The document outlines surge protection device (SPD) requirements, including protective conductor sizes and equipment specifications based on installation type. It provides details on minimum sizes for conductors to protect against lightning and overvoltage, specifying different current ratings and installation categories. Additionally, it includes information on permissible voltage stress and durations for electrical systems.

1. SPD surge protection
SPD Protective conductor sizes
Type Name Location Protective Conductor CSA Protection
1
Equipotential bonding or
lightning protection
current SDP
Origin of installation
16mm minimum. Length of tails
ideally <0.5m but no longer than
1mtr
Protection against flashover from
direct lightning strikes to structure or to
LV overhead supply
2 Overvoltage SPD Distribution board
4mm or equal to CSA of circuit
conductors
Protection against overvoltage's
which can stress the electrical
installation
3 Overvoltage SPD Terminal equipment
2.5mm or equal to CSA of circuit
conductors
Protection against overvoltage's and
high currents on items of equipment
Required minimum impulse withstand voltage kV (L-E)
Nominal Supply
Voltage
Cat IV Equipment with
very high impulse
voltage
Cat III Equipment
with high impulse
voltage
Cat II Equipment with normal
impulse voltage
Cat I Equipment with reduced impulse
voltage
230/240 6 kV 4 kV 2.5 kV 1.5 kV
277/480 6 kV 4 kV 2.5 kV 1.5 kV
400/690 8 kV 6 kV 4 kV 2.5 kV
1000 12 kV 8 kV 6 kV 4 kV
Permissible power frequency stress voltage
Duration of
earth fault in HV
system (t)
> 5s
< 5s
Printed from the Electrical Tools & Reference App
Permissible power frequency stress voltage on equipment in LV installation
Uo + 250V
Uo + 1200V
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