TURBOGENERATORS:

In our complex ,18 .4mw Captive power plant was installed in 1985 to improve the reliability of power.There are two Turbogenerators TG I 5.4 MW -Extraction type TG II 13.0 MW -Condensing typeGenerator make : Fuji electric,JapanTurbine make : NKK, Japan

A Basic Electric Governor mainly consists of 4 parts: 1. A device to sense the speed of the prime mover. 2. A speed set reference to which the prime mover can be

compared. 3. A comparator / amplifier with output proportional to fuel/steam

reqd. To maintain desired speed. 4. An actuator to position the valve.

Various control circuits like PID control are incorporated for proper transient response in the amplifier section to fine tune the control action.

SPEED CONTROL: A.ISOCHRONOUS CONTROL. B.DROOP CONTROL.A.ISOCHRONOUS CONTROL:

MAINTAINS THE PRIME MOVER AT A CONSTANT SPEED IRRESPECTIVE OF THE LOAD (NO LOAD OR 100% LOAD) ON THE MACHINE. SPEED CAN BE CHANGED IN AN ISOCHRONOUS SYSTEM BY ADJUSTING THE SPEED REFERENCE SET. 50 HzSPEED

0 100% LOAD

B.DROOP Speed is allowed to change as the load of the machine changes within the droop limits. It is a simple feedback obtained by feeding back a % of the output back to the input,which provides better stability for the system.. It is represented as a % of rated speed change from no load to full load. Droop = (No load speed - Full load speed) --------------------------------------------- * 100 % No load speed

Woodward 2301A Governing system consists of :1..Two magnetic speed pickups.2.Current & Potential transformers for load sensing.3.2301 Load sharing and speed control unit.4.Digital reference unit for speed.5.Digital reference unit for KW.6.Fuel Limiter7.EGB 10P actuator

I. 2301 LOAD SHARING & SPEED CONTROL UNIT:(LSSC) # It is an electric governing control to provide isochroous control with load sharing. # It consists of a single PCB housed in a metal chassis. # It performs two major functions namely, 1.Speed control & 2.Load sharing

Basic function: # The turbine speed is detected with a magnetic pick up placed near the gear which is rotating at a speed proportional to the turbine speed.

# Generates an AC voltage whose frequency is proportional to speed which is converted to a dc voltage inversely proportional to turbine speed.

# Speed set voltage is compared at the control amplifier with the speed voltage.The control amplifier output drives the proportional actuator. #If speed is greater than speed set ,then the amplifier O/P decreases and

vice versa. # Load sharing between two generators is done through the load sensing and paralleling lines.

# A Ramp generator controls the acceleration from idle speed to rated speed.

# The speed sensing fail safe mode is available thro’ jumper selection which shutdown the turbine for any failure of speed pick up signal . # Ramp generator controls the acceleration from idle speed to rated speed.

# The speed sensing fail- safe mode is available through jumper selection which shutdown the turbine for any failure of speed pick up signal . A 1.0 v ac signal will indicate that the magnetic pick up is functionally OK.

Termination details:TB 1,2& 3 : Potential TransformersTB 4,5 ; 6,7; 8,9 : Current transformers These are for Load sensing.

TB 10,11 : Load sharing lines TB 12, 13 : Power supply 20 - 40 V DC TB 14,15 : To be Opened for deceleration and to be closed for

accelerationTB 16,17 : Output to actuator (To Fuel limiter)TB 18,19 : Magnetic pick upsTB 20,21 : Remote speed adjusterTB 27, 28 : To be opened for Droop control and to be closed for

isochronous control.TB 29,30 : Failsafe action Jumper

II.DIGITAL REFERENCE UNIT: # It Consists of 2 PCB’s mounted in a metal chassis.

# There are 8 potentiometers for adjusting reference levels and 3 LED’s for limit indications.# The terminal block is on the bottom with 22 terminals.

# It generates a precise voltage that may be used as a reference signal for Speed, Load etc. in the LSSC.#It operates on a power supply of 18 -40 v dc connected at TB1,2# There are four different ramp rates available1.Fast (4.8 -9.8 sec)2. Instant (70 mSec)3.Slow (25 -440 sec)4.Medium (25 -440 sec).

# TB 4 & 5 are selection for Ramp rates.

a)For Instantaneous rate,4 is shorted with 3b) For Fast rate,5 is shorted with 3 c) For Slow rate,4 & 5 are left open.d) For Medium rate, both 4 & 5 are shorted with 3.

# TB 6-11 are for selecting six different outputs ranging from Min to Max.

1.If Min O/P (TB6) is selected , the MIN led will glow ,also the contact at TB17,18 will close and the system will control at desired level if not can be achieved by R8 pot for Min limit offset.

2. If Max O/P(TB11) is selected,the max led will glow also the contact at TB21,22 will close and the system will control at desired level if not can be achieved by R7 pot for Max limit offset.

3.If Intermediate reference output 1 to 4 are selected via TB 6 -10 and internal switches (SI 1-4),the Intermediate LED will glow, also contacts TB 19,20 will close and the offset can be adjusted by R1 to R4 set point

pots.

# The Reference moving Led will glow during transition of the reference output from one level to another.

# The Reference signal output is connected to the LSSC via terminals 15 & 16.

# A local meter signal is connected at terminals 13 & 14.

III.FUEL LIMITER: # It is an electronic device that limits the maximum voltage that a speed

control is allowed to output to the actuator.# It is connected between the actuator and the speed governor. # Power supply is 20 - 40 V dc

Fuel limiter

MODES OF OPERATION:

1.INDEPENDENT OPERATION OF TG’s -SPEED CONTROL(DROOP)

2.TWO TG’s PARALLEL -LOAD SHARING(DROOP)

3.TG1 AND/OR TG2 PARALLEL WITH GRID - LOAD LIMIT CONTROL

I.INDEPENDENT MODE: During independent mode operation, as the load is increased,the turbine speed is controlled slightly lower level due to the speed droop characteristics of the governor. The speed setting has to be adjusted by DR/speed to keep the governor frequency at 50 Hz.

II.LOAD SHARING MODE When the two TG’s are operated in parallel but are isolated from the grid,their load sharing is determined by the speed droop characteristics. The load sharing of the 2 TG’s can be specified by adjusting the droop and the speed set of the governor. The load sharing percentages of the two TG’s should be determined in consideration of steam & Elec. And the speed setting adjusted.

III.LOAD LIMIT CONTROL MODE An abrupt fluctuation in grid causes the instantaneous loading and shedding of the generator providing unfavourable operation of TG’s & steam system. To overcome this, TG’s are operated in load limit mode. The Fuel Limiter processes the signals set by the DR-LL & LSSC and transmits the lower signal to the governor actuator.

If DR-LL set is set at the position represented by pt. C, the generator output remains constant at ‘C’ kw independent of grid frequency.

The stable operation is achieved by raising speed set to maximum and operating governor depending upon DR-LL setting.

THANK YOU

104% SPEED SET

51 HZ

50 HZ4% DROOP

TG-I TG-II

5.4 MW

13 MW

6.5 MW2.7 MW