Yes, the fact that your parallel feeders are not bundled together in a triad formation is very likely the cause of the voltage readings you're seeing. Here's a breakdown of why

Understanding the Phenomenon
Inductive Reactance (Inductance) and Magnetic Fields

When AC current flows through a conductor, it creates a magnetic field around it. This magnetic field induces a voltage in nearby conductors, a phenomenon known as inductive reactance. The strength of this induced voltage depends on several factors, including:

Current magnitude

Higher current = stronger magnetic field.

Frequency

Higher frequency = stronger inductive effect.

Proximity of conductors

Closer conductors = greater inductive coupling.

Geometry of conductors

The spatial arrangement of conductors significantly affects the magnetic field distribution and inductive reactance.

Triad Formation and Cancellation

When conductors of a 3-phase system (A, B, C) are bundled together in a tight, symmetrical configuration (triad or trefoil), the magnetic fields produced by each phase largely cancel each other out. This minimizes the inductive reactance and reduces the induced voltage on other objects (like the enclosure or the ground bus).

Flat Configuration and Imbalance

When the conductors are laid flat, as you describe, the symmetry is broken. The magnetic fields from each phase do not effectively cancel. This results in:

Uneven Magnetic Field Distribution

The magnetic field becomes much stronger and more concentrated in certain areas around the conductors.

Increased Inductive Reactance

The higher, unbalanced magnetic fields induce larger voltages on nearby conductive objects.

Voltage to Ground

The metal enclosure and ground bus become paths for these induced voltages to appear.

Why the Voltage Readings?

Your voltage meter is essentially measuring the small voltage induced in the enclosure (and, consequently, the ground bus) by the magnetic fields from the phase conductors. Since the magnetic fields are not balanced due to the flat configuration, the induced voltages are also unbalanced (hence your 15V, 30V, 15V readings).

Why This Matters

While these voltages might seem small, they can be problematic for a few reasons: Increased Losses

Even small currents circulating due to the induced voltage represent wasted energy.

Electromagnetic Interference (EMI)

The unbalanced magnetic fields can radiate and interfere with sensitive electronic equipment nearby.

Personnel Safety

Although unlikely to be lethal at these levels, sustained induced voltages can be a shock hazard under certain conditions.

Equipment Malfunction

In some cases, the induced voltages and circulating currents can contribute to the premature failure of equipment.

Solutions1. Bundle the Parallel Feeders into Triads (Best Solution)

This is the most effective solution. Arrange the conductors into two separate triads (one triad for each set of parallel conductors). Securely bind them together with cable ties or other appropriate methods. This will significantly reduce the inductive reactance and the induced voltages.2.

Increase Spacing

If you cannot bundle the conductors tightly, increasing the spacing between the phases might help slightly. However, this is generally less effective than bundling.3.

Shielding

In some cases, you might consider using shielded cables. The shield can help to contain the magnetic fields and reduce the induced voltages. However, this is usually a more expensive option and requires proper grounding of the shield.4.

Shorten the Run

Reduce the distance of the flat run as much as possible.

Important Considerations Safety

Always de-energize and lock out the equipment before working on the conductors.

NEC Compliance

The National Electrical Code (NEC) has requirements for the installation of conductors, including considerations for inductive reactance. Consult the NEC for specific requirements in your jurisdiction.

Grounding

Ensure that the enclosure and ground bus are properly grounded to provide a low-impedance path for any circulating currents.

Professional Advice

It's always best to consult with a qualified electrical engineer or electrician to assess the situation and recommend the most appropriate solution.

In summary: Your voltage readings are almost certainly due to the unbalanced magnetic fields caused by the flat arrangement of your parallel feeders. Bundling the conductors into triads is the best way to correct this issue and improve the performance and safety of your electrical system. Flag for review