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    Electrical Thumb Rules - (Part-3)

    Uploaded by

    Electrical Radical
    This document provides various electrical thumb rules and standards related to: - Capacitor sizing for power factor correction in motors and transformers - Earthing resistance values for different electrical systems - Voltage limits according to different authorities - Voltage variation limits - Insulation class temperature ratings - Standard voltage classifications - Electrical connection standards based on voltage and load - Approximate load calculations for building areas - Contracted load calculations for high-rise buildings - Sanctioned load classifications for buildings

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Electrical Thumb Rules - (Part-3)

    Uploaded by

    Electrical Radical
    342 views5 pages
    This document provides various electrical thumb rules and standards related to: - Capacitor sizing for power factor correction in motors and transformers - Earthing resistance values for different electrical systems - Voltage limits according to different authorities - Voltage variation limits - Insulation class temperature ratings - Standard voltage classifications - Electrical connection standards based on voltage and load - Approximate load calculations for building areas - Contracted load calculations for high-rise buildings - Sanctioned load classifications for buildings

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    Electrical Thumb Rules-(Part-3)

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    This document provides various electrical thumb rules and standards related to: - Capacitor sizing for power factor correction in motors and transformers - Earthing resistance values for different electrical systems - Voltage limits according to different authorities - Voltage variation limits - Insulation class temperature ratings - Standard voltage classifications - Electrical connection standards based on voltage and load - Approximate load calculations for building areas - Contracted load calculations for high-rise buildings - Sanctioned load classifications for buildings

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    342 views5 pages

    Electrical Thumb Rules - (Part-3)

    Uploaded by

    Electrical Radical
    This document provides various electrical thumb rules and standards related to: - Capacitor sizing for power factor correction in motors and transformers - Earthing resistance values for different electrical systems - Voltage limits according to different authorities - Voltage variation limits - Insulation class temperature ratings - Standard voltage classifications - Electrical connection standards based on voltage and load - Approximate load calculations for building areas - Contracted load calculations for high-rise buildings - Sanctioned load classifications for buildings

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 5
    At a glance
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    The document discusses various electrical thumb rules related to capacitor sizing, earthing resistance values, voltage limits, voltage classifications, meter room sizes and sanctioned load for buildings.

    Some of the thumb rules mentioned include capacitor sizing based on motor/transformer ratings, earthing resistance values for different electrical installations, and voltage limits according to CPWD and Kerala Electricity Board classifications.

    The standard voltage classifications mentioned are ELV, LV, MV, HV and EHV based on IEC and Indian Electricity Rule standards.

    10/15/2019 Electrical Thumb Rules-(Part-3) | Electrical Notes & Articles

    Electrical Notes & Articles

    Sharing Abstracts,Notes on various Electrical Engineering Topics.

    Electrical Thumb Rules-(Part-3)

    AUGUST 8, 2013 19 COMMENTS


    (HTTPS://ELECTRICALNOTES.WORDPRESS.COM/2013/08/08/ELECTRICAL-THUMB-RULES-
    PART-3/#COMMENTS)

    Size of Capacitor for P.F 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

    https://electricalnotes.wordpress.com/2013/08/08/electrical-thumb-rules-part-3/ 1/8
    10/15/2019 Electrical Thumb Rules-(Part-3) | Electrical Notes & Articles

    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

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    10/15/2019 Electrical Thumb Rules-(Part-3) | Electrical Notes & Articles

    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

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    10/15/2019 Electrical Thumb Rules-(Part-3) | Electrical Notes & Articles

    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 wa per 100 Sq. foot of the constructed area.
    For Commercial 1500 wa per 100 Sq. foot of the constructed area
    For lift, water lifting pump, streetlight if any,
    Other Common Load corridor/campus lighting and other common
    facilities, actual load shall be calculated
    Staircase Light 11KW/Flat Ex: 200Flat=200×11=2.2KW

    https://electricalnotes.wordpress.com/2013/08/08/electrical-thumb-rules-part-3/ 4/8
    10/15/2019 Electrical Thumb Rules-(Part-3) | Electrical Notes & Articles

    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 33kV feeder from 33 kV or 110 kV sub station
    kVA)
    8500 kW (10,000 kVA) 110 kV feeder from nearest 110 kV or 220 kV sub-
    station
    FILED UNDER UNCATEGORIZED

    About Jignesh.Parmar
    Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of
    Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16
    years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical
    Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He
    is Presently associate with one of the leading business group as a Deputy Manager at
    Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical
    India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications)
    Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical
    Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi,
    Gujarati, French languages. He wants to Share his experience & Knowledge and help technical
    enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

    19 Responses to Electrical Thumb Rules-(Part-3)

    Kuldip Singh says:


    August 8, 2013 at 3:37 pm
    excellent ! I have kept electrical thumb rules part 1 to 3 on my desk top ready to refer at any time.
    Mr. Jignesh is doing a good service to electrical engg. community. Appreciating and all the best.

    Regards

    kuldip Singh

    Reply
    carlos rivera says:
    August 9, 2013 at 4:43 am
    HI. Can you help me with this harmonic distortion problem? We have THD>30% on 3a, 5a, 15a,
    17a, 20a and 22a harmonic . Is it necessary to improve all these levels? Can I only improve the 3a,
    5a and 15a harmonics to solve this?

    Regards.

    https://electricalnotes.wordpress.com/2013/08/08/electrical-thumb-rules-part-3/ 5/8

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