Accurately calculating voltage drop results in lower voltage drops which leads to smaller cable sizes and saves money.
To accurately calculate voltage drop in cables utilise:
- Conductor resistance (Rc) values based on actual cable operating temperature (percent loading).
- Conductor reactance (Xc) values. Xc = 0 for d.c. installations.
- Load power factor (cosθ).
- Accurate cable route length (L).
- Actual maximum operating load current (I).
For single phase:
For three phase:
The values for Rc and Xc are provided in the Standards. They can also be calculated.
Standard AS/NZS 3008.1.1 Electrical Installations-Selection of cables