Installation of a Surge Protector

Coordination of protectors

Many facilities need more than one protection step. This achieves higher discharge capacity while ensuring a lower residual voltage. 

To achieve the coordinated actuation of protection stages based on different technologies, a minimum clearance of 10 m must be maintained between protection devices. This ensures that the first step of protection (P1) is activated first and discharges the majority of the energy. The second step (P2) will subsequently perform the function of reducing the residual voltage at the output of the first protection device.

In panels in which the two protection steps are centralised and there is no 10 m clearance, combined protection devices must be used or decoupling coils must be fitted to simulate the cable clearance.

Indication of end of life of the protection device

• Visual indication: Models with visual indication feature a viewer on the front for local end-of-life signalling of the protection device.

• Remote indication: Models with remote indication (IR) have a dry contact for remote signalling of the protector end of life.

Connection cabling

The length and type of cabling are critical for minimising the voltage received by the equipment. Increasing the length of the feed cables to the protection device
reduces the effectiveness of overvoltage protection (Figure a). For optimum protection, these conductors should be as short as possible. The performance of a V-cable at the input and/or output device can help reduce this effect (Figure b).
The IEC installation directive requires that lengths a+b (Figure c) and c (Figure d) should preferably not exceed 0.5 m, and in no case should exceed 1 m.

Back-up fuses

Surge protection devices are connected downstream of a circuit breaker or fuse (F1), in parallel with the installation to be protected. Depending on the size of the fuse, it may be necessary to install an additional disconnection element F2 (circuit breaker or fuse). Specifically, the installation of the F2 element is compulsory where the calibre of F1 is higher than a certain value. This value is different for each protector and is specified in its technical documentation. 

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