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Electricity is like a kitchen knife. If you use it wisely, it can cut food and prepare delicacies. If you use it unwisely, it can end up cutting your finger. Electricity flows through anything that is a “conductor.” Interestingly, humans are very good conductors of electricity!
What Is Insulation Resistance?
Insulation resistance is the resistance offered by a cable’s insulation against unwanted current leakage. It shows how effectively the insulation prevents electricity from escaping the conductor.
It is usually measured in megaohms (MΩ) using an insulation resistance tester or Megger. Higher insulation resistance indicates better cable safety and performance.
Why are Cables Insulated?
Since electricity is a form of energy, a strong current has the ability to seriously harm you. If the current is strong enough, you can be fatally injured. Due to the strong possibility of a fatal injury occurring, electric cables are insulated. Another important reason why they are insulated is to prevent energy from dissipating into the surroundings, allowing it to be conserved.
Why Insulation Resistance Matters
Insulation resistance is important because it helps prevent:
- Electrical leakage
- Short circuits
- Equipment damage
- Electric shock hazards
- Power loss
Low insulation resistance may indicate moisture, aging, contamination, or damaged cable insulation.
How are Cables Insulated?
Cables and wires are insulated using electrical insulators. The electrical insulators are non-conducting materials that encircle the cables and provide a buffer between the cable and anyone or anything that may come in contact with it. Wood is a very good insulator. Rubber and plastic are the most common types of insulators that you would find on cables today. These are usually referred to as Polyvinyl Chloride, or PVC, insulators.
How Insulation Resistance Is Measured
Insulation resistance is measured using a Megger or insulation resistance tester.
The device applies DC voltage to the cable and measures leakage current through the insulation. The result is displayed in megaohms (MΩ).
Basic Testing Steps:
- Disconnect the cable from power.
- Connect the Megger to the conductor and ground.
- Apply the test voltage.
- Read the insulation resistance value.
Higher readings generally indicate healthier cable insulation.
Features of Cable Insulators
The features of materials that are used as insulators is as follows:
- High levels of insulation with resistance
- Resistance to physical damage varying from cuts to abrasions
- Efficient mechanical as well as electrical properties
- Resistance to liquids such as oil as well as chemical solvents
- Resistance to weather elements such as rain, strong winds, and dust
- Resistance to naturally occurring ozone in the atmosphere
Coaxial Cables
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Coaxial cables are multi-layered cables designed for better insulation and protection. They contain several insulated layers that help prevent electrical interference and improve grounding, making them useful for high-power electrical applications.
- Inner Core – The inner core is usually made of copper and carries the electrical current through the cable. Copper is commonly used because it allows electricity to flow easily with low resistance.
- Middle Layers – These layers provide insulation and help reduce electrical interference. They are commonly made with aluminum foil and copper strands for added protection.
- Outer Layer – The outer PVC layer protects the cable from electricity leakage, moisture, sunlight, heat, and physical damage.
Compared to standard single-core cables, coaxial cables provide better insulation and grounding. Their layered design helps contain electrical and magnetic fields, improving safety and reducing interference. Without proper insulation, electrical devices and cables would not operate safely.
