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typically trip at a value closer to their rating.
2. Configure the trip current of the inverter’ internal RCD to a lower value than the trip current of the
external RCD. The internal RCD will trip if the current is higher than the allowed current, but because the
internal inverter RCD automatically resets when the residual currents are low it saves the manual reset.
2.3 Surge Protection Devices (SPDs) for PV Installation
WARNING!
Over-voltage protection with surge arresters should be provided when the PV power system is
installed. The grid connected inverter is not fitted with SPDs in both PV input side and mains side.
Lightning will cause damage either from a direct strike or from surges due to a nearby strike.
Induced surges are the most likely cause of lightning damage in majority or installations, especially
in rural areas where electricity is usually provided by long overhead lines. Surges may impact on
both the PV array conduction and the AC cables leading to the building. Specialists in lightning
protection should be consulted during the end use application. Using appropriate external lightning
protection, the effect of a direct lightning strike into a building can be mitigated in a controlled way,
and the lightning current can be discharged into the ground.
Installation of SPDs to protect the inverter against mechanical damage and excessive stress include
a surge arrester in case of a building with external lightning protection system (LPS) when
separation distance is kept. To protect the DC system, surge suppression device (SPD type2) should
be fitted at the inverter end of the DC cabling and at the array located between the inverter and the
PV generator, if the voltage protection level (VP) of the surge arresters is greater than 1100V, an
additional SPD type 3 is required for surge protection for electrical devices.
To protect the AC system, surge suppression devices (SPD type2) should be fitted at the main
incoming point of AC supply (at the consumer’s cutout), located between the inverter and the
meter/distribution system; SPD (test impulse D1) for signal line according to EN 61632-1. All DC
cables should be installed to provide as short a run as possible, and positive and negative cables of
the string or main DC supply should be bundled together.
Avoiding the creation of loops in the system. This requirement for short runs and bundling includes
any associated earth bundling conductors. Spark gap devices are not suitable to be used in DC
circuits once conducting; they won’t stop conducting until the voltage across their terminals is
typically below 30 volts.
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