WELCOME TO
THE PRESENTATION ON
STEAM TURBINE
PROTECTIONS AND
GOVERNING SYSTEMS
AT
ESCI, HYDERABAD
BY
BHEL – PS SR, CHENNAI
8-9 Dec, 2004
CONTROLS OF LARGE
UTILITY TURBINES
Presentation By
Srinivasan Selvaraj
Main Control Systems
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Electro-Hydraulic Governing System (EHTC)
Turbine Stress Evaluator (TSE)
LP Bypass Control System (LPBP)
Gland Steam Control System (GSC)
Protection System
Turbovisory System (TSI)
Automatic Turbine Tester (ATT)
Electro-Hydraulic Governing
System (EHTC)
EHTC: Advantages
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Safe Operation of Turbine in
conjunction with Turbine Stress
Evaluator (TSC)
Excellent Operation Reliability and
Dependability
Low transient and steady state speed
deviations
EHTC: Advantages

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Dependable control during load
rejection
Reliable Operation in case of Isolated
Grid
Critical Measuring Devices
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Speed Probes (3 Nos.) and associated
circuit elements
Load Transducers (3 Nos.)
Electro-hydraulic Converter housed in
Governing Rack (1 No.)
Position Feedback Transmitter of EHC
Control Loops
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Speed Control
Load Control
Pressure Control
Speed Control: Main Functions
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PD Controller
Start Up & Shut Down of Turbine
Synchronizing with grid
Providing Min. Load
Operation of Turbine over entire range
of Load in case of Load Controller
Failure
Load Control: Main Functions
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PI Controller
Provision of load reference limiter
Frequency influence option
Pressure Control:Main Functions
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PI Controller
Initial pressure control
Limit pressure control
Nr
_
Nrtd
+
Nact
Pr
Prtd
+
+
Pmax
+
Prsu
m
SPEED
CONT. PD
M
I
N
_
+
LOAD
CONT. PI
M
A
X
M
I
N
M
I
N
EL
HYD
Pact
Fact
_
+
Fref
pREF
_
_
+
+
PRESSURE
CONT. PI
pACT
0
P
LIMIT PRES.
R
INIT. PRES.
S
Governing Scheme for
KWU Turbines
FROM ELEC
CONTROLLER
EL
HYD
STARTING
DEVICE
MIN
M
I
N
TO CONTROL
VALVES
HYD
HYD
SPEEDER
GEAR
Governing Scheme for
KWU Turbines
Additional Functions
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Tracking device option
Load shedding relay
Auto Synchronizer
Isolated grid operation
Tracking Device Functions
The starting device keeps varying
automatically with variation in the
position of EHC. In case the EHC fails
the starting device will restrict the
raise in the load.
Load Shedding Relay Functions
During sudden load throw–off conditions,
there will tendency for the speed to raise
rapidly. To avoid such conditions the LSR
gives a close command for closure of the
control valves for a brief moment. The
magnitude of load throw,time duration of
closure of control valves are settable in
the LSR.
Auto synchronizer Functions
The auto synchronizer accepts Gen and Grid
Potential transformer signals. To match the
frequency and voltage of the Generator, the
auto. Sync. Unit gives Speed raise/lower
command to EHTC and voltage raise/lower
command to AVR.
After parameter matching the auto sync. Unit
generates a command for Synchronizing the
unit
Auto synchronizer Functions
After parameter matching the auto sync.
Unit generates a command for
Synchronizing the unit
Turbine Stress Evaluator
(TSE)
Turbine Stress Evaluator
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Compares thermal stress in the
monitored components with the
permissible limits and generates
margins.
The temperature margin is fed to the
set point controller – speed and load.
Derives start up criteria for ATRS
TSE: Components Monitored
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Emergency stop valve.
HP control valve.
HP casing.
HP shaft.
IP shaft.
TSE: Measuring Points
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Surface and mid wall temperatures of ESV
(Ti & Tm)
Surface and mid wall temperatures of HPCV
Surface and mid wall temperatures of HP
casing.
Derived value for HP and IP shaft
temperatures from specified locations in
respective casings.
TSE: Operating Modes
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Three modes viz., fast, normal, slow
available.
The increased fatigue rate associated
with fast mode can be compensated by
more slow mode operation.
TSE: Margins
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For any component, the difference Ti –Tm
represents the actual thermal stresses.
Depending on the value of Tm and
operating mode the permissible value of
thermal stress is determined.
From the difference between the
permissible stress and prevailing actual
stress the margin is derived.
TSE: Margins
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The margins of different components are
provided in the Bar graph form in the
TSE monitor.
The reference variable derived from the
minimum margin acts directly on the
turbine control system.
LP Bypass Control System
(LPBP)
LPBP system: Main Features
Enables alternative path for dumping
steam from RH outlet to condenser
bypassing IP and LP turbine.
Maintains RH pressure from a criteria
representing the HP turbine flow.
Works in conjunction with HP bypass
systems and when necessitated by the
system.

LPBP system: Main Features
Provides fixed and variable set point.
Protects the condenser by water
injection.
Hydraulically protects the system when
the water injection press. is v low or
condenser press. is v high

LPBP system: Pressure control
Process variable for control loop is
acquired from Press. Transmitter in RH
line.
Two set values viz. Fixed set point and
variable set points are formed and
maximum value is used as reference.

LPBP system: Pressure control
Fixed set point is varied with push
button in the control desk.
Variable set point is derived from I stage
pressure of HP turbine which is an
indicative parameter of steam flow.
Manual operation of valves is possible
with push buttons in the control desk.

I stg.
press
PT
f(x)
Fixed
setpoint
M
A
X
+
PI
Cont.
From EHC LVDT
-
PT
+
Valve
Lift PID
To EHC
RH press
LPBP Scheme for KWU turbines
Gland Steam Control System
(GSC)
Gland Steam Pressure Control
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Maintains the Gland steam header
pressure at required value.
Provided with two control valves viz.
seal steam control valve and gland
steam control valve.
Process variable is the header pressure
from a transmitter.
Gland Steam Pressure Control


The electro-hydraulic actuator have
inbuilt pump and it is powered by
separate power supply.
In the event of pump failure,the valve
remains stay put.
Seal steam valve
Set
point.
+
-
PI
Cont.
f(x)
EHC
PT
Leak steam valve
GS header
press
100
EHC
Leak steam valve
Seal steam valve
Command
To
Valve
0
f(x)
Cont.output
100
GSPC Scheme for KWU turbines
Protection Systems
Protection Systems
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Electrical Protection Systems
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Hydraulic Protection Systems
Electrical Protection Systems
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Emergency PB (UCB)
Lub Oil Pressure Very Low (2 out of 3)
Fire Protection Trip
Turbine Trip from ATRS
Axial Shift Very High (2 out of 3)
Over-speed Trip
MFT Relay Acted from Boiler (2 out of 3)
Electrical Protection Systems
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Generator Protection Trip
Vacuum Low Trip
HP Exhaust Temperature Very High(2 out of 3)
Generator Cold Gas Temperature Very High
Exciter Hot Air Temperature Very High
Liquid Level in Generator Bushing Very High
(2 out of 3)
Hydraulic Protection Systems
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Over-speed Trip 1 & 2
Vacuum Low Trip
Axial Shift
Hand Trip Lever 1 & 2
Features of Protection Systems
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Cyclic Test done periodically for each
Trip input
Fault at input level will be annunciated
Testing can be done online
2 out of 3 logic ensures reliability and
avoid spurious trippings
2 separate Processor Units realize the
Protection Logic with dedicated IOs.
Features of Protection Systems
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Data of both processors matched
through Serial Communication and
discrepancy annunciated
2 separate Solenoids provided in
Hydraulic System for redundancy
First cause of trip will be annunciated
Online Testing of Final Tripping
elements through ATT
Resetting of Protection
Turbine Trip Solenoid stays in energised
condition until the following conditions
are fulfilled.
 Command from individual Trip ceases
 Both ESVs Closed
 Trip Oil Pressure less than 2 kg/sq.cm
Turbovisory System (TSI)
Turbovisory Instruments
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Absolute bearing vibration
Absolute shaft vibration
Axial shift
Relative expansion – HP
Relative expansion – IP
Relative expansion – LP
Overall expansion
Automatic Turbine Tester
(ATT)
ATT : Features
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Individual testing of each turbine
protective devices.
Pretest ensures substitute devices.
Monitoring of program steps for
execution within a certain time.
Interruption if trip is initiated.
Automatic reset of program after a
fault.
Automatic Turbine Tester
Sub group – Safety Devices.
 Sub group – HP/IP valves.
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ATT: Safety devices
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Remote trip device 1 & 2.
Over speed trip device 1 & 2.
Low vacuum trip device.
Thrust bearing trip.
ATT: HP/IP Valves
HP stop & control valve 1
 HP stop & control valve 2
 IP stop & control valve 1
 IP stop & control valve 2

ATT: LOGICS for safety devices
Release condition for start
 All protective device in operating
condition.
1st step command
 Checking of Provision of control fluid for
enabling test
ATT: LOGICS for safety devices
Release condition for 2nd step
 Pressure before changeover valve > 5
kg/sq cm.
2nd step command
 Takes care of over speed trip-1 during
test.
ATT: LOGICS for safety devices
Release condition for 3rd step
 Pressure before changeover valve < 2
kg/sq cm.
 Pressure between sol. valve >5 kg/sq cm.
3rd step command
 Takes care of over speed trip-2 during
test.
ATT: LOGICS for safety devices
Release condition for 4th step
 Pressure between sol. valve <2 kg/sq
cm.
4th step command
 Provision of control fluid.
ATT: LOGICS for safety devices
Release condition for 5th step
 Pressure before changeover valve >5
kg/sq cm.
5th step command
 Changeover valve to test position.
ATT: LOGICS for safety devices
Release condition for 6th step
 Trip oil Pressure >5 kg/sq cm.
 Changeover valve test position.
 Aux startup fluid < 2 kg/sq cm.
6th step command
 Testing of remote trip device 1 & 2.
ATT: LOGICS for safety devices
7th step command
 Testing of over speed trip device 1 & 2.
8th step command
 Testing of low vacuum trip device
9th step command
 Testing of thrust bearing trip device
ATT: LOGICS for valves
Start conditions
 All stop valves 100 % position
 Load controller in action
 Load < 66.6 %
 Trip oil pressure > 2 kg
ATT: LOGICS for valves
Step I command
 Control valves - HP & IP
Step II command
 Stop valves – HP & IP
Automatic Turbine
Run-up System
(ATRS)
Automatic Turbine Run-up
System (ATRS)
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Acquisition, analysis and collation of
various parameters during Startup
Sequential Control of Drives
Unit Synchronization and Minimum Load
Operation
Organised and hierarchically arranged
as Sub Group Control (SGC), Sub-loop
Control (SLC), and Control Interface
ATRS: Functional Group
ATRS
SGC (Oil)
SGC (Cond & Evac)
SGC (Turbine)
SLC (Turning Gear)
SLC (CEP)
SLC (Drains)
SLC (AOP1)
SLC (Vac. Pump)
Warm Up Controller
SLC (AOP2)
SLC (Vac. Brkr)
Starting Device
SLC (EOP)
Set Point Device
(Speed & Load)
SLC (JOP)
Autosynchroniser
THANK YOU !