What is Surge Protection?

A surge protection is an appliance designed to protect electrical devices from voltage spikes. It is also known as Surge arrester. 

Why do we need to protect the surge with fuses?

The 3 phases lines and the neutral are wired directly to the load which is your UPS, while the surge protection is wired, as seen, parallel with respect to the load, towards the earth. That is, the 3 phase current passes directly to the load, not through the surge protection. Hence, the surge arrester or protector is then an open circuit from the earth …

If an electric surge (from lightning or from industrial switching) is passing to the load, on either one or on all the 3 phases lines and/or the neutral, the surge protection will react very quickly (less than 5 nanoseconds, a figure to compare with other surge protections, as seen in the data sheet “Novaris SDD3”) and will connect the relative line(s) and/or the neutral to the earth. By that, it will become normally closed to earth, thus discharging the electric surge to earth.

If the surge is less than 100 kAmps, the surge arrester will go back to its normal position of open circuit within 2 seconds. By that, if you had used the surge arrester for protecting your home, the lights will switch off however will be back within 2 seconds… confirming the surge arrester has performed correctly. The process occurs by cutting the inlet power for 2 seconds, grounding the lines and/or neutral to earth and getting back to normal …

In figure 2, the circuit breaker will isolate the load and the destroyed surge protection, thus blocking a second electric surge to pass by and destroy your UPS.

At some situations where the load ought to remain alive but the surge could not be replaced immediately … say at the TV/radio relay stations at the top of the mountains where there are no technicians at night. From statistics, they know that up to say 5 electric surges might pass by in one night … maybe 7 sets of surge protectors with relative fuses are installed in parallel. If one set is destroyed, the load will remain powered and still protected through 6 other sets of surge protectors with relative fuses.

Based on the situation of your project, you ought to decide to use fuses in parallel to isolate your UPS in case the surge protection is destroyed … or install the surge arrester behind a 3 x 50 Amps circuit breaker in series with your UPS. 

Figures 1 and 2            novaris

A Surge Protection is like a neon lamp

It will protect electric surges of 10 kAmps for up to 10 times and then get destroyed with the 11th electric surge. When as well, it will get destroyed with a single electric surge of above 100 kAmps. 

What happens when a Surge Protection gets destroyed?

When the surge protection is destroyed, it is in a closed circuit to earth which is when the fuses installed in series with the surge protection are required, then the normal electricity of the premises will flow through the surge protection to earth. Hence, the surge protection will heat up soon and start burning from the normal electricity flowing through it to earth and set fire to the surrounding. Unless the fuses blow out to isolate the surge protection from the normal electricity lines … thus preventing the surge protection to burn and set fire around it!

But then if a second lower intensity electric surge arrives, it will destroy the load, that is your UPS and that is because the fuses had already blown out as the surge protection was destroyed from the earlier higher intensity electric surge!!!

In Conclusion

Evidently, the alarm output will trigger as soon as the surge protection is destroyed to alert the personnel of the premises. So, it is better to have an independent power source rather than the mains 220 vac. And it is also suggested to combine it to a fire alarm panel.
DHAS team also installs fire alarms as Solution Partners Of Siemens since above 3 decades.