POWER GRID CORPORATION OF POWER GRID CORPORATION OF INDIA LIMITEDINDIA LIMITED

Presentation on Presentation on

‘‘FREE GOVERNOR OPERATION”FREE GOVERNOR OPERATION”

By D.K.Guru & S.P.BarnwalBy D.K.Guru & S.P.Barnwal

FREE GOVERNOR OPERATION

WHYFREQ COMPARISION

MAY-02 & MAY-03

GOVERNOR

BEFORE GOVERNORGOVERNOR RESPONSE

IN NER

DEAD BAND GOVERNOR TIME LAG

BLOCKED GOVERNOR

ROLE

DROOPFREQUENCY DECAY RATE BACKLASH

TYPES OF CONTROLSDROOP RESPONSE IN SR

ABT & GOVERNOR

ADVANTAGES

GOVERNOR TYPES

TIME DELAY

CHARACTERISTICS

PROBLEMS A FINAL WORD

ROLE OF SYSTEM OPERATOR

• LOAD GENERATION BALANCE

50

WHY DOES FREQUENCY DROP ?WHY DOES FREQUENCY DROP ?

Sudden addition of load causes a drop in frequency.

An increased load is supplied through an increase in the load angle by which the rotor lags the stator field.

It means a loss of Kinetic Energy of the rotating M/c and a slower speed of rotation i.e. a lower frequency.

f = (P/2) X (N/60)

Where f = frequency of the system

P = no of poles of the M/c.

N = rpm of the M/c.

• Load Frequency control

• Free Governor Opertaion

• Under Frequency Operation

PRIMARY CONTROLSPRIMARY CONTROLS

ABT AND GOVERNORABT AND GOVERNOR

POST ABT FREQUENCY WITHIN 49 TO 50.5HZ

ACHIEVED BY STAGGERING OF LOADS

FLUCTUATION IN FREQUENCY INCREASED

FREQUENCY COMPARISON FOR

47.50

48.00

48.50

49.00

49.50

50.00

50.50

51.00

51.50

00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23

04-MARCH 02 & 03

Frequency Variation based on data integrated over ONE minute interval

2003

2002

HUMAN GOVERNOR OPERATIONHUMAN GOVERNOR OPERATION

SYSTEM~TGX

GOVERNOR

GOVERNORGOVERNOR

SPEED GOVERNOR IS THE CONTROLLING MECHANISM WHICH

CONTROLS THE INPUT TO THE PRIME MOVER AUTOMATICALLY

WHEN THERE IS A CHANGE IN SYSTEM SPEED (FREQUENCY)

WHEN THERE IS A CHANGE IN SYSTEM FREQUENCY GOVERNOR

RESPOND BY CAUSING VALVES/GATES TO OPEN/CLOSE TO

INCREASE/DECREASE THE INPUT TO THE PRIME MOVER

MISCONCEPTIONMISCONCEPTION

Governors attempt to restore frequency to normal.

In reality, Governors attempt to restore load generation balance, using frequency change as a signal.

CHARACTERISTICSCHARACTERISTICS

1.1. Respond promptly to a small change Respond promptly to a small change in in speed.speed.

2.2. Adjust the throttle valve with a Adjust the throttle valve with a minimum minimum of overshoot.of overshoot.

3.3. Have sufficient power to overcome Have sufficient power to overcome friction losses and unbalance forces in friction losses and unbalance forces in

the throttle valve.the throttle valve.4.4. Permit very little speed fluctuation Permit very little speed fluctuation

under under constant load and steam constant load and steam conditions.conditions.

► There are several basic types of governors utilizing the above principles:There are several basic types of governors utilizing the above principles:► 1.Mechanical shaft - The familiar fly weight type.  A hand adjustment 1.Mechanical shaft - The familiar fly weight type.  A hand adjustment

permits speed regulation at the machine.permits speed regulation at the machine.► 2.Direct acting orifice - This consists of a shaft driven positive displacement 2.Direct acting orifice - This consists of a shaft driven positive displacement

type oil pump which delivers pressure to a spring diaphragm connected to type oil pump which delivers pressure to a spring diaphragm connected to the governor valve stem.  Since the delivered oil pressure is directly the governor valve stem.  Since the delivered oil pressure is directly proportional to shaft speed, control is accomplished.  Hand or automatic proportional to shaft speed, control is accomplished.  Hand or automatic speed regulation is possible.speed regulation is possible.

► 3.Oil relay - Built to utilize lube oil pressure or a separate governor oil 3.Oil relay - Built to utilize lube oil pressure or a separate governor oil pressure, a double acting oil relay piston permits more precise control of pressure, a double acting oil relay piston permits more precise control of the governor valve.  It is integral to the turbine and usually designed by the the governor valve.  It is integral to the turbine and usually designed by the turbine manufacturer.turbine manufacturer.

► 4.Precision oil relay - A separate shaft-driven oil relay offers more precise 4.Precision oil relay - A separate shaft-driven oil relay offers more precise control. Utilizing its own oil system, this type governor is not made by the control. Utilizing its own oil system, this type governor is not made by the turbine manufacturer. If more governor valve operating force is needed, a turbine manufacturer. If more governor valve operating force is needed, a second double acting servo-motor may be utilized.second double acting servo-motor may be utilized.

► 5.The electronic governor usually provides more precise and reliable speed 5.The electronic governor usually provides more precise and reliable speed control. The speed measurement signal can be generated in two ways. control. The speed measurement signal can be generated in two ways. One method is by utilizing a magnetic pickup in proximity to a toothed One method is by utilizing a magnetic pickup in proximity to a toothed wheel/gear mounted on the turbine shaft. Another method is to utilize a wheel/gear mounted on the turbine shaft. Another method is to utilize a shaft-mounted permanent magnet generator where the poles rotate and shaft-mounted permanent magnet generator where the poles rotate and produce an electronic pulse measured by a microprocessor. In the first produce an electronic pulse measured by a microprocessor. In the first case, only two pairs of wires connect to the unit. One supplies 48 VDC that case, only two pairs of wires connect to the unit. One supplies 48 VDC that is the required operating voltage; the other connects to a magnetic pickup is the required operating voltage; the other connects to a magnetic pickup on the turbine shaft. In the second case, no external power is required, as on the turbine shaft. In the second case, no external power is required, as the unit is powered from the turbine shaft rotation. In the first case, output the unit is powered from the turbine shaft rotation. In the first case, output air (normally 3-15 lbs.) goes to the diaphragm of a standard control valve in air (normally 3-15 lbs.) goes to the diaphragm of a standard control valve in the inlet steam line to the turbine. In the second case, hydraulic pressure the inlet steam line to the turbine. In the second case, hydraulic pressure drives a pre-piloted servo-motor that operates the governor valve.drives a pre-piloted servo-motor that operates the governor valve.

DEAD BANDDEAD BAND

DEAD BAND OF THE SPEED GOVERNORING SYSTEM IS THE TOTAL AMOUNT OF CHANGE IN STEADY STATE SPEED WITHIN WHICH

THERE IS NO ACTION BY GOVERNOR.

Turbine rated Turbine rated output MWoutput MW

Dead band percent of Dead band percent of rated speedrated speed

IN 50HZ BASEIN 50HZ BASE

< 5MW< 5MW 0.150.15 0.075HZ0.075HZ

5 to 30mw5 to 30mw 0.100.10 0.050HZ0.050HZ

> 30mw > 30mw 0.060.06 0.030HZ0.030HZ

IEC - 45

DROOP CHARACTERISTICSDROOP CHARACTERISTICS

THE AMOUNT OF SPEED (OR FREQUENCY) CHANGE THAT IS NECESSARY TO CAUSE THE MAIN PRIME MOVER CONTROL

MECHANISM TO MOVE FROM FULLY CLOSED TO FULLY OPEN.

NORMAL RANGE - 3 TO 5%

THE MINIMUM RATE OF CHANGE OF SPEED SHOULD NOT BE LESS THAN 0.4 TIMES OF ITS DROOP.

THE MAXIMUM RATE OF CHANGE OF SPEED SHOULD NOT BE MORE THAN 3 TIMES OF ITS DROOP.

5% DROOP ON 200MW GENERATOR

0

40

80

120

160

200

49 49.5 50 50.5 51 51.5

FREQ IN HZ --->

GE

NE

RA

TIO

N I

N M

W -

-->

PARTICIPATION OF 5% DROOP ON 200MW & 500MW GENERATORS

0

100

200

300

400

500

600

49 49.5 50 50.5 51 51.5

FREQ IN HZ --->

GE

NE

RA

TIO

N IN

MW

---

>

100MW for 0.5HZ Frequency

40MW for 0.5HZ Frequency

GOVERNOR DROOP 5% (500MW UNIT)

0

100

200

300

400

500

600

47 47.5 48 48.5 49 49.5 50 50.5 51 51.5 52 52.5 53

FREQ IN HZ --->

GE

NE

RA

TIO

N IN

MW

---

->

600

500

300

200

0

GOVERNOR DROOP 5% (210MW UNIT)

0

50

100

150

200

250

47 47.5 48 48.5 49 49.5 50 50.5 51 51.5 52 52.5 53

FREQ IN HZ --->

GE

NE

RA

TIO

N IN

MW

---

->

250

210

125

85

0

RESPONSE BY A 500 MW GENERATOR WITH DIFFRENT DROOP

0

375

125

0

200

500

400

300

100

500

250

0

50

100

150

200

250

300

350

400

450

500

48 48.5 49 49.5 50 50.5 51 51.5HZ->

MW

->

5 % DROOP

4 % DROOP

GOVERNOR TIME LAGGOVERNOR TIME LAG

TIME TAKEN BY GOVERNOR TO JUST BEGIN CHANGING POWER OUTPUT TO STABILISE FREQUENCY.

OR

TIME BETWEEN A CHANGE IN GENERATOR SPEED & CHANGE IN TURBINE POWER.

• Dead band 0.25 sec

• Valve opening 0.5 sec

• Steam flow 4 seconds

• During transient state Governor is of little help.

• Effect is felt during steady state

TIME DELAY IN GOVERNOR TIME DELAY IN GOVERNOR OPERATIONOPERATION

BLOCKED GOVERNORBLOCKED GOVERNOR

BYPASSING THE GOVERNING FEEDBACK MECHANISM TO MAINTAIN FIXED GENERATOR OUTPUT.

DISADVANTAGES:-

• SYSTEM INSTABILITY

• RESTORATION OF SYSTEM FREQUENCY TO NORMAL TAKES MORE TIME AFTER A DISTURBANCE.

FREQUENCY DECAY RATEFREQUENCY DECAY RATE

Approximate Freq 5 X Lost Generation

Decay Rate = --------------------------------------

In Hz / sec Remaining Generation

Example:-

2200MW200MW

Generation Lost

Freq decay rate = (5 X 200) / 2000 = 0.5 Hz /second

NEYVELI U-4 ON FGM ON 19/06/2003

160

170

180

190

200

210

220

11:00 11:15 11:30 11:45 12:00 12:15 12:30 12:45 13:00

TIME ->

MW

->

49

49.2

49.4

49.6

49.8

50

50.2

50.4

HZ

->

GENERATION

FREQUENCY

DROOP CHARACTERISTICS OF NYL U4

170

175

180

185

190

195

200

205

210

49.6 49.7 49.8 49.9 50 50.1 50.2 50.3 50.4 50.5

FREQ CHANGE 49.7 - > 50.4 0.7HzGEN CHANGE 205 -> 177 35MW CHANGE IN GEN 28 MW FOR 0.7 Hz CHANGE IN FREQFOR 200 MW CHANGE IN GEN FREQ CHANGE REQD =(200*0.7)/28 = 5 Hzi.e 5*100 /50 = 10% Droop

NLY U6 ON FGM ON 15/07/03

145

150

155

160

165

170

175

180

185

190

195

11:30 11:45 12:00 12:15 12:30

TIME-->

MW

-->

49

49.2

49.4

49.6

49.8

50

50.2

50.4

50.6

HZ

-->

GENERATION

FREQUENCY

DROOP CHARACTERISTICS OF NYL U6

160

165

170

175

180

185

190

195

49.8 49.9 50 50.1 50.2 50.3 50.4 50.5 50.6 50.7

FREQ CHANGE 49.9 - > 50.5 0.6HzGEN CHANGE 191 -> 168 23MW CHANGE IN GEN 24 MW FOR 0.6 Hz CHANGE IN FREQFOR 200 MW CHANGE IN GEN FREQ CHANGE REQD =(200*0.6)/24 = 5 Hzi.e 5*100 /50 = 10% Droop

IDUKKI GENERATION ON 16/07/2003

0

50

100

150

200

250

300

350

400

0 2 4 6 8 10 12 14 16 18 20 22 0

MW

48.5

49

49.5

50

50.5

51

FR

EQ

->

FREQUENCY

GENERATION

DROOP CHARACTERSTICS OF IDUKKI

0

50

100

150

200

250

300

350

400

49.3 49.4 49.5 49.6 49.7 49.8 49.9 50 50.1

49.849.1 49.749.649.549.449.2 49.3 49.9

POINT APOINT B

POINT C

POINT D

POINT A - GENERATION LOSS

POINT B – GOVERNOR ACTION STARTED

POINT C - FREQUENCY AFTER GOVERNER ACTION

POINT D – FREQUENCY AFTER OPERATOR ACTION

The distance through which one part of connected machinery, as a

wheel, piston, or screw, can be moved without moving the connected parts.

BACKLASHBACKLASH

BOILER CONTROLSBOILER CONTROLS

• BOILER FOLLOWING SYSTEM

• TURBINE FOLLOWING SYSTEM

• INTEGRATED CONTROL SYSTEM

ADVANTAGESADVANTAGES

1. Reduce the random change of frequency

2. Mitigate effect of load generation mismatch

3. Prevents wastage of fuel during low load condition

4. Faster restoration from grid disturbance

PROBLEMSPROBLEMS1.1. Steam deposits on the valve stem (or stems).Steam deposits on the valve stem (or stems).

2.2. Lubrication deposits (i.e., soaps, dirt, detergents, Lubrication deposits (i.e., soaps, dirt, detergents, etc.) in the top works of the valve exposed to the etc.) in the top works of the valve exposed to the

elements.elements.3.3. Mechanical failures of the valve resulting from Mechanical failures of the valve resulting from bent stems, either in the valve proper or the upper bent stems, either in the valve proper or the upper

works, damaged split couplings, etc., all within works, damaged split couplings, etc., all within about a 6" area near the center of the valve about a 6" area near the center of the valve

mechanism.mechanism.4.4. Galling of the piston in the hydraulic latch cylinder.Galling of the piston in the hydraulic latch cylinder.

5.5. Jamming of the screw spindle in the larger Jamming of the screw spindle in the larger cylinder-type valve design due to forcing by cylinder-type valve design due to forcing by

operations personneloperations personnel

FREE GOVERNOR OPERATIONFREE GOVERNOR OPERATION

Mother of all Controls

Self healing mechanism

Collectively Control

Most equitable

Reduces risk of collapse

Makes restoration easy

World wide mandatory practice