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Electrical Safety Requirements
We all agree that the Electrical safety of human and installation both has paramount importance. But do you wonder what relationship Electrical Safety has with Type Tested Switchboards? Very interesting question. Traditionally majority of us in the industry don’t care about the guidelines laid down by relevant standards for both LV & MV Switchboards. The major argument is “सब चलता है” (everything works). We all know the importance of switchboards in our homes, commercial buildings and industrial establishments. Wherever there is electricity there will be a switchboard to distribute, manage and control electrical power.
The main function of a Switchboard is Power Distribution, Control and Protection of the systems, humans, machines and assets. There is no denying that a single major short circuit even after ten years of successful operation of the switchboard can create havoc. Suppose if it fails in its function, then what? It may result in a major fire and a big threat to life and assets. There are various aspects of safe & reliable operation of a switchboard but here we will restrict our discussion to Type Tested switchboards as the title of this article suggests.
Electrical Safety and Switchboard Design
Let us look at the table below and try to understand possible fault lines and their impact on safety if the Switchboard is not designed as per relevant “Standard guidelines”.
In the above table, we have taken only major type tests suggested by IEC-61439-2 for LV and IEC-62271-200 for MV Switchboards. If the switchboard is not designed in line with the guidelines, we may either end up in overdesign leading to higher costs or under design leading to poor performance and potentially unsafe switchboard. From the above table, we can easily make out how we are compromising safety and what kind of possible life-threatening accidents can occur. All the fault lines can convert into a major fire and safety gets severely compromised.
Type Tests basically verify the switchboard’s design and withstand against designated parameters of switchboards like Thermal Rating, Short Circuit Rating, Impulse Level, Internal Arc Classification etc. That means if rating parameters like Thermal rating or fault parameters like Short Circuit Rating, Impulse Level, and Internal Arc Classification are within the limits of designated parameters, the switchboard is Electrically safe.
Example
Let us understand this with an example. Suppose we have to manufacture, supply and install a switchboard with a short circuit rating of 50kA in an industrial complex. This means if there is an external or internal short circuit event of up to 50kA, the switchboard must withstand it safely without any harm to the switchboard itself, the operating personnel and the asset. If it is not verified by Type Test then the switchboard’s behaviour under short circuit conditions is unpredictable and may lead to fire because of excessive heat & electrodynamic forces due to short circuit.
The above example can be applied to other fault conditions in line with their impact as different fault conditions has different impact. But one adverse impact is common and any fault condition may lead to fire. Please refer above table.
Take another example of the Arc Flash fault. In that case, very high let-through energy is released at the point of arching because of sustained arching. This energy creates a very high temperature inside the switchboard enclosure. Due to high temperature, high air pressure is generated inside the enclosure. If enclosure strength is not designed and tested to sustain high pressure and stop leakage of hot gases outside the enclosure except by designated route can lead to a major fire. But if the switchboard is tested for Internal Arc condition, this possibility of major fire can be prevented.
Conclusion
So, we can conclude that verified assemblies ensure the safe and reliable operation of LV & MV switchboards and offer safety to men, machines and assets.
All guiding standards like IEC or the country’s own standards organizations are in place. These organizations have laid down guidelines in the form of “Standards” to design safe & reliable switchboards. The main issue is compliance with these standards. There must be regulation to completely ban the use of non-verified switchboard assemblies for use in any kind of application.
The main deterrent for getting the type test done is, the cost involved and the required engineering strength of the manufacturers to develop a prototype. We need to change our mindset and consider cost as an investment for safety. In extreme eventuality, there could be loss of life where any investment to prevent it, is less.
Slowly things are changing for the better but still, we need to go a long way in ensuring all the switchboards are type tested. All manufacturers and users must focus on the above aspects with sensitivity.
Designing switchboard is a very deep engineering activity. We need to take care of various service conditions. We also need to consider guidelines stipulated in IEC. Please go through the article and post your comment/queries in comment section.