Q: How to handle the small impedance angle in the zero sequence impedance test results?
Answer: The small impedance angle of zero sequence impedance is mainly due to the large resistance part. The following aspects can be checked:
1. Whether the grounding is good should be connected to the grounding grid inside the substation, and tower grounding devices or direct connection to the overhead ground wire leads should not be used.
2. The connection between terminal N and the ground grid must be reliably connected with a dedicated grounding wire of no less than 6 square meters to reduce the impact of contact resistance and the grounding wire's own resistance on zero sequence impedance.
3. A large grounding resistance in a substation can affect the impedance angle of zero sequence impedance, especially in short circuits where grounding resistance accounts for a large proportion of zero sequence resistance.
