Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
4809
AUTOMATIC HYDRAULIC TURBINE STARTING DEVICE
The present invention relates to hydraulic tubine con-
trol arrangements, and more particularly to automatic hydraulic
turbine starting devices.
The invention can most advantageously be used in turbo-
generator units with relatively small flywheel moments, operating
at considerable water head variations at a hydro-electric power
station.
Setting the width of the initial opening of the wicket
gate is especially important during turbine startup, for it serves
to admit water to the turbine runner. The initial opening of the
wicket gate provides for a turbine rotor torque sufficient for the
rotor start running and gradually gain the rated speed of rotation. ;
Under unfavourable turbine operating conditions, e.g. in the case
of wide water head variations, the setting adjustment of the
initial opening according to head becomes vital because the in-
ability to adjust the opening in accordance with water head varia-
tiGns leads to deterioration of the turbine startup conditions and
even to a possible failure of the turbine.
Known in the art is a device (cf. USSR Inventor's Certi-
ficate No. 271,402), wherein a mechanism for limiting the opening
of the hydraulic turbine wicket gate, and a water head sensor
actuating element with a profile cam are provided in a hydraulic
turbine starting system, said mechanism and element being indepen-
dently connected with the main distributing valve of the wicket
gate servomotor via leverage, said valve being hydraulically con-
nected with said servomotor.
The device serves to open the wicket gate to the re-
quired initial opening width at the moment of turbine startup,
said width remaining unchanged until the turbine rotor speed
governor starts operating. The rated rotational speed of the
turbine rotor having been achieved, the governor takes over
-- 2
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whereby the wicket gate initial opening width is automatically
reduced to a width corresponding to no-load operation of the
turbine.
The initial gate opening width at which the turbine
rotor starts running and constituting from 20 to 30 per cent of
the maximum gate opening is much greater than the width corres-
ponding to no-load operation, which is from 10 to 15 per cent
of maximum opening. This may result in an overshoot of the
rotational speed of the rotor during the turbine startup period,
which is especially true in the case of turbo-generator units
with small flywheel moments; also, a turbine overspeed may occur
in case the automatic speed governor fails.
Manual adjustment of the initial gate opening along with
automatic limiting of the maximum gate opening according to head
are accomplished in the above device. No automatic correction of
the initial opening is effected, which may generally result in an
overshoot of the rotor speed at high heads or in deterioation of
startup conditions, namely, in the rotor's inability to start
running at low heads.
With these and other objects in view there is proposed
an automatic starting hydraulic turbine device, comprising a gate
limit mechanism and a water head sensor actuating element with a
profile cam, said mechanism and said element being connected with
a main distributing valve of a gate servomotor via a leverage,
while the gate limit mechanism, according to the invention, is
kinematically linked with the water head sensor actuating element
by means of a lever, connected to a solenoid core with a speed
switch connected in the winding circuit of said solenoid, said
speed switch being adjusted to operate at a predetermined speed
achieved by a hydraulic turbine rotor.
It is expedient that the speed switch be adjusted to
operate at a speed from 30 to 50 per cent of the rated rotational
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speed of the turbine rotor.
The proposed automatic hydraulic turbine starting device
permits a smooth startup, vlz. a gradual rise in the rotor speed
until its rated value is reached.
These and other objects and advantages of the present
invention will be readily apparent from the following detailed
description of specific embodiments thereof, taken in conjunction
with the accompan~7ing drawings, wherein:
Fig. 1 is a block diagram with kinematic links of an .
automatie hydraulie turbine starting deviee, according to the
invention;
Fig. 2 is a graph showing changes in the hydraulic tur-
bine gate opening width at startup, effeeted by the automatic
starting device according to the invention.
The automatic hydraulic turbine starting device com-
prises a gate limit meehanism 1 of a wicket gate 2, ineluding a
threaded rod 3 eonnected with a shaft 5 by means of a worm couple
4, the shaft 5 having cams 6 operatively associated with micro-
eontacts 7 of a drive motor 8 of the threaded rod 3. The threaded
rod 3 of the gate limit mechanism 1 is connected with a rod 16
via a leverage comprising levers 9 and 10, a shaft 11 rotatable
in bearings 12, levers 13, 14 and 15, said rod 16 belonging to a
main distributing valve 17 hydraulically connected with a servo-
motor 19 via transmissions 18. A rod 20 of the servomotor 19 is
eonneeted with the wicket gate 2. The automatic hydraulic tur-
bine starting device also comprises an actuating element 21 of a
water head sensor 22, said element including a rotatable profile
cam 23. The profile cam 23 of the actuating element 21 is intro-
dueed into the kinematic linkage between the gate limit mechanism
1 and the main distributing valve 17 at a point 25 by means of
the lever 9 urged by a spring 24. A core 27 of a solenoid 28 is
introduced into the same linkage via a portion 26 of the lever 9,
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with the speed switch 30 being connected in the electric circuit
of a solenoid winding 29 and being adjusted to operate at a speed
from 30 to 50 per cent of the rated speed of the rotor. Thus,
the gate limit mechanism 1 of the wicket gate 2 and the actuating
element 21 of the water head sensor 22 are interconnected via the
lever 9.
An actuating element 31 of a turbine rotor speed governor
(not shown) is also operatively associated with the rod 16 of the
main distributing valve 17. Besides, the servomotor 19 of the
wicket gate 2 is connected with the main distributing valve 17 by
means of the reversed kinematic linkage, by virtue of the rod 20
of the servomotor 19 and the rod 16 of the main distributing valve
; 17 being interconnected via levers 32 and 15.
The operation of the above described automatic hydraulic
turbine starting device is as follows.
Prior to startup, the winding 29 of the solenoid 28 is
de-energized, the core 27 of the solenoid 28 is in the uppermost
position, while the threaded rod 3 of the gate limit mechanism 1
of the wicket gate 2 is in the lowermost position. Meanwhile, one
end of the spring-loaded lever 9 is pressed against the profile
cam 23, its other end being pressed against the threaded rod 3.
At the same time, the rod 16 of the main distributing valve 17 is
displaced for closing, the servomotor 19 being in a fully closed
position. The operation of the automatic starting device elements
for closing the wicket gate 2 is indicated by arrows in the draw-
ing. The direction of the operating fluid fed to the main distri-
buting valve 17 and sump is also indicated by arrows.
At turbine startup, the drive motor 8 of the threaded
rod 3 of the gate limit mechanism 1 of the wicket gate 2 becomes
energized, initiating upward movement of the threaded rod 3. The
threaded rod 3 moves upward covering a distance preset by means
of the cams 6 on the shaft 5, said distance corresponding to the
lOB4809
width of the initial opening of the wicket gate 2, depending on
the water head, mode of operation and type of turbine. The dis-
placement of the threaded rod 3 sets into motion thelevers 9, 10,
the shaft 11, the levers 13, 14 and 15, actuating the rod 16 of
the main distributing value 17, thereby setting the servomotor 19
to the initial opening position of the wicket gate 2. The open-
ing of the wicket gate 2 results in rotation of the turbine rotor,
caused by water coming to the runner. Meanwhile, the core 27 of
the solenoid 28 remains in the uppermost position.
The described stage of the automatic starting device's
operation is in conformity with rising portion A of a curve 33 on
the graph showing changes in the opening width of the wicket gate
2 (Fig. 2), said curve being shown as a thick solid line. In this
graph, time is plotted on the abscissa, while width Y of opening
of the wicket gate 2 is plotted on the ordinates together with
turbine rotor speed X, Y being expressed as percentage of the
maximum width and X, in terms of the rated value.
On attainment of the predetermined width of opening of
the wicket gate 2 (Fig. 1), the drive motor 8 is de-energized by
means of the microcontacts 7, the threaded rod 3 stops moving,
whereby opening of the wicket gate 2 discontinues. This takes
place at instant Tl (Fig. 2) corresponding to a point 34 on the
graph. Flat portion B of the curve 33 (Fig. 2) corresponds to a
constant width of opening of the wicket gate 2 (Fig. 1) within
this time interval. However, the turbine rotor speed goes on
rising in conformity with a curve 35 represented on the graph as
a thin solid curved line.
On attainment of 30 to 50 per cent of the rated speed
by the rotor, the speed switch 30 (Fig. 1) starts to operate with
further operation of the solenoid 28 at instant T2 (Fig. 2) cor-
responding to a point 36 on portion B of the curve 33, thereby
initiating the downward movement of the core 27 (Fig. 1) of the
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solenoid 28, the portion 26 of lever 9, and levers 10, said por-
tion 26 being connected with said core 27, and the lever 10 being
connected with the levers 9. The movement of the core 27 is
further transmitted to the levers 13, 14, 15 and the rod 16 of the
main distributing valve 17, initiating displacement of the rod 20
of the servomotor 19 for closing the wicket gate 2, which corres-
ponds to sloping portion C (Fig. 2) of the curve 33. The core
27 (Fig. 1) of the solenoid 28 is displaced to a position corres-
ponding to an intermediate width of opening of the wicket gate 2,
said width exceeding that corresponding to no-load operation by
2 to 4 per cent. This happens at instant T3 (Fig. 2) which cor-
responds to a point 37 on portion C of the curve 33.
The intermediate width of opening of the wicket gate 2
is maintained till the rated speed of the rotor is achieved, which
corresponds to flat portion D of the curve 33. The rotor having
achieved the rated speed of rotation at instant T4 corresponding
to a point 38 on the curve 33, the turbine speed governor reduces
the opening of the wicket gate 2 down to the width corresponding
to no-load operation, via its actuating element 31 (Fig. 1) acting
upon the rod 16 of the main distributing valve 17. Synchroniza-
tion of the generator (not shown) is effected during no-load oper-
ation corresponding to flat portion E (Fig. 2) on the curve 33,
the wicket gate 2 being opened to 10 to 15 per cent of the maxi-
mum opening width. The generator having been synchronized, the
wicket gate 2 is opened still wider to allow for normal operation
of the turbine/rising portion F of the curve 33/.
Automatic changing of the initial opening width of the
wicket gate 2, as well as of the width corresponding to no-load
operation, according to head, is accomplished as follows.
A change in the water head is sensed by the head sensor
22 (Fig. 1), resulting in rotation of the profile cam 23 of the
actuating element 21 of said sensor 22. The profile cam 23
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rotating in either direction, a corresponding change in the posi-
tion of the lever 9 takes place, the lever 9 interacting with
the cam 23, while the resulting movement of the levers 10 con-
nected with the lever 9, the shaft 11, the levers 13, 14 and 15
is transmitted to the servomotor 19 via the main distributing
valve 17, bringing about a corresponding change in the opening
width of the wicket gate 2.
The operation of the automatic starting device is
illustrated in the graph (Fig. 2), wherein the operation at low
head, indicated by an upper curve 39 is represented as a thick
dot-and-dash line, whereas the operation at high head, indicated
by a lower curve 40 is represented as a thick dashed line.
Analysis of the curves suggests that a correction accord-
ing to head can be accomplished with the aid of the proposed
device not only to change the initial opening width of the wicket
gate, but also the intermediate width, which is by 2 - 4 per cent
greater than that corresponding to no-load operation, said inter-
mediate width being the one up to which the initial opening width
is brought at the turbine operation time under consideration, viz.
both widths of the wicket gate opening increase at low head and
decrease at high head.
The proposed automatic hydraulic turbine starting device,
when compared to those known in the art, improves the turbine
operating conditions, enhance its reliability, while overspeed
or overshoot of the turbine speed at startup is obviated.
It is to be understood that various modifications and
embodiments of the claimed automatic hydraulic turbine starting
device are possible within the scope and nature of the present
invention.
