Infeed: Line currents not symmetrical

What does 206207 mean?

This fault indicates excessively high asymmetry in the line phase currents, with the most probable cause being the failure of one or more line phases. This condition leads to imbalanced loading of the infeed unit. If left unaddressed, this can result in overheating of components, reduced efficiency, and potentially premature failure of the infeed unit or connected equipment due to prolonged electrical stress.

• Blown fuse or tripped circuit breaker in one of the line supply phases (e.g., L1, L2, or L3) to the infeed unit.
• Loose or corroded connection on one phase at the main contactor, input terminals (e.g., U1, V1, W1), or input choke.
• Failure of one phase of the input rectifier bridge within the infeed unit itself (requires internal inspection).
• Significant imbalance in the utility grid supply voltages (e.g., one phase voltage deviates by more than 10% from others).
• Damage to input line filter or choke components causing unequal impedance across phases.

Click steps to track your progress.

1. 1

   1. Measure the line-to-line and line-to-neutral voltages at the infeed unit's input terminals (e.g., L1, L2, L3) to check for phase loss or imbalance.

2. 2

   2. Measure the current in each input line phase (e.g., I_L1, I_L2, I_L3) using a clamp meter to identify the asymmetric phase under load.

3. 3

   3. Inspect and test all upstream fuses and circuit breakers for the infeed unit (e.g., F1, F2, F3) to ensure they are intact and closed.

4. 4

   4. Check all power connections from the main supply to the infeed unit's input terminals for tightness and corrosion.

5. 5

   5. If external checks are clear, perform a diode test on the infeed unit's input rectifier bridge (with power off) to detect internal component failure.