Cause : One or several line phases failed comes when failure overvoltage in one or several line supply phases. The fault can be output in two operating states:

1. During the power-on phase of the infeed unit. The measured line supply angle deviates from the regular characteristic for a 3-phase system - the PLL cannot be synchronized. The fault occurs immediately after power-up if, when operating with a Voltage Sensing Module (VSM), the phase assignment L1, L2, L3 at the VSM differs from the phase assignment at the power unit.

2. While the infeed is operational. After a voltage dip has been detected or an overvoltage (note A06205) in one or several line phases a fault occurred within 100 ms (also refer to other relevant messages). Generally, before fault message F06200 is output, Alarm A06205 occurs at least once, whose warning value can provide information regarding the cause of the line supply fault.

Possible causes:

- voltage dip on the line side or phase failure or overvoltage lasting longer than 10 ms.
- overload condition on the load side with peak current.
- line reactor missing.

- check the line supply and fuses.
- check the connection and size (rating) of the line reactor.
- check and correct the phase assignment at the VSM (X521 or X522) and at the power unit.
- check the load.
- if failed in operation, carefully note the previous alarm messages A6205 with alarm values.

See also: p3463 (Infeed line angle change phase failure detection)