In the manufacturing fields of power equipment—such as high and low voltage switchgear, busways (busducts), circuit breakers, and dry-type transformers—the selection of insulation sheets directly determines the safety level, service life, and comprehensive production costs of the equipment.
The GPO-3 insulation sheet (also known as UPGM203 polyester glass mat laminate) has become the preferred material for core insulation components in medium and high voltage power distribution equipment. This popularity is thanks to its industry-leading arc resistance, high Comparative Tracking Index (CTI), and halogen-free UL94 V-0 flame-retardant properties.
This comprehensive GPO-3 material selection guide breaks down the core performance indicators and industry scenario matching to help engineers make the right choice.
1. What is GPO-3? Basic Structure and Core Technical Indicators
A GPO-3 insulation sheet is made of alkali-free continuous fiberglass mat impregnated with unsaturated polyester resin, combined with halogen-free flame-retardant fillers, and molded under high-temperature compression.
Unlike traditional epoxy sheets or G10 sheets pressed from woven fiberglass cloth, the disordered distribution of the fiberglass mat endows GPO-3 with excellent isotropic properties. This ensures uniform mechanical strength and insulation performance in both horizontal and vertical directions without significant drops, making it perfectly suited for irregular cutting and multi-directional force-bearing structural components.
When evaluating a GPO-3 insulation sheet for engineering selection, you must prioritize the verification of four rigid safety indicators:
- Arc Resistance (≥ 180s): Tested under the ASTM D495 standard, its arc resistance far exceeds that of standard epoxy sheets. When a short-circuit arc occurs, it does not carbonize to form conductive paths, providing core protection for arc-extinguishing barriers and phase barriers.
- Comparative Tracking Index (CTI ≥ 600V): GPO-3 does not easily prone to surface tracking under highly polluted and humid working conditions. This allows it to adapt perfectly to outdoor distribution cabinets as well as harsh environments in metallurgy and chemical industries.
- Flame Retardancy Rating (UL94 V-0): It self-extinguishes within 10 seconds after an open flame is removed. With low smoke and non-toxic properties, it strictly meets the fire safety regulations of rail transit and public power distribution.
- Heat Resistance Grade F (155°C): It maintains stable performance under long-term working environments with a heat deflection temperature exceeding 200°C. It will not soften or deform under continuous heating conditions of high-load busbars.
Engineering Note: In terms of basic mechanical properties, GPO-3 possesses moderate flexural and impact strength, highlighting an outstanding cost-performance ratio. This makes it ideal for large-sized structural parts such as large-area insulation barriers and long busbar lining plates.
2. GPO-3 Material Selection for Different Industrial Scenarios
Medium and High Voltage Switchgear & Ring Main Units (RMU) (600V - 35kV)
Arc-extinguishing chamber barriers, interphase insulation barriers, arc-shielding walls, and circuit breaker safety shutters inside switchgears are the most mainstream applications of the GPO-3 insulation sheet. The opening and closing operations of this equipment generate instantaneous arcs.
Traditional epoxy-type sheets lack sufficient arc resistance, and surface carbonization after multiple switching operations can easily cause interphase short circuits. The ultra-high arc resistance of GPO-3 can withstand arc erosion for the long term, meeting strict IEC high-voltage equipment insulation standards.
Busways and Copper Busbar Insulation Supporting Components
GPO-3 is the preferred material for lining plates inside compact busways, copper busbar insulation blocks, and support columns. Busbars generate significant heat during long-term electrification, and their surfaces easily accumulate dust.
The high CTI value (≥ 600V) effectively prevents tracking and electrical leakage. Additionally, large-specification whole sheets can be cut directly without the need for multi-layer bonding, reducing processing steps and lowering mass production costs.
Molded Case Circuit Breakers (MCCB) / Air Circuit Breakers (ACB)
For internal gaskets, insulation bases, and breaking phase barriers of circuit breakers, the working conditions are accompanied by frequent arc impacts. The halogen-free flame-retardant formula complies with global environmental certifications for electrical equipment, perfectly fitting the manufacturing requirements of export-oriented circuit breakers.
Dry-type Transformers & Heavy-duty Motors
For transformer winding isolation plates, motor slot wedges, and carbon brush insulation seats, electrical attenuation remains slow even under humid and high-temperature working conditions. Compared to phenolic paperboards, the insulation stability is significantly enhanced.
3. GPO-3 Specification and Color Selection
Thickness and Dimension Selection
Conventional standard sheet sizes for GPO-3 are 1010×2020mm and 1250×2500mm, with a full thickness coverage from 0.8mm to 60mm:
- 0.8mm - 3mm (Thin models): Used for isolation phases in small circuit breakers.
- 5mm - 20mm (Mainstream thicknesses): Fits switchgear barriers and interphase walls perfectly.
- Above 20mm (Thick plates): Heavy-duty usage for busbar support blocks and high-voltage insulation bases.
Color and Formula Selection
- Red GPO-3: The mainstream red sheet on the market is the universal standard model, balancing premium flame-retardant and arc-resistance performance.
- White GPO-3: Mostly used in indoor distribution cabinets or medical-grade power setups that require high visual cleanliness.
4. Summary: Core Logic of GPO-3 Procurement
The irreplaceable nature of the GPO-3 insulation sheet is concentrated in four major advantages: arc protection, anti-tracking, halogen-free safety, and batch cost-efficiency. As long as the equipment operation involves breaking arcs, dust, humidity, or high-voltage interphase isolation requirements, it is the optimal insulation sheet material.
The core selection process is:
- Confirm the voltage level and arc conditions of your equipment.
- 2. Determine the exact thickness specifications of the sheet.
- 3. Verify a full set of electrical certifications (UL, SGS, CTI) during procurement.
By following this process, you can completely avoid equipment insulation failure, certification rejection, and cost waste from the source.
Partner with RDS for Your Custom GPO-3 Solutions
Choosing the right insulation material requires balancing strict technical compliance with manufacturing cost-efficiency. At RDS, we don't just supply raw materials—we provide engineering peace of mind.
Whether you need standard red or high-cleanliness white GPO-3 sheets, or precision CNC machined components customized to your exact blueprints, our technical team is ready to support your project. All our materials meet rigid international safety regulations and electrical certifications.
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