Surge Voltage Proteciton ; Transient surge voltage arise as s result of lightning discharge , switching operations in electric systems and electrostatic discharge.Without protective measures inculiding lightning current and surge voltage arresters,the power involved in lightning discarge is top much for even the sturdily built low voltage power supply of a building or industrial plant. The surge voltages occur only briefly in the range of a millonth of a second. In spite of this , most very high voltages are capable of destroying electronics circuits or the insulation between printed circuits.

Even if electric or electronic equipment has passed the voltage resistance test in acc. With IEC 1000-4-5 necessary for granting the CE,mark, it is stil not capable of resisting all environmental influences with respect to EMC without damage.

In order to prevent surge voltage from destroying electrical systems, all the interfaces risk, such as signal inputs and power supplies , must be connected to surge voltage protection devices. Despending on the application , components such us spark gaps, gas filled surge voltage arresters, varistors and suppressor diyotes are arranged individually or combined in protective circuits since the components differ in their arresting and discharge data.

BY “ efficent Protective Circuit” we mean complete protection againits surge voltages.

The first step toward planning such a protection concept is to list all devices and areas of the system that need to be protected. This is followed by an eavaluation of the level of protection required for all the devices registered. The different types of circuits are differentaited between in the following areas;

• Power supply
• Measurement and control technology(MCR)
• Data processing systems
• Telecommunications
• Transceiver systems

One must think of the system or device to be protected as being in a protected zone, see illustraions. At all the intersections “ Line Protective Circuit” surge voltage protective devices ar to be installed to match the nominal data of the particular type of circuit or interface of the deive to be protected. The area within the protective circuit is thus so safe that voltage coupling from outside is not possible.