8.How do we calculate Cabel sizing? Formula for Voltage drop? How do we calculate resistive & Inductive drop? Why do we limit voltage drop to 5 percent?

Question

Accepted Answer

Cable sizing is calculated using the formula for voltage drop, which takes into account resistive and inductive drop. Voltage drop is limited to 5% to ensure efficient power transmission.

Cable sizing is determined by calculating the voltage drop using the formula: VD = (I * L * R * 2) / 1000
Resistive drop is calculated using Ohm's Law: Vr = I * R
Inductive drop is calculated using the formula: Vi = I * X
Voltage drop is limited to 5% to prevent excessive power loss and ensure efficient power transmission
Examples of cable sizing calculations and voltage drop calculations can be provided based on specific parameters

Accepted Answer

For cable sizing as per IEC 60865

Input data

1 short ckt current

2 capacity (kw/Kva)

Step first

Calculate size of cable withstand short ckt current

Amm2 = Ish(ampere) * root t / K

Step 2:-

Calculate full load current = kw/ root 3* kv

Step 3rd from the cable catalog select size of cable which withstand full load current.

Selected cable and current rating cable we called Base current.

Step 4 :-

Calculte Actual current rating of cable = base current * derating factor

Derating factor

1 cable depth

2 grouping factor

3. Temp factor

4. Thermal resitivity of soil

Actual current rating > Full load current

Step 5 calculate percentage voltage drop

%v should be in between 1 to 3 percentage

%V = root 3 * Flc * cable length " ( R cos @ + X sin @) / Voltage (v) * Number of cable run

Thank you

SandeepThapliyal 111@ gmail.com

Accepted Answer

8.How do we calculate Cabel sizing? Formula for Voltage drop? How do we calculate resistive & Inductive drop? Why do we limit voltage drop to 5 percent?

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8.How do we calculate Cabel sizing? Formula for Voltage drop? How do we calculate resistive &amp; Inductive drop? Why do we limit voltage drop to 5 percent?

Top Burns & McDonnell Electrical Design Engineer interview questions & answers

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8.How do we calculate Cabel sizing? Formula for Voltage drop? How do we calculate resistive & Inductive drop? Why do we limit voltage drop to 5 percent?