SELECTION OF LIGHTNING & SURGE ARRESTERS
In accordance with IEC 61643-11, SPDs (surge protection devices) are divided into three type classes – type 1, type 2 and type 3 (classes I, II and III). These standards contain regulations, requirements and tests for surge protection devices used in AC networks with nominal voltages of up to 1,000 V AC and nominal frequencies of be 50 AND 60Hz.
Lightning current arrester type 1
Lightning Current arresters of type 1 are used at the entry to the building. The connection is connected parallel to the main incoming power lines of electrical system.
Surge arrester type 2
Surge arresters of type 2 are used in main and sub-distributors. The protection devices must be used before a residual current protective device (RCD), as it would otherwise interpret the surge current as a residual current and interrupt the power circuit.
Surge arrester, type 3
Type 3 surge arresters are used to protect against inductive coupling and switching surges in the device power circuits. These surge voltages occur primarily between the phase (L) and the neutral cable (N). The Y circuit protects the L and N lines with varistor circuits and makes the connection to the PE line through a spark gap. Thanks to this protection circuit, transverse voltages are arrested without the residual current device (RCD) interpreting the surge current as a residual current and interrupting the power circuit. To protect sensitive controllers, the protection level must be below 1,500 V.
Choosing the right surge protection devices
The classification of surge protection devices into types means they can be matched to different requirements with regards to location, protection level and current-carrying capacity.
Co-ordinations of Arrestors
To utilize maximum protection efficiency, it is necessary to create the correct co-ordination between Type 1 and Type 2 SPD in a protection system. If Type 1 and Type 2 SPDs are installed side by side in the same distribution board (location), it will be necessary to install a decoupling element or a Combined Type 1 & 2 SPD.
Power supply networks are built following different wiring systems, defined in low voltage codes. It is necessary to know this information about the line to be protected in order to determine the overvoltage protection installation.
Electrical supply systems are characterized by their connections, on the one hand, with the distribution or supply grounding network and, on the other, the receiver installation ground.
Systems are named using a letter code indicating the situation of the supply with respect to the earthing
T – indicates direct connection,
I – indicates isolation,
N – indicates connection to neutral
