ZOTUP IN PILLS | HOW DOES A SURGE PROTECTOR BEHAVE DURING TEMPORARY SURGES (50 Hz)?

As of01/12/2021, the eighth edition of the CEI 64-8 standard comes into forcewhich specifies the need for to use a support fuse at the top of the arrester in order to protect systems and equipment from the so-calledTemporary Overvoltages(also calledTOV,from the English acronym of Temporary Overvoltage). But what are TOV and how should a surge arrester behave?

An SPD is created to protect systems from lightning strikes and network switching/operations, i.e. high frequency events (kHz - MHz) lasting microseconds. This which is often not taken into consideration are faults that occur at 50 Hz, i.e. TOV, overvoltages at industrial frequency and not of an impulsive nature, which tend to persist for relatively long periods of time.

When such system shortouts (TOVs) occur, which can range from a few seconds to even minutes,the SPD can react in two ways:

• In Mode Held (Withstand Mode - W), in which it is capable of resisting system failures without damaging itselfand this represents the optimal condition;
• In Mode o Safe Failure Mode - S in which the SPD fails but in a safe way (without catching fire and maintaining its IP rating). This constitutes minimum acceptable conditionwhich, however, involves the loss of protection.

Furthermore, a standard surge protector normally requires a backup fuse to safeguard the SPD in the event that the latter dies in a short circuit, an extremely dangerous condition because it could lead to the device itself exploding. Using the fuse, however, is not only not always possible but other timesit can even prove counterproductive.

The surge arresters by ZOTUP thanks to the Integrated Fuse Function (ff), do not need additional external fuses and  they guarantee the death of the SPD in open circuit.In addition, when it comes to temporary overvoltages, they have the ability  keep the TOVs in Mode Sealing (W),completely regardless of the presence or absence of the fuse.

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