New IEC Standard For Inverters

• A new international test standard for solar PV inverters to detect arc faults has been published
• The IEC 63027 is considered as an improvement over old US standard UL 1699B that did not simulate real operation sufficiently
• Fraunhofer ISE has installed a new test bench to test inverters according to the new standard

A new international test standard for solar PV inverters has been published by the IEC. The new standard, 63027:2023 'applies to equipment used for the detection and optionally the interruption of electric DC arcs in photovoltaic  system circuits, and covers test procedures for the detection of series arcs within PV circuits, and the response times of equipment employed to interrupt the arcs.'

Leading German solar research group Fraunhofer Institute for Solar Energy Systems ISE said the 'unique' modular test IEC 63027 works for products with integrated arc fault detection, enabling more reliable and realistic tests.

Due to reasons as faulty solder joints in the module or in the DC wiring of the inverter, serial arc faults take place and can also lead to fire in case of high temperatures. The arc fault detectors (AFD), it shares, can detect the arc and switch off the inverter before 'a critical energy' is reached.

While inverters in the US are mandated to have the AFD for newly installed systems since 2011, Fraunhofer ISE says European manufacturers offer it on voluntary basis. The new standard now also eliminates some of the weaknesses of the old US standard UL 1699B that did not simulate real operation sufficiently, explains the institute.

The new standard uses an electronic DC source as a PV simulator instead of real PV modules. Current then flows from the simulator to the inverter through a connection point that can be precisely disconnected. A filter network is connected between the inverter and the simulated PV system to ensure the measurement result is not influenced by the PV simulator.

"A realistic test setup can significantly reduce the risk of undetected arcs and false tripping. In the test, it should be possible to ignite the arc as realistically as possible and under repeatable conditions," said Fraunhofer ISE's Felix Kulenkampff who was part of the standardization committee to develop the new IEC standard.

The time until the inverter is switched off is decisive for the proper functioning of the arc detector, according to the team. "The less time an arc burns, the lower the energy input is into the faulty contact point, i.e., short switch-off times reliably prevent a fire from starting. If the energy is between 200 and 750 joules and the switch-off time is less than 2.5 seconds, the detector passes the test," it adds.

A new test bench has been installed at Fraunhofer's TestLab Power Electronics and is suitable for DC voltages up to 1,500 V with 3 DC inputs for up to 16 A and 1 DC input for up to 32 A.

"With the new test bench, we are expanding the range of services offered by our TestLab Power Electronics, where we perform accredited tests in accordance with grid codes, efficiency measurements and impedance spectroscopy investigations of inverters," says Steffen Eyhorn, head of TestLab Power Electronics.

Recently, the German institute introduced a new outdoor performance solar test field for reliable insights in real life conditions (see New PV System Test Infrastructure).