How to Calculate Maximum Cable Distance Without Exceeding Voltage Drop?

What is the maximum distance a #4 Cu cable can be run without exceeding a voltage drop of 2% and 3%?

Assume a balanced 3-phase inverter output to a medium voltage transformer that will supply a balanced 6500 V (phase voltage) Y-connected output of 26 A to the utility distribution system. If #4 Cu cable is used between the transformer secondary and the power lines, how far can the cable be run without exceeding a voltage drop of 2% and 3%?

Calculating Maximum Cable Distance

For a #4 Cu cable with a balanced 3-phase inverter output to a medium voltage transformer supplying 6500 V (phase voltage) and 26 A to the utility distribution system, we can calculate the maximum distance without exceeding the voltage drop:

The resistance of a 1000 ft #4 Cu cable is 0.248 ohms per conductor. For a three-conductor cable, the total resistance is 0.0827 ohms per 1000 ft. The cable length for a 2% drop is calculated to be 9,856 ft or approximately 1.9 miles.

Using the same calculations, the maximum distance for a 3% voltage drop is determined to be 6,570 ft or around 1.25 miles.

When dealing with electrical systems and cable distances, it is crucial to consider the voltage drop to ensure efficient power transmission. By calculating the maximum cable distance without exceeding the allowed voltage drop percentage, you can optimize the system's performance and prevent power losses.

In this scenario, we determined that for a 2% voltage drop, the maximum distance for a #4 Cu cable is approximately 1.9 miles. Similarly, for a 3% voltage drop, the maximum distance is around 1.25 miles. These calculations help in designing and planning the cable layout to meet the specific requirements of the utility distribution system.

It is essential to always refer to the technical specifications and standards applicable to the electrical installation to ensure safe and reliable operation. Regular maintenance and monitoring of the system can also help in detecting and addressing any issues related to voltage drop and cable distances.