Engineering Dielectric Strength: What Makes a Material Perform Under Pressure?
In high-voltage environments, the performance of electrical components hinges on one invisible but critical attribute: dielectric strength. This property defines a material’s ability to resist electrical breakdown and maintain insulation under high voltages. But not all dielectric materials are created equal—and in the context of aging infrastructure, grid modernization, and extreme weather, selecting the right material is more important than ever.
At Piedmont Bushing & Insulators (PBI), we specialize in high-performance dielectric components built to withstand the mechanical, thermal, and electrical stresses of the most demanding applications. In this blog, we’ll explore what dielectric strength really means, how it’s measured, and why material selection is a pivotal engineering decision in today’s utility and OEM systems.
What Is Dielectric Strength?
Dielectric strength is defined as the maximum electric field a material can withstand without breaking down. It’s typically expressed in kilovolts per millimeter (kV/mm) or volts per mil (V/mil). Beyond this threshold, the material loses its insulating properties and becomes conductive—potentially leading to arcing, component failure, or equipment damage.
Dielectric strength is not just a theoretical number—it’s a real-world benchmark that guides decisions on:
Creepage and clearance distances
Material thicknesses
Component layout in compact designs
Voltage ratings for bushings, insulators, and arc chutes
How Dielectric Strength Is Tested
Dielectric strength is measured using standardized high-voltage testing, such as ASTM D149. During testing, voltage is gradually increased across a material sample until breakdown occurs. Key variables include:
Test temperature and humidity
Sample thickness
Electrode type and spacing
Voltage ramp rate
It’s important to note that thinner samples generally exhibit higher apparent dielectric strength—but aren’t necessarily better in real-world use. That’s why material performance must be considered in the context of total design requirements, including mechanical load, thermal exposure, and aging behavior.
What Affects Dielectric Strength?
Several factors influence a material’s ability to resist electrical breakdown:
1. Chemical Composition
Materials with high electrical resistivity and low ionic mobility tend to perform better. Ceramic composites, advanced polymers, and engineered resins often outperform natural materials.
2. Moisture Absorption
Even trace amounts of water can reduce dielectric performance. That’s why materials must maintain low water absorption—especially for outdoor or high-humidity environments.
3. Surface Condition
Smooth, clean surfaces are more resistant to tracking and surface arcing. Rough or contaminated surfaces lower dielectric integrity, particularly under high pollution or wet conditions.
4. Thermal Stability
High dielectric strength must be maintained across the operating temperature range. Materials prone to thermal degradation may lose insulating ability after extended use.
Real-World Applications Where Dielectric Strength Matters
Insulators
As electrical equipment becomes more compact, insulators are expected to withstand higher field strengths within tighter spaces. Materials like Polykeram support these evolving demands by enabling reduced clearances while maintaining reliable dielectric performance and safety margins.
Industry Trends Driving Better Material Choices
Utilities and OEMs are increasingly reevaluating materials in light of several market shifts:
Grid Modernization
As voltage levels rise and space becomes constrained, higher dielectric strength materials allow for compact, high-performance designs.
Resilience and Reliability Goals
With greater emphasis on outage prevention and asset durability, utilities are seeking components that perform reliably over longer lifecycles—especially under environmental extremes.
Supply Chain Disruption
OEMs can’t afford to wait months for imported parts made with outdated materials. Domestic sources like PBI offer faster delivery and advanced materials that meet or exceed legacy specs.
Sustainability and Lifecycle Cost
Materials like Polykeram reduce replacements by lasting longer, resisting environmental wear, and delivering consistent electrical performance year after year.
What to Look for in a Dielectric Material
When specifying dielectric components for critical systems, engineers should evaluate:
Dielectric strength (kV/mm)
Thermal aging behavior
Water absorption and tracking resistance
Mechanical performance under load
Compatibility with molding or custom shaping
The goal is not just to meet minimum specs—but to ensure the material performs consistently across the component’s expected lifecycle and service environment.
Dielectric strength is the foundation of every safe, high-voltage system. Whether you’re designing switchgear, refurbishing legacy breakers, or developing sensor assemblies, selecting the right material is a critical engineering decision. At PBI, our solutions deliver proven dielectric performance—engineered and manufactured entirely in the U.S.—to help utilities and OEMs build more resilient, efficient, and future-ready systems.
Let’s build components that hold up under pressure—for decades.