IS 3043:1987 is the Indian Standard (BIS) for earthing. This code provides comprehensive guidelines for the design, installation, calculation, and measurement of electrical earthing systems. It covers the determination of earth fault currents, soil resistivity, selection and sizing of earth electrodes and conductors, and safety measures against electric shock.
Provides guidelines for design, installation, and maintenance of earthing systems for electrical installations to ensure safety and proper operation.
Key limits for earth resistance, minimum dimensions for electrodes and conductors, and critical design factors for earthing systems.
| Reference | Value | Clause |
|---|---|---|
| Max Earth Resistance, Large Power Station | 0.5 Ω | Cl. 9.2.2 |
| Max Earth Resistance, Major Sub-station | 1.0 Ω | Cl. 9.2.2 |
| Max Earth Resistance, Minor Sub-station | 2.0 Ω | Cl. 9.2.2 |
| Max Earth Resistance, General Installations— In soil, where rock is not encountered. | 8.0 Ω | Cl. 9.2.2 |
| Max Tower Footing Resistance— For lightning protection of overhead lines. | 10 Ω | Cl. 23.2 |
| Earthing Conductor Sizing Formula— A=Area (mm²), I=Fault Current (A), t=Time (s), k=Material Factor | A = (I * √t) / k | Cl. 12.2.2.1 |
| Material Factor 'k', Copper | 205 | Cl. 12.2.2.1 (Table 8) |
| Material Factor 'k', Galvanized Steel | 80 | Cl. 12.2.2.1 (Table 8) |
| Material Factor 'k', Aluminium | 126 | Cl. 12.2.2.1 (Table 8) |
| Min. Burial Depth of Electrode— Below ground level. | 1.25 m | Cl. 20.2.3 |
| Min. Burial Depth of Earthing Conductor— Below ground level. | 60 cm | Cl. 21.1.2 |
| Min. Spacing between Parallel Electrodes | 2 x Length of electrode | Cl. 20.2.4 |
| Min. Length, Rod/Pipe Electrode | 2.5 m | Cl. 20.2.1 (Table 9) |
| Min. Dia, Copper Rod Electrode | 12.5 mm | Cl. 20.2.1 (Table 9) |
| Min. Dia, GI Rod Electrode | 16 mm | Cl. 20.2.1 (Table 9) |
| Min. Size, Copper Strip Electrode | 25 mm x 1.6 mm | Cl. 20.2.1 (Table 9) |
| Min. Size, GI Strip Electrode | 25 mm x 4 mm | Cl. 20.2.1 (Table 9) |
| Min. Dia, GI Pipe Electrode (Light Duty) | 38 mm | Cl. 20.2.1 (Table 9) |
| Max. Current Density, Copper Electrode— For 1 second fault duration. | 200 A/m² | Cl. 11.2 (Table 7) |
| Max. Current Density, Steel Electrode— For 1 second fault duration. | 70 A/m² | Cl. 11.2 (Table 7) |
| FOP Test, Potential Probe Position— Position P1 relative to current electrode C1 and earth electrode E. | 61.8% of C1-E distance | Cl. 34.3.3 |
| Soil Treatment Layer Thickness— Alternate layers of charcoal and salt around the electrode. | ~15 cm | Fig. 6 & 7 |
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Assumed Human Body Resistance | 1000 ohms for safety calculations. | 1000 ohms is used as a reference, but safety limits are based on tolerable current as a function of time. | IEEE Std 80-2013 |
| Minimum GI/Steel Pipe Electrode | 38 mm internal diameter, 2.5 m length. | 19 mm (3/4 in) trade size, 2.44 m (8 ft) minimum length. | NFPA 70 (NEC) 250.52(A)(5) |
| Minimum GI/Steel Plate Electrode | 60 cm x 60 cm x 6.3 mm. | Minimum surface area of 0.186 m² (2 sq ft); for iron/steel, minimum thickness of 6.4 mm (1/4 in). | NFPA 70 (NEC) 250.52(A)(7) |
| Electrode Backfill Recommendation | Alternate layers of charcoal and salt. | Conductive, non-corrosive materials like bentonite clay or conductive cement. Salt is not recommended. | BS 7430:2011+A1:2015 |
| Minimum Burial Depth (Top of Plate Electrode) | Not less than 1.5 m below ground level. | Not less than 750 mm (30 in) below finished grade. | NFPA 70 (NEC) 250.53(G) |
| Use of Concrete-Encased Electrode (Ufer) | Not specified as a standard electrode type. | Permitted and defined: at least 6.0 m (20 ft) of steel rebar or copper wire encased in concrete. | NFPA 70 (NEC) 250.52(A)(3) |
| Minimum Size of Earthing Conductor (Copper) | 3 mm² (14 SWG) for wires; 25mm x 1.6mm for strips. | 8.37 mm² (8 AWG) for connection to rod/pipe/plate electrodes. | NFPA 70 (NEC) 250.66(A) |