Ground Resistance / Electrode
Estimate single-rod ground resistance from soil resistivity and electrode dimensions, then compute parallel resistance and the number of rods needed for the target.
Key points
Ground Resistance / Electrode: Estimate single-rod ground resistance from soil resistivity and electrode dimensions, then compute parallel resistance and the number of rods needed for the target. Formula: R₁ = ρ/(2πL)·(ln(4L/d) − 1) ｜ R_n = R₁/(n·η). Enter parameters on the DD-CAT IDE online tool page to get results instantly, with a calculation-model diagram that updates with the inputs. The vertical-rod formula assumes uniform soil and a single driven round rod; layered soil, seasonal variation, and nearby electrodes can change results significantly. Parallel rods are not simply divided by n; the utilization factor η drops as rod count rises and spacing shrinks, commonly 0.6–0.9.
Inputs
R₁ = ρ/(2πL)·(ln(4L/d) − 1) ｜ R_n = R₁/(n·η)Calculation model (updates with parameters)
| Single vertical rod resistance R₁ | 29.82 Ω | ρ/(2πL)·(ln(4L/d)−1) |
| 1 根Shunt接地Resistance R_n | 29.82 Ω | R₁/(n·η)，η=0.80 |
| Rods required for target | 10 根 | ceil(R₁/(R_target·η)) |
| Target ground resistance | 4 Ω | 按规范 / Equipment要求填写 |
| Target met? | 未达标 ✗ | 需增加接地极或降阻措施 |
| Average resistance per rod | 29.82 Ω | Shunt后总Resistance × 根数，用于观察利用系数影响 |
| Soil resistivity | 100 Ω·m | 随季knot / 含水率变化，设计取最不利Value |
Engineering notes
- The vertical-rod formula assumes uniform soil and a single driven round rod; layered soil, seasonal variation, and nearby electrodes can change results significantly.
- Parallel rods are not simply divided by n; the utilization factor η drops as rod count rises and spacing shrinks, commonly 0.6–0.9.
- Protective, lightning, and electronic grounding have different requirements; measure with a ground resistance tester after installation, not just calculations.
FAQ
- What is Ground Resistance / Electrode for?
- Estimate single-rod ground resistance from soil resistivity and electrode dimensions, then compute parallel resistance and the number of rods needed for the target.
- What is the formula for Ground Resistance / Electrode?
- Core formula: R₁ = ρ/(2πL)·(ln(4L/d) − 1) ｜ R_n = R₁/(n·η). The tool returns results instantly using this formula and the selected parameters.
- What engineering notes should I keep in mind when using Ground Resistance / Electrode?
- The vertical-rod formula assumes uniform soil and a single driven round rod; layered soil, seasonal variation, and nearby electrodes can change results significantly. Parallel rods are not simply divided by n; the utilization factor η drops as rod count rises and spacing shrinks, commonly 0.6–0.9. Protective, lightning, and electronic grounding have different requirements; measure with a ground resistance tester after installation, not just calculations.