Need help about Surge Protective Device

Subpra · Apr 28, 2024

Recently I have installed Type 2 Surge Protective Device SPD 20 to 40kA, Type1+2, Phase + Neutral + Earth (2 Pole 275 Volt AC) (Uc-275VAC, In-20KA, Imax-40KA, Up ≤ 1.5 KV) after 64A DP MCB at home MDB. The home lode is around 1.75KW. We have 220 VAC main line here.

At the evening of 3rd day after installation, the SPD was exploded. I find that the cartridge of Phase side was damaged and it was totally short with earthing terminal. But cartridge of neutral side was in good condition. There was no sign of lightning nearby. No neighbour was affected with Spikes and surges at that time. I am confused about the reason how the SPD got damaged!

Now I am going to replace the SPD with “Type 2 Surge Protective Device SPD (Phase side: Uc-320VAC, In-20KA, Imax-40KA, Up ≤ 1.5 KV Neutral Side: Uc-255VAC, In-20KA, Imax-40KA, Up ≤ 1.5 KV). Will it be good?

Thanks.

pc1966 · Apr 28, 2024

A starting point is what make/model of SPD did you fit? A photo might help here.

Normally SPD have internal thermal fuses to deal with overheating, and for worst-case protection they depend on either the incoming supply's over-current protection, or for smaller SPD they depend on a MCB just for the SPD.

SPD are designed to deal with very short-term surges, so tens of microseconds from induced lightning current or the switching of large motors, etc. Where they are at serious risk of overheating is when you have a long-duration over-voltage situation, for example, a power cross situation (when a HV cable falls and strikes a LV cable) or an open neutral in an unbalanced 3-phase system, etc.

However, any reputable SPD should fail safe in such conditions with the internal thermal fuse (basically solder joint) opening to disconnect before it reaches a dangerous temperature.

What will case even a good SPD to fail catastrophically is a short surge beyond its energy handling limits, but that is unusual outside of a direct lightning strike the the building, or to a strike to an overhead power line within a km or so of the SPD. You are down as from India, that has more thunderstorm days than the UK where I am by an order of magnitude but I guess it varies dramatically over your country.

pc1966 · Apr 28, 2024

This document (about 18MB PDF download) has a lot of useful guidance on lightning protection:

https://www.nvent.com/sites/default/files/acquiadam/assets/E907W-WWEN.pdf

pc1966 · Apr 28, 2024

These are not the cheapest of brands, but they have a good reputation and appear to have an office in India:

https://www.dehn.in/store/f/41912671/Artikelnummer_PDF/941110.pdf

pc1966 · Apr 28, 2024

This might also be worth considering:

Mersen, STPT2-40 Surge Protection Device 275 V ac Maximum Voltage Rating 40kA Maximum Surge Current Type 2 Mersen SPD | Mersen | RS Components India

83020116 / STPT2-40K275V-2PG Mersen | Mersen, STPT2-40 Surge Protection Device 275 V ac Maximum Voltage Rating 40kA Maximum Surge Current Type 2 Mersen SPD | 179-3059 | RS Components

in.rsdelivers.com

Subpra · Apr 28, 2024

pc1966 said:
A starting point is what make/model of SPD did you fit? A photo might help here.

Normally SPD have internal thermal fuses to deal with overheating, and for worst-case protection they depend on either the incoming supply's over-current protection, or for smaller SPD they depend on a MCB just for the SPD.

SPD are designed to deal with very short-term surges, so tens of microseconds from induced lightning current or the switching of large motors, etc. Where they are at serious risk of overheating is when you have a long-duration over-voltage situation, for example, a power cross situation (when a HV cable falls and strikes a LV cable) or an open neutral in an unbalanced 3-phase system, etc.

However, any reputable SPD should fail safe in such conditions with the internal thermal fuse (basically solder joint) opening to disconnect before it reaches a dangerous temperature.

What will case even a good SPD to fail catastrophically is a short surge beyond its energy handling limits, but that is unusual outside of a direct lightning strike the the building, or to a strike to an overhead power line within a km or so of the SPD. You are down as from India, that has more thunderstorm days than the UK where I am by an order of magnitude but I guess it varies dramatically over your country.

Subpra · Apr 29, 2024

pc1966 said:
This might also be worth considering:

Mersen, STPT2-40 Surge Protection Device 275 V ac Maximum Voltage Rating 40kA Maximum Surge Current Type 2 Mersen SPD | Mersen | RS Components India

83020116 / STPT2-40K275V-2PG Mersen | Mersen, STPT2-40 Surge Protection Device 275 V ac Maximum Voltage Rating 40kA Maximum Surge Current Type 2 Mersen SPD | 179-3059 | RS Components

in.rsdelivers.com

What is your opinion about this

Type 2 AC Surge Protection Device

www.havells.com

pc1966 · Apr 30, 2024

Subpra said:
What is your opinion about this

Type 2 AC Surge Protection Device

Type 2 AC Surge Protection Device

www.havells.com

It is not a brand that I know, but on the appearance it would look like a good enough choice for most situations where you do not expect a direct strike.

Type 2 SPD are for induced surges, i.e. nearby strike, whereas Type 1 or Type 1+2 are able to cope with higher energy surges from a hit to the building's lightning protection system, or to an overhead cable some distance away.