IEC 61439: Ensure Insulating Material Properties To Protect Electrical Panels

Author: Pascal Lepretre Schneider Electric Blog

My first post in this series covered why IEC 61439 was introduced, the second detailed why it’s important to respect the rated current for devices and the third discussed reasons to satisfy clearances and creepage distances. The net result of following the standard and implementing its rules is that electrical panels and switchboards work as they should now and will continue to do so in the future.

By adhering to the standard, you ensure electrical panel safety and reliability, and you don’t end up with fireworks due to an arc flash caused by an electrical fault. Specifying higher quality electrical panels will prevent that and stop many other problems. After all, electrical issues are responsible for more than half of all industrial disasters in India.

A higher quality electrical panel design and components also prevents a loss of service and associated downtime costs, saving end users money. For specifiers, this means the product is more reliable and business, therefore, is better.

Here, I will go over another path to improve reliability and ality: ensuring proper insulation. Having the correct insulation means that even in extreme situations such as abnormal heat and fire, the material acts as a resistor, an important factor to prevent damaging arc flash.

How are the insulating material properties ensured to be correct?

In section 10.2.3 and 10.2.4 of IEC 61439-1 tests are specified for:

• Thermal stability (to insulating enclosure)
• Resistance to normal heat
• Resistance to abnormal heat and fire
• Resistance to ultraviolet (UV) radiation (in an outside application)

These tests verify that the material still acts as an acceptable insulator even when stressed by environmental conditions. In turn, that robustness means that the enclosure, panel and entire system will as designed for years to come.

Regarding resistance to normal heat, IEC 61439 10.2.3.2 states that the original manufacturer will verify that the insulating materials do not change mechanical performance at temperatures of 125^o C for current-carrying parts and 70^o C for everything else. Following these guidelines guarantees performance during the life of the panel. Because of the temperature requirements, plastic insulation cannot be part of a compliant electrical panel. Normally, plastic insulation may appear less expensive, but it is not once the heat and fire resistance performance are considered.

As for abnormal heat and fire, IEC 61439 10.2.3.3 says the manufacturer will verify insulator properties when subjected to temperatures of 960^o C for live, current carrying parts and 650^o C for all other parts. (See below for an example illustration of how such a test is done.)

These flammability resistance and heat tolerance properties ensure protection during normal operation and when problems arise due to internal electrical .

Finally, some panels and enclosures sit outside, exposed to the Sun’s UV rays. The intensity of this light can range from low to extreme. The highest UV levels can burn skin and eyes in minutes. IEC 61439 calls for a total test period of 500 hours. Verification of performance, in the case of insulating enclosures, involves checking structural strength and resistance to impact. By passing these tests, the performance of the insulating material is such allows enclosures to be exposed to the Sun for an extended period.

These tests for UV resistance, normal heat and abnormal heat ensure the quality of the insulating material. As a result, they assure panel specifiers that the quality of the final system will not be compromised over time by the weather and environmental conditions. So, the quality of the panel and enclosure stays at a level comparable to that when the system was new.

Schneider Electric has a complete range of main and distribution busbars, prefabricated connections and distribution blocks, and design rules in its catalog.