The Most Comprehensive Reference of Grounding Currents and Resistor Values under Different System Voltages

Writer： admin Time：2025-09-19 09:59:40 Browse：331℃

In power systems, proper design of neutral grounding and grounding resistors is critical for ensuring safe operation.

 Grounding not only provides a return path for fault currents to allow protective devices to operate promptly, but also 

helps control fault voltages, preventing insulation damage to equipment and reducing the risk of electric shock. In 

distribution systems, different voltage levels and grounding methods have a significant impact on the magnitude of 

fault currents.

For example, low-voltage systems often use high-resistance grounding or solid grounding to limit fault current, prevent 

equipment damage, and avoid system maloperation; medium-voltage industrial systems may adopt low-resistance or 

high-resistance grounding depending on protection requirements; while high-voltage transmission networks generally

use solid grounding, with the grounding current primarily determined by system scale. By scientifically selecting grounding 

methods and resistor values, it is possible to effectively control the current and voltage during single-phase ground faults, 

reduce hazards to equipment and personnel, and improve grid stability and reliability. To facilitate engineering design and 

operational management, this document provides a reference table of common international distribution system voltage 

levels and their corresponding grounding currents, aiding in the selection of appropriate grounding schemes.

System Voltage Level	Common Grounding Method	Typical Single-Phase Ground  Fault Current Range	Description
Low Voltage ≤ 1 kV (400/230V, 480/277V etc.)	High Resistance Grounding (HRG) or Solid Grounding	HRG: 5–10 A Solid Grounding: several hundred A (depending on short-circuit capacity)	HRG improves system continuity and reduces arc hazards; Solid grounding is suitable for simple protection.
3–6 kV Medium Voltage	High Resistance Grounding / Low Resistance Grounding	HRG: 10–25 A LRG: 100–300 A	HRG is commonly used in industrial systems;  LRG ensures reliable operation of protective relays.
10–15 kV Medium Voltage (commonly 10kV, 13.8kV)	Low Resistance Grounding (LRG) or Arc Suppression Coil	LRG: 200–400 A Arc Suppression Coil: <10 A (remaining current after compensation)	Common in 10kV distribution networks;  Arc suppression coils are widely used in overhead lines.
20–35 kV Medium-High Voltage	Low Resistance Grounding / Arc Suppression Coil	LRG: 200–800 A Arc Suppression Coil: several to tens of A	Common in medium-high voltage urban or industrial networks.
≥66 kV Transmission Network	Solid Grounding or Reactor Grounding	Several hundred to several thousand A (depending on short-circuit capacity)	Fast protection response, suitable for stable operation of large grids.

HRG system: The current should be greater than the system’s capacitive current (generally 5–10 A) to avoid maloperation.

LRG system: The current must be sufficient to operate the protective relay (generally 100–600 A), but not so large as to damage equipment.

Arc-suppression coil: Mainly used to limit overvoltages from ground arcs, making the residual current close to zero.

High-voltage transmission network: Often uses solid grounding, with the grounding current determined by the system scale and not artificially limited.

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