Hi michal07,

I think only way to get reliable information if thebreaker is working well is to do a test by using the handheld test device for 3WL.

Information about is given in the operating instructions starting on page 9-134.

Next Siemens office should be able to help you with this device or people there can do the test be their own.

Please let me remark that energy supply of the breaker is not done via voltage transformers (or control power tranformer)but by CTs. There needs to be a minimum load current of 60 A to ensure power supply of the ETU (see page 9-23 in the instructions), however, when switching on an existing short circuit ETU will trip the breaker with a delay of maximum delay of 15 ms for activating.

Best regards

Sentronix