RECOMMENDED SURGE RATINGS
AS/NZS 1768-2007 is the first major standard in the world to clearly
defined and recommend surge ratings for SPD’s (8/20us).
Table 5.1 now recommends what rating Surge Protective Devices
should be installed at various strategic installation locations.
NEW DEFINITION GIVEN TO DEFINING THE PERFORMANCE OF AN SURGE FILTER
The performance specification for Surge Filters has never been
well specified in previous and/or other Standards, and AS1768-2007
finally places some parameters into print which should remove
much of the confusion that surrounds what does and does not constitute
a Surge Filter, in a power protection application.
The main reason for incorporating a filter component into SPD
design is to reduce the dv/dt, and dI/dT associated with transient
activity. A suggested performance measure is now included specifically
for application for those who wish to consider, or are specifying
Surge Filters.
TOV TEMPORARY OVER VOLTAGE
This new AS1768-2007 Section 5.6.3.6 relates to SPD’s installation
safety, especially where SPD’s may be subjected to ”TOV” Temporary
Over Voltage conditions at 50 Hz.
In some TOV Fault conditions, SPD’s can overheat, and have been
known to have caused switchboard fires.
5.6.3.6 now recommends a test regime that SPD manufacturers are
urged to comply to, which safely deals with this risk.
|
