SPD efficiency state is now simplified. A progressive indicator from green, to orange and then red, allows you to check in a simple and immediate way the level of protection that the SPD is still able to offer to the system. The assurance of being able to control progressively the level of efficiency of the SPD and then to program its replacement, is our first point of strength.
More than these features, the line of surge arresters ZOTUP presents many components: integrated fuse function in case of failure of the SPD and the possibility to use the SPD in environments with a high pollution rate (grade 3). Don't miss our next videos.


Discharge capacity is an important parameter in choosing SPD. There are also other important parameters such as:

• Maximum Continuous Operating Voltage;
• Immunity to temporary overvoltage TOV;
• Test class (test values with current and impulsive voltage);
• Short circuit withstand capability;
• Stand alone extinction capacity of the network following current at Uc;
NFC No follow current®;
• Protection level;
• Reaction time;
• Coordination;
• Attenuation noise level.

Maximum Continuous Operating Voltage Uc:

The maximum continuous operating voltage is the maximum value of voltage that can be continuously applied to the terminals of the SPD; it is determined with reference to:
• the rated voltage of the protected circuit;
• low voltage energy distribution system (TN, TT, IT);
• type of installation (phase >earth; phase >neutral; neutral >earth);
• overvoltage withstand of the SPD to TOV.

Total immunity to TOV (Temporary Over Voltage) is guaranteed by following Uc values:

 features 1

Autonomous extinction of the network following current at Uc:

It is the ability of the SPD to autonomously extinguish the subsequent network current at the point of installation. According to the regulations IEC 60346-5-534, that capacity must be higher than the maximum value of current expected at the installation point. In SPDs using spark gap technology, occasionally the
limitation of the follow on current is not adequate or coordinated with the other protections and may cause a service lack.

NFC No Follow Current®:

Thanks to their design characteristics, SPDs of the NFC No Follow Current® variety, are able to impede the circulation of follow up currents and avoid the untimely intervention of the over-current limitation device and subsequent service lack.

Protection levels Up:

This is defined as the maximum instantaneous level at the terminals of the SPD during its operating phase.
Depending on the type of technology used in the SPD the protection level corresponds to:

• In Limitation SPDs: the residual voltage with a nominal impulse discharge current ≤ nominal discharge current.
• In Triggered SPDs: the higher value between the trigger impulse voltage 1,2/50 μs and the residual voltage at the input to the equipment during the discharge.

The level of protection provided by the SPD must be set against the impulse voltage rating of the equipment at various places within the system.

Reaction time Ta:

The standard IEC 61643-11 ed. 1 (2011-03) neglects the reaction time. However, the semi-conductors used in the control systems of electrical equipment could be damaged in very short time, this means that reaction time is very important. The phenomena of overvoltage in the installations has duration of some μs, the reaction time of SPDs has duration of ns, some categories of semiconductors could be damaged in shorter time (magnitude of ps). 


The effectiveness of the SPD operation is ensured through an energy and voltage coordination of the different SPDs. This coordination is supplied by the manufacturer. In large electrical systems the coordination is difficult to achieve because of the high impedance of the installation protected circuits. In this conditions the SPDs operate independently.

Total discharge current (Itotal 10/350 and Itotal 8/20):

Surge current which can circulate within earth conductor of a multipole SPD during total discharge current test. This test is necessary in order to simulate the effect of different protection modes during the SPD operation, for example common mode and differential mode. Itotal is particularly important for SPD of Test Class I and it is useful for lightning equipotential bonding, as indicated in EN 62305-1/4.

Attenuation noise level:

This is the distinctive feature of filters with reference to electromagnetic interferences both in common and differential mode, in the range of 150 kHz – 30 MHz.
To the most advanced SPD is linked a network filter for high-frequency interference. In this way they face and complete the protection against interferences conducted in the field of the electromagnetic compatibility (EMC).

features 2 

Pollution Degree:

It is the classification of conductive pollution present or that can become present by condensation effects in installation SPD site.
P.D. 1: No pollution or only non-conductive.
P.D. 2: Normally non-conductive pollution. Temporary condensation effects are possible.
P.D. 3: Presence of conductive pollution. Frequent condensation.
This feature of the SPD should be thoroughly checked in order to determine its eligibility for installation.
It is particular relevance, for examples, in photovoltaic installation, public lighting and wind farms, as well as in industrial environments such as steel mills, cement factories.







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