🌍 Calculadora de Resistência de Aterramento
Calcule a resistência de uma haste de aterramento vertical a partir da resistividade do solo, do comprimento e do diâmetro da haste, e descubra quantas hastes você precisa para atingir uma resistência alvo.
⚙️ Electrode
📊 Result
Para engenheiros que projetam sistemas de aterramento de subestações e equipamentos.
Como é calculado
· Haste única: R = ρ ÷ (2πL) × ln(4L ÷ d).
· Múltiplas hastes: Rn = R ÷ (n × 0,8), com fator de utilização de 0,8.
· Hastes necessárias: n = ceil(R ÷ (alvo × 0,8)).
Normas de referência
| Standard | Scope |
|---|---|
| IEEE 80 | Guia de segurança para aterramento de subestações CA |
| IEC 62305 | Proteção contra raios — terminação de aterramento |
Exemplo resolvido — solo de 100 Ω·m → 39,6 Ω por haste
1. ρ = 100 Ω·m, L = 2,5 m, d = 20 mm.
2. R = 100 ÷ (2π × 2,5) × ln(4 × 2,5 ÷ 0,02) = 6,37 × 6,21 = 39,6 Ω.
3. Para atingir ≤ 10 Ω: n = ceil(39,6 ÷ (10 × 0,8)) = 5 hastes.
FAQ
What is an acceptable earth resistance for a substation?
IEEE 80 recommends Substation ground resistance below 1-5 ohms for large installations, while IEC 60364 allows up to 10 ohms for many LV systems. A 1-ohm target is standard for MV substations; the calculator sizes the number of rods to meet your target.
How many earth rods do I need?
Rod count depends on soil resistivity and target resistance. In 100 ohm-m soil, a single 2.4 m rod gives roughly 35-40 ohms; reaching 10 ohms needs 4-5 rods spaced 2.4 m apart, and 1 ohm needs 40-50 rods (or a grid). The calculator computes the single-rod resistance and the count for the target.
How does soil resistivity affect grounding?
Soil resistivity varies from ~10 ohm-m (wet clay) to 1000+ ohm-m (dry rock). Higher resistivity means more rods or a larger grid for the same resistance. Sandy or rocky sites often need chemical treatment or deep-driven rods. The calculator takes soil resistivity as input and sizes the electrode accordingly.
Why does grounding rod spacing matter?
Rods placed closer than their length interfere, raising the combined resistance. Spacing rods at least one rod length apart (typically 2.4 m) gives nearly independent rods and the full benefit. Closer spacing wastes material. The calculator applies the standard spacing rule.
What is the difference between earth resistance and touch/step voltage?
Earth resistance is the electrode-to-earth impedance; touch and step voltages are the voltages a person can experience during a fault, which depend on the surface layer and grid geometry, not just resistance. IEEE 80 limits touch voltage to ~50-100 V depending on fault duration. The calculator sizes for resistance; full touch/step study needs IEEE 80 grid analysis.
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