16 User Manual THEIA HE-t String Inverters 357115.013, Issue 1.0, 2011 March
AC Fuses
• AC fuses protect the supply conductors between the inverter and the utility grid.
• They are not part of the scope of supply, and must be provided by the system installer.
• Follow the local and national electrical regulations regarding rating of the AC fuses.
Table 3.3.2: AC current characteristics and fuse rating
Inverter Model Max AC Current Fuse Ratings Tripping Characteristics Type
THEIA 2.0 HE-t
THEIA 2.9 HE-t
THEIA 3.8 HE-t
THEIA 4.4 HE-t
10.5 A
15.2 A
19.7 A
23.0 A
15 A
20 A
25 A
30 A
B or C
Double
Pole
3.3.3. Surge Protection Devices
Overvoltage protection is used to prevent voltage surges through sensitive equipment. The
THEIA HE-t inverters are equipped with Temperature protected Metal Oxide Varistors
(TMOV) on both the DC and the AC side, which conduct excessive current from voltage
surges to ground.
• PV systems mounted in an open or exposed environment need added protection on both the
DC and AC side, as they can act as lightning rods.
• When the conductors are exposed to transients, their behavior limits the effectiveness of a
surge arrester. One or more surge arresters are needed in installations with long conductors
to obtain the required level of protection.
• Always use qualified assesment when selecting the appropriate kA ratings for the
overvoltage protection device!
• IEEE provides a good base for selecting kA ratings of the surge arrester: The THEIA HE-t
inverters are designed for category B: 100 kA – 150 kA per phase.
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