In challenging environments, silicone cables can be highly heat resistant and bendable, but their performance capability in terms of electrical properties determines their value in the application. Silicone cables’ electrical performance under high temperatures, in control systems, and in high voltage applications are important to understand, as they can lead to serious issues that engineers can easily avoid.
The guide presents practical examples of how to apply these properties for realism in selection and design.
Basic Electrical Concepts – Insulation Resistance, Dielectric Strength and Leakage
By understanding the basics, engineers can assess the suitability of silicone cables for their projects.
What Is Insulation Resistance and Why It Matters
Insulation resistance measures the resistance that the insulating material of the cable offers to the flow of current between conductors or from conductor to ground. It is usually specified in megaohms or in terms of volume resistivity (Ω·m). Higher values result in lower leakage currents, lower energy dissipation and reduced risk in humid and aging installations.
For example, in the field of industrial automation and robotics, where long cable lengths and fragile signal paths are frequently found, high insulation resistance ensures reliable operation.
What Is Dielectric Strength and How It’s Tested
It is the capacity of an insulating material to withstand an electric field before it breaks down, typically expressed in kV/mm, and is tested by the manufacturer by applying increasing voltage to the insulation material until it breaks down, such as ASTM D149 or IEC 60243.
This property is a direct impact on the selection of safe operating voltages and insulation thickness, enabling compact and powerful cable designs.
Leakage Current – Small But Important in Sensitive Circuits
Leakage current is defined as the small current that flows through or across the insulation, when it is unintended. It is caused by incomplete resistance or contamination on surfaces or by moisture. Measuring systems or precision electronics may present noise or safety problems with small amounts of leakage, such as micro-amperes. The high resistivity and surface properties of silicone help to maintain low currents.
Electrical Properties of Silicone Cable Insulation – Indicative Values and Behavior
Quality silicone rubber insulation provides consistent performance in the face of challenging conditions.
Rated Voltage and Typical Application Ranges
The standard flexible silicone cable can carry a rated voltage of 300-600V, with special designs that can withstand higher voltages in the kV range for power distribution and accessories. Actual ratings will vary with insulation thickness, stranding and applicable standards.
Insulation Resistance Ranges for Silicone Cables
The volume resistance of premium silicone cable insulation is usually between 10¹²Ω·m and 10¹⁴Ω·m. This prevents the insulation resistance from dropping to the unacceptable level after long service, and keeps leakage at a low level in various service environments.
Dielectric Strength and Dielectric Constant of Silicone Rubber
The typical dielectric strength of silicone rubber is 20–35 kV/mm, which is dependent on formulation and thickness. The material has a typical dielectric constant in the range of 2.5–3.0, which ensures stable capacitive properties.
How Temperature, Humidity and Aging Affect Silicone Cable Electrical Performance
The impact of temperature, humidity and aging on the electrical performance of silicone cable.
Stability Across Wide Temperature Ranges
From -60°C up to 180-200°C continuously (peaks higher) silicone insulation retains good electrical properties compared to many polymers which deteriorate rapidly. Silicone offers resistance to insulation and dielectric strength that change relatively little with increasing temperature and is very useful in heater, ovens and motor leads.
Moisture, Surface Contamination and Hydrophobicity
The silicone rubber itself is hydrophobic, which means it repels water and prevents it from spreading, maintaining the surface’s resistance and minimizing leakage even in wet or dirty environments. This property is particularly useful for installations outdoors or those that can be washed down.
Aging, Thermal Stress and Electrical Property Drift
The chemicals and heat over time will cause changes to happen but good silicone will hold up better to electrical properties than many. It’s crucial to regularly monitor critical circuits.
Leakage Considerations in High-Voltage and Sensitive Applications
As the voltage increases or the environment becomes increasingly harsh, leakage control becomes increasingly important.
Leakage Current Paths and Their Risks
Leakage may be through bulk material, along surfaces or at interfaces. When they are present in abundance, they can cause energy loss, distortion of signals or the risk of flashover. These paths are very well reduced, silicone being hydrophobic and having high bulk resistivity
Silicone Rubber in High-Voltage Insulators and Accessories
Silicone’s high voltage tracking resistance and hydrophobicity are highly applicable to flexible silicone cables when used in similar conditions within an outdoor environment.
Comparing Silicone Cable Electrical Performance with Other Insulation Materials
To find the best material, it is helpful to have a context.
Silicone vs PVC and XLPE for Electrical Insulation
PVC has good low voltage characteristics but poor high voltage characteristics. XLPE also offers excellent dielectric properties for power cables but not the same level as silicone for flexibility and repeated motion resistance.
Silicone vs PTFE for High-Frequency or Extreme High-Voltage
In some cases, especially for RF use, the highest dielectric strength and low-loss properties are achieved with PTFE, while in many moderate-high voltage, high-temperature situations, the mechanical flexibility properties of silicone are very similar.
Practical Design and Selection Guidelines – Using Silicone Cable Electrical Properties Wisely
Implement what you’ve learned in your projects.
Matching Rated Voltage, Insulation Thickness and Application Needs
Always check manufacturer information for the voltage, temperature, and mechanical specifications. Optimum thickness means it provides a compromise between dielectric strength and flexibility.
Considering Leakage and Insulation Resistance in System Design
State minimum insulation resistance for the most extreme temperature and humidity conditions. Take into account the creepage distances in contaminated environments.
When Silicone Cable Is the Right Electrical Choice
Use silicone cables for high temp industrial wiring, flexible robotics connections, high voltage outdoor wiring or when thermal performance and reliable insulation comes into play. Notable for ultra-high Frequency or extreme voltage requirements, consider fluoropolymers in addition to silicone.
We at Hulk Electric design cables for high temperature use that deliver the electrical performance you need in the most demanding applications. Our UL recognized and certified solutions provide engineers with the insulation resistance, dielectric strength and reliability that they are looking for in various industry applications.