Direct Answer

When the earthing resistance in mountainous/sandy-stone areas cannot reach the standard no matter what, which resistance-reduction measure should be used? The answer: first judge whether the high resistivity is in the shallow or deep layer — for a high-resistivity shallow layer, replace the soil and use resistance-reduction agents to improve the dissipation near the electrode; when a low-resistivity layer exists in the deep layer, a deep-well vertical earth electrode is more effective; earth modules suit places with limited space where the dissipation area must be enlarged. The choice depends on the soil layering and the site — the more expensive deep well is not always better.

At a mountainous substation, the measured earthing resistance exceeded the limit; three deep wells were blindly drilled, costly and limited in effect — the wells still penetrated the high-resistivity rock. After a layered soil-resistivity test confirmed a high-resistivity sandy shallow layer and a low-resistivity groundwater deep layer, one deep well reaching the low-resistivity layer plus shallow replacement brought the resistance to standard at lower cost. The key distinction: resistance reduction is not "the more expensive, the better" — test the layering first and choose by "whether the high resistivity is shallow or deep"; a deep well drilled in the wrong place wastes the money.

Why:

  • Layering first: measure the shallow/deep resistivity before deciding;
  • Resistance-reduction agents: improve the dissipation near the electrode (shallow);
  • Earth modules: enlarge the dissipation area (limited space);
  • Deep-well earthing: reaches the deep low-resistivity layer (effective when deep).

Key insight: "Choose the measure by the soil layering: replacement/agents for the shallow, deep wells for the deep, modules when space is limited — test the layering before spending; a well in the wrong place wastes the money."

At a park, the site was too constrained to spread a horizontal grid and the resistance never reached the standard; earth modules enlarged the dissipation area and it passed. Lesson: the site constraint decides the measure — the deep well is not universal; when space is limited, modules plus agents are more practical.

1. Test the Soil-Resistivity Layering First

Step one: is the high resistivity shallow or deep?

Why layering matters:

  • Shallow high resistivity → replacement/agents;
  • Deep low resistivity → a deep well penetrating;
  • Choosing the wrong measure wastes money;
  • Layering is the starting point of selection.

The test method:

  • The four-probe method measures the resistivity;
  • Different spacings measure different depths;
  • A resistivity-vs-depth curve;
  • Identifying the shallow/deep high-low.

Reading points:

  • Shallow high, deep low → a well is most effective;
  • High everywhere → replacement + a larger dissipation surface;
  • A local low layer → aim the well at it;
  • The test guides the scheme, not guesswork.

Key insight: "Layer first, then reduce: the four-probe method gives the resistivity-vs-depth curve — see whether the high resistivity is shallow or deep, and the measure follows the layering."

2. Resistance-Reduction Agents: Improving the Dissipation Near the Electrode

Step two: what to do about a shallow high-resistivity layer.

The role of the agents:

  • Wrapping the electrode and lowering the contact resistance;
  • Improving the dissipation near the electrode;
  • Enlarging the effective dissipation radius;
  • The first choice for a shallow high-resistivity layer.

Applicable conditions:

  • A shallow high-resistivity layer and the site allows excavation;
  • Poor dissipation near the electrode;
  • Combined with low-resistivity replacement;
  • The amount follows the electrode geometry.

Notes:

  • Choose long-lasting agents (prevent loss);
  • Avoid corrosion of the electrode;
  • Combine with the horizontal grid;
  • Monitor the effect regularly.

Key insight: "Agents improve the dissipation near the electrode and enlarge the effective radius — first choice when the shallow layer is high-resistivity and excavatable; mind the durability and corrosion."

3. Earth Modules: Enlarging the Dissipation Area

Step three: what to do about limited space.

The role of the modules:

  • Adding dissipation area in module form;
  • Replacing a spread grid when space is limited;
  • Combined with electrodes/grids;
  • Efficient dissipation.

Applicable conditions:

  • The site is too constrained to spread a horizontal grid;
  • The dissipation area must be enlarged;
  • Combined with agents/replacement;
  • Flexible vertical/horizontal layout.

Notes:

  • Reliable connections between modules;
  • Conducting to the main grid;
  • Burial depth matched to the environment;
  • Monitor the resistance-reduction effect.

Key insight: "Modules enlarge the dissipation area when space is limited — when the grid cannot spread, use modules; combining with agents is more practical."

4. Deep-Well Earthing: Penetrating to the Deep Low-Resistivity Layer

Step four: what to do about a deep low-resistivity layer.

The role of the deep well:

  • A vertical earth electrode penetrating the high-resistivity shallow layer;
  • Reaching the deep low-resistivity layer/groundwater;
  • Deep dissipation, a large drop in resistance;
  • Most effective when the deep layer is low-resistivity.

Applicable conditions:

  • A low-resistivity layer exists in the deep;
  • The shallow layer cannot be fixed by replacement;
  • The site allows vertical space;
  • Effective only when aimed at the low layer.

Notes:

  • Confirm the low-layer position by layering first;
  • A well in the wrong place has limited effect;
  • The depth/diameter match the geology;
  • Connected to the shallow grid.

Key insight: "A deep well penetrates the high-resistivity shallow layer to the low-resistivity layer — but first confirm the low layer exists; a well in the wrong place wastes the money."

5. Weighing the Measure against the Site and Cost

Step five: how to set the scheme comprehensively.

The selection logic:

  • Test the layering first;
  • Shallow high → replacement/agents;
  • Deep low → a deep well;
  • Limited space → modules.

The cost trade-off:

  • Deep wells are expensive and depend on the geology;
  • Agents/replacement are cheaper and suit the shallow;
  • Modules suit constrained sites;
  • A combined scheme is the best.

Practice verification:

  • Measure the resistance after construction;
  • Monitor online with the FR Earth-Resistance Monitor;
  • Recheck the seasonal variation;
  • Add measures when it still fails.

Key insight: "Set the scheme by layering + site + cost: replacement/agents for the shallow, deep wells for the deep, modules when constrained — verify by measurement after construction."

6. Product Implementation: Resistance Reduction and Monitoring as One

WeiWuLian products manage the resistance-reduction system:

  • FR Earth-Resistance Monitor: online monitoring of the earthing resistance;
  • Layered testing: digitizing the soil resistivity;
  • Effect recheck: verifying after resistance reduction;
  • Data loop: reduction-monitoring-maintenance closed.

The design principle in one sentence: "Test the layering, choose by the layer, verify after construction, measure online — manage the reduction system with data."

7. Common Misjudgments

  1. "The more expensive the deep well, the better": ignoring the layering. Result: a well in the wrong place wastes money. Correct: test the layering first.
  2. "Use agents everywhere": ignoring the applicable conditions. Result: works shallow, fails deep. Correct: choose by the layer.
  3. "The deep well is universal": ignoring the site constraints. Result: cannot spread in a constrained site. Correct: combine modules.
  4. "Just do it without testing": ignoring the layering test. Result: the wrong measure. Correct: measure with the four-probe method first.
  5. "Done after construction": ignoring the effect verification. Result: a failure goes unnoticed. Correct: measure and monitor online.

Scope and Limitations

This article explains the resistance-reduction paths for high-soil-resistivity scenarios (layering first, and the applicable conditions and trade-offs of agents/earth modules/deep wells), applicable to selecting and understanding resistance-reduction schemes. The exact processes and parameters follow GB 50057-2010, related standards and the manufacturers' data; this article explains only the selection logic and judgment basis. All cases are anonymized (a mountainous substation, a park) and do not refer to any specific customer.