What is the highest voltage in the distribution box

The maximum voltage level for a standard low-voltage distribution box is typically 690V AC, while medium-voltage distribution systems can go up to 35 kV.

Low-

Voltage Distribution BoxesLow-voltage distribution boxes, also known as consumer units or panelboards, are designed for residential, commercial, and light industrial applications.

According to IE

C 61439 and BS 7671 standards, these panels are rated for voltages up to 690V AC and must comply with safety requirements such as proper insulation, creepage distances, and dielectric strength testing. The rated voltage indicates the maximum voltage at which the panel can operate safely; exceeding this voltage can damage equipment or create safety hazards. Typical low-voltage distribution voltages include 230V single-phase and 400–415V three-phase systems.

Medium-

Voltage Distribution Systems

For primary distribution networks, voltages are higher, generally ranging from 4 kV to 35 kV. Common voltage classes include 11 kV, 22 kV, and 33 kV, which are used to carry power from substations to local transformers before stepping down to low-voltage levels for end users. Distribution boxes in these systems are designed with equipment rated for the corresponding voltage class, including insulators, bushings, and switchgear.

The maximum voltage in this context is determined by the voltage class of the equipment, not the nominal system voltage.

Key Considerations

Rated Voltage vs. Nominal Voltage: The rated voltage of a distribution box is the maximum safe operating voltage, while the nominal voltage is the typical system voltage it serves. Safety Standards: Panels must meet IEC 61439 requirements for dielectric strength, temperature rise, and protection against accidental contact.

Application Type: Residential and commercial panels are low-voltage (up to 690V), whereas industrial or utility distribution boxes may handle medium voltages up to 35 kV. In summary, residential and commercial distribution boxes are limited to 690V AC, while medium-voltage distribution boxes for primary networks can handle up to 35 kV, depending on the voltage class and equipment specifications. Proper selection according to IEC standards ensures safety, reliability, and compliance.