Ht and lt scheme dc system

HT/LT Supply , AC supply system
S.O.Katiyar
consultant

STG
MM
MW-160
MVA-188.23
186.2MVA
CT-1
CT-1
1189T
1189A
CVT
WT
BAY-10
SAMAYPUR-2
BAY-9
SAMAYPUR-1
M
M
M
M
M
MM
MM
BAY-8
GT-2
BAY-7
TBC
GT-2
BAY-3
PALLA-1
BAY-4
PALLA-2
BAY-5
BUS
COUPLER
BAY-6
GT-1
GT-1MW-144.6
MVA-170.117
MVA-153.5
M
889A
989T989L
989B
989A
1089T1089G1
1089B
1089A
1052
952
752
852
552
652
352
452
489B
789T
789B
789A
889G2
1189G2
889T889G1
889B
489A
589B
589A
689T689G1689B
689A
389T389L
389B
389A
489T489L
689G2
SINGLE LINE DIAGRAM OF 220 KV SWITCHYARD FGPS
220 KV MAIN BUS-1
220 KV MAIN BUS-2
220 KV TRANSFER BUS
LEGEND
M
220 KV C.B
220 KV ISOLATOR
WAVE TRAP
CVT
CT
2500 AMP,40 KA
2500 AMP,40 KA
BAY-11
STG

Auxilliary supply for coal power station
• Coal transfer from Track
hopper/wagon tippler to
bunker
• Coal crusher
• Coal mills and feeders and
PA fan
• FD fan APH
• Flue gas path
• ESP and ID Fan
• DM water path from BFP
to Boiler Drum
• Circulating water path
• Lub oil system of TG
• Seal oil system
• Equipment cooling water
system
• Stator water cooling system
• Hydrogen system
• DM water system
• Raw water system
• Ash handling plant
• Liquid fuel unloading station

27 November 2016 PMI Revision 00 5
AC Supply
System

•Importance of Elect System for
Auxiliary
•Classification of Auxiliaries
•Choice of Voltage for Aux
• Aux. Power supply system
•Emergency AC Supply
Presentation outline

Auxiliary Power Supply System
The purpose of an Electrical system is to generate
and supply electrical energy .
The system should be designed and managed to
deliver power with Reliability and Economy.
As these two requirements are quite opposed a
balance is required to have an optimum design of
Auxiliary power supply system
The auxiliaries have Ratings range from a few
watts to few Mega Watts & Located over a large
area
Work under varied Operating Conditions

 Failure of Auxiliaries can cause Outage of Power Plant
 Auxiliaries need Reliable Power Supply
 System designed to cater to this need
 Loads segregated on the basis of
Rating (to decide Voltage)
Location (to decide the Feeding
Point)
 Change-over schemes & Alternate Power Supply arrangement
to ensure Reliability

Elements of Aux. Power System
More than 95% of the auxiliaries are driven by
Motors
Different Voltage levels are interconnected
through Transformers
Miscellaneous Elements
Incomers
Ties
Diesel Generators

Auxiliary Power Supply
• Voltage Rating of Motors Decided based on kW Rating
 Rating ≤ 160kW – 415V (LV), Contactor
 > 160kW & ≤ 200kW – 415V (LV), Breaker
 > 200kW & ≤ 1500kW – 3.3kV (MV), Breaker
 > 1500kW – 11kV (MV), Breaker
 Frequent Start / Stop Operations (Coal Conveyor
Motors) – MV Vacuum Contactor
• List of Boards / Feeding Points arrived at based on
Location of Load Centers / Systems
• Quantity & Rating of Transformers calculated based on
Load & Operational Requirements
• Rating of Board Calculated based on the Operating Load
& Transformer Rating

MV Switchgears – System Parameters
Nominal System voltage 6.6kV 11kV 3.3kV
Highest System voltage 7.2 kV 12kV 3.6kV
Rated Frequency 50Hz 50Hz 50Hz
Number of phases/ poles Three Three Three
System Neutral Earthing
Earthed through Resistance of 6.35Ω to Limit E/F
Current to 300A
One minute power frequency
withstand voltage
20kV 28kV 10kV
Impulse withstand voltage 60kV (peak) 75kV (peak) 40kV (peak)
Maximum System Fault Level 40kA (rms)
Short time rating of Eqpt. 40kA (rms) for 1 second
Dynamic withstand rating 100kA (peak)

LV Switchgears – System Parameters
Nominal System voltage 415V, ±10%
Rated Frequency 50Hz
Number of phases Three
System Neutral Earthing Solidly Earthed
Maximum System Fault
Level
45kA (rms)
Short time rating of Eqpt. 45kA (rms) for 1 second
Dynamic withstand rating 105kA (peak)

• Sizing of Unit & Station transformer
• Start up source short circuit power
• Feeding offsite areas loads
• Rating of the Switchgear
• Loads
• Power Supply arrangement
• 6.6& 0.415kV System
• 11 & 3.3 & 0.415kV System

Auxiliary Power Supply
INTRODUCTION
• Commonly used voltage level up to 200 MW unit
size- 6.6kV, 415V
• Initially same voltage level (6.6 kv, 415v) were
adopted for 500 MW unit size as well.
• With 500 MW unit, quantitative and qualitative
change in auxiliaries took place.
• However no significant change in SWGR available in
market.Need for optimizing and cost effective
solution

Aux. Supply system(500MW)
• Grid Voltage- Normally 400kV for most of the200,
500MW units in India except few deviations
• Any Intermediate Voltage Available-to provide
reliable start-up power source and to meet initial
commissioning activities as well as to supply bulk
loads(CW system, make-up water etc.) away from
the main plants.Generally used Intermediate
voltage levels are 220kV, 132kV, 33kV
• Nature of Auxiliaries i.e. ratings, basic
characteristics and location

Auxiliary Power Supply-500MW
• Selection of voltage levels to be
adopted for 500MW and above unit
size.
• a) 6.6 KV and 415 V system
• b) 11& 3.3 kV system

HT/LT Supply System
G
UAT-A Dyn1
UAT-B
16.5 KV
6.6 KV Ynd11
GT
Ynyn0
Station TRF-1
UNIT SWGR--A
UNIT SWGR--B
Stn. SWGR-SA SB
UST
‘A’
ESP TRF-A
S/Serv.
Trf.-B
UST-B ESP TRF-B
USS-A USS-B 415 V Unit EMG SWGR
X
From DG SWGR
X
Blr MCC
Turb MCC
BFP
ID Fan
Air Compr
Trf
X X
X
Stn Serv
Trf-A
DMP Serv
Trf
1)SWYD
Serv
Trf-1
2)Ash
Handl T/
1600KVA
6.6 KV
B.C.
N.O.
TMCC
Fdr to
Clarif
Water
SWGR

Transformer feeder Details
To PMCC
MCC/PCCM
edium
Voltage
Magnetic
Contactor
SFUCB
To ACDB
Motor Feeder
Unit Service
Transformer
To PMCC
Magnetic
Contactor
SFU
To ACDB
Motor Feeder
Dyn11
C.B.
415 V
6.6 KV

X X
X X
X X
X X
DG-1 DG-3 DG-2
DG SWGR-1 DG SWGR-2
UNIT EMER
SWGR-1 UNIT EMER
SWGR-2
UNIT EMER
SWGR-3
UNIT EMER
SWGR-4

EMCC
(1) AOP-1 (2) Em. Lighting Trf.
(3) TVDC Reserve Supply (4) UPS Ch.
(5) Scanner Air Fan (6) BVDC Reserve Supply
(7) AC Seal Oil Pump (8) Air Heater Lub Oil Panel
(9) Jacking Oil Pump (10) Stator Water Pump-B
(11) Barring Gear (12) +26 v DC ATRS Ch. ‘B’
(13) -26V DC ATRS Ch.’B’ (14) 26V DC FSSS Ch. ‘B’
(15) 26V DC DDC (digital distribution control)Ch. ‘A’

From Unit SWGR ‘A’ Normally
(1) BFP-1C (2) BFP-1A
(3) PA Fan-1A (4) ID Fan -1A
(5) UST-1A (6) ESP T/F -1A
(7) FD Fan -1A (8) Coal Mill- 1A, C, E
(9) CEP-1A,C (10) ACW Booster Pump-1A
(11) Bus V.T.

USS ‘A’
(1) Unit Em. SWGR (2) Boiler MCC
(3) BVDC ‘A’ (4) Turb. MCC ‘A’
(5) 220V Dc Ch. ‘A’ (6) +24 DC ATRS Ch. ‘A’
(7) -24V DC ATRS Ch.’A’ (8) Turb ACDB ‘A’
(9) +24 V DDCMIS (monitoring information system)Ch. ‘B’
10 GRP
(11) Boiler ACDB ‘A’ a) Grav. Feeder A,B, C,D,E,F
b) S/B MCC Feeder-1
c) INC From USS ‘B’
(12) MOT Centrifuge

1B1A SA 2A 2B SB 3A 3B SC 4A 4B SD
GT-1
UAT-1A
UAT-1B
ST-1 GT-2
UAT-2A
UAT-2B
UAT-3A
UAT-3B
GT-3
ST-2
GT-4
UAT-4A
UAT-4B
GA DRAWING OF GT ST ,UAT AND 6.6 KB BUSES
G
4
G
3
G
2G
1

SA SC 1A 3A 2A 4A SB SD SA SC SB SD
DM PLANT SWGR AIR COMP SWGR-1 AIR COMP SWGR-2
SOFTENING SWGR FOPH SWGR WORK SHOP SWGR
SB SD SB SD
AMMIN SWGR SWYD SWGR
GA DRAWING OF OFF-SITE ELECTRICAL SYSTEM

SA 1A 1B SB 2A 2B SC 3A 3B SD 4A 4B
SSS-1 USS-1 ESP-1 SSS-2 USS-2 ESP-2 SSS-3 USS-3 ESP-3 SSS-4 USS-4 ESP-4
UES-1 UES-2 UES-3 UES-4
DG-1 DG-3 DG-2
GA DRAWING OF 6.6 KV/415 VOLTS SYSTEMS
LO MCC-1 LOMCC-2 LOMCC-3
LOMCC-4

B/C
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B
GT1 UAT-1 UAT-2GT2
6.6 KC MCC-1 6.6 KC MCC-2

Motor feeder
46 – negative phase sequence
49- thermal overload
50-instantaneous o/c
50N-Instantenous E/F
50LR1-AC inverse time o/c

Transformer
feeder
46- negative ph seq
50- instant. o/c
51-inverse time o/c
64- earth fault

THANK YOU

Ht and lt scheme dc system

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