# Presentation on “FREE GOVERNOR MODE OPERATION”

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Presentation on “FREE GOVERNOR MODE OPERATION”

FREE GOVERNOR OPERATION
ROLE WHY FREQ COMPARISION MAY-02 & MAY-03 ABT & GOVERNOR BEFORE GOVERNOR BLOCKED GOVERNOR GOVERNOR RESPONSE IN NER CHARACTERISTICS GOVERNOR GOVERNOR TYPES GOVERNOR TIME LAG DEAD BAND TIME DELAY BACKLASH FREQUENCY DECAY RATE DROOP TYPES OF CONTROLS DROOP RESPONSE IN SR ADVANTAGES UCPE/NERC PROBLEMS LIST OF GENERATORS FREQUENCY BASED DISPATCH SUPPRESSED GOVERNOR ACTION FREQUENCY BASED DISPATCH PTI TAPE ORDERS PID CONTROL

ORDERS IEGC 6.2 (e) & 6.2(f) IEGC 6.2 (g) IEGC 1.6 CERC ORDER ON
FREE GOVERNOR OPERATION IEGC 6.2 (h) CERC ORDER ON WB dt 02/01/01 KERALA LETTER ON FGM

ROLE OF SYSTEM OPERATOR

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. Next

PRIMARY CONTROLS Load dependent on frequency Free Governor Operation
Under Frequency Operation

PRIMARY CONTROL …… (UCPE)
Primary control involves the action of turbine speed governors in generating units, which will respond where the speed (frequency) deviates from the speed (frequency) set point as a result of an imbalance between generation and demand in the synchronously interconnected network as a whole. Technical solidarity between members will involve the simultaneous action of primary control on all generating units involved in system control. Next

PRIMARY CONTROL…… (UCPE)
The various assumptions, characteristics and parameters applied to primary control are as follows: The maximum instantaneous deviation ∆P between generation and demand to be corrected by primary control is 2000 MW For the whole system, with a peak load of the order of MW and an off-peak load of the order of MW, assuming 1% self-regulation of load, the quasi-steady-state frequency deviation must not exceed 180 mHz and the instantaneous frequency must not fall below 49.2 Hz in response to a shortfall in generation capacity equal to or less than 2000 MW. The overall network power frequency characteristic for the system is set at 1000 MW/Hz NEXT

FREQUENCY RESPONSE …… (NERC)

ABT AND GOVERNOR POST ABT FREQUENCY WITHIN 49 TO 50.5HZ
ACHIEVED BY STAGGERING OF LOADS FLUCTUATION IN FREQUENCY INCREASED Show Me

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HUMAN GOVERNOR OPERATION
SYSTEM TG ~ X GOVERNOR

GOVERNOR 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 RESPONSE BY CAUSING VALVES/GATES TO OPEN/CLOSE TO INCREASE/DECREASE THE INPUT TO THE PRIME MOVER Next BTG

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

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CHARACTERISTICS 1. Respond promptly to a small change in speed.
2. Adjust the throttle valve with a minimum of overshoot. 3. Have sufficient power to overcome friction losses and unbalance forces in the throttle valve. 4. Permit very little speed fluctuation under constant load and steam conditions.

Mechanical shaft Direct acting orifice Oil relay Precision oil relay
TYPES OF GOVERNORS Mechanical shaft Direct acting orifice Oil relay Precision oil relay Electronic governor

DEAD BAND Turbine rated output MW Dead band percent of rated speed
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 output MW Dead band percent of rated speed IN 50HZ BASE < 5MW 0.15 0.075HZ 5 to 30mw 0.10 0.050HZ > 30mw 0.06 0.030HZ IEC - 45

DROOP 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. Next

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GOVERNOR 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.

TIME DELAY IN GOVERNOR OPERATION
Dead band sec Valve opening sec Steam flow seconds During transient state Governor is of little help. Effect is felt during steady state

BLOCKED 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 RATE Approximate Freq 5 X Lost Generation
In Hz / sec Remaining Generation Example:- 2200MW 200MW Generation Lost Freq decay rate = (5 X 200) / = Hz /second

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49.1 49.2 49.3 49.4 49.5 49.6 49.7 49.8 49.9 POINT C POINT D POINT B POINT A POINT A - GENERATION LOSS POINT B – GOVERNOR ACTION STARTED POINT C - FREQUENCY AFTER GOVERNER ACTION POINT D – FREQUENCY AFTER OPERATOR ACTION

BACKLASH The distance through which one part of connected machinery, as a wheel, piston, or screw, can be moved without moving the connected parts.

BOILER CONTROLS BOILER FOLLOWING SYSTEM TURBINE FOLLOWING SYSTEM
INTEGRATED CONTROL SYSTEM SHOW SYSTEM

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ADVANTAGES Reduce the random change of frequency
Mitigate effect of load generation mismatch Prevents wastage of fuel during low load condition Faster restoration from grid disturbance

PROBLEMS Steam deposits on the valve stem .
Lubrication deposits (i.e., soaps, dirt, detergents, etc.) in the top works of the valve exposed to the elements. Mechanical failures of the valve resulting from bent stems, either in the valve proper or the upper works, damaged split couplings, etc., all within about a 6" area near the center of the valve mechanism. Galling of the piston in the hydraulic latch cylinder. Jamming of the screw spindle in the larger cylinder-type valve design due to forcing by operations personnel

FREE GOVERNOR OPERATION
Mother of all Controls Self healing mechanism Collectively Control Most equitable Reduces risk of collapse Makes restoration easy World wide mandatory practice

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AT 50 HZ GEN= 190MW NEXT

NEXT OVER GENERATED BY 5% FREQUENCY DIPPED TO 49.8 HZ
GENERATION INCREASED BY 10 MW NEXT

OVER GENERATED BY 5% NEXT

AT 50 HZ GEN= 190MW NEXT

INITIAL UI PRICE = 84 Ps NEXT FREQUENCY RISE UPTO 50.2 HZ
GENERATION DECREASED BY 17MW UI PRICE = 84 Ps NEXT

INITIAL UI PRICE = 84 Ps NEXT FREQUENCY RISE UPTO 50.2 HZ
GENERATION DECREASED BY 17MW UI PRICE = 84 Ps NEXT

FINAL NEXT SINCE VARIABLE COST OF STATION B < UI PRICE
GENERATION INCREASED BY 17MW NEXT

FINAL SINCE VARIABLE COST OF STATION A > UI PRICE
GENERATION FURTHER REDUCED BY 17MW

PROPORTIONAL CONTROL A simple form of control, where the controller response is proportional to the control error. Kc FB Provides immediate controller response to setpoint change, but speed may not settle exactly on SP using proportional control alone NEXT

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INTEGRAL CONTROL Control action is control error integrated over time.
Kc 1/Tc ∫ fdt NEXT FB Integrates the error over time to overcome the offset from Proportional alone such that speed = SP. However, Integral action may cause overshoot, oscillation and/or instability problems

PID Parameter Tuning – PI only
This graphic presents how adding both proportional and integral control to your system permits you to adjust for initial response time and drive the process variable to the setpoint. However, too much integral action can lead to excessive oscillation as shown in the slide. NEXT

DIFFERENTIAL CONTROL In differential control, control action is based on the change (derivative) of the control error. Td df/dt Kc NEXT FB Used to put the reigns on PI control to prevent overshoot and oscillation and to add stability

PID CONTROL A form of control based on the three basic types of control: proportional, integral and differential control. PID Controllers are created by combining P, I and D elements to get the desired control characteristic. NEXT

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SUPPRESSED GOVERNOR OPERATION
OPEN NEXT

1.6 Free-Governor Action:
QUOTE CERC ORDER ON ‘IEGC’ DATED Free-Governor Action: The dates from which the stipulations under sections 4.8(c), 4.8(d), 6.2(e), 6.2(f), 6.2(g) and 6.2(h) would come into effect shall be as under : (i) All thermal generating units of installed capacity 200 MW and above and reservoir based hydro units of installed capacity 50 MW and above : Southern Region } } Eastern Region } } Northern Region } The date for the } implementation of the Western Region } Commercial mechanism } mentioned in Section 7.1(d) (ii) All thermal and reservoir based hydro } for the respective region. generating units of installed capacity } 10 MW and above in North Eastern Region } (iii) All other generating units - three months after the above dates for the respective regions except in the case of Nuclear Power Stations which shall be exempted till the next review of the IEGC. Any exemption from the above may be granted only by CERC for which the concerned constituent shall file a petition in advance. UNQUOTE

QUOTE CERC ORDER ON ‘IEGC’ DATED 6.2(e) All generating units, which are synchronised with the grid, irrespective of their ownership, type and size, shall have their governors in normal operation at all times. If any generating unit of over fifty (50) MW size (10 MW for North Eastern Region) is required to be operated without its governor in normal operation, the RLDC shall be immediately advised about the reason and duration of such operation. All governors shall have a droop of between 3% and 6%. 6.2(f) Facilities available with/in load limiters, Automatic Turbine Run up System (ATRS), Turbine supervisory control, coordinated control system, etc. shall not be used to suppress the normal governor action in any manner. No dead bands and/or time delays shall be deliberately introduced. UNQUOTE

QUOTE CERC ORDER ON ‘IEGC’ DATED 6.2(g) All Generating Units, operating at/up to 100% of their Maximum Continuous Rating (MCR) shall normally be capable of (and shall not in any way be prevented from) instantaneously picking up five per cent (5%) extra load for at least five (5) minutes or within technical limits prescribed by the manufacturer when frequency falls due to a system contingency. The generating units operating at above 100% of their MCR shall be capable of (and shall not be prevented from) going at least up to 105% of their MCR when frequency falls suddenly. Any generating unit of over fifty (50) MW size (10 MW for NER) not complying with the above requirement, shall be kept in operation (synchronised with the Regional grid) only after obtaining the permission of RLDC. However, the constituent can make up the corresponding short fall in spinning reserve by maintaining an extra spinning reserve on the other generating units of the constituent. UNQUOTE

QUOTE CERC ORDER ON ‘IEGC’ DATED 6.2(h) The recommended rate for changing the governor setting, i.e. supplementary control for increasing or decreasing the output (generation level) for all generating .units, irrespective of their type and size, would be one (1.0) per cent per minute or as per manufacturer's limits. However, if frequency falls below 49.5 Hz, all partly loaded generating units shall pick up additional load at a faster rate, according to their capability. UNQUOTE

FREE GOVERNOR MODE OF OPERATION
CERC Order ON ‘IEGC’ dated Quote 6.2 (c) All generating units, which are synchronised with the grid, irrespective of their ownership, type and size, shall have their governors in normal operation at all times. If any generating unit of over fifty (50) MW size (10 MW for North Eastern Region) is required to be operated without its governor in normal operation, the RLDC shall be immediately advised about the reason and duration of such operation. All governors shall have a droop of between 3% and 6%. Unquote SRLDC Requested all constituents including ISGS vide letter dated 3rd Jan 03 to take a lead in this matter. PAGE 1 OF 2

FREE GOVERNOR MODE OF OPERATION
The matter discussed in 368th OCC meeting All SR constituents/ISGS agreed to convey their readiness by SRLDC again requested all constituents vide letter dt to intimate unit/station wise status/ programme Matter discussed in 109th TCC/131st SREB meeting. ISGS/SR constituents agreed for FGM by 1st May 2003. Discussed in 369th, 370th, 371st & 372nd OCC meetings. KSEB & TNEB furnished unit wise/ station wise program/ constraint/ preparedness APTRANSCO conveyed readiness for FGM of all generators except thermal units of APGENCO Freq response characteristics calculation details covering 3 events furnished for examination & necessary feedback by the constituents. Constituents Actual response Shortfall (AVG) (AVG) AP % % KAR % % KER % % TN % % Matter again discussed in 110th TCC/132nd SREB meeting. All SR constituents/ISGS agreed for FGM by 1st August 2003. Action by constituents to achieve the target to be discussed. Present status to be reviewed. NERC Report NLY-II U#4 LETTERS GENERATOR LIST PAGE 2 OF 2

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