In September 2018, TNO was asked to conduct an investigation into fire accidents involving rooftop PV systems reported by Dutch media at the time. In April 2019, the research institute ended its investigation and stated that around 70% of the fires were caused by faulty connectors, and especially by cross-mating, which happens when connectors of different kinds are mated. We asked our trusted suppliers Sungrow, Stäubli and Helukabel to share with us their solutions to best prevent fire incidents in PV systems.
Our inverters feature several built-in protections in order to minimise the risk of fire. Such as:
Our products are fully compliant with relevant standards as IEC 60947-3 (DC Switches) and IEC 61643-11 and 31 (SPDs). More information about Sungrow’s built-in protection features to reduce fire risks will be published in a follow-up.
We ensure the lowest possible transition resistance (<0.25mΩ) when applying our MC4 connectors correctly. In addition, we use non-flammable materials in our connectors.
DC cables must meet the standards that are required by the NEN1010 (NEN EN 50618). This means that the cable must, among other things, be UV-resistant and halogen free and have tinned copper cores. At Helukabel we ensure that our DC cables are produced according to this standard at all times.
We would recommend that the installation environment is free of any flammable or explosive materials. Always reserve enough clearance around the inverter to ensure sufficient space for ventilation/heat dissipation. Following the installation manual guideline, check the torque settings of all electrical connections or terminals.
Do not mix connector brands (cross connection), use correct tools for stripping and crimping as well as for tightening the gland. Do not leave flammable materials near connectors, think for example of sawdust.
Our DC cable always meets the same outer diameter of the connector, which is very important for the compatibility with the connectors. Both cables have to be stripped the same, so that they can be placed perfect into the connector. That is why a good stripping tool and professional crimping tool is necessary. If these tools are not used properly you have the chance of loose contacts, which can result in issues in the connection and lead to fire.
IEC 62109 applies to all our inverters. At the moment IEC 63027 ED1 is under development and defines the standards for DC arc detection and interruption in photovoltaic power systems.
Our connectors have the flame class UL certification – UL94-V0
For DC cables we need to meet NEN EN 50618.
We would recommend (as minimum) the following actions:
Check the connectors with a thermal imaging camera looking for hot spots that indicates high resistance.
When a cable is installed and used correctly, we expect this cable to last at least 25 years. We as Helukabel wouldn’t advice an annual inspection for your cables. Instead make sure you have high quality cables and good cable management, this will ensure that your cables will last 25 years.