Below voltage drop calculator tool will help to quickly check voltage drop on a cable run. The input required is voltage level, load rating, and cable parameters. The type of cable used for calculation is 50Hz XLPE/SWA in accordance with IEC 60502 or IEC 60092. The result of voltage drop calculator for 3 cores cable data (i.e. resistance and reactance) can be applied on 4 cores cable. Also, note that cable resistance implemented in the calculation has been converted to XLPE operating temperature viz. 90^{o}C.

### Voltage Drop Calculator Input

**Select System**: Choose from dropdown list AC MV 3 Phase, AC LV 1 Phase, AC LV 3 Phases or DC

**System Voltage**: Choose from dropdown list voltage with respect to system AC 6kV, AC 3kV, AC 400V, AC 380V, AC 230V, AC 220V, DC 110V, DC 24V or DC 12V

**Load Rating**: Input load rating in kW or kVA. Should kVA is used, power factor is 1 (unity) in next step

**Power factor**: Power factor of AC load, use 1 (unity) for DC load

**Number of Cable Run**: How many cable in parallel

**Select Cable Size (sqmm)**: Choose cable size (i.e. 3C x 90) in sq mm

**Cable Length**: Input cable length in meter

### Voltage Drop Formula

The voltage drop will be calculated using the following formulas:

**Thee-phase circuit voltage drop formula:**

**Single phase circuit voltage drop formula:**

**DC circuit voltage drop formula:**

where: | |||

V_{D} | : | Voltage drop, in volts | |

cosΦ | : | Load power factor | |

R | : | Resistance of cable, in ohms per phase per 1000m | |

X | : | Reactance of cable, in ohms per phase per 1000m | |

I | : | Load current, in amperes | |

L | : | Total length of cable, in meter |

### Cable resistance and reactance

Following cable resistance and reactance is applied to calculation:

- Low voltage AC cable and DC cable

No. | Cable Size | Resistance (ohm/km) | Reactance (ohm/km) |
---|---|---|---|

1 | 2.5 | 9.45 | 0.0932 |

2 | 4 | 5.88 | 0.0875 |

3 | 6 | 3.93 | 0.0837 |

4 | 10 | 2.33 | 0.0785 |

5 | 16 | 1.47 | 0.0761 |

6 | 25 | 0.927 | 0.0768 |

7 | 35 | 0.669 | 0.0743 |

8 | 50 | 0.494 | 0.0739 |

9 | 70 | 0.342 | 0.0726 |

10 | 95 | 0.247 | 0.0708 |

11 | 120 | 0.196 | 0.0705 |

12 | 150 | 0.16 | 0.0709 |

13 | 185 | 0.128 | 0.0712 |

14 | 240 | 0.0987 | 0.0703 |

- AC Medium Voltage 3kV cable

No. | Cable Size | Resistance (ohm/km) | Reactance (ohm/km) |
---|---|---|---|

1 | 10 | 2.33 | 0.107 |

2 | 16 | 1.47 | 0.102 |

3 | 25 | 0.927 | 0.0949 |

4 | 35 | 0.668 | 0.0905 |

5 | 50 | 0.494 | 0.0878 |

6 | 70 | 0.342 | 0.0836 |

7 | 95 | 0.247 | 0.0806 |

8 | 120 | 0.196 | 0.0786 |

9 | 150 | 0.16 | 0.0768 |

10 | 185 | 0.128 | 0.0753 |

11 | 240 | 0.0986 | 0.0733 |

- AC Medium Voltage 6kV cable

No. | Cable Size | Resistance (ohm/km) | Reactance (ohm/km) |
---|---|---|---|

1 | 10 | 2.33 | 0.115 |

2 | 16 | 1.47 | 0.11 |

3 | 25 | 0.927 | 0.102 |

4 | 35 | 0.668 | 0.0972 |

5 | 50 | 0.494 | 0.094 |

6 | 70 | 0.342 | 0.0891 |

7 | 95 | 0.247 | 0.0855 |

8 | 120 | 0.196 | 0.0831 |

9 | 150 | 0.159 | 0.081 |

10 | 185 | 0.128 | 0.0792 |

11 | 240 | 0.0984 | 0.0773 |

### How to calculate voltage drop ?

Example 1 - MV motor feeder during normal operation

A 1100 kW induction motor is connected to a 6 kV 3-phase 50 Hz supply. The motor has the following performance data:

- Power factor is reading from manufacturer motor nameplate: 0.83
- Cable length from electrical SWG/MCC to motor: 350 m
- Cable size: 3C x 120 sqmm in 1 run

Step 1: Full load current, I_{FL} = 1100 / 1.73 / 6 / 0.83 = 127.67 A

Step 2: Derive 3C x 120 sqmm 6kV cable resistance and reactance from table:

R = 0.196 (Ω/km)

X = 0.0831 (Ω/km)

Step 3: Voltage drop of 3 phase motor feeder using above formula

V_{D} = 1.73 * 127.67 * (0.196 * 0.83 + 0.0831 * 0.56) * 350 / 1000 = 16.17 V

V_{D} (%) = 16.11 / 6000 *100 = 0.269%

Example 2 - MV motor feeder during startup

Using the same motor as example 1, we will calculate voltage drop during motor starting.

- Power factor during starting: 0.2
- Starting current factor: 5.5 for MV motor

Step No. 1: Starting current, I_{s} = 5.5 * I_{FL} = 5.5 * 127.67 = 702.23 A

Step No. 2: Using same data as example 1

Step No. 3: Voltage drop of 3 phase motor feeder using above formula

V_{D} = 1.73 * 702.23 * (0.196 * 0.2 + 0.0831 * 0.98) * 350 / 1000 = 51.29 V

V_{D} (%) = 51.29 / 6000 *100 = 0.85%