1
1
X
X
2
2
3
3
.
.
5
5
M
M
W
W
C
C
E
E
M
M
E
E
N
N
T
T
P
P
L
L
A
A
N
N
T
T
W
W
H
H
R
R
P
P
O
O
W
W
E
E
R
R
P
P
L
L
A
A
N
N
T
T
A
A
T
T
R
R
A
A
S
S
,
,
R
R
A
A
J
J
A
A
S
S
T
T
H
H
A
A
N
N
.
.
D
D
E
E
S
S
I
I
G
G
N
N
B
B
A
A
S
S
I
I
S
S
R
R
E
E
P
P
O
O
R
R
T
T
(ELECTRICAL)
DOC NO: DALIANEAST-CCE-20006-DBR-XXX-800
JULY 2013
E
E
P
P
C
C
C
C
O
O
N
N
T
T
R
R
A
A
C
C
T
T
O
O
R
R
M/s. DALIAN EAST NEW ENERGY DEVELOPMENT CO., LTD.
DALIAN, CHINA.
E
E
N
N
G
G
I
I
N
N
E
E
E
E
R
R
I
I
N
N
G
G
C
C
O
O
N
N
S
S
U
U
L
L
T
T
A
A
N
N
T
T
CETHAR CONSULTING ENGINEERS LIMITED
.
(
100% Owned by
TRACTEBEL Engineering Pvt. Ltd)
No.672/476, Ground FLOOR, TEMPLE TOWER
NANDANAM, CHENNAI- 600 035,
D
D
E
E
S
S
I
I
G
G
N
N
B
B
A
A
S
S
I
I
S
S
R
R
E
E
P
P
O
O
R
R
T
T
(
(
E
E
l
l
e
e
c
c
t
t
r
r
i
i
c
c
a
a
l
l
)
)
DALIANEAST-CCE-20006-DBR-XXX-800 / REV 0026.07.13 00 C.Sudarmathi P.Manivannan S.Manivel
Document No. Issue
Date
Rev
No. Prepared By Reviewed By Approved By
1.00.00. INTRODUCTION
This Design basis report covers the features of Electrical system/ equipment and design philosophy to be adopted for 1 x 23.5MW WHRB Power Plant at Shree Cement Limited, Ras, and Pali District- Rajasthan State. Detail engineering works would be carried out in accordance with the concepts developed in this report. This report covers the major features and design philosophy proposed to be adopted for the following
Power Generation System and Evacuation (Via Tie feeder) Generator
AVR Panel LAVT Panel NGR Panel
Generator relay and control panel Synchronizing Panel
segregated phase bus duct 11kV Switchgear
Auxiliary distribution transformers Non- segregated phase bus duct LT PCC / MCC / APFC/DBs DC System
Cabling system Plant lighting system
Plant earthing and Lightning protection system
2.00.00. PROJECT SITE DATA:
Location : BangurCity, RAS Pali District,Rajasthan
Altitude : 378.0 m above MSL
Ambient air temperature : (Dry)
- Minimum: 9°C
- Maximum: 48°C
Design temperature for : 50°C electrical equipment
Design relative humidity : 40%
Average annual rain fall : 368.34 mm
Seismic zone : Zone III
3.00.00. CODES & STANDARDS
All the electrical equipment and materials shall generally conform to Indian Standards and CBIP recommendations for power station design. Statutory guidelines of the following will also be observed in implementation of Power plant.
Indian Factories act Indian Electricity Act Indian Electricity rules
TAC (Fire protection) Regulations for electrical equipment
Indian Standard Code.
CBIP Recommendations.
IEC.
IEEE.
3.01.00. Standards in below to be followed for the Respective equipment as
per contract.
Transformer : IS 2026
Circuit Breaker : IEC - 56 / IS 13118
LT Switchgear : IS 4237 / IS 4047 LT Cables : IS 1554 / IS 7098 Part I Current Transformer : IS 2705 Potential Transformer : IS 3156 Earthing : IS 3043 Lightning Protection : IS 2309 Motors : IS 325 / IS 4029
4.00.00. DESIGN CONSIDERATIONS
The Electrical system will be designed based on the requirements for the safe, reliable performance, easy operation and maintenance of all equipments covered in this report and the associated electrical system.
4.01.00. Basic Design Basis Data:
Proposed Capacity : 23.5 MW
Configuration & rating : 1 x 23.5 MW
System Frequency : 50 Hz ± 5%
Generation voltage : 11kV
CPP Auxiliary Voltage : 11000V & 415V (± 10% )
DC System Voltage : 110V
Control Supply Voltage : 110 V ± 10% for AC, 110 V, - 15% for DC
Design Max. ambient temp : 50 deg C
Design life : At least 30 years
Periodic maintenance interval: Greater than 4 years
Environment : Tropical,dusty,chemical,laden, atmosphere
VFD selection : VFD power selection shall be considered after derating at
max. ambient temp
4.01.01. Following fault levels will be considered for design of all electrical
equipment at various voltage levels. Fault levels shall be restricted to the same.
System Fault Level Duration
11 KV System 40KA 1 seconds
415 V System 50KA 1 seconds
4.01.02. The system details at various utilization equipment voltages will be as given below
S.No. Service Voltage Phase System Neutral
Earthing
01. Generation 11 KV AC, 3Ph Low Resistance
02. HV Distribution 11 KV AC, 3Ph Non Effectively Earthed 04. LV Panels 415V AC, 3Ph Solidly earth at transformer star point
05. LV Motors 415V AC, 3Ph Earthed
06. Lighting / Space heater Circuits 230V AC,1Ph&N Earthed
07. UPS 230V AC, 1Ph&N Earthed
08. DC System 110V DC DC (2 Wires) Unearthed
4.01.03. The system details at various utilization equipment
Auxiliary/Control voltages will be as given below
Sl.
No. Service Voltage Remarks
01. Control Voltage
(HT Panel) 110V DC
Protection, Breaker control and indication
02. Aux. Voltage
(HT Panel) 230 V UPS Metering
03. Control Voltage
(PCC)
110V DC / AC
Protection, Breaker control and indication
04. Aux. Voltage
(PCC) 110 V AC Metering
05. Control Voltage
(MCC) 230V AC
Breaker control and its indication
06. Aux. Voltage
(MCC)
110V AC (2 Wire)
Feeder Control and its indication
07. Aux.Voltage
(MCC)
240 V AC (2 Wire)
Space heater/cubicle lamp, etc.
5.00.00. System Configuration
5.01.00. Power Generation & Evacuation
One no rated 25 MW, 11kV at 0.8 pf and synchronous generator with brush less excitation system will generate power for the plant with excitation transformer.
One number Evacuation feeder in HT panel will be used for evacuation of power.
The Plant auxiliary supply will be taken through 2 nos of 2.5 MVA 11/0.433 kV auxiliary distribution transformers.
5.02.00. Plant start up power & Normal Running
The plant start up power is fed through customer 11 KV Cement plant panel in Evacuation feeder. The plant auxiliaries are started through by closing evacuation feeder breaker which is connected to customer 11kV cement plant panel.
Once the STG is started, the incomer breaker of the generator feeder connecting to the 11 kV switchgear at CPP can be closed i.e. the generator will be synchronized with the start-up supply source. When the STG is in service it will feed its own auxiliary loads and excess power will be evacuated through evacuation breaker.
6.00.00. Equipment Design
6.01.00. Generator:
The generator will be 2 poles, 50Hz, star connected, 3 phase type and it is designed for continuous operation at its rated output of 25 MW at 0.8pf. The cooling system will be closed air circuit water cooled (CACW) type.
The generator will be capable of continuous operation at rated MVA & power factor at any voltage from 90% to 110% of rated voltage and within a frequency range of 45 to 55 Hz.
The generator will be of cylindrical rotor design, degree of protection conforming to IP 54 for alternator & IP 54 for exciter. The generator will be provided with brushless digital excitation system. The generator is resin rich type with class F insulation and class B temp rise.
6.02.00. AVR panel:
The excitation system shall be with Microprocessor based Digital AVR with 2 nos auto channel and 2 nos manual channel. The digital Auto excitation regulator will be fed through excitation transformer.
6.03.00. LASCPT PANEL
11 KV HT LASCPT panel shall include Surge Capacitor, Lightning arrestor Excitation transformers, and Potential transformers. Degree of protection for LASCPT Panel shall be IP55.
Surge Capacitor : 12kV, 0.25µF
Lightening arrestor : 12kV, 10kA
Excitation Transformer : 11KV / 220V, YD11
Potential transformers : 11 kV/√3 /110V/√3/110V/√3/110V/√3
The following table illustrates the Potential Transformers considered in LASCPT Panel.
Sl.No PTs CORE 1 CORE 2 CORE 3
1 PT – 1
CL – 0.2, 100VA (For AVR Panel
metering) CL – 3P, 100VA (For GPR -2) CL – 3P , 100VA (For GPR-2) 2 PT – 2 CL – 0.2, 100VA (For Generator Metering cum Syn
Panel) CL – 3P , 100VA (For GPR -1) CL – 3P , 100VA (For GPR-1) 3 PT – 3 (Spare PT) CL – 0.2, 100VA (Spare) CL – 3P , 100VA (Spare) CL – 3P , 100VA (Spare) 6.04.00. NGR Panel :
11 KV HT NGR panel having Current transformers for phase and standby E/F,63.51 Ohm Resistance , 100 Amps , for 30 sec, max limit up to temperature rise 375 deg C and Motorized neutral isolator with vacuum contactor. Degree of protection for NGR Panel shall be IP55 for enclosure and IP42 for resistance.
Resistance : 11kV, 63.51 Ohm, 100A for 30 sec
The following table illustrates the Current Transformers considered in NGR Panel.
CTs RATIO CORE 1 CORE 2 CORE 3
CT-1 100 / 1A CL : 0. 2, 10VA (Generator Metering Cum Syn Panel) CL:5P20,10VA (GPR-1) CL:5P20,10VA ( For GPR-2) CT - 2 2500 / 1A CL : 0. 2, 30VA , Imag ≤ 15 (For AVR Metering) CL : PS , KPV ≥ 250 ( For GPR-2) - CT - 3 2500 / 1A CL : 0. 2, 30VA , Imag ≤ 15 (Spare) CL : PS , KPV ≥ 250 (For GPR-1) - CT - 4 2500 / 1A CL : 0. 2, 30VA , Imag ≤ 15 (Spare) CL : PS , KPV ≥ 250 (For Generator Metering cum Syn Panel) -
6.05.00. Generator Relay panel.
Protection of the generator shall be achieved through microprocessor based, 2 Nos Numerical relay (P-343), one as primary and the other as back up. This panel shall be of free standing, floor mounting, sheet steel enclosed type. Degree of protection shall be of IP55. The panel mainly consists of:
Metering for Generator.
Generator protection relay. Auxiliary relays for protection.
6.05.01. The following protections are envisaged in protection relay of generator-
Generator Differential Relay (87G)
Over Fluxing (24)
Negative Phase Sequence (46)
Non – directional phase over current ( 50)
Inadvertent Energisation (Dead machine) (50/27)
Neutral voltage displacement / Residual over voltage (59N) Voltage restrained over current (51V)
Non – directional earth fault (51) Loss of Excitation (40)
Generator VT fuse failure protection (60)
Reverse power Relay (32 )
Low Forward Power protection (37)
Under & over Frequency Relay (81U / 81O) Thermal over load relay ( 49)
Rotor earth fault Relay (I & II stage) (64R) Stator earth fault Relay(51N)
Circuit breaker failure protection Relay (CBFP) AC control Supply Failure Relay
DC control supply Failure Relay 100% stator earth fault relay (27TN)
Under Voltage Relay(27)
Over voltage relay (59) Earth fault relay (64F)
Master trip relay (86-T A&B, 86-G A&B, 86C) Trip circuit supervision relays (95)
Check synchronizing relay(25C)
Guard relay (25G)
No volt relay (27 I)
Auto synchronizer (25A)
PT protection & supervision relay (60) CT protection & supervision relay
6.06.00. Generator Control , Metering cum Synchronizing Panel
Considering various operating conditions of power plant Synchronizing facility will be provided as under:
Auto, Manual synchronizing facility shall be provided for Generator breaker, evacuation feeder breaker, Spare Power Evacuation Feeder breaker and Generator incomer breaker will be provided through Auto/Manual selector switch in Generator Control, metering & synchronizing panel (GCMSP). Degree of protection shall be of IP55.
To facilitate auto synchronizing one number Auto synchronizer shall be provided.
To facilitate manual synchronizing of breakers, double voltmeter, double frequency meter, Synchroscope with cutoff switch, Synchro check relay, Live/ Dead bus synchronizing switch and necessary lamps will be provided.
2 Nos 24 window annunciator shall be considered foe alarm and indication purpose. Emergency push button for Generator and turbine trip shall be provided. All the meters shall be digital with 0.5 accuracy class.
Transducers for 3P-4Wire MW (4 output), MVAr (2 Output), 3 Nos Voltage (Two output), Frequency (Two Output), 3 Nos Current (2 Output) shall be provided. It shall be programmable type with accuracy class ± 0.5%, 4-20 milli Amps output & auxiliary supply shall be 230V AC.
6.07.00. GENERATOR BUS DUCT ( SPBD)
11 KV, 3 Phase 3200 Amps, Segregated Phase Bus dud (SPBD) shall be provided for generator Phase terminal to LASCPT Panel and Generator Neutral terminal lo NGR panel. Maximum allowable temperature rise on bus duct shall be 40 deg C and enclosure shall be 25 deg C. The degree of protection for enclosure shall be IP55.
6.08.00. High Voltage Switchgear:
The following High Voltage switchgear is envisaged. The design basis of High Voltage switchgear will be as follows.
Type : Metal clad, draw out
Service : Indoor
Rated voltage : 11kV
rated current : 3200A
Bus Bar Material : Copper
Degree of protection : IP4X for enclosure
Type of circuit breaker : VCB
Duty cycle of breaker : O-0.3sec-CO-3min-CO
Closing mechanism at CB : Spring charged stored energy
Short Circuit Rating : 40kA for 1 sec
6.08.01. FEEDER DETAILS
Generator Feeder with PT 1 No. + 1 SPARE
Transformer feeder (2.5 MVA) 2 Nos + 1 SPARE
Power Evacuation feeder with PT 1 No. + 1 SPARE
Bus PT 1 NO
6.08.02. Protection & Metering Envisaged:
The protections envisaged for different feeders are listed below. Main protective relays will be Numerical fixed type. However auxiliary relays will be electromechanical type only.
A) 11 KV Incomer feeders:
Instantaneous and definite time over current protection. (50/51) Directional over current and earth fault protection. (67/67N) Under voltage protection with timer (27+2)
Master trip relay(86)
Anti pumping relay(94)
DC Fail relay(27D)
B) 11 KV Power evacuation feeder:
Instantaneous and IDMT over current protection.(50/51) Directional over current and earth fault protection. ((67/67N) Cable differential protection (87C)
Under voltage protection with timer (27+2) Trip circuit supervision relay(74)
Master trip relay(86)
Anti pumping relay(94)
Neutral voltage displacement (59N)
DC Fail relay(27 D)
C) Auxiliary transformer feeder:
Instantaneous and definite time over current protection. Instantaneous and definite time earth fault protection.
Winding temperature protection (49 WT)
Oil temperature protection (49 OT) Bucholz relay (63).
Trip circuit supervision relay(74) Master trip relay(86)
Anti pumping relay(94)
DC Fail relay(27 D)
D) Bus PT feeder
Under voltage relay with timer (27+2)
DC Fail relay(27 D)
6.08.03. Metering:
Incoming feeder shall be provided with energy meters of class 0.5 accuracy, Digital Ammeter & Digital voltmeter. Auxiliary transformer feeder shall be provided with Energy meter and Ammeter. However evacuation feeder shall be provided with 0.2 accuracy class Trivector meter & Digital ammeter.
6.09.00. LV Transformers:
6.09.01. LV Auxiliary Transformers
Auxiliary Transformers are Oil impressed type, 2.5 MVA rated ,2 x 100% capacity, 11/ 0.433kV, ONAN cooled, Dyn11 vector group, 8.25 % impedance, 99.5% efficiency at 50% load, 99.0% efficiency at 100% load, outdoor type. This transformer will be provided with off load tap switch having +5 to -5 % taps in steps of 2.5% on HV side. The LV side neutral of this transformer will be solidly grounded.
The following assumptions as per normal power plant practice had been made in sizing the transformer
Load factor = 0.8 for continuous load, 0.2 for intermittent load
Coincidence factor = 0.05 for motorized valves, 0.5 for AC & heater unit, 1 for continuous load
General:
The flux density considered is 1.67 T for the core and yoke at the rated MVA, voltage & frequency. The transformer & all its accessories including CTs shall be designed to withstand without any injury the thermal & mechanical effects caused due to short circuit fault. Transformers shall withstand, without injurious heating, the combined voltage & frequency fluctuations.
The transformer will be provided with following accessories and fittings:
Double float type buchholz relay having alarm and trip contacts Dial type (150 mm) oil temperature indicator with alarm and trip
contacts.
Dial type (150 mm) winding temperature indicator (WTI) with alarm and trip contacts.
Magnetic oil level gauge, with low level alarm contact. Tap position indicator (Local )
Jacking pads.
Bi-directional flange wheels with suitable locking arrangement. LV neutral CT for LV REF protection and standby earth fault
protection.
Rating & Diagram Plate
Earthing Terminals
Lifting Lugs
Radiators
Silica Gel Breather
Explosion Vent with Diaphragm
Bottom drain cum Filter Valve
Top Filter Valve Pressure relief valve.
6.09.02. Lighting Transformers:
Two no 2X100% dry type lighting transformer of 100 KVA, 415/415, Dyn11, AN, 8.25 % impedance, greater than 99.5% efficiency at 50% load, 99.0% efficiency at 100% load, ±10% variations on secondary side in 2.5% steps shall be provided. Lighting transformer shall be of class H insulation with temperature rise limited to class F.
6.10.00. NSPBD:
415 V, 3 Phase + Neutral 4000 Amps TPN Sand witch type Non Segregated Phase Bus duct (NSPBD) shall be considered for connecting
between auxiliary distribution transformer and 415V PCC. Maximum allowable temperature rise on bus duct is 40 deg C and enclosure is 25 deg C. The degree of protection for enclosure shall be IP54.Bus conductor & Bus enclosure shall be Electrolytic grade Aluminum & MS respectively. Bus bar material shall be of Aluminum flats grade 83401 WP, IS 5082
6.11.00. Low Voltage Switchgear - 415V
6.11.01. LTPCC:
Type : Fixed type
Service : Indoor
Current Rating : 4000 A
Short circuit Rating : 50kA for 1 Sec.
Protection : IP4X
Busbar material : Aluminium
Maximum current density : 0.8A/mm2
Incomers : Two with 4000 A ACB breaker
Closing/tripping of ACB : 110 V DC / AC
The protections envisaged for different feeders were listed below.
a) LTPCC Incomers:
Instantaneous and IDMT over current protection (50/51) Instantaneous and IDMT earth fault protection (50/51N) Restricted earth fault relay (64R)
Standby earth fault Relay (51N)
Under voltage protection with timer(27+2) DC failure relay (27 D)
b) LTPCC outgoing feeders
Thermal & magnetic releases for overcurrent & short circuit protection shall be provided.
c) LTPCC Bus PT feeders
Under voltage relay (27)
Metering:
Energy meter shall be provided in the all incoming and outgoing feeders of PCC. Analog type ammeter and voltmeter with selector switch shall be provided on the incoming feeders. For Bus PT feeders voltmeter with selector switch will be provided
6.11.02. MCC
MCC shall be double front as per the contract. MCC shall have uniform height placed side by side.
Type : Free standing fixed type
Service : Indoor
Short circuit Rating : 50kA for 1 Sec.
Current Rating : as per requirement
Enclosure : IP 52
Rated voltage : 415V
Maximum current density : 0.8A/mm2
Bus bar Material : Aluminum
Incomers : Two
The CPP shall have following MCCs:
TG MCC
Boiler MCC (1 No for each PH + 1 No for each AQC)
A/C, P&V MCC ACC & CWS MCC WTP MCC ACDB, MLDB, DCDB APFC MCC Emergency MCC
6.12.00. 415V Motors
Motors are of TEFC IP55 enclosure with Class `F’ insulation with a temperature rise limited to Class `B’. LT motors shall have premium efficiency (IE-3 type). Protection class shall be IP65. All the S1 Duty Cycle (continuous running) motors shall be compatible with VFD (Inverter grade for VFD application).
Local Push Button Station (LPBS) shall be provided for all the motors and MOV's (for VFD LPBS shall have RPM meter and raise lower push buttons). For motors 3.7 kW and above ,LPBS shall be equipped with Ammeter.
All motors below 75 kW: 415V rated, 3 phase/SFU+110 V (from MCC) AC control contactor + O/L relay with single phase preventer
From 75 kW and above: 415 V rated, 3 phase contactor/ circuit controlled from MCC through Digital motor protection relay with bearing temp.
For above 22kW motors ammeters shall be provided. For above 30kW motors Space heaters shall be provided. For 75kW and above motors bearing & winding temperature monitoring shall be provided.
7.00.00. DC system
One no 800AH 1X100% (2V X 55), 110 Volts , 2 wire ungrounded system , four (4) hours back up Vented type Plante Lead acid Battery of adequate capacity with their Float cum Boost charger shall be considered for DC loads with associated FRP battery racks etc..
110 V DC power supply is the most reliable source of power supply for control, protection, interlock and annunciation requirements of the power station.
The rating of charger will be calculated as below:
Float charger:
Continuous DC load + trickle charging current of battery +15 % margin.
Boost charger
Boost charging current of battery+ continuous DC load.
Float cum Boost charger: Boost charging current of battery.
Battery Charger
Type - One float and float cum Boost charger
Voltage regulation - 110V ± 1%
Service - Indoor
Enclosure - Sheet steel Degree of protection - IP – 42
AC input - 415V, 3ph, 3W, 50Hz, 50kA
Busbar Material – Aluminum
7.00.01. DC Distribution Board
DC Distribution Board constructional features will be given below
Type - Fixed type NON-Compartmentalized
Service - Indoor
Enclosure - Sheet steel Degree of protection - IP – 42
Short circuit rating - 10kA for 1 sec (Tentative)
8.00.00. Auto Power Factor Correction Panel
2 Nos x 500 WAR , 113 STEPS (50 KVAR OF -10 Nos ) capacitor units shall be hermetically sealed type, with two bushings and shall be designed to carry a minimum of 1 .5 times the rated current at 110% of rated voltage and 1.35 times rated reactive power, continuously. The capacitors should be of non PCB type, suitable for operation in tropical areas
9.00.00. Cabling System:
9.01.00. Cables:
9.01.01. HT Power cable
HT power cable used for 11 kV systems will be 12.7/22kV (E) grade. The cable will be heavy-duty, stranded Aluminum conductor with FRLS, conductor screened with semiconductor, extruded XLPE insulation and insulation screen (semiconductor +copper tape), extruded PVC inner sheath, G.S flat (for multi-core)/aluminium wire (for single core) armoured and extruded PVC (ST-2) outer sheathed conforming to IS7098 part-II. Maximum operating temperature under normal condition for XLPE insulation cables will be 90°C. Trefoil Clamps for HT Cable shall be provided.
The following rating of HT cable XLPE (UE) insulated shall be envisaged for the Plant
LASCPT panel to HT switch gear panel - 4RX 1C X 630 Sq.mm/ph
GPP-4 HT panel to Existing HT Panel for power evacuation - 4R X 1C X 630 Sq.mm/ph
GPP-4 HT Panel to Auxiliary transformer 1 & 2 - 1R X 3C X 300 Sq.mm
9.01.02. LT Power cable
LT power cable used for 415V AC, 230VAC, 110V AC & 110 V DC system will be 1.1kV (E) grade, stranded aluminum conductor with FRLS, XLPE insulated, not extruded PVC inner sheath, G.S. Flat/round wire with armoured, extruded PVC (ST-2) outer sheath conforming to IS 7098 part-I. Maximum operating temperature under normal condition for XLPE insulation cables will be 90°C. Cables less than 10 sq.mm shall be of copper conductor. DC Power cables for EOP will be UNINYVIN CABLE & Cable for UPS will be Copper armour cable. Separate earthing cable shall be laid from each VFD to respective Motor.
9.01.03. Control cable
Control cables will be 1100V (E) grade, multi-core with stranded 1.5 mm² and copper conductor with FRLS, PVC insulated, extruded PVC inner sheath, G.S. flat / round wire armoured and extruded sheath of PVC (ST-1) with numbering of all cores, conforming to IS 1554 part-I/IS 5831.
9.02.00. Cable Tagging
Cable tagging shall be at both end & at every 20 meter considered for all cable. Anodised type tagging plate will be provided.
9.03.00. Cable Trays
Cables laid in overhead racks shall be GI ladder/perforated type trays for electrical/instruments with proper prefabricated bends respectively in outdoor areas and supports shall be MS (painted). The top cable tray shall be covered with GI sheet canopy/GI sheet covering in outdoor cable racks. All outdoor cable racks shall be vertically oriented. Galvanized cable trays for Boiler, Turbine, ACC and BOP area shall be supplied. For WTP area all cable tray shall be FRP type only.
Separate cable tray for HT Power, LT Power, Control Cable, Instt. Analog Input/output cable each, Instt. Digital Input/output cables each & Compensating Cable shall be considered.
No. Of Cable layers per Cable tray shall be as follows:
HT Power Cable & LT Power(up to 120 mm2) Cable - One Layer
LT Power Cable (below 120mm2) - Two Layer
Control Cable - Three Layer Instt. Cables - Three Layer
10.00.00. llumination System:
10.01.00. Basic Concept
The system provides lighting and service power at 240V, single phase 50 Hz to receptacles and single phase feeders in plant areas. The plant illumination system includes normal cum Emergency lighting and critical DC lighting.
10.02.00. 100 % Normal cum Emergency A.C lighting
Normal cum Emergency A.C. lighting will be provided by lighting fixtures distributed throughout the plant. Separate circuits with timers will be provided where round the clock lighting is not required. Lighting fixtures will be fed from respective area lighting panels, which in turn receive supply from lighting distribution board. MLDB shall be provided with Dual incomer. LDBs shall be equipped with 30 mA ELCB. In Normal condition the Main lighting distribution board will be fed from 415V PCC & Emergency MCC through 2 x 100%, lighting transformer. In blackout condition then the supply for MLDB shall be fed from Emergency MCC (which is connected to Customer DG set) through lighting transformer.
10.03.00. Emergency DC Lighting
Critical DC lighting will be provided with bulk head lamps at Cable Cellar MCC room, CCR, TG house, stair cases, steam drums on all boilers & Start up vents. This DC lighting will remain OFF normally and will be switched ON automatically when main AC supply fails. The power supply for lighting will be fed from 110V DCDB. FL DC lamp with integral battery shall be provided for Boiler area MCC room.
10.04.00. Power Receptacles / Welding Sockets
1 Phase & 3 Phase power receptacles will be provided for alternative floors of Boiler area, each floor ACC areas and at least 3 Nos in TG building, MCC room, cable cellar area. 3 Phase Welding Sockets will be provided at each stage of boiler, TG Floor & as required in ACC area etc. 24 Volt AC power receptacles with transformers and proper distribution at all location of boilers, ACC floors will be provided.
10.05.00. The type of fixtures & type of luminaries for different areas is listed below:
Area Description Type of Fixture Type of Luminaries
Cable gallery, Transformer Area Compressor room, Battery charger room, P&V room & Storeroom
Industrial Trough Type 2x28 W Fluorescent
Lamp
MCC Switchgear room
Industrial Trough type with Reflector
Arrangement
2x36 W Fluorescent Lamp
Battery rooms Corrosion Proof 2x36 W Fluorescent Lamp
Control Rooms & Office rooms
Industrial Trough type with mirror optics
2x28 W Fluorescent Lamp
Turbine houses Integral Well glass
Industrial type 1 X 80W HPMV
TG Building Operating floor
Industrial type high
bay 1x400 W MH Lamp
Boiler area, Boiler platforms ACC, & WTP
Integral Well glass Industrial type
1x70 W MH Lamp
Toilet areas Integral Well glass
Industrial type
1 X 36 W Fluorescent Lamp
Street Lights & Outdoor lights
Integral Well glass Industrial type with timer arrangement
1 x 150 W MH Lamp
DC lights in TG Building Bulk head type 1X 100W GLS
DC lights in Boiler area MCC room
FL with integral battery type
2x28 W Fluorescent Lamp
11.00.00. Earthing & Lightning Protection System
11.01.00. Plant Earthing:
System earthing will be adopted to facilitate earth fault relaying and to reduce the magnitude of transient over-voltage. The system earthing involves earthing of the neutrals of generator. Low impedance earthing is used for 11 KV system to limit the earth fault current to about 100 A by grounding generator neutral by means of Neutral Grounding Resistor (NGR).
A ground grid of 32mm MS Rod will be provided encircling the plant through a system of grounding electrodes and pits to keep ground resistance less than one ohm. Earth mat shall be laid below 500mm below absolute ground level and earth pits shall be 1.5 meter away from nearby building walls. Every electrical system will have dual earthing.
Treated earth pits will be considered for generator NGR, Aux. Transformer Neutral, lightning arrestor & equipments. All Earthing electrodes shall be of Gel type maintenance free (homogeneous readymade mixture).
All instrument earth pits shall be maintenance free and configuring delta spaced by 6 meter with redundant copper cable connection.
The underground grid shall be connected with lightning protection earth electrodes below ground at average depth of 500 mm.
11.01.01. Equipment Earthing:
Electrical equipment shall be provided with two separate and distinct grounding pads, each complete with tapped hole, galvanized bolt and spring washer for connection to station ground conductors.
The neutral of generator and transformer shall be earthed through two dedicated earth pits.
Flat from the main earthing grid to local network and electrical equipment will be GI flats of suitable size, except for smaller items, which will be connected using steel wire. However, for portable equipment, if one of the conductors of the connecting cable/plug socket is earthed, no other earth connection is required.
An earthing conductor will be installed along the entire length of top most power cable trays. The tray earth will be connected at various locations to the station earth grid. The offsite areas will be connected through the earth flats running along the cable trays. Earth continuity will be provided for all cable trays & conduits. The following aspects will be addressed during design, of the equipment earthing system to be adopted.
Availability of sufficient earth current for effective relaying. Stabilization of circuit potential with respect to earth.
The size of earth conductor used for individual equipment earthing
Main Ground Conductor: 32 mm MS rod
Earth Electrodes : MS Rod 32 mm dia, 3 m long pipe
Generator and Transformer Body: 75 mm x 10 mm GI Flat.
Transformer and Generator Neutral: 75 mm x 10 mm GI Flat.
HT switchgear Panels: 50 mm x 6 mm GI Flat.
415V PMCC, MCC, DCDB, MLDB Structures, Bus duct, Control
Panel, Cable
LT AC Motors from 110kW up to 132 KW: 50 mm x 6 mm GI Flat.
LT AC Motors above 30kW up to 90 KW: 25 mm x 6 mm GI Flat.
LT AC Motors from 5.5kW up to 30 KW: 25 mm x 3 mm GI Flat.
LT AC Motors below 5.5 KW : 8 SWG GI wire
Local Panels, LPBS, Switch sockets, LDBs, JB,Receptacles: 8 SWG GI wire
11.02.00. Lightning Protection:
The main purpose of the lightning protection system is to provide protection to structures from lightning strokes and provide a low resistance-conducting path for lightning discharge to earth. For metal structures, which are continuous down to the ground level, no lightning protection is required except adequate grounding connections. Air termination network with down conductor and earthing electrodes will be provided on the basis of IS-2309 recommendations.
The zone of protection will depend on each structure height, overall shape, and physical location in relation to other structures.
