BU I LDI NG SOLUT IONS
— Overvoltage protection
Electromagnetic conditions of different severity are associated to the protection zones, with a reduction of the LEMP from upstream to downstream, in relation to the level of impulse resistanceof the equipment insulations. The zones are defined as follows
Class 1 and Class 2 surge arresters are complementary and provide protection from the origin of the installation to the terminal equipment. Class 1 arresters protect against direct lightning strikes and are capable of diverting a considerable amount of energy. They allow a small part of the impulse current to enter the installation, which must be handled by the finer Class 2 protectors. Downstream of the Class 1 arresters it is necessary to install a Class 2 arrester to protect sensitive equipment. Class 2 arresters protect against indirect lightning strikes and are designed to protect against a large number of discharges, quickly and with an excellent level of protection. They should be installed near the equipment to be protected.
LPZ 0A outdoor zone, not protected by the external LPS, in which the elements present, being exposed to direct atmospheric discharges must withstand the total current generated by them and are subjected to the total magnetic field;
LPZ 0B zone contained in the volume protected by the external LPS, for which protection from direct lightning is assured, but the danger derives from total exposure to the magnetic field;
Type or class
Class 1 or Class 2
They are tested with 10/350 µs pulses
They are tested with 8/20 µs discharges
They are tested both with impulsive currents of wave 10/350 µs and with discharges of wave 8/20 µs They protect against both direct and indirect electrocution. They are used in small installations that integrate sensitive equipment (e.g. telecommunications). Usually combined technology (varistor + spark gap)
LPZ 1 zone inside the structure, in which the objects are not exposed to direct atmospheric discharges and in which the induced currents are minor compared to zone 0A. It is characterized by the presence of shielding and the installation of suitable SPDs on incoming lines; LPZ 2, LPZ n zones in which there is additional shielding and the presence of additional SPDs, both at the borders of the various zones and to protect the terminal users, which allow a reduction in induced currents, in relation to the requirements of the equipment to be protected.
Protect against impulsive lightning currents entering the system directly, e.g. from lightning rods or overhead lines
Protect against surges induced by lightning strikes falling on or near the building and from surges resulting from electrical switching operations Usually with varistors, combined versions (varistor + spark gap) can be installed
Composition Usually spark gaps
upstream of the earth leakage circuit breaker
Are installed at the origin of the system
Are installed in all switchboards of the system, close to sensitive equipment.
Install at the origin of the system with limited space, near sensitive equipment
Powered by FlippingBook