Handbook of Electrical Installation Practice - BeKnowledge

Lightning Protection 243
Table 9.18 General indication of potential system impairments which manufacturers of
transient overvoltage protectors should provide.
Protectors for mains
supplies Protectors for data lines
Low Radio
Parallel In-line frequency Network frequency
protectors protectors protectors protectors protectors
Nominal operating ✓ ✓ ✓ ✓ ✓
voltage
Maximum operating ✓ ✓ ✓ ✓ ✓
voltage
Leakage current ✓ ✓ ✓ ✓ ✓
Nominal current rating ✗ ✓ ✓ ✓ ✓
Max continuous current ✗ ✓ ✓ ✓ ✓
rating
In-line impedance ✗ ✗ ✓ ✓ ✓
Shunt capacitance ✗ ✗ ✗ ✓ ✓
Bandwidth ✗ ✗ ✓ ✓ ✓
Voltage standing wave ✗ ✗ ✗ ✓ ✓
ratio
Derived from Furse Electronic Systems Protection Handbook, 1994.
therefore document values for their protector for all the characteristics indicated.
The question of the protector being incompatible with the system it is trying to
protect most commonly arises with data communication, signal and telephone
systems. However, when a mains power protector is based on a gas-discharge tube
connected across the supply, operation of the gas-discharge tube can short-circuit
the supply. The large mains current flowing through the tube is likely to destroy the
tube and disrupt the power supply.
Specifying lightning and transient overvoltage protection
A number of products are available which claim to protect electronic equipment
against lightning and transient overvoltages. However, testing shows many of these