[0083] However, once the blackout accident occurs in the plant, a
gland steam exhauster stops and a function of recovering the seal
steam is lost. While the internal pressure is the negative
pressure, the seal steam is drawn into the condenser 107.
Therefore, leakage does not occur through the clearances at the
passing-through portions or is suppressed if it occurs.
[0084] However, if the internal pressure reaches the atmospheric
pressure, the seal steam leaks from the clearances at the
passing-through portions and the steam and water mix into bearing
oil. Or the bearing oil may be carried by the leaking seal steam
and come in contact with a high-temperature object to cause a
fire.
[0085] It is important to prevent the rupture of the atmosphere
discharge discs 100a and 100b. However, while the internal pressure
is the negative pressure, it is also important to maintain the
negative pressure.
[0086] Therefore, considering these two points, i.e., prevention of
the rupture of the atmosphere discharge discs 100a and 100b and
maintenance of the internal pressure at the negative pressure, the
first embodiment is configured as follows:
[0087] To be prepared for an accident in which an amount of the
residual heat of the boiler is relatively small and an enough
amount of heat to increase the internal pressure to the positive
pressure does not flow in, the vacuum breaker valve 103 is
maintained in a closed state to maintain the negative pressure as
long as possible.
[0088] From this state, at a low positive pressure immediately
after the internal pressure turns into the positive pressure, the
vacuum breaker valve 103 is opened to release the steam. As the
positive pressure at this time, as described above, the set value m
is set at 105.09 kPaabs which is slightly higher than the
atmospheric pressure (101.42 kPaabs).
[0089] If the internal pressure turns from the negative pressure
into the positive pressure, it greatly affects operation of the
power-generation plant. Therefore, it is important that the
protection device informs an operator of this change.
[0090] Therefore, as shown in FIG. 3, the monitoring controller 201
includes the setter 207 and the comparator 208.
[0091] A set value p is set in advance in the setter 207. The
saturated pressure k output from the converter 204 and the set
value p output from the setter 207 are given to the comparator 208.
They are compared to each other in the comparator 208 and an alarm
q is output when the saturated pressure k exceeds the set value p.
The set value p is set at 99 kPaabs which is the internal pressure
immediately before turning from the negative pressure into the
positive pressure.
[0092] As described above, according to the first embodiment, by
opening the vacuum breaker valve 103 when the internal pressure
turns from the negative pressure into the positive pressure and
reaches 105.09 kPa, breakage of rupture of the atmosphere discharge
discs 100a and 100b can be prevented and breakage of the turbine
exhaust chamber and the condenser can be prevented without
requiring much time and cost for the repair.
(2) Second Embodiment
[0093] A protection device for a turbine exhaust chamber and a
condenser and a monitoring controller for a turbine exhaust chamber
and a condenser according to a second embodiment of the invention
will be described by using the drawings.
[0094] In the second embodiment, a monitoring controller 401 has a
different configuration from the monitoring controller 201 in the
first embodiment. As shown in FIG. 4, an arithmetic section circuit
402 provided in the monitoring controller 401 includes a high value
selector 403, a setter 405, and a comparator 406. The comparator
406 forms an output means for generating an external output n.
[0095] The internal temperatures g and h are input to the high
value selector 403, and higher one of the internal temperatures g
and h is output as a steam temperature j and input to the
comparator 406 without through converter.
[0096] In the setter 405, 101.degree. C. is set in advance as a set
value r. The set steam temperature of 101.degree. C. corresponds to
the steam pressure of 105.09 kPa at which the vacuum breaker valve
103 is opened in FIG. 2.
[0097] The set value r is input to the comparator 406 and the steam
temperature j and the set value r are compared to each other. When
the steam temperature j exceeds the set value r, the output n is
turned on. After that, similarly to the first embodiment, the
vacuum breaker valve 103 is opened when the external output n is
produced.
[0098] In this manner, in the second embodiment, the set value r is
given as a set value of temperature. The steam temperature j output
from the high value selector 403 is input to the comparator 406
without being converted into the steam pressure by a converter.
Because the converter is unnecessary, a circuit configuration of
the arithmetic section circuit 402 is simplified and cost is
reduced.
[0099] However, considering review and revision of the steam
pressure at which the vacuum breaker valve is opened, it is more
convenient if the steam pressure is directly set in the setter 205
and the set value m and the steam pressure k are compared to each
other in the comparator 206 as in the first embodiment.
[0100] As described above, according to the second embodiment, by
opening the vacuum breaker valve 103 when the temperature
101.degree. C., corresponding to the internal pressure turning from
the negative pressure into the positive pressure and reaching
105.09 kPa, is reached, rupture of the atmosphere discharge discs
100a and 100b can be prevented and breakage of the turbine exhaust
chamber and the condenser can be prevented without requiring much
time and cost for the repair. Moreover, the configuration of the
arithmetic section circuit 402 is simplified, which contributes to
cost reduction.
[0101] Although a few embodiments of the invention have been
described, these embodiments are shown as examples and are not
intended to limit a technical scope of the invention. These novel
embodiments can be carried out in other various forms and various
omissions, replacement, and modifications can be made without
departing from the gist of the invention. These embodiments and
their variations are included in the technical scope and the gist
of the invention and included in the invention described in the
claims and a scope equivalent to the invention.
[0102] For example, in the first and second embodiments, the
saturated pressure at which the vacuum breaker valve 103 is opened
is 109.09 kPa. However, this value is merely an example and the
saturated pressure is not limited to it.
[0103] In the first embodiment, the set value of 99 kPaabs is set
as the pressure at which the alarm is output. However, the pressure
is not limited to this value and the set value p can be set at a
desired value.
[0104] In the second embodiment, in order to output an alarm
similarly to the first embodiment, it may be configured to output
an alarm when the steam temperature j reaches a predetermined
pressure value.
* * * * *