Weidmüller subjects its terminal blocks destined for installation in photovoltaic systems to a partial discharge test with DC voltage. This is to date a unique test of quality of terminal blocks. Put succinctly, Weidmüller is the first and presently the only manufacturer that tests the long-term stability of the insulation of its terminal blocks under "DC conditions". That enables Weidmüller to guarantee its terminal blocks are able to withstand a voltage of 1000 VDC under all climatic conditions. And it is only terminal blocks that have passed this test of quality that ensure safe and reliable operation of PV systems at voltages of 1000 VDC.
Insulated lines react completely differently to partial discharge tests with AC voltage than to partial discharge tests with DC voltage. It is not possible to draw conclusions as to whether a terminal block is suitable or not for 1000 VDC applications simply by considering the thickness of the insulation, its dimensions or other physical attributes in isolation. When dealing with DC applications these design features of a terminal block must be considered in combination, because it is in combination that they qualify a terminal block to provide guaranteed reliability. For that reason Weidmüller approves each type of terminal block for different configurations of terminal rails. A list of approved terminal blocks is available for downloading from the Weidmüller website.
