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# Dictionary Glossary & Useful Equations for Electrical Engineering

Cable Capacity

• For Cu Wire Current Capacity (Up to 30 Sq.mm) = 6X Size of Wire in Sq.mm
• Ex. For 2.5 Sq.mm=6×2.5=15 Amp, For 1 Sq.mm=6×1=6 Amp, For 1.5 Sq.mm=6×1.5=9 Amp
• For Cable Current Capacity = 4X Size of Cable in Sq.mm ,Ex. For 2.5 Sq.mm=4×2.5=9 Amp.
• Nomenclature for cable Rating = Uo/U
• where Uo=Phase-Ground Voltage, U=Phase-Phase Voltage, Um=Highest Permissible Voltage

## Current Capacity of Equipment’s:

• 1 Phase Motor draws Current=7Amp per HP.
• 3 Phase Motor draws Current=1.25Amp per HP.
• Full Load Current of 3 Phase Motor=HPx1.5
• Full Load Current of 1 Phase Motor=HPx6
• No Load Current of 3 Phase Motor =30% of FLC
• KW Rating of Motor=HPx0.75
• Full Load Current of equipment =1.39xKVA (for 3 Phase 415Volt)
• Full Load Current of equipment =1.74xKw (for 3 Phase 415Volt)

### Earthing Resistance:

• Earthing Resistance for Single Pit=5Ω ,Earthing Grid=0.5Ω
• As per NEC 1985 Earthing Resistance should be <5Ω.
• Voltage between Neutral and Earth <=2 Volts
• Resistance between Neutral and Earth <=1Ω
• Creepage Distance=18 to 22mm/KV (Moderate Polluted Air) or
• Creepage Distance=25 to 33mm/KV (Highly Polluted Air)

#### Minimum Bending Radius:

• Minimum Bending Radius for LT Power Cable=12xDia of Cable.
• Minimum Bending Radius for HT Power Cable=20xDia of Cable.
• Minimum Bending Radius for Control Cable=10xDia of Cable.

## Insulation Resistance:

• Insulation Resistance Value for Rotating Machine= (KV+1) MΩ.
• Insulation Resistance Value for Motor (IS 732) = ((20xVoltage (L-L)) / (1000+ (2xKW)).
• Insulation Resistance Value for Equipment (<1KV) = Minimum 1 MΩ.
• Insulation Resistance Value for Equipment (>1KV) = KV 1 MΩ per 1KV.
• Insulation Resistance Value for Panel = 2 x KV rating of the panel.
• Min Insulation Resistance Value (Domestic) = 50 MΩ / No of Points. (All Electrical Points with Electrical fitting & Plugs). Should be less than 0.5 MΩ
• Min Insulation Resistance Value (Commercial) = 100 MΩ / No of Points. (All Electrical Points without fitting & Plugs).Should be less than 0.5 MΩ.
• Test Voltage (A.C) for Meggering = (2X Name Plate Voltage) +1000
• Test Voltage (D.C) for Meggering = (2X Name Plate Voltage).
• Submersible Pump Take 0.4 KWH of extra Energy at 1 meter drop of Water.

## Lighting Arrestor:

• Arrestor have Two Rating=
• (1) MCOV=Max. Continuous Line to Ground Operating Voltage.
• (2) Duty Cycle Voltage. (Duty Cycle Voltage>MCOV).

## Transformer:

• Current Rating of Transformer=KVAx1.4
• Short Circuit Current of T.C /Generator= Current Rating / % Impedance
• No Load Current of Transformer=<2% of Transformer Rated current
• Capacitor Current (Ic)=KVAR / 1.732xVolt (Phase-Phase)
• Typically the local utility provides transformers rated up to 500kVA For maximum connected load of 99kW,
• Typically the local utility provides transformers rated up to 1250kVA For maximum connected load of 150kW.
• The diversity they would apply to apartments is around 60%
• Maximum HT (11kV) connected load will be around 4.5MVA per circuit.
• 4No. earth pits per transformer (2No. for body and 2No. for neutral earthing),
• Clearances, approx.1000mm around TC allow for transformer movement for replacement.

## Diesel Generator:

• Diesel Generator Set Produces=3.87 Units (KWH) in 1 Litter of Diesel.
• Requirement Area of Diesel Generator = for 25KW to 48KW=56 Sq.meter, 100KW=65 Sq.meter.
• DG less than or equal to 1000kVA must be in a canopy.
• DG greater 1000kVA can either be in a canopy or skid mounted in an acoustically treated room
• DG noise levels to be less than 75dBA @ 1meter.
• DG fuel storage tanks should be a maximum of 990 Litter per unit Storage tanks above this level will trigger more stringent explosion protection provision.

### Current Transformer:

• Nomenclature: CT
• Ratio: input / output current ratio
• Burden (VA): total burden including pilot wires. (2.5, 5, 10, 15 and 30VA.)
• Class: Accuracy required for operation (Metering: 0.2, 0.5, 1 or 3, Protection: 5, 10, 15, 20, 30).
• Accuracy Limit Factor:
• Nomenclature of CT: Ratio, VA Burden, Accuracy Class, Accuracy Limit Factor.Example: 1600/5, 15VA 5P10  (Ratio: 1600/5, Burden: 15VA, Accuracy Class: 5P, ALF: 10)
• As per IEEE Metering CT: 0.3B0.1 rated Metering CT is accu­rate to 0.3 percent if the connected secondary burden if imped­ance does not exceed 0.1 ohms.
• As per IEEE Relaying (Protection) CT: 2.5C100 Relaying CT is accurate within 2.5 percent if the secondary burden is less than 1.0 ohm (100 volts/100A).

### Size of Capacitor for P.F Correction:

 For Motor Advertisement: Size of Capacitor = 1/3 Hp of Motor ( 0.12x KW of Motor) For Transformer < 315 KVA 5% of KVA Rating 315 KVA to 1000 KVA 6% of KVA Rating >1000 KVA 8% of KVA Rating

## Earthing Resistance value:

 Earthing Resistance Value Power Station 0.5 Ω Sub Station Major 1.0 Ω Sub Station Minor 2.0 Ω Distribution Transformer 5.0 Ω Transmission Line 10 Ω Single Isolate Earth Pit 5.0 Ω Earthing Grid 0.5 Ω As per NEC Earthing Resistance should be <5.0 Ω

## Voltage Limit (As per CPWD & Kerala Elect.Board):

 Voltage Limit (As Per CPWD) 240V < 5 KW 415V <100 KVA 11KV MVA 22KV <6 MVA 33KV <12 MVA 66KV <20 MVA 110KV <40 MVA 220KV >40 MVA

## Voltage Variation

 > 33 KV (-) 12.5% to (+) 10% < 33 KV (-) 9% to (+) 6% Low Voltage (-) 6% to (+) 6%

## Insulation Class:

 Insulation Temperature Class A 105°C Class E 120°C Class B 130°C Class F 155°C Class H 180°C Class N 200°C

## Standard Voltage Limit:

 Voltage IEC (60038) IEC (6100:3.6) Indian Elect. Rule ELV < 50 V LV 50 V to 1 KV <=1 KV < 250 V MV <= 35 KV 250 V to 650 V HV > 1KV <= 230 KV 650 V to 33 KV EHV > 230 KV > 33 KV

## Standard Electrical Connection (As per GERC):

 As per Type of Connection Connection Voltage LT Connection <=440V HT connection 440V to 66KV EHT connection >= 66KV As per Electrical Load Demand Up 6W Load demand 1 Phase 230V Supply 6W to 100KVA(100KW) 3 Phase 440V Supply 100KVA to 2500KVA 11KV,22KV,33KV Above 2500KVA 66KV HT Connection Earthing H.T Connection’s Earthing Strip 20mmX4mm Cu. Strip CT & PT bodies 2Nos PT Secondary 1Nos CT Secondary 1Nos I/C and O/G Cable+ Cubicle Body 2Nos

## Standard Meter Room Size (As per GERC):

 Meter Box Height Upper level does not beyond 1.7 meter and Lower level should not below 1.2 meter from ground. Facing of Meter Box Meter Box should be at front area of Building at Ground Floor. Meter Room / Closed Shade 4 meter square Size

## Approximate Load as per Sq.ft Area (As per DHBVN):

 Sq.ft Area Required Load (Connected) < 900 Sq.ft 8 KW 901 Sq.ft to 1600 Sq.ft 16 KW 1601 Sq.ft to 2500 Sq.ft 20 KW > 2500 Sq.ft 24 KW For Flats :100 Sq.ft / 1 KW For Flats USS /TC: 100 Sq.ft / 23 KVA

## Contracted Load in case of High-rise Building:

 For Domestic Load 500 watt per 100 Sq. foot of the constructed area. For Commercial 1500 watt per 100 Sq. foot of the constructed area Other Common Load For lift, water lifting pump, streetlight if any, corridor/campus lighting and other common facilities, actual load shall be calculated Staircase Light 11KW/Flat Ex: 200Flat=200×11=2.2KW Sanctioned Load for Building Up to 50 kW The L.T. existing mains shall be strengthened. 50 kW to 450 kW (500 kVA) 11 kV existing feeders shall be extended if spare capacity is available otherwise, new 11 kV feeders shall be constructed. 450 kW to 2550 kW (3000 kVA) 11 kV feeder shall be constructed from the nearest 33 kV or 110 kV substation 2550 kW to 8500 kW (10,000 kVA) 33kV feeder from 33 kV or 110 kV sub station 8500 kW (10,000 kVA) 110 kV feeder from nearest 110 kV or 220 kV sub-station

## Sub Station Capacity & Short Circuit Current Capacity:

 As per GERC Voltage Sub Station Capacity Short Circuit Current 400 KV Up to 1000 MVA 40 KA  (1 to 3 Sec) 220 KV Up to 320 MVA 40 KA  (1 to 3 Sec) 132 KV Up to 150 MVA 32 KA  (1 to 3 Sec) 66 KV Up to 80 MVA 25 KA  (1 to 3 Sec) 33 KV 1.5 MVA to 5 MVA 35 KA (Urban) (1 to 3 Sec) 11 KV 150 KVA to 1.5 MVA 25 KA (Rural) (1 to 3 Sec) 415 V 6  KVA to 150 KVA 10 KA  (1 to 3 Sec) 220 V Up to 6 KVA 6 KA  (1 to 3 Sec)

## Sub Station Capacity & Short Circuit Current Capacity:

 As per Central Electricity Authority Voltage Sub Station Capacity Short Circuit Current 765 KV 4500 MVA 31.5 KA for 1 Sec 400 KV 1500 MVA 31.5 KA for 1 Sec 220 KV 500 MVA 40 KA for 1 Sec 110/132 KV 150 MVA 40 KA or 50 KA for 1 Sec 66 KV 75 MVA 40 KA or 50 KA for 1 Sec

## Minimum Ground Clearance and Fault Clearing Time:

 Voltage Min. Ground Clearance Fault Clear Time 400 KV 8.8 Meter 100 mille second 220 KV 8.0 Meter 120 mille second 132 KV 6.1 Meter 160 mille second 66 KV 5.1 Meter 300 mille second 33 KV 3.7 Meter 11 KV 2.7 Meter

## Bus bar Ampere Rating:

 For Phase Bus bar Aluminium 130 Amp / Sq.cm or 800Amp / Sq.inch. For Phase Bus bar Copper 160 Amp / Sq.cm or 1000Amp / Sq.inch For Neutral Bus bar Same as Phase Bus bar up to 200 Amp than Size of Neutral Bus bar is at least half of Phase Bus bar.

## Bus bar Spacing:

 Between Phase and Earth 26mm (Min) Between Phase and Phase 32mm (Min) Bus bar Support between Two Insulator 250mm.

## Sound Level of Diesel Generator (ANSI 89.2&NEMA 51.20):

 KVA Max. Sound Level <9 KVA 40 DB 10 KVA to 50 KVA 45 DB 51 KVA to 150 KVA 50 DB 151 KVA to 300 KVA 55 DB 301 KVA to 500 KVA 60 DB

## IR Value of Transformer:

 IR Value of Transformer Voltage 30°C 40°C 50°C >66KV 600MΩ 300MΩ 150MΩ 22KV to 33KV 500MΩ 250MΩ 125MΩ 6.6KV to 11KV 400MΩ 200MΩ 100MΩ <6.6KV 200MΩ 100MΩ 50MΩ 415V 100MΩ 50MΩ 20MΩ

## Standard Size of MCB/MCCB/ELCB/RCCB/SFU/Fuse:

 MCB Up to 63 Amp (80Amp and 100 Amp a    per Request) MCCB Up to 1600 Amp (2000 Amp as per Request) ACB Above 1000 Amp MCB Rating 6A,10A,16A,20A,32A,40A,50A,63A MCCB Rating 0.5A,1A,2A,4A,6A,10A,16A,20A,32A,40A,50A,63A,80A,100A (Domestic Max 6A) RCCB/ELCB 6A,10A,16A,20A,32A,40A,50A,63A,80A,100A Sen. of ELCB 30ma (Domestic),100ma (Industrial),300ma DPIC (Double Pole Iron Clad) main switch 5A,15A,30 A for 250V TPIC (Triple Pole Iron Clad) main switch 30A, 60A, 100A, 200 A For 500 V DPMCB 5A, 10A, 16A, 32A and 63 A for 250V TPMCCB 100A,200A, 300Aand 500 A For 660 V TPN main switch 30A, 60A, 100A, 200A, 300 A For 500 V TPNMCB 16A, 32A,63A For 500 V, beyond this TPNMCCB: 100A, 200A, 300A, 500 A For 660 V TPN Fuse Unit (Rewirable) 16A,32A,63A,100A,200A Change over switch (Off Load) 32A,63A,100A,200A,300A,400A,630A,800A SFU (Switch Fuse Unit) 32A,63A,100A,125A,160A,200A,250A,315A,400A,630A HRC Fuse TPN (Bakelite) 125A,160A,200A,250A,400A.630A HRC Fuse DPN (Bakelite) 16A,32A,63A MCB/MCCB/ELCB Termination Wire / Cable Up to 20A MCB Max. 25 Sq.mm 20A to 63A MCB Max. 35 Sq.mm MCCB Max. 25 Sq.mm 6A to 45A ELCB 16 Sq.mm 24A to 63A ELCB 35 Sq.mm 80A to 100A ELCB 50 Sq.mm

## Transformer Earthing Wire / Strip Size:

 Size of T.C or DG Body Earthing Neutral Earthing <315 KVA 25×3 mm Cu / 40×6 mm GI Strip 25×3 mm Cu Strip 315 KVA to 500 KVA 25×3 mm Cu / 40×6 mm GI Strip 25×3 mm Cu Strip 500 KVA to 750 KVA 25×3 mm Cu / 40×6 mm GI Strip 40×3 mm Cu Strip 750 KVA to 1000 KVA 25×3 mm Cu / 40×6 mm GI Strip 50×3 mm Cu Strip

## Motor Earthing Wire / Strip Size:

 Size of Motor Body Earthing < 5.5 KW 85 SWG GI Wire 5.5 KW to 22 KW 25×6 mm GI Strip 22 KW to 55 KW 40×6 mm GI Strip >55 KW 50×6 mm GI Strip

## Panel Earthing Wire / Strip Size:

 Type of Panel Body Earthing Lighting & Local Panel 25×6 mm GI Strip Control & Relay Panel 25×6 mm GI Strip D.G & Exciter Panel 50×6 mm GI Strip D.G & T/C Neutral 50×6 mm Cu Strip

## Electrical Equipment Earthing:

 Equipment Body Earthing LA (5KA,9KA) 25×3 mm Cu Strip HT Switchgear 50×6 mm GI Strip Structure 50×6 mm GI Strip Cable Tray 50×6 mm GI Strip Fence / Rail Gate 50×6 mm GI Strip

## Earthing Wire (As per BS 7671)

 Cross Section Area of Phase, Neutral Conductor(S) mm2 Minimum Cross Section area of Earthing Conductor (mm2) S<=16 S (Not less than 2.5 mm2) 1635 S/2

## Area for Transformer Room: (As per NBC-2005):

 Transformer Size Min. Transformer Room Area (M2) Min. Total Sub Station Area( Incoming HV,LV Panel, T.C Roof) (M2) Min. Space Width (Meter) 1X160 14 90 9 2X160 28 118 13.5 1X250 15 91 9 2X250 30 121 13.5 1X400 16.5 93 9 2X400 33 125 13.5 3X400 49.5 167 18 2X500 36 130 14.5 3X500 54 172 19 2X630 36 132 14.5 3X630 54 176 19 2X800 39 135 14.5 3X800 58 181 14 2X1000 39 149 14.5 3X1000 58 197 19
•  The Capacitor Bank should be automatic Switched type for Sub Station of 5MVA and Higher.
• Transformer up to 25KVA can be mounted direct on Pole.
• Transformer from 25KVA to 250KVA can be mounted either on “H” Frame of Plinth.
• Transformer above 250KVA can be mounted Plinth only.
• Transformer above 100MVA shall be protected by Drop out Fuse or Circuit Breaker.

## Span of Transmission Line (Central Electricity Authority):

 Voltage Normal Span 765 KV 400 to 450 Meter 400 KV 400 Meter 220 KV 335,350,375 Meter 132 KV 315,325,335 Meter 66 KV 240,250,275 Meter

## Max. Lock Rotor Amp for 1 Phase 230 V Motor (NEMA)

 HP Amp 1 HP 45 Amp 1.5 HP 50 Amp 2 HP 65 Amp 3 HP 90 Amp 5 HP 135 Amp 7.5 HP 200 Amp 10 HP 260 Amp

## Three Phase Motor Code (NEMA)

 HP Code <1 HP L 1.5 to 2.0 HP L,M 3 HP K 5 HP J 7 to 10 HPPHPHPHHHHH H >15 HP G

## Service Factor of Motor:

 HP Synchronous Speed (RPM) 3600 RPM 1800 RPM 1200 RPM 900 RPM 720 RPM 600 RPM 514 RPM 1 HP 1.25 1.15 1.15 1.15 1 1 1 1.5 to 1.25  HP 1.15 1.15 1.15 1.15 1.15 1.15 1.15 150 HP 1.15 1.15 1.15 1.15 1.15 1.15 1 200 HP 1.15 1.15 1.15 1.15 1.15 1 1 > 200 HP 1 1.15 1 1 1 1 1

## Type of Contactor:

 Type Application AC1 Non Inductive Load or Slightly Inductive Load AC2 Slip Ring Motor, Starting, Switching OFF AC3 Squirrel Cage Motor AC4,AC5,AC5a, AC5b,AC6a Rapid Start & Rapid Stop AC 5a Auxiliary Control circuit AC 5b Electrical discharge Lamp AC 6a Electrical Incandescent Lamp AC 6b Transformer Switching AC 7a Switching of Capacitor Bank AC 7b Slightly Inductive Load in Household AC 5a Motor Load in Household AC 8a Hermetic refrigerant compressor motor with Manual Reset O/L  Relay AC 8b Hermetic refrigerant compressor motor with Automatic Reset O/L  Relay AC 12 Control of Resistive Load & Solid State Load AC 13 Control of Resistive Load & Solid State Load with Transformer Isolation AC 14 Control of small Electro Magnetic Load (<72 VA) AC 15 Control of Electro Magnetic Load (>72 VA)

## Contactor Coil:

 Coil Voltage Suffix 24 Volt T 48 Volt W 110 to 127 Volt A 220 to 240 Volt B 277 Volt H 380 to 415 Volt L

## Overhead Conductor /Cable Size:

 Voltage Overhead Conductor Cable Size 33 KV ACSR-Panther/Wolf/Dog , AAAC 150,185,300,400,240 mm2 Cable 11 KV ACSR-Dog/Recon/Rabbit , AAAC 120, 150,185,300 mm2 Cable LT ACSR-Dog/Recon/Rabbit , AAC,AAAC 95,120, 150,185,300 mm2 Cable

## Transmission / Distribution Line:

 Span Height of Tower 400KV=400 Meter 400KV=30Meter (Base 8.8 Meter) 220KV=350 Meter 220KV=23Meter (Base 5.2 Meter) 132KV=335 Meter 220KV Double Circuit=28 Meter 66KV=210 Meter 66KV=13Meter Conductor Ampere Voltage wise Conductor Dog=300Amp 400KV=Moose ACSR=500MVA Load Panther=514Amp 220KV=Zebra ACSR=200MVA Load Zebra=720Amp 132KV=Panther ACSR=75MVA Load Rabbit=208Amp 66KV=Dog ACSR=50MVA Load Moose=218Amp

## Type of Tower:

 Type Used Angle/Deviation A Suspension Tower Up to 2° B Small Angle Tower 2° to 15° C Medium Angle Tower 15° to 30° D Large Angle / Dead End Tower 30° to 60° & Dead End

## Tower Swing Angle Clearance (Metal Part to Live Part):

 Swing Angle Live Part to Metal Part Clearance (mm) 66KV 132KV 220KV 400KV 0° 915mm 1530mm 2130mm 3050mm 15° 915mm 1530mm 2130mm – 22° – – – 3050mm 30° 760mm 1370mm 1830mm – 44° – – – 1860mm 44° 610mm 1220mm 1675mm –

## Cable Coding (IS 1554) ???? A2XFY / FRLS / FRPVC / FRLA / PILC)

 A Aluminium 2X XLPE F Flat Armoured W Wire Armoured Y Outer PVC Insulation Sheath W Steel Round Wire WW Steel double round wire Armoured YY Steel double Strip Armoured FR Fire Retardation LS Low Smoke LA Low Acid Gas Emission WA Non Magnetic round wire Armoured FA Non Magnetic Flat wire Armoured FF Double Steel Round Wire Armoured

## Corona Ring Size:

 Voltage Size <170 KV 160mm Ring put at HV end >170 KV 350mm Ring put at HV end >275 KV 450mm Ring put at HV end & 350 mm Ring put at Earth end

## Load as per Sq.Ft:

 Type of Load Load/Sq.Ft Diversity Factor Industrial 1000 Watt/Sq.Ft 0.5 Commercial 30 Watt/Sq.Ft 0.8 Domestic 15 Watt/Sq.Ft 0.4 Lighting 15 Watt/Sq.Ft 0.8

## Size of Ventilation Shaft:

 Height of Building in meter Size of ventilation shaft in sq meter Minimum size of shaft in meter 9.0 1.5 1.0 12.5 3.0 1.2 15 and above 4.0 1.5

## Accuracy Class of Metering CT:

 Metering Class CT Class Applications 0.1 To 0.2 Precision measurements 0.5 High grade kilowatt hour meters for commercial grade kilowatt hour meters 3 General industrial measurements 3 OR 5 Approximate measurements

## Accuracy Class Letter of CT:

 Metering Class CT Accuracy Class Applications B Metering Purpose Protection Class CT C CT has low leakage flux. T CT can have significant leakage flux. H CT accuracy is applicable within the entire range of secondary currents from 5 to 20 times the nominal CT rating. (Typically wound CTs.) L CT accuracy applies at the maximum rated secondary burden at 20 time rated only. The ratio accuracy can be up to four times greater than the listed value, depending on connected burden and fault current. (Typically window, busing, or bar-type CTs.)

## Accuracy Class of Protection CT:

 Class Applications 10P5 Instantaneous over current relays & trip coils: 2.5VA 10P10 Thermal inverse time relays: 7.5VA 10P10 Low consumption Relay: 2.5VA 10P10/5 Inverse definite min. time relays (IDMT) over current 10P10 IDMT Earth fault relays with approximate time grading:15VA 5P10 IDMT Earth fault relays with phase fault stability or accurate time grading: 15VA

## Electrical Useful Equations

• For Sinusoidal Current : Form Factor = RMS Value/Average Value=1.11
• For Sinusoidal Current : Peak Factor = Max Value/RMS Value =1.414
• Average Value of Sinusoidal Current(Iav)=0.637xIm (Im= Max.Value)
• RMS Value of Sinusoidal Current(Irms)=0.707xIm (Im= Max.Value)
• A.C Current=D.C Current/0.636.
• Phase Difference between Phase= 360/ No of Phase (1 Phase=230/1=360°,2Phase=360/2=180°)
• Short Circuit Level of Cable in KA (Isc)=(0.094xCable Dia in Sq.mm)/√ Short Circuit Time (Sec)
• Max.Cross Section Area of Earthing Strip(mm2) =√(Fault Current x Fault Current x Operating Time of Disconnected Device ) / K
• K=Material Factor, K for Cu=159, K for Alu=105, K for steel=58 , K for GI=80
• Most Economical Voltage at given Distance=5.5x√ ((km/1.6)+(kw/100))
• Cable Voltage Drop(%)=(1.732xcurrentx(RcosǾ+jsinǾ)x1.732xLength (km)x100)/(Volt(L-L)x Cable Run.
• Spacing of Conductor in Transmission Line (mm) = 500 + 18x (P-P Volt) + (2x (Span in Length)/50).
• Protection radius of Lighting Arrestor = √hx (2D-h) + (2D+L). Where h= height of L.A, D-distance of equipment (20, 40, 60 Meter), L=Vxt (V=1m/ms, t=Discharge Time).
• Size of Lighting Arrestor= 1.5x Phase to Earth Voltage or 1.5x (System Voltage/1.732).
• Maximum Voltage of the System= 1.1xRated Voltage (Ex. 66KV=1.1×66=72.6KV)
• Load Factor=Average Power/Peak Power
• If Load Factor is 1 or 100% = This is best situation for System and Consumer both.
• If Load Factor is Low (0 or 25%) =you are paying maximum amount of KWH consumption. Load Factor may be increased by switching or use of your Electrical Application.
• Demand Factor= Maximum Demand / Total Connected Load (Demand Factor <1)
• Demand factor should be applied for Group Load
• Diversity Factor= Sum of Maximum Power Demand / Maximum Demand (Demand Factor >1)
• Diversity factor should be consider for individual Load
• Plant Factor(Plant Capacity)= Average Load / Capacity of Plant
• Fusing Factor=Minimum Fusing Current / Current Rating (Fusing Factor>1).
• Voltage Variation(1 to 1.5%)= ((Average Voltage-Min Voltage)x100)/Average Voltage
• Ex: 462V, 463V, 455V, Voltage Variation= ((460-455) x100)/455=1.1%.
• Current Variation(10%)= ((Average Current-Min Current)x100)/Average Current
• Ex:30A,35A,30A, Current Variation=((35-31.7)x100)/31.7=10.4%
• Fault Level at TC Secondary=TC (VA) x100 / Transformer Secondary (V) x Impedance (%)
• Motor Full Load Current= Kw /1.732xKVxP.FxEfficiency
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