excitation system.pdf
TRANSCRIPT
Excitation System
ByBySusobhan Patra
5/8/2014
Ef
X I cosØ
• General Conception• Different Types of Excitation systems• Operational characteristics• Case studies- sharing ideas
Excitation System
δVt
Ia
j XsI t
Xs IacosØ
Ø
Phasor diagram
Xs IasinØ
Basic dynamo principleΦ = B cos Ø A
= BA cos ωt
Change of magnetic flux = dΦ/ dt
Rate of change of magnetic flux dΦ/ dt = -BAω sin ωti.e. e = NBAω sin ωt
e0 = NBAωe = e0 sin ωt
GeneratorWhen a closed coil is rotated rapidly in a strong magnetic field, the number of magnetic flux lines passing through the coil changes continuously. Hence, an emf is induced in the coil and a current flows in it in a direction given by FRH Rule
MotorWhen a current is passed through a coil placed in a magnetic field, the coil experiences a torque in a direction given by FLH Rule. The torque gives a continuous rotary motion to the coil in the magnetic field.
If UgSynchronous
Machine
AVR- Automatic voltage control system
Controller
Excitation System
Specification (TGS)
• Apparent power in air 70.59 MVA• Active power 60 MW• Phase Current 3881 amps• No of phases 3• No of poles 2• Terminal Voltage 10.5 ± 5 KV• Speed 3000 rpm• Frequency 50 Hz• Frequency 50 Hz• Power factor 0.85 (lagging)• Field current for rated output 833 amps• Field voltage 202 V
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PILOT EXCITER
MAIN EXCITER FIELD
ALTERNATORFIELD
ALTERNATOR OUTPUT
CONNVENTIONAL EXCITATION SYSTEM FOR ALTERNATOR
PILOT EXCITER MAIN EXCITER 3-Ph ALTERNATOR
R FIELD
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MANUAL Channel Thyristor
bridge
Pulse from Manual channel control
Pulse from Auto channel control
Field Breaker
AUTI Channel Thyristor
bridge
From PMG
Gen
Gen. Rotor Rotating Diode Bridge Main Exciter
Schematic Diagram for Brush Less excitation System
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Main Exciter
PMG
Rotating Diode Bridge
Brush Less excitation System5/8/2014
Case studies:• Failure of PMG• Failure of fuse• Failure of Magnet• Rise in PMG Temp
- +
..
. ...
.
...
.
...
.
.. . .
5/1 AC.T.
GENERATOR
AUXILIARY SLIPRINGS
ROTATING RECTIFIER UNIT
EXCITER
P.M.G. SINGLE PHASE PILOT EXCITER
500/5AC.T.
R
Y
B
BRUSHLESS EXCITATION SUSTEM
EXCITER TERMINAL BOARD
X 1 2 5 6 7 8 9 10 113 4XXJ2
A.V.R. CUBICLE
+ -
FOR TEST ONLY
12A
V31
AXCITER/ GEN. FIELDCURRENT AMMETER
J1
EXCITER TERMINAL BOARD
+
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PMGMain
Exciter Armature
Rotating Rectifier
Slip Ring for rotor voltage FB &
protection
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Excitation System: SpecificationMain Exciter
• Maxm continuous rating 207 KW• Rated terminal voltage (at 225 VDC
Rectifier DC terminals)• Rated current (at rectifier 920 ADC
DC terminal• Frequency 150 Hz• Rated speed 3000 rpm• No of phases 3• No of poles 6• Rotating Rectifier• Diodes (Positive) type IR GB 490 / U• Diodes (Negative) type IR GB 491 / UR• Diodes (Negative) type IR GB 491 / UR• No of rings 2• No. of + ve diodes per ring 9• No. of - ve diodes per ring 9• Peak inverse voltage of diodes 2200 V repetitive peak volts• Connections Full wave, 3 arm bridge with 3 parallel paths per arm• Fuse type EE GSA 250• No of fuses 18• Fuse current rating 250 A rms• Fuse voltage rating 240 A rms• Neon indicators 18 (one per parallel path)
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PERMANENT MAGNET FIELD ON ROTOR, ARMATURE ON STATOR
ARMATURE ON ROTOR, FIELD WINDING ON STATOR
SILICON DIODE BRIDGE ON SHAFT
PILOT EXCITER MAIN EXCITER ROTATING RECIFIER
HOLLOW SHAFT
SOLID SHAFT
REGULATOR
THYRISTOR CONTORLLED BRIDGE
Controlled dc to field on stator
Alternator terminal
3-ph power(1-Ph 200Hz at TGS)
3-Ph (3-ph 150 Hz at TGS)
Alternator field
C.T
P.T
AVR
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Rotating Rectifier Ring
+VE
Rotating Rectifier Ring
-VE
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Carbon Brush on slip rings for measurement of Rotor Voltage & protection Terminal block
POSITIVE DIODE CARRING RING
NEON LAMP
AUX. SLIP RING
RO
TO
R W
IND
ING
1P 2P 3P 4P 5P 6P 7P 8P 9P
ROTATING RECTIFIER ASSEMBLY OF BRUSHLESS EXCITATION SYSTEM
A2 B2 C2 A2 B2 C2 A2 B2 C21 2 3 4 5 6 7 8 9
FUSEDIODE
NEGATIVE DIODE CARRING RING AUX. SLIP RING
RO
TO
R W
IND
ING
1N 2N 3N 4N 5N 6N 7N 8N 9N
TO ROTOR VOLT METERAND ROTOR E/F RELAY
1P, 2P, 3P, 4P………….9P : DIODE & FUSE ASSEMBLY ON POSITIVE RING1N, 2N, 3N, 4N………..9P : DIODE & FUSE ASSEMBLY ON NEGATIVE RING
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FuseDiodeLamp
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Brushless Excitation
• No use of any brush
• PMG output is fed to the AVR
• AVR output is the field for the main exciter
• Main exciter output is directly coupled with the rotating rectifier
• The output from rectifier is directly connected to the generator • The output from rectifier is directly connected to the generator rotor
• Carbon brushes are used for voltage measurement & rotor protection system- rotor E/F
• There are two channels for operation control
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AUTO Mode• It is built as a voltage regulator and is ON during normal
operation & the reference point is set through manual switch
• Various limiters and corrective control circuits are used for stable operation up to operating limits.
• In case of any malfunction the AVR will change over to manual modemode
MANUAL Mode:
• It is built as a simple field current regulator
• It serves as a back up channel in case of failure of the AUTO channel.
• Operations in this channel require expert adjustment and continuous monitoring of the parameters as there is no automatic limiter action.
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Digital AVR with BL Excitation
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n UNITROL 6080 Hardware Devices (D1..D4)Power INterface
PIN6080
PIN6080
PIN6080
3.2.3 UN6080 Control HW
CCM6080 CCM6080CCM6080
Combined IO
Communication Control
Measuring
n Communication Control Measuring CCM6080 (UC D240)
CCM6080 CCM6080CCM6080
3.2.3 UN6080 Control HW
UG IG
AO
Optical Links Ethernet
CCM 6080 X12 X113 X14
PIN – 6080 X12 X113 X14
DCS800 Box
D1…D4
CCM 6080 X12 X13
X113
GDI X113
PIN – 51 X12 X13
D5
• Providing variable DC current with short time overload capability
• Control terminal voltage on preset value with required accuracy
• Ensure stable operation with network and/ or other machines
• Keep machine within permissible operating range.
• Contribution to transient stability subsequent to a fault.
• Communicate with the power plant control system
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• Display of actual values• Local operation of the excitation system• Parameter settings• Transient recorder• Event/Fault recorder
Excitation Control Terminal
Band pass filter
Rippledetection
Diode failure
Rotating Diode Failure
Rotating rectifier
t
Ie
Diode failure
filter
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UG set point
UG nominalU
UG max setpoint
Setting range V/Hz
Set point V/Hz Limiter
ff nominal
UG min set point
Allowed range of operation
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Static Excitation (Digital Voltage regulator)
• The DVR regulates the voltage of the synchronous machine by direct control of the rotor current using thyristor converter.
• Redundancy in the regulator section is ensured by means of two fully separate channels with independent measuring inputs, control and monitoring
Thyristor Converter for Excitation Control
• 3 Phase fully controlled thyristor bridges, each bridge consisting of 6 thyristors, arm fuses & snubber circuit.
• Cooling fan for keeping the junction temperature rise of every device within safe limits.
• Pulse transformers for electrical isolation between power & control circuits and coupling the firing pulses to the gates.
• Fuse monitoring Unit
• Air Flow Monitoring Unit
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SEE
5/8/2014Regulation Field Flushing
AVR
Thyristor
Usyn
U>70%
Ug
t
Field flashing off
Thyristor bridgestarts to conduct
U>70%
U>10%Field flashing characteristic
Field flashing failedFCB Trip
10sField flashing OFF
5s
100%Softstart
Ug Sequence:
Field Flashing Circuit
Generator
AuxiliarySources
~ +
DiodeBridge
Thyristorbridge
U>70%
Field flashing breaker
• Field breaker CLOSE
• Excitation ON
• Pulses to the thyristors are released
• Field Flashing breaker closes if start up with residual machine voltage is to low
• Stator voltage raises
• Field flashing breaker opens
• The softstart function raises the generator voltage smoothly up to itsnominal value.
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SEE
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One Thyristor panel
Complete Thyristor cubicle- 3 Channels
SEE- Case study
Damaged holder
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Slip Ring & Carbon Brush Holder
CB-32x32x64
Channel 1 (The AUTO):• It is built as a voltage regulator and is ON during normal operation.
• Various limiters and corrective control circuits are used for stable operation up to operating limits.
• In case of any malfunction the DVR will change over to Channel 2.
Channel 2 (The MANUAL):Channel 2 (The MANUAL):• It is built as a simple field current regulator
• It serves as a back up channel in case of failure of the AUTO channel.
• No special limiters.
• Operations in this channel require expert adjustment and continuous monitoring of the operating parameters.
• In case of any malfunction of channel 2 it will lead to excitation failure.
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Pulse Trafo
Pulse Trafo
Pulse TrafoAVR
CT
PT
E.T.
THYRISTORBRIDGE
3 CHANNELS
BACK
GROTOR
Q1
Q2
SCHEMATIC DIAGRAM FOR STATIC EXCITATION SYSTEM FIELD FLASHING SUPPLY
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Q&A
Thank you very much
Save Energy
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