How does poor grounding of the power FTU affect protection operation?

Poor grounding can cause reference potential drift, affecting the accuracy and reliability of FTU protection operations. Specific impacts include: false positives in zero-sequence protection, ground fault detection errors exceeding 10%; increased unbalanced current in differential protection; and overcurrent protection threshold drift. Solutions include: using independent grounding stakes with a grounding resistance less than 0.1Ω; employing shielded twisted-pair cable in the protection circuit with single-point grounding of the shielding layer; using an independent ground plane on the PCB for the protection circuit, connected to the main ground via a PBZ1608A-102Z0T ferrite bead; and using an ISO7240C isolation amplifier for isolated sampling. Through optimized grounding, the protection operation error is less than 1%, and the operation time dispersion is less than 5ms, meeting the requirements of the IEC 60255 protection relay standard.