When the voltage at the terminal point (end) of a length of cable is lower than the voltage at the starting position of the cable run, this phenomenon is known as voltage drop (V_{Drop}).

Running a current through any length (or) size of wires will result in a certain amount of resistance. Running a current across this dc resistance will result in a decrease in voltage.

Both the cable’s resistance and its reactance go up in direct proportion to the increase in the length of the cable. Because of this, V_{Drop} is especially problematic in conditions where there is a significant distance for cables to go, such as in bigger buildings (or) on larger holdings such as farms.

This method is used rather often in the process of accurately sizing conductors across any three-phase, single-phase electrical circuit. A voltage drop calculator may be used to determine the value of voltage dropped.

**Formulas to determine Voltage Drop (V**_{Drop})

_{Drop})

- V
_{Drop}for Three Phase (3Ø) = (1.73 X I X L X K) /cmil - V
_{Drop}for Single Phase (1Ø) = (2 X I X L X K) /cmil - V
_{Drop}Percentage = V_{Drop}/V

For Copper, K = 12.6 and

For Aluminium, K=21.2

**Note**

AWG | cmil |

18 | 1620 |

16 | 2580 |

14 | 4110 |

12 | 6530 |

10 | 10380 |

8 | 16510 |

6 | 26240 |

4 | 41740 |

3 | 52620 |

2 | 66360 |

1 | 83690 |

1/0 | 105600 |

2/0 | 133100 |

3/0 | 167800 |

4/0 | 211600 |

250 | 250000 |

400 | 400000 |

500 | 500000 |

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