What Is Dielectric Withstand Strength and How Is It Defined?
Dielectric withstand strength describes the ability of a material or electrical component to withstand a specific electrical voltage without voltage breakdown or electrical conductivity occurring within the insulating material. Measurement typically takes place in volts per millimeter (V/mm) or kilovolts per millimeter (kV/mm). It is essential for the quality of electrical insulators, cable insulation and high-voltage components.
Difference between Dielectric Withstand Strength and Dielectric Strength
- Dielectric withstand strength: Maximum voltage a material can permanently withstand without electrical breakdown
- Dielectric strength: Voltage at which the insulating material completely fails and becomes conductive
GOBA supplies insulation materials and voltage-resistant polyester films tested to defined voltage resistance values.
Experimental Determination of Dielectric Withstand Strength
Measurement Methods
- DC voltage test: Constant DC voltage is applied
- AC voltage test: High-frequency AC voltage
- Impulse voltage test: Short, high-energy impulses
Typical Experimental Values
- Air: approx. 3 kV/mm
- Ceramics: approx. 10 to 20 kV/mm
- Polyimide: approx. 300 kV/mm
- Insulating oil: approx. 15 kV/mm
Role of Dielectric Withstand Strength in Electrical Components
Dielectric withstand strength is central to the safety and reliability of electrical systems:
- Capacitors require high dielectric withstand strength for efficient charge storage
- Transformers require materials with high dielectric withstand strength to avoid insulation losses and arcing
Safety factors are necessary to avoid overload and to ensure long-term safe operation.
Differences between DC and AC Voltage
- AC voltage: Often lower dielectric withstand strength due to cyclic stress
- DC voltage: Materials generally withstand higher voltages
Standards and Norms
- IEC 60243: Specifies how the dielectric strength of insulating materials is measured
- Rated voltage: Indicates the voltage at which a device can be operated safely and continuously
Improving Dielectric Withstand Strength
Techniques to Increase Dielectric Strength
- Innovative insulating materials with high dielectric strength (polyimide, ceramics)
- Multilayer insulation materials for better field distribution
- Special protective coatings to reduce water absorption
Innovative Materials
- Nanocomposites
- Silicone-based insulators
- Glass-fiber-reinforced plastic (GRP)
Challenges in Modern Applications
High-voltage Engineering
- Film capacitors with extremely resistant dielectrics
- High-voltage direct current (HVDC) transmission with voltages of 800 kV and above
Electromobility
- Battery insulation materials must exhibit high dielectric withstand strength
- Fast-charging stations require special protective insulation
Future Trends
- New insulating materials with improved dielectric properties
- Nanotechnology to optimize electric field strength
- Self-healing insulation materials
GOBA Takeaway
Dielectric withstand strength is one of the most important properties of electrical insulating materials and electrical components. It determines up to which voltage a material operates reliably without breakdown or flashover. Ongoing research on innovative materials and new measurement methods is improving dielectric withstand strength for future high-voltage applications.