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
Another important aspect is the electric field strength. It indicates how strong the electric field within the insulating material is and whether ionization or field emission of electrons occurs.
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
The actual values depend strongly on the test conditions, such as temperature, humidity and air pressure, as well as on material purity.
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, as no permanent polarity reversals occur
The differences in dielectric withstand strength are regulated by standards such as IEC 60243 or DIN VDE.
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 for improved electric field distribution
- Silicone-based insulators for high-voltage lines
- Glass-fiber-reinforced plastic (GRP) for transformer housings
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 (DC high-power charging) require special protective insulation
Future Trends
- New insulating materials with improved dielectric properties
- Nanotechnology to optimize electric field strength in high-voltage applications
- Self-healing insulation materials that automatically repair microcracks
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.