U.S. patent number 3,724,214 [Application Number 05/121,317] was granted by the patent office on 1973-04-03 for extraction control system for a turbogenerator set.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to Ozro N. Bryant.
United States Patent |
3,724,214 |
Bryant |
April 3, 1973 |
EXTRACTION CONTROL SYSTEM FOR A TURBOGENERATOR SET
Abstract
A turbogenerator set having an extraction control system for
maintaining a selected pressure at each steam extraction point
regardless of the flow at individual extraction points and
irrespective of whether the load on the generator is maintained at
a selected load or whether the load is varied, as long as the load
on the generator is greater than the power supplied by that portion
of the extracted steam which passes through the turbine.
Inventors: |
Bryant; Ozro N. (Chester,
PA) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
Family
ID: |
22395902 |
Appl.
No.: |
05/121,317 |
Filed: |
March 5, 1971 |
Current U.S.
Class: |
60/685;
60/648 |
Current CPC
Class: |
F01K
7/345 (20130101); F01K 17/04 (20130101) |
Current International
Class: |
F01K
17/04 (20060101); F01K 7/34 (20060101); F01K
17/00 (20060101); F01K 7/00 (20060101); F01k
013/02 (); F01k 017/02 (); F01k 007/16 () |
Field of
Search: |
;60/70,73,102,105 |
Foreign Patent Documents
Primary Examiner: Cohan; Alan
Assistant Examiner: Ostrager; Allen M.
Claims
What is claimed is:
1. In a turbogenerator set comprising a first turbine unit having a
first motive steam inlet control valve and an extraction steam
outlet, a second turbine unit having a second motive steam inlet
control valve provided with steam by said extraction steam outlet,
said extraction steam outlet also being adapted to supply steam to
a process having varying steam demands, and a load carried by said
first and second turbine units;
a control system for maintaining a set speed on said turbines and
supplying said varying demands for steam of said process
comprising
means responsive to the speed of the turbine unit for jointly
governing said first and second inlet control valves, and
means responsive to the steam pressure in said extraction steam
outlet for opposing and modifying the governing effect of said
speed responsive means on said first inlet control valve to supply
the varying demands of steam of said process and maintaining a set
speed on said turbines.
2. A control system as set forth in claim 1 and further
comprising
means responsive to load for modifying the governing effect of the
speed responsive means jointly on the first and second inlet
control valves and being capable of maintaining said load at a
selected value, and being capable of supplying the varying demands
for steam of the process.
3. A control system as set forth in claim 1 and further
comprising
means responsive to a system load for modifying the governing
effect of the speed responsive means to proportion the load on the
turbines relative to said system load, and being capable of
supplying the varying demands for steam of the process.
4. In a turbogenerator set as set forth in claim 1, wherein
the second turbine unit has a second extraction steam outlet, and
further comprises
a third turbine unit having a third motive steam inlet control
valve provided with steam from said second extraction steam outlet,
said second extraction steam outlet also being adapted to supply
varying demands for steam of a second process;
the control system having means responsive to the speed of said
turbine units for governing all the inlet control valves and means
responsive to the steam pressure, in said second extraction steam
outlet, for modifying and opposing the governing effect of said
speed responsive means on said third inlet control valve, to supply
the varying demands for steam of said second process.
5. In a turbogenerator set as set forth in claim 1, wherein
the second turbine unit has a second extraction steam outlet, and
further comprises
a third turbine unit having a third motive steam inlet control
valve provided with steam from said second extraction steam outlet,
said second extraction steam outlet also being adapted to supply
varying demands for steam of a second process;
the control system having means responsive to the speed of the
turbine units for governing all the inlet control valves;
means responsive to load for modifying the governing effect of the
speed responsive means on all said inlet control valves, and being
capable of maintaining the load at a selected value, and
means responsive to the steam pressure in said second extraction
steam outlet for modifying and opposing said modified governing
effect of the speed and load responsive means on said third inlet
control valve to supply the varying demands for steam of said
second process.
6. In a turbogenerator set as set forth in claim 1, wherein
the second turbine unit has a second extracting steam outlet
supplying varying demands for steam of a second process and further
comprises,
a third turbine unit having a third motive steam inlet control
valve provided with steam from said second extraction steam
outlet,
the control system having means responsive to the speed of the
turbine units for governing all the inlet control valves,
means responsive to a system load for modifying the governing
effect of the speed responsive means on all the inlet control
valves to proportion the load on the turbine units relative to a
system load, and
means responsive to the steam pressure in said second extraction
outlet for modifying and opposing said modified governing effect of
the speed and system load responsive means on said third inlet
control valve to supply the varying demands for steam of said
second process.
7. In a steam turbogenerator set comprising
a high pressure turbine unit having a first extraction steam
outlet, which supplies varying demands for steam of a first
process,
an intermediate turbine unit provided with motive steam by said
first outlet and having a second extraction steam outlet, which
supplies varying demands for steam of a second process,
a low pressure turbine unit provided with motive steam by said
second outlet, and
a load carried by said turbine units;
a control system for maintaining said load at a selected value with
varying demand for steam at selected pressure levels for said
processes, comprising
a first steam inlet control valve for regulating flow of high
pressure motive steam to said high pressure unit,
a second steam inlet control valve interposed between said first
extraction outlet and said intermediate pressure turbine unit for
regulating flow of intermediate pressure motive steam to the latter
unit,
a third steam inlet control valve interposed between said second
extraction steam outlet and said low pressure turbine unit for
regulating flow of low pressure motive steam to the low pressure
turbine unit,
means responsive to speed of said turbine units and providing a
speed signal effective to urge each of said control valves in
closing direction with increasing speed,
means responsive to said load and providing a load signal modifying
said speed signal and effective to augment the speed signal with
increasing load,
means responsive to steam pressure in said first extraction steam
outlet and providing a first extraction pressure signal effective
to oppose said modified signal and urge said first control valve in
opening direction with decreasing extraction steam pressure,
and
means responsive to steam pressure in said second extraction steam
outlet and providing a second extraction pressure signal effective
to oppose said modified signal and urge said third control valve in
opening direction with increasing extraction steam pressure in
opposition to the effect of said modified signal.
Description
BACKGROUND OF THE INVENTION
This invention relates to a control system for a turbogenerator set
having extraction points for supplying various quantities of
heating or process steam while carrying a set load on the
generator. Presently employed extraction control systems
substantially follow the same basic philosophy of
"load-compensation," i.e., schemes employing indirect "open-loop"
systems that are predicated on the proposition that if each set of
steam inlet control valves has a straight-line flow versus travel
characteristic, it is possible to move these valves in proportional
amounts to obtain steam flow conditions which are correctly
proportioned to maintain a constant load on the turbine as the
demands for extraction steam change.
Such schemes have two main objections, the first being the
difficulty of providing valves having straight-line flow versus
travel characteristics, and the second being the proportional
relationship of the valves change as the extraction pressure levels
are altered, thus requiring skilled servicemen to reset the control
system.
More particularly, "load-compensation" is inherently difficult to
employ and inaccurate in operation, because process steam is
extracted from a turbine after only partial expansion and hence
does less work in carrying load than steam which passes through the
entire turbine.
Accordingly, if steam is extracted, enough additional steam must be
added to the turbine steam flow to balance the power loss due to
extraction, otherwise the load is reduced. Theoretically, if the
flow of extracted steam were to be measured, a proportionate
measured amount of steam flow to the turbine could be added by the
high pressure steam inlet control valve to balance the load demand.
But this involves measuring two steam flow rates and creates
additional complexities.
Furthermore, the proportions change as the extraction pressure is
altered to suit various process requirements. If the steam inlet
control valve for the various turbine sections or units all had
uniform straight-line characteristics of steam flow versus valve
travel, the valve actuator could be designed to move in the
required correct relation to maintain a constant load as the demand
for extraction steam flow changed. The above is uneconomical and
unreliable, since as mentioned previously, it is very difficult to
produce steam inlet control valves having the required
characteristics, particularly when the extraction steam pressure
values are changed, as required.
In addition to the above, extraction turbines carrying an
electrical load, such as a generator, required to satisfy the
customers' electrical requirements, are often connected to large
electrical utility tie-lines, so that additional power is provided
in the event that greater electrical load is required by the
customer than can be provided by the turbine. Under such
installation conditions, the frequency of the generator output is
determined by that of the utility tie-line.
In other instances, the turbine control system may not be effective
to maintain its required selected load and the utility tie-line
will be required to provide the balance.
SUMMARY OF THE INVENTION
In general, a control system made in accordance with this invention
controls a turbogenerator set comprising a first turbine unit
having a first motive steam inlet control valve and an extraction
steam outlet, a second turbine unit having a second motive steam
inlet control valve provided with steam by the extraction steam
outlet, and a load carried by the first and second turbine units.
Such a control system maintains a selected extraction steam outlet
pressure regardless of the flow through the steam outlet and
irrespective of the load on the generator and comprises means
responsive to the speed of the turbine units for governing the
inlet control valves, and means responsive to the steam pressure in
the extraction steam outlet for modifying the governing effect on
the first inlet control valve.
BRIEF DESCRIPTION OF THE DRAWINGS
The objects and advantages of this invention will become more
apparent from reading the following detailed description in
connection with the accompanying drawings, in which:
FIG. 1 diagrammatically shows a turbogenerator set having a control
system made in accordance with this invention;
FIG. 2 diagrammatically shows a turbogenerator set having a
hydraulic control system made in accordance with this
invention;
FIG. 3 diagrammatically shows an electrical system and various
inputs to a response device for a control system made in accordance
with this invention.
PREFERRED EMBODIMENT
Referring now to the drawings in detail, FIG. 1 diagrammatically
shows a turbogenerator set comprising a high pressure or first
turbine unit 1, an intermediate pressure or second turbine unit 2,
and a low pressure or third turbine unit 3. The turbine units are
mounted in tandem on a single shaft 4 with a generator 5. It is
understood the turbine units may be in one casing or on separate
shafts, the arrangement in FIG. 1 being shown for simplicity of
explanation.
Steam from a boiler (not shown) flows through an inlet pipe 6, then
through a first motive steam control valve 7, through the first
turbine unit 1, and then through an extraction steam outlet or
extraction point 9. A portion of the steam leaving the extraction
steam outlet 9 is used for heating or for process steam, indicated
by the box 10, and the remainder of the exhaust from turbine 1
flows through a second motive steam control valve 11, via pipe 12,
to the intermediate turbine unit 2. After flowing through the
intermediate turbine 2, the steam flows through a second extraction
steam outlet or extraction point 13. A portion of the steam from
the second extraction outlet 13 is used for heating or process
steam, indicated by the box 14, and the remainder of the steam
flows through a third motive steam control valve 15, via pipe 16.
The steam then flows through the low pressure turbine unit 3 into a
condenser C.
FIG. 1 also shows a control system for maintaining a selected
extraction steam pressure at each extraction point, regardless of
the steam flow through the steam outlets and irrespective of
whether the loading on the generator 5 is maintained at a selected
load or whether the loading is varied. The control system comprises
a device 17 responsive to the spead of the turbine units capable of
producing a signal (electric, pneumatic or hydraulic) for governing
the control valves 7, 11 and 15, causing them to be urged in
closing direction as the speed increases above a preset value, and
causing them to be urged in opening direction, if the speed
decreases below this preset value. The signal from the speed
responsive device is transmitted, via lines 18, to the various
control valves.
Shown at 19 is a device responsive to the load on the generator
capable of producing a signal for modifying the governing effect of
the speed responsive device 17 on the control valves 7, 11 and 15.
The load responsive device 19 is only made active when it is
desirable to maintain a constant load on the generator or a load
proportional to some reference load, i.e., the load of another
generator or a system load. The load responsive device 19 is
adapted to be made non-responsive to load or is disconnected from
the control system if it is desired to allow the load on the
generator to vary while maintaining the extraction steam pressures
at their set values. The signal from the load responsive device is
transmitted to the control valves 7, 11 and 15 via lines 20.
At 21 and 23, in FIG. 1, are shown devices responsive to the steam
pressure of the extraction steam outlets 9 and 13, respectively.
The pressure responsive devices 21 and 23 are capable of producing
a signal that modifies and opposes the governing effect of the
speed responsive device and the load responsive device on the
control valve 7 and 15, respectively. An increase in pressure in
the first extraction steam outlet 9 causes the pressure responsive
device 21 to produce a signal which urges the first control valve 7
in closing direction and a pressure reduction in the first
extraction steam outlet causes the opposite affect. An increase in
the pressure in the second extraction outlet 13 causes the pressure
responsive device 23 to produce a signal which urges the third
control valve 15 in opening direction. A reduction in the second
extraction pressure causes the opposite effect. Thus, it becomes
apparent that the speed responsive and load responsive devices
operate all the control valves to regulate the output of the
turbogenerator while the pressure responsive devices 21 and 23
operate control valves 7 and 15, respectively, through lines 24 and
25 to regulate the pressures of the extraction steam outlets. Thus,
even through the control valves do not have straight line flow
versus travel characteristics, the steam pressure at the extraction
points will be maintained constant as the load set on the generator
is varied or as the requirements for process steam vary.
The operation of the control system can best be understood by
following the action of the various components during a normal
operating cycle. Assume a preset load on the generator 5 and a
selected pressure for the process steam to the processes indicated
by the boxes 10 and 14, which would provide a specific pressure in
the extraction outlets 9 and 13. With the load responsive device 19
set to maintain a selected load, a decrease in the demand for steam
to process 10 or to process 14, or to both, causes additional steam
to pass through the turbine units 3 or turbine units 2 and 3, which
would tend to make the turbogenerator set speed up. The speed
responsive device 17 would sense the increase in speed and send a
signal to control valves 7, 11 and 15 causing each valve to tend to
close. If the generator 5 were connected to an electrical system
with several other turbogenerator units, the increase in speed
would cause an increase in load. The load responsive device sensing
this load increase would send a modifying signal to control valves
7, 11 and 15 causing them to close further. If the process 10 by
itself were to have the decrease in demand (increase in pressure at
the extraction outlet 9), the control valve 7 would also receive a
signal from the pressure responsive device 21 causing it to be
urged in closing direction, thus it would close to a greater extent
than control valves 11 and 15.
To rebalance the system for the new flow conditions requiring less
steam for process 10, it becomes necessary to close control valve 7
more than control valves 11 and 15. If the demand for steam for
process 14 were to decrease, the speed and load responsive devices
17 and 19 would sense an increase in speed and load due to the
additional steam flowing through the low pressure turbine unit 3
and send signals to the control valves 7, 11 and 15 urging them in
closing direction. The reduction in flow to the process 14
(increase in the pressure in the extraction outlet 13) would cause
the pressure responsive device 23 to send a signal to control valve
15 modifying and opposing the signal from the load and speed
responsive device causing control valve 15 not to close as much as
the other control valves 7 and 11, or if the pressure change were
large enough, the signal from the pressure responsive device 23
could cause the control valve 15 to move in opening direction. A
reduction in the demand of steam for process 14 necessitates the
smaller flow of steam through turbine units 1 and 2 and the greater
flow through turbine unit 3, to maintain the same load on the
generator, which this control system provides.
A decrease in the flow requirements of both processes 10 and 14
(pressure at extraction outlets 9 and 13 increase) would cause the
turbine speed and load to increase. The speed and load responsive
devices 17 and 19 sensing these changes would send signals to urge
control valves 7, 11 and 15 in closing direction, the pressure
responsive device 21 would modify the signal to control valve 7
causing it to close a greater amount, and the pressure responsive
device 23 would modify the signal to control valve 15 to cause it
to close less or even to move in opening direction, depending on
the degree of reduction in the flow of steam to process 14. The new
flow conditions required for reduction of flow to processes 10 and
14 would necessitate a reduction in the steam flow to the high
pressure turbine, a slightly smaller reduction in the steam flow to
the intermediate pressure turbine, and a very slight reduction or
an increase in the flow of steam to the low pressure turbine, which
this control system provides.
It has been noted that the pressure responsive devices move only
one control valve, while the load and speed responsive devices
cause simultaneous action on all control valves to hold the load at
its selected value. Load variations follow steam flow changes with
very small time delay, whereas the change in pressure in the
extraction piping system has a long time constant, because of the
large volume of steam normally in such systems. Thus, to obtain
close steady state control, a long time constant must be used to
compensate for the flow changes in the extraction outlets. The
speed and load responsive devices trim the steam flow as the
pressure responsive devices return the pressure to its selected
value, providing precise steam pressure control at the extraction
points, although the valves do not have straight line flow versus
travel characteristics.
As noted earlier, the sensing devices can produce electrical,
hydraulic or pneumatic signals, therefore it is understood that the
control system of this invention may use electrical, hydraulic or
pneumatic media or any combination thereof for controlling the
turbogenerator set.
FIG. 2 diagrammatically shows a control system of this invention
using hydraulic controls. As noted, it is understood that
pneumatic, electrical, or any combination thereof, may also be
employed. As in FIG. 1, the turbogenerator set in FIG. 2 comprises
the high pressure turbine 1, the intermediate turbine 2, the low
pressure turbine 3, and the generator 5 mounted on a single shaft
4. Motive steam from the boiler (not shown) flows through the inlet
piping 6, the first motive steam control valve 7, and then through
the high pressure turbine 1. The motive steam is exhausted from
turbine 1 through the extraction outlet 9. A portion of the steam
leaving the extraction outlet 9 is used for heating or process
steam, indicated by the box 10. The remainder of the exhaust from
turbine 1 flows through a second motive steam valve 11 via pipe 12
before entering the intermediate turbine 2. The exhaust from
turbine 2 flows through the extraction outlet 13 and then divides.
A portion of the steam is utilized for heating or process steam,
indicated by box 14, and the remainder of the steam flows through
the third motive control valve 15 via line 16, through the low
pressure turbine 3 and then into the condenser C.
FIG. 2 also shows a hydraulic control system for maintaining
selected extraction pressures at the extraction points, regardless
of the steam flow, when the load on the generator is maintained at
a selected value.
The hydraulic control system, as shown in FIG. 2, comprises three
servomotors or hydraulic cylinders 31, 32 and 33 which operate the
control valves 7, 11 and 15, respectively. Each servomotor has a
piston 34, 35 and 36 which divides the servomotor into upper and
lower chambers 37, 38 and 39 and 40, 41 and 42, respectively. If
the pressure in the upper chambers 37, 38 and 39 exceeds the
pressure in the lower chambers 40, 41 and 42 the valves will open
and vice versa. The lower chambers 40, 41 and 42 of the servomotors
31, 32 and 33 are in communication with a hydraulic conduit 45. The
conduit 45 is in communication with a supply of high pressure
hydraulic fluid 46, the flow of the fluid from the supply being
controlled by restrictions 47 and 48 disposed in a cover plate 49
of a reservoir 50. Check valves 51 and 53 are disposed adjacent
each end of the conduit 45 downstream of the restrictions.
The conduit 45 is in communication with the hydraulic reservoir 50.
Controlling the flow of hydraulic fluid from the conduit 45 to the
reservoir 50 are cup valves 57 and 59, which seat on the cover
plate 49. Cup valve 57 is controlled by the speed responsive device
17 which in FIG. 2 is shown to comprise an impeller 61, mounted on
the turbine shaft 4 to produce a hydraulic pressure which increases
as the square of the speed. Hydraulic conduit 63 transmits the
pressure produced by the impeller 61 to a bellows 65 disposed in a
cavity 66 in the cover plate 49. A balance bar 67, pivotally
mounted at its midpoint to the cover plate 49 by a mounting bracket
68, controls the movement of the cup valve 57, which is
cooperatively associated with one end thereof. The other end of the
balance bar 67 is biased in a downward direction by pressure in
conduit 63 acting on the bellow 65 and biased in an upward
direction by a compression spring 69 mounted in the reservoir 50.
The bias of the spring 69 may be changed manually by the hand wheel
71 mounted outside of the reservoir 50 for turning a screw 72
extending into the reservoir to increase the compression on the
spring 69. The bellows 65, spring 69 and cup valve 57 are so
disposed relative to the balance bar 67, that an increase in speed
of the turbine and governing impeller 61 causes an increase in
pressure in line 63, resulting in cup valve 57 moving in closing
direction and an increase in the pressure in the conduit 45 which
causes the pistons 34, 35 and 36 of the servomotors 31, 32 and 33
to move upwardly, urging the control valves 7, 11 and 15 in closing
direction to return the turbine to its set speed. A reduction in
speed causes a reduction in pressure in conduit 63 and causes the
servomotors 31, 32 and 33 to urge the control valves 7, 11 and 15
in opening direction.
The load responsive device 19 is shown in FIG. 2 to comprise a
transducer 73 which controls an electrical motor 74 having a torque
arm 75 extending through the side of the reservoir 50. The torque
arm 75 is biased in a counterclockwise direction by a tension
spring 77 disposed in the reservoir. The bias of the spring 77 is
regulated by a hand wheel 79 mounted outside the reservoir 50 for
turning a screw 80 extending into the reservoir to increase or
decrease the tension on the spring 77. The cup valve 59 is
cooperatively associated with the torque arm 75 and moves in
closing direction toward the cover plate 49 when the torque arm 75
moves in clockwise direction. Upon sensing an increase in load, the
load responsive device sends a signal to the motor 73 via lines 81
causing the motor 74 to rotate the torque arm in clockwise
direction operating the cup valves 59 in closing direction to
increase the pressure in the conduit 45. This causes the pistons
34, 35 and 36 to move in an upward direction to urge the control
valves 7, 11 and 15 to move in closing direction. A bleed conduit
83 connects conduit 45 to reservoir 50 and a restriction 85
controls the rate of flow through conduit 83. The check valves 51
and 53 and bleed conduit 83 cooperate to allow either impeller 61
and its associated controls responsive to the turbine speed or
transducer 73 and its associated controls responsive to the
generator load to override the other when one of these controllers
produces a higher pressure in conduit 45 than the other. Thus, it
is possible to set the load controller to some minimum load,
presumably higher than the power produced by the required process
steam as it passes through the turbine units, and allow the speed
responsive controller to control the turbogenerator unit as the
generator load varies above this preset minimum level.
As shown in FIG. 2, the servomotor 31 has its upper chamber 37 in
communication with hydraulic conduit 87, which has the flow from
one end thereof regulated by cup valve 89, which seats against the
cover plate 49. Conduit 87 is in communication with the supply of
high pressure hydraulic fluid 46 disposed in the cover plate 49.
The flow of hydraulic fluid from the supply 46 to conduit 87 is
regulated by a restriction 90, also disposed in the cover plate 49.
A bellows 91 is disposed in a cavity 66' in the cover plate in
communication with the extraction outlet 9 via conduit 92. A link
93 is pivotally mounted at one of its ends on a mounting bracket
68' fastened to the cover plate 49 and is biased downwardly by a
pressure acting on the bellows 91 and is biased upwardly by a
compression spring 94 disposed within the reservoir 50. The upward
bias of the spring 94 may be increased or decreased by turning the
hand wheel 95 mounted outside the reservoir 50 which operates a
screw 96 extending into the reservoir to increase and decrease the
compression on the spring 94. The cup valve 89 is cooperatively
associated with the link 93 in such a manner, that a decrease in
pressure at the exhaust point 9 and in conduit 92 causes the cup
valve to move in closing direction, toward the cover plate 49,
resulting in an increase in pressure in conduit 87 and in the upper
chamber 37 of the servomotor 31. Thus, causing the control valve 7
to be urged in opening direction, resulting in greater steam flow
to the high pressure turbine and an increase in the pressure at the
extraction outlet 9.
An increase in the pressure at the extraction outlet 9 causes the
control valve 7 to move in the opposite direction, that is, in a
closing direction. This, of course, would cause a decrease in the
pressure at the extraction point 9. The upper chamber 38 of the
servomotor 32 is in communication with the high pressure hydraulic
fluid supply via conduit 97 and restrictions 99 and 100 fix the
pressure in the upward chamber 38 so that the servomotor 32 is only
responsive to changes in the pressure in conduit 45, which is
regulated by the cup valves 57 and 59 which in turn are part of the
speed and load responsive devices 17 and 19, respectively. The
upper chamber 39 of the servomotor 33 is in communication with a
conduit 101. The conduit 101 is supplied with pressurized hydraulic
fluid from the supply 46 through a restriction 103, disposed within
the cover plate 49, and a cup valve 105 which seats on the cover
plate 49 regulates the pressure within the conduit 101. A balance
arm 107 is pivotally mounted at its midpoint on a mounting bracket
68" and has one end biased in downward direction by the pressure of
the second extraction outlet 13 acting via conduit 108 on a bellows
109 disposed in a cavity 66" in the cover plate 49. A compression
spring 113 exerts an upward bias on the one end of the balance arm
107 to counteract the bias in the downward direction exerted by the
bellows 109. A hand wheel 115 disposed outside the reservoir 50 is
used to turn a screw 116 which extends into the reservoir to
increase or decrease the bias of the spring 113. The cup valve 105
is cooperatively associated with the balance arm 107 in such a
manner that an increase in pressure at the extraction outlet 13 is
transmitted to the bellows 109, via conduit 108, causing the cup
valve 105 to move in closing direction, resulting in an increase in
pressure in the conduit 101 and in the upper chamber 39 of the
servomotor 33. This causes the piston 36 to move downwardly and the
control valve 15 to be urged in opening direction. This in turn
reduces the pressure of the extraction outlet 13.
The lower chambers 40, 41 and 42 of the servomotors 31, 32 and 33
are subject to the control of either the speed or load responsive
devices or a combination thereof to change the flow of steam to all
three turbine units upon a change in speed of the shaft or a change
in the load on the generator. The upper chambers 37 and 39 are
subject to changes in the extraction outlet pressures to urge the
control valves 7 and 15 in opening or closing directions to
maintain the extraction outlets at their set pressure by opposing
or modifying the affects of changes in pressure in the lower
chambers 40, 41 and 42. The hydraulic control system, as shown in
FIG. 2 and herebefore described, among other functions will
maintain the extraction points at a set pressure even with large
variation in load, although the control valves do not have straight
line flow versus travel characteristics.
As shown in FIG. 3, the load responsive device can also be made
responsive to the load on another generator 117, an electrical tie
line as indicated at 119 or a factory load 121 to proportion the
output of the generator 5 relative to the output of the other
generators, a system load, or factory load.
Transducers 73, 123 and 125, as shown in FIG. 3, respond to the
controlled turbogenerator's load 5, the load on another generator
117 or the factory load 121, respectively, to transmit a signal via
lines 131, 133 and 135, respectively, to a selector 137. The
selector 137 receives the signal from the various transducers,
integrates them, and sends a signal via line 139 to the motor 74,
which operates the cup valve 59 to urge the control valves 7, 11
and 15 in opening or closing directions (see FIG. 2). The selector
may be set so that the signal from the transducer 73 responsive to
the load on the controlled generator 5 is transmitted directly to
the motor 74 to urge the control valve in opening or closing
directions to maintain a set load on the generator 5. If desired,
the selector may be set to receive signals from the controlled
generator's transducer 73 as well as from the other generator's
transducer 123 via lines 131 and 133, to integrate the signal and
to transmit a signal to the motor 74 via line 139 causing the motor
to operate the cup valve 59 to urge the control valve in opening or
closing directions for maintaining a load on the controlled
generator 5 proportional to the load on the other generator
117.
In a similar manner the selector may be set to receive signals from
the factory load's transducer 125 and the controlled generator's
transducer 73, integrate the signals and transmit the integrated
signals to the motor 74 to cause the control valves to be urged in
opening or closing directions to maintain a load on the control
generator 5 proportional to the factory load.
The load on the controlled generator may be made proportional to a
system load, shown in FIG. 3 to comprise the output of the
generators 5 and 117, the input or output of the tie line 119, and
the factory load 121. The transducers 73, 123 and 125 each send
signals to the selector 137 and the selector integrates the signals
and sends a signal via line 139 to the motor 74 to cause control
valves 7, 11 and 15 to be urged in opening or closing directions to
maintain the load on the generator proportional to the system load.
Thus, the hydraulic control systems shown in FIG. 2 combined with
the load responsive devices shown in FIG. 3 produce a versatile
control system for turbogenerator sets having one or more
extraction points.
* * * * *