When your plant’s electrical system and equipment are brand new, the electrical insulation is typically in excellent condition. Manufacturers of wires, cables, motors, and other electrical components have consistently improved their insulation materials for industrial use. However, despite these advancements, insulation remains susceptible to various factors that can lead to its deterioration. These factors include mechanical damage, vibrations, extreme temperatures (both hot and cold), exposure to dirt, oil, corrosive substances, moisture from industrial processes, and even high humidity on particularly muggy days.
Over time, these threats to insulation quality combine with the inherent electrical stresses that exist within electrical systems. As insulation develops pinholes or cracks, moisture and foreign substances can penetrate its surface, creating low-resistance paths for leakage current. Once this process begins, these various factors tend to exacerbate one another, allowing excessive current to flow through the insulation.
In some cases, the drop in insulation resistance occurs suddenly, such as when equipment is exposed to flooding. However, more often than not, insulation degradation is a gradual process, providing warning signs when monitored periodically. Regular checks enable planned maintenance and reconditioning before insulation failure occurs. Without these checks, a motor with deteriorated insulation, for instance, can become not only dangerous to touch when voltage is applied but also at risk of burning out. What was initially good insulation has transformed into a partial conductor.
In summary, insulation deterioration results from a combination of mechanical, environmental, and electrical factors. Regular inspections and maintenance are crucial for identifying and addressing these issues before they compromise the safety and reliability of electrical systems.
Related Articles:
What is Good insulation?
What Makes Insulation Go Bad?
How Insulation Resistance is Measured.
How to Interpret Resistance Readings.
Factors Affecting Insulation Resistance Readings.
Types of Insulation Resistance Tests.
Test Voltage vs. Equipment Rating.
AC Testing vs. DC.
Use of DC Dielectric Test Set.
Tests During Drying out of Equipment.
Effect of Temperature on insulation Resistance.
Effects of humidity.
Preparation of Apparatus to test.
Safety Precautions.
Connections for testing insulation resistance of electrical equipment.
Additional Notes About using A Megger Insulation Tester.
Interpretation-Minimum Values.
Minimum Values for Insulation Resistance.
Tests Using Multi-Voltage Megger Insulation Testers.
Step-Voltage Method.
Use of a Guard Terminal.
Outdoor Oil Circuit Breaker.