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DESIGN OF EHV SUBSTATION AT FACT UDC
Done by : Arunkumar M.P
Bijesh K.B Jijo Francis
Lipin A.K
ABOUT
FACT is a doyen among the manufactures in India. It started production in 1944 on the bank of river Periyar. It was then the first large scale fertilizer factory in the entire country. FACT has three manufacturing divisions, two divisions at Udyogamandal and one at Ambalamedu. The overall production capacity of the company is in the range of 2.58 lakhs of phosphates ad 50,000 tones of caprolactum.
FACT has also successfully branched out to the field of chemical and
fertilizer technology and design capabilities research , development and fabrication engineering services. FACT engineering and design organization (FEDO) and FACT engineering works (FEW) are well known names today not only in India but also outside countries.
FACT has also successfully branched out to the field of chemical and fertilizer
technology and design capabilities research , development and fabrication engineering services. FACT engineering and design organization (FEDO) and FACT engineering works (FEW) are well known names today not only in India but also outside countries.
FACT Udyogamandal division is the oldest in FACT with an installed capacity of 450TPD of ammonium phosphate and 680TPD of ammonium sulphate fertilizers.
Besides power received from KSEB, it is also generated in both Udyogamandal and Ambalamedu complexes ; In Udyogamandal two turbo generators of 6MW and 16MW capacities are available for power generation. KSEB power is received at Udyogamandal from Kalamassery 220KV substation.
LIST OF CONTENTS
INTRODUCTIONSINGLE LINE DIAGRAM SYSTEM COMPONENTS FAULT LEVEL CALCULATION EARTHING SYSTEM EARTH GRID CALCULATIONDESIGNREFERENCES
INTRODUCTION
SUBSTATION :
Defined as : An Assembly of apparatus which transforms the characteristics of Electrical Energy from one form to another.
For economical transmission and distribution, higher voltage should be used.
Consumers do not use very high voltages.
So they must be transformed into low voltages by means of transformers in sub-stations.
Thus, a substation may be called as link between the generating stations and consumers.
The distribution voltages generally used in practice are 66KV, 11KV and 33KV. But in this project work, we are considering 110KV sub station.
SINGLE LINE DIAGRAM
FAULT LEVEL CALCULATION
Kalamassery fault level = 3600 MVA2.5% future expansion = 4500 MVA10% voltage Regulation = 5445 MVABase MVA = 100 MVASource Impedance = Base MVA x100 Fault level MVA
= 100x100 = 1.8365 5445Length of ACSR = 5.1 KmOhmic impedance of the calculator = 0.292+0.5772
= 0.0841+0.332929
= 0.6458/Km = 0.6458x5.1 = 3.29Ω% Z = KVA x Z = 3.29x100x1000 = 2.72% 10 x KV2 10x1102
% impedance of 110 KV bus at UDL = 1.8365+2.72 = 4.5565Fault level = 100x100 = 2194.67MVA 4.5565 Fault current = 2194.6 = 11.53 KA 3x110% Impedence of 20 MVA Transformer = 15.6%% Impedence of 100 MVA base = 100x15.6 = 78 20
% Impedence of 11KV side of Transformer = 78 + 4.5565
= 82.5565Fault level of 11Kv side of Transformer = 100 x100 = 121.13 MVA
82.5565
Fault current = 121.13 / 3x11 = 6.365 KA
DESIGN OF SUBSTATION
Earth Resistively 4 spike method Earth Resistance 10m distance - 0.03 Ω
5m distance - 0.45 Ω Earth pit - 0.31Ω
P,C, R shorted and is connected to the earth
pit. P2 & C2 are connected to the two terminals which are connected to the 2 electrodes which are at 20m distances.
SITE SELECTION
Main points to be considered while selecting the site for EHV Sub-Station are as follows:i) The site chosen should be as near to the load center as possible.ii) It should be easily approachable by road or rail for transportation of equipments.iii) Land should be fairly leveled to minimize development cost.iv) Source of water should be as near to the site as possible. This is because water is requiredfor various construction activities; (especially civil works, earthing and for drinking purposes etc.)v) The sub-station site should be as near to the town but should be clear of public places, aerodromes and Military / police installations.
vi) The land should be have sufficient ground area to accommodate substation equipments,
buildings, staff quarters, space for storage of material, such as store yards and store sheds. with roads and space for future expansion.vii) Set back distances from various roads such as National Highways, State Highways should be observed as per the regulations in force.viii) While selecting the land for the substation preference to be given to the Govt. land over private land.ix) The land should not have water logging problem.x) The site should permit easy and safe approach to outlets for EHV lines.
RESISTIVITY
r= 40x3.14x0.03 = 40x3.14x0.03 = 20.93 1.89 - 0.71 0.18
EARTH GRID AREA CALCULATIONS
Ac2 = If (tc.Tr.Sr.x104/TCAP)/ln(1+(TmTo)(Ko+To))Where, If = Fault current = 25980A
Tc = Fault current duration = 1SecAr = Efficient if thermal expansion = 0.00423Sr = Soil resistively = 20.93 Ω m
TCAP = Thermal capacity /unit volume in J/cm3 0C = SHxSWx4.184 = 4.184x0.114x07.8
= 3.749Where, SH = Specific heat SW = Specific weightAt 4500C, Tm = Maximum allowable temp in 0c = 6200C
To = Ambient Temp in 0C =500C
KO = (1-Tr) = 216.64 TrTr = reference temperature for material constant = 20 0C
Earth grid area , Ac2= 25.980 (1x0.00423x104x20.93/3.749)/
ln(1+(620-50)/(216+50))= 533501.28m2
AC = 730:41m2
By including earth satellite earth mat the area of the earth grid can be increased to 075 m2 (35x25)
DESIGNConductor size :
Ondor clonk’s formula provides a reasonable method to compute the area of iron section for earthing.
A =I t : (74/10g10 (1+(Tm-To)/(234+To)x10-3)Where , A = Area of iron section in m2
I = rms current in amps Tm = Max allowable temp in 0C To = Ambient Temperature in 0CMax allowable temp for steel in 620oc for welded joint and 3100C for bolted joints.
The formula is simplified as : A=KI t
Initial designAssume a preliminary layout of 21mx18m grid with equally spied conductors and shown in figure with spacing D=15m grid burial depth h=0.75m
Grounding mat design :Considering further expansion fault current for the design procedure as 259804. For grounding mat and welded joint are to be provided.
Area of cross section = A=K I t = 0.0122-259801 = 317m2
Area of 40mm dia. rod = 40x317 = 1257m2
Hence area of cross section is sufficient earth matis designed at a normal spacing of 15m b/w conductors. As per initial design length of earth grid including down rods = 36220mNo: of lowers is assumed as 3 and lower foot resistance as : 10 ΩResistance of 3 lowers =10/3 = 3.33 ΩTotal resistance of line = Resistance of lower + Resistance of ground wire
Resistance of ground wire :
Resistance of ground wire is assumed as : 3 ΩTotal resistance of one line = 3.33 +3 = 6.33 ΩTotal resistance of two lines together = 6.33/2
= 3.165 Ω The resistance of the earth grid may be calculated as
R=(s/4r) +(s/l)S = 20.93 ΩmR = Radius of the equivalent surface of the grid
= (area of yard /3.14) = 875/3.14 = 16.68mR = (20.93/4x16.68+20.93/36220) = 0.31 ΩValue of electrode resistance = 1/((1/0.31)+1/3.165)
= 0.28
For fault current of 25980 A in 110Kv bas grid ground return current = 0.357x0.28x11530 = 1152.54A
Minimum length of ground conductor required :L=Km x Ki x gt/(116+0.174xCsxSs)Where,
K = 1/2 [ ln ([D2 / 16 h.d] + [(D+2.h)/ 8Dd]2 –[h / 4d] +[Kit/Kh] x ln(8/ (2n-1))]
D = spacing of conductor = 15md = diameter of conductor = 0.04mH= depth of buried conductor = 0.75mN= 14x1q=16
BUS BAR
Used to interconnect the loads and sources of electrical power It connects incoming and outgoing transmission linesAlso connect generator and main transformer in power plantMaterial used: Copper or Aluminium Size of bus bar to determine max. amount of current passed
POWER TRANSFORMERS :
A transformer is a static device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying voltage in the secondary winding. This effect is called mutual induction.
Power transformers are usually the largest single item in a substation. Due to large quantity of oil, it is essential to take precaution against the spread of fire.
TRANSFORMER No.4
Make TELK-TRANDORMER WITH ON LOAD TAP CHANGER
Transformer Specification Ref.No.IS 2026-1977
Maker’s Sl No. 120270-2
Type SALOCR
Form 3NYCP
Year of Manufacture 1988
Rated KVA HV 12500/20000
LV 12500/20000
Volts – no load HV 110000V
HV 65.7/105.1
Amperes LV 657/1051
ONAN/ONAF
Type of cooling 15.60%
Impedance voltage (20MVA base) HV/LV HV 3
Phase LV 3
50Hz
Frequency C/S YNyno
Vector Symbol 24000Kg
Transportation Mass 20000Kg
Un-tanking Mass 9495 Kg
Total of oil 41000Kg
Oil Liters 10550 Litres
Air Circulation 8x90 m3/min
POSITION HV CONNECTION HV VOLTS HV CURRENT
1 1N-15 116600 99.2
2 1N-14 114950 110.6
3 1N-13 113300 102
4 1N-12 11650 103.5
5 1N-11 110000 105.1
6 1N-10 108350 106.1
7 1N-9 106700 108.4
8 1N-8 105050 110.1
9 1N-7 103400 111.8
10 1N-6 101750 113.6
11 1N-5 100100 115.5
12 1N-4 98450 117.4
13 1N-3 96800 119.4
CIRCUIT BREAKERS
A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.
Its function is to interrupt continuity, to immediately discontinue electrical flow.
SF6 CIRCUIT BREAKERS
The SF6 is an electro-negative gas and has a strong tendency to absorb free electrons. The contacts of the breaker are opened in a high pressure flow of SF6 gas and an arc is struck between them. The conducting free electrons in the arc are rapidly captured by the gas to form relatively immobile negative ions.
This loss of conducting electrons in the arc quickly builds up enough insulation strength to extinguish the arc.
FEEDER CIRCUIT BREAKER
Make Crompton greaves everyday solutions
Type GAS CIRCUIT BREAKER 120-SFM-32B
Year of Manufacture 2006
Rated voltage 145Kv
Rated Frequency 50Hz
Rated Normal Current 3150 A
Rated making capacity 100 KAP
Rated short circuit breaking capacity 40 Ka
Rated short time current 40Ka for 3 seconds
Rated lightening impulse withstand voltage 650 KVP
First pole to clear factor 1.5
Rated opr.Seq. 0-0.3sec-CO-3 Min-CO
Rated Gas pressure 7Kg/Cm2-g(at200c)
Gas Wt 8 Kg
Total Weight 1550 Kg
Closing 110V DC, Tripping 110V DC
230V AC
If, 230V AC
TRANSFORMER CIRCUIT BREAKERS
Make Crompton greaves Nasik, INDIA
Type GAS CIRCUIT BREAKER 120-SFM-32B
Year of Manufacture 1990
Rated voltage 145Kv
Rated Frequency 50Hz
Rated Normal Current 31.50 A
Rated making capacity
Rated short circuit breaking capacity 31.50 KA
Rated short time current 31.5 Ka for 3 seconds
Rated lightening impulse withstand voltage 650 KVP
First pole to clear factor 1.5
Rated opr.Seq. 0-0.3sec-CO-3 Min-CO
Rated Gas pressure 7Kg/Cm2-g(at200c)
Gas Wt 9 Kg
11.) ISOLATORS
These are essentially off load devices although they arecapable of dealing with small charging currents ofBus bars and connections. The design of isolators is closely related to the design ofsubstations. Isolator design is considered in the followingaspects:
• Space Factor• Insulation Security• Standardization• Ease of Maintenance• Cost
Some types of isolators include:• Horizontal Isolation types• Vertical Isolation types• Moving Bushing types
FEEDER ISOLATORS WITH EARTH SWITCH
Make G power switch gear ltd, jeedimetla, hydrabad, 500055
Type DB
KV Rating 123
Current Rating 1600A
Year of Manufacture 2005
Impulse Voltage 550Kv peak
Short time current for 1 sec 26.24 Ka rms
Operating Mechanism Motor
Control voltage 110V DC
What exactly does a Lightning Arrestor Do?
It Does not Absorb the Lightning
It Does not Stop the Lightning
It Does Divert the Lightning to Ground
It Does Clamp (limit) the Voltage produced by the Lightning
It Only protects equipment electrically in parallel with it.
LIGHTENING ARRESTOR
Name of the manufacturer OBLUM ELECTRICAL INDUSTRIES PVT LTD
Trade mark Oblum
Type of identification Metovar
Rated voltage 96Kv
Continuous operating voltage 81Kv (RMS)max
Rated frequency 50Hz
Nominal discharge current 10Ka
Long duration discharge class 3
Pressure relief class ‘A’
CURRENT TRANSFORMER
The current transformer is used to measure the very high current passing through the bus.
It step downs the current and measurements are taken in the control room the ratings of CT is based on the ampere.
These CTs are connected to the control room through cables.
FEEDER CURRENT TRANSFORMER -1 (FCT-1)
Ring winding current transformers
Make Brown Boveri-Stromeandler
Type TMRg 110
Year of Manufacture 1957
Voltage 110/220Kv
Ratio 300-150-75-/1/1/1
Power 60VA
Class 0.5 & S20
I Therm 24/12/6
1 Dyn 60/30/15
TRANSFORMER CTs (TCT-4)
Make Transformer &Electricals Kerala Ltd-TELK
Manufacturing No. 220104
Sl No. 1R,2R,3R
PO No. 19109211 Dt:21/195
Type NPOULVZ-R
Basic Ins level 230/550Kv
Rated Voltage 126Kv
1995
Frequency 50 Hz
Standard Is 2705(Parts 1,2,3) 1992
VOLTAGE TRANSFORMER
This is a step down transformer, which step down the high voltage to a value that can be measured using the measuring instruments in the control room. This has an additional core for the carrier communication. The CVT are connected between phase and ground in parallel to the circuit.
CAPACITOR VOLTAGE TRANSFORMER VOLTAGE TRANSFORMER
REFERENCES
IEEE RED DATA BOOK, 1993
NEWNESS ELECTRICAL ENGINEER’S HAND BOOK, D.F.WAENE, SECOND EDITION.
ISO MANUAL ELECTRICAL SYSTEM STUDY AND FAULT LEVEL CALCULATION BY FEDO.
POWER GENERATION OPERATION ANDCONTROL BY ALLEN JWOOD AND BRUDE T W WOLLENBERG.
ISO MANUAL FOR EARTHING AND SYSTEM STABILITY CALCULATION BY FEDO.
STD 80-2000 IEEE GUIDE FOR SAFETY