18
INDUSTRIAL
SPD
25 kA
20 kA
15 kA
10 kA
0 kA
25 kV
20 kV
15 kV
10 kV
0 kV
0
200
250
100
150
50
300
350
400
t µs
Corrente di cresta
Impulso combinato
IEC 61643-11
(2011-03)
CEI EN
61643-11/A11
SPD
WAVE
FORM
DISCHARGE
CURRENT
COMBINED
PULSE
Class 1 SPD
Type 1 SPD T
SPD
for lightning current
Tested with limp pulse current (10/350 µs) and with the nominal In
discharge current (8/20 µs)
10/350 μs
limp 25 kA
-
Class 2 SPD
Type 2 SPD T
Overvoltage
limiter
Tested with nominal In discharge current (8/20 µs) and with
maximum Imax discharge current (8/20 µs). The Imax, nevertheless,
is neither useful nor usable to choose the SPD
8/20 μs
limp 20 kA
-
Class 3 SPD
Type 3 SPD T
Overvoltage
limiter
Tested with the combined generator
that applies Uoc no-load voltage (1,2/50 µs)
and in short circuit a presumed In current (8/20 µs)
1.2/50 μs
-
10 kV
Undefined causes 14%
Other causes 41%
Overvoltage 45%
DAMAGE TO THE
ELECTRONICS
IN SPD
SYSTEMS (OVERVOLTAGE LIMITERS)
THESE DAYS, WITH THE EVER-INCREASING USE OF ELECTRICAL EQUIPMENT
AND WITH THE EXPONENTIAL INCREASE OF THE LEVEL OF SEMICONDUCTOR
INTEGRATION, MORE AND MORE ATTENTION IS GIVEN TO THE PHENOMENA
RELATED TO TRANSITORY SURGE VOLTAGE OF ATMOSPHERIC ORIGINS AND
SURGE VOLTAGE DUE TO ELECTRICAL SWITCHING ON DISTRIBUTION SYSTEMS
BECAUSE OF THE SUBSTANTIAL ECONOMIC DAMAGE THAT THEY CAN CAUSE.
THERE IS CONSEQUENTLY A NEED TO ADOPT INCREASINGLY GREATER SAFETY
MEASURES INSIDE BUILDING AND SYSTEM INFRASTRUCTURES IN ORDER
TO ENSURE THAT THE ELECTRICAL AND ELECTRONIC EQUIPMENT IS NOT
DAMAGED AND CAN PROVIDE ITS PERFORMANCE, EVEN IN THE PRESENCE
OF INTERFERENCES. THE SPDS, DEPENDING ON THE PARAMETERS OF THE
LIGHTING CURRENT PULSE THEY ARE CALLED UPON TO DISCHARGE TO EARTH,
ARE TESTED AND THEN CLASSIFIED IN DIFFERENT WAYS. THE IEC 61643-11
ED.1 (2011-03) STANDARD AND THE CORRESPONDING CEI EN 61643-11/A11
STANDARD, ALTHOUGH USING DIFFERENT, BUT SUBSTANTIALLY IDENTICAL
DEFINITIONS, DIVIDE THEM UP AS FOLLOWS:
