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Energizer
Solar Inverter | Installer Manual [4]
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In every photovoltaic (PV) installation, several elements contribute to the current leakage to protective earth (PE).
These elements can be divided into two main types.
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Capacitive discharge current
- Discharge current is generated mainly by the parasitic capacitance of the
PV modules to PE. The module type, the environmental conditions (rain, humidity) and even the distance of
the modules from the roof can affect the discharge current. Other factors that may contribute to the parasitic
capacitance are the inverter’s internal capacitance to PE and external protection elements such as lighting
protection.
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During operation, the DC bus is connected to the alternating current grid via the inverter. Thus, a portion of the
alternating voltage amplitude arrives at the DC bus. The fluctuating voltage constantly changes the charge state
of the parasitic PV capacitor (i.e capacitance to PE). This is associated with a displacement current, which is
proportional to the capacitance and the applied voltage amplitude.
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Residual current
- If there is a fault, such as defective insulation, where an energized cable comes into contact
with a grounded person, an additional current flows, known as a residual current.
Residual Current Device (RCD)
All
Energizer
solar inverters incorporate a certified internal RCD (Residual Current Device) to protect against possible
electrocution in case of a malfunction of the PV array, cables or inverter (DC). The RCD in
Energizer
solar inverters
can detect leakage on the DC side. There are 2 trip thresholds for the RCD as required by the DIN VDE 0126-1-1
standard. A low threshold is used to protect against rapid changes in leakage typical of direct contact by people. A
higher threshold is used for slowly rising leakage currents, to limit the current in grounding conductors for the safety.
The default value for higher speed personal protection is 30mA, and 300mA per unit for lower speed fire safety.
Installation and Selection of an External RCD device
An external RCD is required in some countries. The installer must check which type of RCD is required by the specific
local electric codes. Installation of an RCD must always be conducted in accordance with local codes and standards.
For this inverter, the use of a type-A RCD is recommended. Unless a lower value is required by the specific local
electric codes, then an RCD value between 100mA and 300mA is recommended.
In installations where the local electric code requires an RCD with a lower leakage setting, the discharge current might
result in nuisance tripping of the external RCD. The following steps are recommended to avoid nuisance tripping of
the external RCD:
1. Selecting the appropriate RCD is important for correct operation of the installation. An RCD with a rating of 30mA
may trip at a leakage as 15mA (according to IEC 61008). High quality RCDs will typically trip at a value closer to their
rating.
2. Configure the trip current of the inverter’s 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 have an impact on both the PV array conduction and the AC cables leading to the building.
