INSTALLATION OF PROTECTORS

Effects of the installation:

The surge voltages generated by a lightning stroke produce very high currents in the electrical conductors (tenths of kA) with a very short duration (some µs).

The conductors present a very high impedance against surge voltages due to the induction produced in the cables. With normal working frequency of 50 Hz the impedance is negligible.

Connection of the protections:

In order to achieve a low residual voltage in the terminals of the equipment or line to be protected, a solution such as shown in the following figures is recommended.

As mentioned in the previous section, the voltage drop in the line can be significant depending on the discharge current and it must be added to the residual voltage. Due to this the connection of the protector should be made as close as possible to the equipment in order to avoid the increase of the residual voltage.

Additional circuit-breaking device:

All the protectors have a thermic disconnector incorporated. The protectors can be complemented with an additional protection against overcurrents and short circuits, in order to isolate the protected equipment from the installation in case of failure.

Imax	Fuses	Overcurrent switch
65 KA 40 KA 15 KA	80 A 40 A 32 A	25 A curva C 10 A curva C 10 A curva C
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Connection of the additional circuit-breaking device:

Depending on the required performance, two connection possibilities exist for the circuit-breaking device.

The first possibility gives priority to the continuity of service. When the fuse or the automatic switch open, then the protection is disconnected, however the equipment has power supply and continues in service. In this case the equipment is unprotected until the protection module is replaced.

The second possibility gives priority to the protection. When the fuse or the automatic switch open, then the power supply and at the same time the equipment and protector are switched off. The power supply of the equipment is disconnected and thus it cannot receive any surge voltage.

Distance between protectors and equipment to be protected:

The more effective the protection should be, the closer it should be installed to the equipment to be protected.

In many installations it is typical to have a distance of more than 30m between the mains input and the location of the equipment which needs to be protected. Due to this it is possible to install more than one protector.

Also, in order to have a high discharge power (Imax) and an appropriate protection level (Up), the installation of more than one protector is necessary.

Therefore, installing a protector in the mains input with high discharge power and then close to the equipment another protector with appropriate protection level while keeping the minimum distance between the protectors, is required to provide a secure protection to the installation.