Yes, using wire insulation rated for 600V on a 15kV system is a major and dangerous error.

Here's why: Voltage Breakdown

Insulation is designed to prevent electricity from leaking or arcing to other conductors or ground. The voltage rating indicates the maximum voltage the insulation can reliably withstand. Exceeding this voltage can cause the insulation to break down, leading to:

Arcing

Electricity jumping across the insulation.

Short Circuits

Direct paths for electricity to flow, bypassing the intended load.

Fire

Heat generated by arcing and short circuits can ignite surrounding materials.

Electrocution

Damaged insulation can expose conductive parts, creating a lethal shock hazard.

Insulation Thickness and Material

15kV systems require much thicker and more robust insulation materials than 600V systems. This is to handle the stress and potential for voltage surges. 600V insulation is simply not designed for this level of electrical stress.*

Safety Codes and Standards

Electrical codes (like the National Electrical Code (NEC) in the US) mandate specific insulation ratings for different voltage levels. Using undersized insulation violates these codes and creates a significant safety hazard.

In summary, using 600V insulation on a 15kV system is a serious electrical safety violation and will almost certainly lead to equipment failure, fire, and potential electrocution. Always use appropriately rated insulation for the voltage level of the system. If you're unsure, consult a qualified electrician or electrical engineer. Flag for review