GPO-3 Insulation sheet in Circuit Breakers: Functions & Advantages

Applications of GPO-3 Insulation Board in Circuit Breakers GPO-3 (UPGM203) is a fiberglass-reinforced unsaturated po...

Applications of GPO-3 Insulation Board in Circuit Breakers

GPO-3 (UPGM203) is a fiberglass-reinforced unsaturated polyester thermoset insulation material known for its excellent mechanical strength, arc resistance, and thermal performance. In medium- and high-voltage switchgear—especially circuit breakers—GPO-3 has become one of the core materials for insulation and structural support.

GPO-3(UPGM203) Glass Polyester Laminated sheet

1. Main Functions in Circuit Breakers

(1) Primary Insulation Barriers

Inside a circuit breaker, multiple conductive components exist, such as contacts, moving/stationary contacts, and operating mechanisms. GPO-3 insulation boards are commonly used as primary insulating barriers to:

Separate conductive components

Provide creepage distance and electrical clearance

Prevent phase-to-phase or phase-to-ground faults

Its high dielectric strength (typically >10 kV/mm) meets the requirements of circuit breakers rated from 12 kV to 40.5 kV and beyond.

(2) Structural Support & Mounting Components

With high rigidity and good machinability, GPO-3 boards can be CNC-processed into complex shapes for use as:

Mechanical support parts

Mounting plates

Frames for contacts, coils, and mechanisms

The lightweight nature of the material helps optimize strength and reduce overall equipment weight.

(3) Arc Barriers & Auxiliary Components of Arc-Quenching Systems

During breaking operations, circuit breakers generate high-temperature arcs. GPO-3’s strong arc resistance (>120 s) allows it to be used for:

Arc barriers

Internal arc protection plates

Insulating parts within arc-quenching assemblies

Its UL94 V-0 fire resistance significantly reduces internal fire risks.

2. Advantages of Choosing GPO-3

3. Typical Circuit Breakers Using GPO-3

GPO-3 insulation boards are widely used in various circuit breaker types, including:

Vacuum Circuit Breakers (VCB)
Used as phase barriers, vacuum interrupter supports, and insulation for moving rods.

Air Circuit Breakers (ACB)
Applies to contact system barriers and arc-chamber partitions.

Molded Case Circuit Breakers (MCCB)
Used for internal insulation and reinforcement components.

Gas-Insulated Circuit Breakers (GIS/CB)
Serves as auxiliary insulation and internal partitions.

4. Summary

Thanks to their excellent electrical insulation, high flame retardancy, strong mechanical strength, and outstanding machinability, GPO-3 insulation boards have become indispensable materials inside circuit breakers. Whether in high-voltage vacuum circuit breakers or medium-/low-voltage molded case breakers, GPO-3 ensures safe operation and enhances overall equipment reliability.