28-29 / 319
Guide to
| Surge Protection Devices
14
Cascading is the term used to describe the method of
combining several levels of surge protection devices into the
one installation.
This takes advantage of the best features of each device
to improve the protection level for the equipment. Hager
recommends using a high surge current capacity device to
divert the bulk of the transient over-voltage at the origin of
the installation.
In the case of a Class 1 & 2 device this would be either the
spark gap arrester or a high current capacity MOV. Should
finer protection be required, the next step is to install a Class
3 device SP202N near the terminal equipment.
Cascading increases the current diverting capacity of the
SPD system whilst maintaining a low voltage (U p ) to ensure
the best protection for valuable equipment.
Selecting SPD of the same manufacturer or make will ensure
correct co-ordination between devices
Cascading
“Cascading increases the
current diverting capacity of the
SPD system whilst maintaining
a low voltage (U p ) to ensure
the best protection for valuable
equipment.”