description hydro governor

8/13/2019 Description Hydro Governor

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DESCRIPTION OF HYDRO

MECHANICAL CABINET OF

GOVERNING SYSTEM FORDEFLECTOR CONTROL

1


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2.1 MECHANICAL -GOVERNOR

2.1.1 INTRODUCTION

The BHEL Mechanical Governor is basically designed for speed control,

however devices are provided to satisfy operation of a hydroset !nder thefollowing condition"

#teady #tate

#$all Transient

Large Transient

Bloc%ed Gate

The Governor is also designed to allow power and fre&!ency control'The basic principle of operation of the Mechanical Governor is as follow"

The (end!l!$, )!adrant and the distrib!ting valve control the $ove$ent of theservo$otor' Te$porary *roop devices +*ashpot etc' receiving a feedbac% fro$

hydra!lic ret!rn $otion cylinder gives a feedbac% signal for controlling the $ove$ent of

the servo$otors witho!t any h!nting'

Governor para$eters Te$porary *roop percent bt and *ecay ti$e constant Td are set to

allow stable operation of the hydroset'

The stability +speed and power o!tp!t oscillations is infl!enced not only by the above

two para$eters b!t also by the T!rbine, Governor, Grid and (ipeline -haracteristics'

(er$anent speed *roop device helps in the reg!lation' .re&!ency /s' Gate servo$otorrelationship can be altered by changing the (er$anent *roop setting to achieve desired

reg!lation'

#peed setting device is provided to allow synchronising, $an!al load control and

fre&!ency control'

Bloc% diagra$ of $ech' Governor is given fig'1

0


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-1

('T2

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1 3p

Td

bp

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4 " -5MM64* #74G6L

bt" TEM(58682 *855(

Td" T7ME -54#T64T 5. THE

*6M(74G *E/7-E'

T2" #E8/5M5T58 8E#(54#E T7ME

b(" (E8M64E4T *855(

( " *7..E8E4T76L 5(E86T58

BLOCK DIAGRAM OF MECHANCAL GOVERNOR (SINGLE STAGE)


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2.1.2 Desc!"#!$%

The Mechanical Governor consists of the following parts"

+i (end!l!$+ii *istrib!ting /alve

+iii Te$porary 8et!rn Motion

+iv (er$anent #peed *roop+v )!adrant

+vi Low #peed *evice

+vii #peed #etting *evice+viii E$ergency -ylinder

+i9 Gate Li$it *evice

+9 7ndication+9i #ervo$otor By pass

#tart solenoid :; #/, and E$ergency #olenoid :; E# are provided to allow re$ote start

and stop' Gate Li$it and speed setting is $otorised, as s!ch re$ote operation fro$-ontrol roo$ or load despatch is possible'


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2.1.2.1 Pe%&''

The pend!l!$ consists of two weights += $o!nted on g!iding springs +1 and held by

two $ains springs +0 which balance the centrif!gal force created by the rotation of thepend!l!$' The pend!l!$ casing + is directly connected to the synchrono!s rel!ctance

$otor +Elec' *evice 4o' :; M. and is $o!nted on ball bearings' The pend!l!$ weights

+= are shaped as ca$s and control the a$o!nt of oil escaping fro$ two no>>les +? onthe pend!l!$ spindle +?' The no>>les receive the oil fro$ the front cha$ber of the

pend!l!$ relay +@' The front cha$ber +@ receives oil press!re thro!gh diaphrag$

+A, and the bac% cha$ber +>le +: always faces the ca$s += beca!se the spindle +? isdriven by the pend!l!$ casing + thro!gh %eys +


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sl!ggishness' The two ball bearings +


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2.1.2. Te"$+ Re#'% M$#!$%

The te$porary ret!rn $otion consists of the ret!rn $otion piston +:, which is rigidly

connected to the servo$otor piston +0=: and operates, in the cylinder +:


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after a load change a ret!rn to the sa$e steady speed of the t!rbine +i'e' ignoring the

effect of the per$anent speed droop, which is &!ite seprate fro$ the te$porary droop'

The $ove$ent of the dashpot piston +0ero, the parallel face of ca$ +@0 is incontact with the roller +?;' This will give no speed variation' 7f the wheel +@ is t!rned,

the ca$ is rotated and presents an inclined face to the roller +?;' The $a9i$!$ slope

will be obtained with the wheel set at :, this will prod!ce the $a9i$!$ speedvariation' 7nter$ediate positions of the wheel +@ will give corresponding speed droops'

The opening sto%e of the servo$otor piston lifts the ca$ +@0 and, e9pect at the >ero

setting of the hand wheel +@, the &!adrant will $ove hori>ontally away fro$ the ca$

@

.ig


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+@0 d!e to its slopping face' This will tend to $ove the distrib!tion valve +00 in the

closing direction'

2.1.2./ 0'+&+%#

There are three basic $ove$ents of the &!adrant +


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e$ergency cylinder +0? to e9ha!st' 8eleasing press!re fro$ the e$ergency cylinder

allows the spring +1=1 to act on the lin% +1=>le +;0 is being starved of oil' The valve

+10@ is then controlling the position of valve +00, which is in t!rn $oved to the right

!ntil e&!ilibri!$ is achieved and the servo$otor cannot open f!rther !ntil the gate li$itis increased' 7t sho!ld be noted that, sho!ld be pilot rod +;1 $ove to the right, the valve

+00 will also $oves to the right and the servo$otor will close the g!ide vanes'

2.1.2.17 I%&!c+#!$%

The gate position as indicated by the ret!rn $otion ca$ is trans$itted electrically

trans$itter +10; to the dial indicator on the control panel' #i$ilarly the gate li$it settingas represented by the gate li$it lever and operator is trans$itted by +10


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2.1.2.11 Se,$$#$ B-P+ss

This bypass is s!pplied with all do!ble acting act!ators so that if the servo$otor which

the act!ator s!pplies has a hand gear for positioning the g!ide vanes, then oil can becirc!lated fro$ one side of the servo$otor to the other' The bypass valve +11A M!st

always be %ept closed e9cept for hand operation of servo$otor, when the governor oil

valve sho!ld be closed'

2.1.2..1 O"e+#!$%

2.1..2 *rop in load F The operation of the governor act!ator can best be e9plained by ta%ing ane9a$ple of the operation of reg!lation, for instance, as it occ!rs on a s!dden drop in load'

Dhen this ta%es place, the speed of the set and th!s the speed of the pend!l!$ increases'

The weight += inside twopend!l!$ casing are s!bCected to an increased centrif!gal

force, which e9pands the springs +0 to a greater e9tent than before'

The ca$s on the pend!l!$ weights will have a tendency to leave the no>>le +: giving

an increased area to discharge oil fro$ these no>>les, releasing, therefore the press!re in

the cha$ber +@' The spindle +? will $ove to the left !nder the action of the press!rein cha$ber +>les +: are again in the i$$ediate neighborhood of the

ca$s'

The pend!l!$ spindle e9tension p!shes the &!adrant +ero, the roller +?; will roll on the parallel side of theca$ +@0 and no change in steady speed will after appear re$oval of the load'

The variation of steady speed between f!ll load and no load can be adC!sted s!ch as todivide the load as desired between parallel r!nning sets'

2.1..2 7ncrease of load F Dhen the load increases the speed of the set drops and so does thespeed of the pend!l!$' The flyballs += develop less centrif!gal forceJ the springs +0

p!ll the weights, and therefore the ca$s on the no>>les +:' This closes the no>>le

openings and press!re in cha$ber +@ b!ilds !p i$$ediately' The piston +


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to the right' 7ts $ove$ent is trans$itted by the spindle e9tensions to the &!adrant +>le +;0

ca!ses valve +00 to $ove to the left and open the servo$otor' The opening rate of theservo$otor is controlled by the dashpot +?= b!t the final position, which the servo$otor

reaches, is deter$ined by the per$anent speed variation setting +@' 7f for e9a$ple this

is set at , a increase of speed control gear setting will ca!se the servo$otor to opento the f!ll load position'

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2.1.. MAINTENANCE8G$,e%$ Ac#'+#$

The Governor 6ct!ators are f!lly tested before leaving the wor%s and all adC!st$ents are

$ade to ens!re correct wor%ing' Dith reco$$ended grade of oil, the governor sho!ld

well with f!rther adC!st$ents site'

The instr!ctions for setting as given below will be fo!nd !sef!l to obtain a better

!nderstanding of the vario!s parts and per$it i$prove$ent on perfor$ance if s!ch are

desired once the $achine has been p!t into service'

a The correct grade of oil $!st be !sed, shell T!rbo :@ or e&!ivalent'

b 7rreg!larities in governing $ay be prod!ced by i$p!rities in the oil' The partseffected sho!ld be re$oved, Dashed in paraffin and p!t bac% in their correct positions,

after caref!lly re$oving possible b!rrs or scratches' 7$p!rities in the oil are liable to

!pset the wor%ing of the diaphrag$s +A, +


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c The vario!s diaphrag$s !sed on the governorite$s +A, +


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Dith an frce gear b!t so$e bac%lash, notches will give a s$oother transition of steering

and the p!lsations of the servo$otor $!st be s!fficient to overr!n the bac%lash'

Dith s$all bac%lash and little friction, the p!lsation and the overlap can be red!ced, the

tapering notches giving the s$ooth control' This gives the best operation' Thereforebac%lash and friction $!st always be %ept as s$all as possible in the control gear

connecting the governor to the t!rbine, as well as in the ret!rn $otion gear'

7n case of h!nting ens!re that diaphrag$s +;


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2.1..9 Mec:+%!c+ 4$,e%$ &!+4+ $; c$%#$ %'*es

+01' (end!l!$ +00' *istrib!ting valve +0' 8et!rn $otion shaft +0les +:' (end!l!$ #pindle +?' .ront -ha$ber of 8elay +@' *iaphrag$ to @+A'

Bac% -ha$ber of 8elay +


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/alve 00'+110'Li$it switch to stop 101 at = Gate (osition +also :; L1 +11'Li$it

switch to stop 101 at 1== Gate (osition +also :; L1+11

description hydro governor

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