The core demand of high-resistance grounding systems (such as power plants and chemical parks) is to limit fault current and reduce arc hazards. Therefore, the selection of earthing/grounding transformers must meet three special requirements: ① The fault withstand time should preferably be 60 seconds or 1 hour grade, because the system needs to maintain the fault state for monitoring and positioning to avoid premature disconnection of the grounding circuit; ② The zero-sequence impedance must be accurately matched with the grounding resistance, usually 30-50 ohms per phase, to ensure that the fault current is controlled within the safe range of 5-10A; ③ Models with auxiliary windings are preferred to provide stable low-voltage power for grounding resistance monitoring and system measurement and control (such as 400V auxiliary windings); ④ The insulation grade needs to be upgraded by one level, because the voltage rise of non-fault phases is greater during system faults, requiring enhanced insulation withstand capacity.

They can be used together (common in low-voltage and medium-voltage distribution networks). The core is to realize fault current suppression and rapid positioning through the combination of "earthing/grounding transformer constructing neutral point + arc suppression coil compensating fault current". Three points should be noted when used in conjunction: ① Impedance matching: The zero-sequence impedance of the earthing/grounding transformer must be coordinated with the reactance value of the arc suppression coil to avoid series resonance; ② Capacity coordination: The short-time capacity of the earthing/grounding transformer must cover the working current of the arc suppression coil to ensure the safe operation of both during faults; ③ Protection coordination: The compensation action of the arc suppression coil must precede the overcurrent protection of the earthing/grounding transformer to avoid protection misoperation cutting off the grounding circuit; ④ Integrated design products (earthing transformer-arc suppression coil combination devices) are preferred to reduce on-site wiring errors and improve operation reliability.