Post on 08-Dec-2015
description
WELCOMEWELCOME TO TO
ALL ALL
STEAM TURBINE GOVERNING SYSTEM
By Mr. V.MANI. ACM/Turbine Efficiency
GOVERNING SYSTEMGOVERNING SYSTEM
Digital Electro-Hydraulic Governing system.
No mechanical Governing back up.
Automatic Startup, Synchronization and Loading of
Turbine.
Automatic Unloading.
Operator actions reduced to the minimum during
normal operation.
DEHC CONTROLSDEHC CONTROLS
Consists of two portions
Digital Electronic controller
Electro-Hydraulic convertor.
Speed control - Speed loop
Unit loading (Manual control)-Manual loop
MW Controller (with Coordinated mode)-Load loop
Main steam pressure controller-Pressure loop
Limiters &Trimming device
Automatic turbine tests.
Rotor Stress Evaluator
EHC CONTROLLER FUNCTIONSEHC CONTROLLER FUNCTIONS
EHC CONTROLLER FUNCTIONSEHC CONTROLLER FUNCTIONS
Speed loop
Manual loop
Load loop
Pressure loop
Selection circuit
Admission controller
Control valve
Used during start up only Speed measurement Speed set. Speed control Critical speed range logic (800-1300&2300-2750rpm) Acceleration limiter action. Synchronization
SPEED CONTROL SPEED CONTROL
SPEED CONTROL SPEED CONTROL
Speed Controller
Speed Target
Speed reference
limiter
From RSE
Speed reference
+
Actual SpeedSet from
DCS
Acceleration protection.-Generator Breaker Open.• Speed > 75%(2250rpm)• Acceleration >25% of rated speed(750 rpm/min)-Generator breaker closed.• Speed > 101%(3030rpm)• Acceleration >20% of rated speed (600rpm/min)
SPEED CONTROL SPEED CONTROL
Initial load pick-up
Manual control
UNIT LOADING (MANUAL MODE)UNIT LOADING (MANUAL MODE)
MS pressure measurement MS pressure set MS pressure controller
MAIN STEAM PRESSURE CONTROLLER MAIN STEAM PRESSURE CONTROLLER
( (TURBINE FOLLOW MODETURBINE FOLLOW MODE))
MAIN STEAM PRESSURE CONTROLLER MAIN STEAM PRESSURE CONTROLLER
( (TURBINE FOLLOW MODETURBINE FOLLOW MODE))
+
Pressure controller
MS Pressure
set
Actual MS
Pressure
MW measurement MW set MW controller MS pressure correction
MW CONTROLLER MW CONTROLLER
(ALONG WITH COORDINATED MODE)(ALONG WITH COORDINATED MODE)
MW CONTROLLER MW CONTROLLER
(ALONG WITH COORDINATED MODE)(ALONG WITH COORDINATED MODE)
Actual MW
+MW Reference
MW controller
HP exhaust temp limiter.
Reheat pressure limiter.
Condenser pressure limiter.
Main steam pressure limiter.
Run-back limiter.
LIMITERSLIMITERS
Adjusts steam flow to HP/IP Turbine during
speed run up and unit loading to avoid churning
of the rotor.
TRIMMING DEVICETRIMMING DEVICE
Coordinate Boiler & Turbine operation.
Run back system operation.
Permissive load >10%.
CO-ORDINATED MODE (CMC MODE)CO-ORDINATED MODE (CMC MODE)
Load setter – Load set By board Engineer.
- Load limiter- Limit the set to Max level & Min level.
- Load rate control- Set By board Engineer or From RSE.
-Load capability limiter- Limit the set by mills capability.
-Load set correction by frequency influence - if enabled.
-Load demand signal to Boiler Master&Turbine MW control
CO-ORDINATED MODE OPERATIONCO-ORDINATED MODE OPERATION
- Load demand signal to Turbine MW control set
point. (corrected by MS pressure controller)
&
- MS pressure controller signal corrected by Load
demand signal to Boiler Master control.
CO-ORDINATED MODE-OPERATIONCO-ORDINATED MODE-OPERATION
Turbine operation.
-Turbine MW control.
-Turbine control valve operation.
CO-ORDINATED MODE (CMC MODE)CO-ORDINATED MODE (CMC MODE)
Boiler operation.
-Boiler Master auto.
-Coal Master auto- controls fuel rate.
-Air Master auto- controls air rate.
CO-ORDINATED MODE (CMC MODE)CO-ORDINATED MODE (CMC MODE)
ROTOR STRESS EVALUATOR(RSE)ROTOR STRESS EVALUATOR(RSE)
Protects the rotor against inadmissible thermal stress.
Calculates the Thermal Stress of HP & IP rotor Indicates Loading &unloading margin The stress capability of Turbine is fully utilised all
the time. Alarm the Board Engineer Trips the Turbine while exceeding the limit. Saves time when running-up the steam turbine. Relieves the Board Engineer from supervisory
functions. RSE can be enabled & disenabled any time in DCS
ROTOR STRESS EVALUATOR(RSE)ROTOR STRESS EVALUATOR(RSE)
• HP& IP starting probe temp is used for calculating HP & IP Loading margin and HP unloading margin.
• Lowest value between the loading margin of HP & IP rotor and unloading margin of HP rotor is normally selected for controlling purpose.
UPPER & LOWER MARGINS OF RSEUPPER & LOWER MARGINS OF RSE
Permissible thermal stress for unloading
Permissible thermal stress for loading
Mean Integral Wall Temp
The
rmal
Str
ess
DT
= T
i - T
m
B
A
C
D
G
E
F
H
Tm
LEGEND
Ti- Inner surface metal temp
Tm- Mean integral wall temp
AC- Current thermal stress while loading the turbine
AB- Upper margin
AD- Lower margin
EG- Current thermal stress while loading the turbine
EH- Upper margin
EF- Lower margin
ROTOR STRESS EVALUATOR(RSE)......ROTOR STRESS EVALUATOR(RSE)......
Rotor Stress EvaluatorRotor Stress Evaluator Calculates:Calculates:• The Accelebration level during start up• The Stop accelebration level(in case of low margin)• The run back level(decrease speed in case of negative
margin.)• The Loading gradient of the Turbine• The very high stress limit when Turbine is loaded.
(Unload the turbine)• The trip levels for extremely high stress.
STEAM TURBINE SUPERVISORY SYSTEMSTEAM TURBINE SUPERVISORY SYSTEM
The turbine must be supervised for safe running conditions.
The turbine supervision system is an inductive / electronic type system.
Parameters measured are used for indication, annunciation and for trip purpose.
STEAM TURBINE SUPERVISORY SYSTEMSTEAM TURBINE SUPERVISORY SYSTEM
Includes measurement of: Absolute Expansion. Differential Expansion. Axial position.(Thrust bearing wear) Relative shaft vibration
Absolute Thermal Expansion of Turbine cylinder with respect to fixed point .
Measured at HPT front pedestal. Measured on LVDT principle. Indicates complete expansion of casing with out
any constraint. Indication purpose only. No protection.
ABSOLUTE CASING EXPANSIONABSOLUTE CASING EXPANSION
Differential Expansion is the difference in the thermal expansion of rotor and casing.
HP differential expansion measured at HPT front pedestal.
LP differential expansion measured at LPT rear pedestal.
Measured by proximity sensors. DE tends to increase during start up, loading and
unloading and shut down. Uncontrolled DE is unsafe for operation. Indication purpose only. No protection.
DIFFERENTIAL EXPANSIONDIFFERENTIAL EXPANSION
Axial shift is the physical shift of rotor due to the action thrust on it.
Turbine rotors are perfectly balanced using balancing pistons.
The shift of rotor happens in case of unbalanced condition.
To maintain proper axial position and take care of any unbalanced axial thrust TG rotor is positioned and supported by collar thrust bearing.
Thrust bearing located between HPT& IPT. Measured on non-contact inductive principle. Trips the Turbine if value exceeds +0.8mm.
AXIAL POSITION (THRUST BEARING WEAR)AXIAL POSITION (THRUST BEARING WEAR)
Indicates the safe running of equipment. Relative shaft vibration is measured in all the 5
bearings at 450 angle &3150 angle Non contact type transducers used. Alarm level 170µ Trip level 260µ
ROTOR VIBRATIONSROTOR VIBRATIONS