RIHAND GOVERNOR for power plant governing system

RIHAND GOVERNOR

1. RIHAND GOVERNOR
GOVERNING SYSTEM CAN BE CONSIDERED IN
TWO PARTS
1.STEAM FLOW COMPUTING AND
2.VALVE CONTROL
THE INTERFACE BETWEEN THESE TWO
PARTS IS AN ARRANGEMENT OF HIGHWAYS
WHICH CARRY VARIOUS VALVE POSITIONING
SIGNALS.

2. STEAM FLOW COMPUTING
THE PRINCIPAL ITEM OF STEAM FLOW
COMPUTING PART IS THE COMPUTING
CHANNEL.THERE ARE THREE COMPUTING
CHANNEL(CC) EACH WORKING INDEPENDENTLY
OF THE OTHER TWO.
BASIC FUNCTION OF CC IS TO MEASURE THE
SPEED OF THE TURBINE, COMPARED THIS WITH
A DEMANDED SPEED (3000RPM) AND THEN
PROCESS THE RESULTING SPEED ERROR SIGNAL
VIA DROOP,BIAS AND RATE OF CHANGE CIRCUIT
TO PROVIDE VALVE POSITION SIGNALS FOR
H.P.STOP, H.P.GOVERNING AND I.P.GOVERNING
VALVES.

3. VALVE CONTROL
EACH VALVE IS PROVIDED WITH ITS OWN
VALVE CONTROLLER WHICH FORMS THE
ELECTRICAL SECTION OF THE ELECTRO-
HYDRAULIC VALVE CONTROLLING
SYSTEM.ITS PURPOSE IS TO PROVIDE A
SUITABLE DRIVE TO THE SERVO-VALVE
SO THAT THE VALVE MAY BE POSITIONED
AS DEMANDED BY THE VALVE POSITION
SIGNALS FROM THE CC.

4. LOW VALUE GATE: FOCAL
POINT OF COMPUTING CH.
THE LOW VALUE GATE(L.V.G.) IS THE FOCAL
POINT OF THE CC MODULE THE INPUTE,TO THE
L.V.G. ARE:
1.PROTECTION
2.RUN-UP GOVERNING (WIDE RANGE
GOVERNING: WRG)
3.RAMP
4.HP GOV. VALVE OPENING LIMIT( 0-105%)
5.SPEED STEAM (NARROW RANGE GOVERNING:
NRG)
6.VACUUM PAY-OFF

5. WRG
•WRG Is single channel and allows its
set point to change from barring gear to
near synchronous speed.
•ATRS:-Uses WRG interface during
run-up. Run-up modules controls of
turbine from barring speed to nominal
speed using a speed reference ramp which
is modulated by ATRS.

6. Speed Steam: NRG
Speed of turbine is computed from rate of pulses
generated by magnetic ups mounted adjacent to a 60-
toothed wheel fitted to turbine shaft. The pulses are
amplified by head amp.& then process thro’ dynamic
compensator,accle. pcb to speed measure pcb which
generate voltage proportional to diff of actual & ref.
speed 3000rpm i.e speed error. This error then amp.
by droop amp. Dead band facility holds the o/p of
droop amp.at zero over a range of speed error signal.

7. Speed steam ( cont.): NRG
•The o/p of droop amp. is added to speed
error reference( SER) whose o/p is the
speed steam.
•The speed error ref.( SER) is a bias applied
to the droop amp.to set the speed steam
signal at a particular turbine speed. The
value of SER is controlled by CCR-desk
raise/lower push button or by other sources.

8. Speed steam ( cont): NRG
•The speed error signal is also fed into a low
value gate on summer pcb. Bias &
amplification applied to speed error signal to
give 10v at 103.5% speed & 0v at 106%
speed( droop: 2.5%). At maximum
measurable speed which is 106.25%. the o/p
of over-speed clipping ckt. is –10%. Where
as governor droop which is 4% can give o/p
at maximum speed is –6.25%.

10. Output of LVG: steam demand
signal
•Valve high way : O/p of LVG is compared with o/p
of other CC. This ckt generates an o/p average of all
3 computing ch.o/p ( if within 5%). The o/p of
average& voter pcb feeds the valve high way amp. as
steam demand signal to
1Hp gov valve high way: driven by function generator
whose in/op characteristics is inverse of valve
lift/flow charac.The valve lift signal is fed to all HP
gov. valve control module.

11. Steam demand signal
2HP stop valve Highway: The stop valve signal
from the run-up module is applied to one input of
LVG.The o/p of average/voter is applied to other
input. The lowest signal is fed to non-linear
amplifier for all HP stop valves
3IP gov valve highway : Its driver sums together
the “steam demand signal” & sequence bias
signal. Accele. Signal also summed. The o/p of
summing amp. Is the valve lift signal which fed to
all IP gov valve control modules.

12. Valve control module
•The valve controller contains the necessary
averaging,L.V.D.T. drive & demodulator ckt. It has
two ch. Control & check L.V.D.T. and when the
monitors detects a discrepancy between these that
exceeds a preset value , the controller will trip its
valve shut and raise an alarm.
•Its purpose is to provide suitable drive to servo
valve so that the valve may be positioned as
demanded by the averaging signal of all three
computing signals.

14. 30003120324028802760
0+120+240-1200%
+100%
-100%
-240
+100%
-100%
DROOP 4% & DEAD BAND+/-2%
TURBINE DROOP 4% & NO DEAD BAND

15. +100%
0%
-10%
GOVERNOR
DROOP 4%
OVERSPEED
CLIPPING
CKT
3060 3105
3187.5 3060 3105
RIHAND DROOP &OVER SPEED CLIPPING