What to do in case of untimely circuit breaking on an installation equipped with DualSun panels?
Untimely circuit-breaking in an installation may be due to leakage currents that are too high, triggering the differential. Leakage currents can have several origins: parasitic capacitance, faulty installation, faulty insulation. The method for detecting untimely tripping of the residual current device should be based on analysis of inverter monitoring. It is also important to check all the wiring in the installation, as well as the earthing of the inverter and the panels.
DualSun panels are all IEC 61215-61730 certified which includes the following tests several times during the certification process:
- MQT03/MST16 - Insulation dielectric test): “Determine whether the PV module is sufficiently well insulated between current-carrying parts and the frame or other externally accessible components. The maximum test voltage shall be 2000V plus four times the maximum system voltage.”This check is carried out on each module as it leaves the production line.
- MQT15/MST17 - Wet leakage current test: ”Assess insulation of the module in humid conditions and check that moisture from rain, fog, dew or sleet does not enter the live parts of the module circuits, where it could cause corrosion, faulty earth or a safety hazard.” This control is carried out randomly on modules.
- MST13 - Continuity test for equipotential bonding: ”Demonstrate that there is a conductive path between all exposed conductive surfaces of the module such that the exposed conductive surfaces can be bonded to earth ground appropriate in a PV system.”This check is carried out on each module as it leaves the production line.
- MST11 Accessibility test: “To determine if uninsulated electrical connections pose a shock hazard to personnel.”Test carried out for panel certification only.
In view of the tests related to insulation of the module, it is quite unlikely that the problems of disjunctions untimely come from the DualSun modules. From experience these problems can often be solved by ensuring that the installation complies with the standards as well as our recommendations and those of the manufacturers inverters.
Measuring leakage currents
It is possible to check that there is no current leakage by measuring the voltage, ideally when it is raining (or using a megohmmeter):
- Open circuit voltage between + and -.
- Open circuit voltage between + and earth
- Open circuit voltage between - and earth
If these measurements indicate an earth leak, the problem must be corrected.
Installation of a 300mA residual current device
This only applies to French standards.
Since amendment A5 of standard NF C 15-100, the AC side of the inverter's production circuit does not have to be protected by a 30 mA earth leakage circuit breaker. A 300mA earth leakage circuit breaker may be installed provided that the earth connection is less than or equal to 167 ohms and that no socket is used on the AC side of the PV side.
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