Why Neutral Cable Size is Half of Phase Cable?
• In electrical systems electrical systems, especially in balanced 3-phase networks, the neutral wire is frequently constructed with a smaller cross-sectional area than the phase cables.
• This is primarily due to the fact that in a perfectly balanced 3-phase system, the currents in the 3 phase conductors are equal in magnitude but 120 degrees out of phase with one another.
• When these currents are vectorially added, the net current in the neutral conductor is potentially zero.
• As a result, the neutral conductor carries just the unbalanced (or) residual current, which is much lower than the phase current.
• As a result, installing a full-size neutral conductor is typically unneeded, increasing the cost and weight of the cable installation.
• To maximize material consumption and save costs, cables like 3.5-core cables are often used, with full-sized three phase conductors and a neutral conductor that is half or 70% the size.
• However, this method is only suitable in systems with balanced loads & low harmonic distortion. In situations where single-phase loads are dominant or harmonic currents exist—as is common in residential (or) commercial installations—the neutral can carry currents equal to or larger than the phase current.
• In such a case, a full-size neutral is required to maintain safety and prevent overheating.
• Finally, the decision to minimize the neutral size should be based on accurate load analysis and adherence to electrical standards & safety requirements.
You can also follow us on AutomationForum.co, Facebook and Linkedin to receive daily Instrumentation updates.
You can also follow us on ForumElectrical.com , Facebook and Linkedin to receive daily Electrical updates.