Continued from second part: Electrical Thumb Rules You MUST Follow (Part 2)
Size of Capacitor for Power Factor Correction
| For Motor | |
| 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 & KEB)
| Voltage Limit (As Per CPWD) | |
| 240V | < 5 KW |
| 415V | <100 KVA |
| 11KV | <3 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 |
Electrical 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 |
Related electrical guides & articles
Jignesh Parmar
Electrical Middle management professional having more than 22 years rich and dynamic experience in Project Execution / Project Management / Designing / Maintenance diversifies from Electrical Power Transmission (400KV/220KV/66KV)- Distribution(11KV/220V) to Lifts-HVAC-Ventilation-Fire Fighting-Fire Alarm-Lifts-CCTV-Stack Parking Works (High Rise Buildings, Townships, Shopping Complex, Commercial Complex, School, Temple).Profile: Jignesh Parmar
Hello Sir,
Can you explain me that thumb rule for the selection of APFCR panel Capacity in LT distribution.
Hi Sir. Can you help me with the formula on calculating motor thermal overload
Hi Sir,
Very Good Morning
This is Krishna from Kuwait.I Want to Know about,How to calculate Voltage Drop and How to select Cable size with consider Ampere.Kindly give me a Example.
what will happen when i connect 300 kvar power factor correction capacitor to fully load 1500kva diesel generator (full load at 1950 amps) please help me to my mail
Many mistakes inside, ,,,,
THANKS FOR SPECIFICATIONS
Fantastic analysis ! I learned a lot from the details – Does someone know where my business could possibly access a blank a form version to fill in ?
In voltage limit you have specified upto 100kVA i can use 415V supply and in sanction load for building you are telling for commercial building 11kV supply for 50kW – 450kW, which one is right here. If my MD is 80kVA can i still use 415V supply to avoid transformer and other high side equipments.
Is there any thumb rule to decide total power load to be considered for commercial premises ie how much kva per sq.ft area can be taken as priliminery thumb rule.
Thanks for this valuable information!!!
@Tarekdia From a simple google search I returned the following assumptions:
GERC = The Gujarat Electricity Regulatory Commission
Dakshin Haryana Bijli Vitran Nigam, also known as DHBVN Limited is an Indian state owned electric utility company
The information, indeed is very useful. It would be much more useful, if you also indicate the corresponding code, where applicable.
In the para “Contracted Load in case of High-rise Building” there seems to be a typo error for Staircase lighting. Instead of 11KW/Flat Ex: 200Flat=200×11=2.2KW it should be 11W/Flat Ex: 200Flat=200×11=2.2KW. could you please verify?
Standard Electrical Connection (As per GERC)
up to “6KW” load demand the connection should be 1phase 230V.It is “KW” not “W” .
tank you very much
yes, agree…because i am from malaysia, not so familiar with the short form as mention commentator above……thank you
please write the legend for the appreviations like GERC and DHBVN