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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.
Quick Reference — Top IS 3043:1987 Values
Key limits for earth resistance, minimum dimensions for electrodes and conductors, and critical design factors for earthing systems.
✓ Verified 2026-04-27
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.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Adding alternate layers of salt and charcoal around the electrode significantly lowers earth resistance but accelerates the corrosion of the electrode.
! Always physically disconnect the earth electrode from the main electrical installation via the test link before measuring its individual earth resistance.
! Plate electrodes are preferred for high fault current applications (like substations), while pipe or rod electrodes are generally sufficient for standard building earthing.
Focuses on the design and safety analysis of earthing grids for HV/EHV AC substations.
BS 7430:2011+A1:2015BSI (UK)
HighCurrent
Code of practice for protective earthing of electrical installations
Provides comprehensive guidance on earthing for a wide range of electrical systems, similar in breadth to IS 3043.
IEC 60364-5-54:2011IEC (International)
MediumCurrent
Low-voltage electrical installations - Part 5-54: Selection and erection of electrical equipment - Earthing arrangements and protective conductors
Covers earthing arrangements and protective conductors specifically for low-voltage installations.
NFPA 70 (NEC) 2023NFPA (US)
MediumCurrent
National Electrical Code®
Article 250 provides extensive, prescriptive rules for grounding and bonding in electrical systems.
Key Differences
≠IS 3043:1987 recommends using alternating layers of charcoal and salt as a backfill material for earth electrodes to reduce soil resistance. Modern international standards like BS 7430 strongly discourage this practice due to the corrosive nature of salt and its environmental impact, recommending stable, non-corrosive materials like bentonite clay instead.
≠For substation earthing design, IS 3043:1987 relies on simplified formulae and graphical methods for calculating step and touch potentials. In contrast, IEEE Std 80-2013 provides highly detailed, complex calculation methodologies that account for two-layer soil models, the effect of surface resistive layers (like crushed rock), and sophisticated grid analysis.
≠IS 3043 is highly prescriptive regarding electrode dimensions (e.g., 60cm x 60cm x 6.3mm GI plate). International standards like the US NEC are often more performance-based, specifying minimum surface areas (e.g., 0.186 m²) or allowing a wider array of electrodes, including concrete-encased electrodes (Ufer grounds), which are not detailed as a primary type in IS 3043.
≠The safety criteria for tolerable body current in IEEE Std 80 are derived from Dalziel's formulae, which relate the current magnitude to the shock duration (I_b = k/√t). IS 3043:1987 adopts a simpler approach, generally assuming a fixed human body resistance of 1000 ohms and using tabulated values for permissible currents.
Key Similarities
≈All standards, including IS 3043, share the same fundamental objectives for earthing: ensuring personnel safety by limiting potential differences during a fault, providing a low-impedance path for fault currents to enable protection systems, and maintaining voltage stability.
≈The Wenner four-point method is the universally recognized and recommended technique for field measurement of soil resistivity in IS 3043, IEEE Std 80, and BS 7430, demonstrating a common foundational approach to site investigation.
≈The basic components of an earthing system, such as vertical electrodes (pipes/rods), horizontal conductors (strips/tapes), and plate electrodes, are common to and described in both IS 3043 and its international counterparts.
≈Both the Indian and international standards emphasize the importance of mitigating corrosion. They provide guidance on selecting appropriate materials (e.g., copper, galvanized steel) and highlight the risks of galvanic corrosion when dissimilar metals are connected within the earthing system.
Parameter Comparison
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)
⚠ Verify details from original standards before use
Key Values8
Quick Reference Values
minimum length of pipe or rod electrode2.5 m
minimum diameter of GI pipe electrode40 mm
minimum dimensions of plate electrode600 mm x 600 mm
minimum thickness of GI plate electrode6.3 mm
minimum thickness of copper plate electrode3.15 mm
maximum earth resistance large power stations0.5 Ohm
maximum earth resistance major substations1.0 Ohm
depth of burial of strip or conductor electrode0.5 m
Key Formulas
S = (I * sqrt(t)) / k — Minimum cross-sectional area of protective conductor (where I is fault current, t is operating time, k is material constant)
R = ρ / (2 * π * l) * ln(4l/d) — Earth resistance of a driven pipe/rod electrode
Tables & Referenced Sections
Key Tables
Table 1 - Soil Resistivity (Typical Values)
Table 2 - Material and Size of Earth Electrodes
Table 3 - Minimum Cross-Sectional Area of Protective Conductors
Table 6 - Values of K for Insulated Protective Conductors
Key Clauses
Clause 9 - Equipment Earthing
Clause 11 - Earth Electrodes
Clause 12 - Current Density at the Surface of an Earth Electrode
Clause 14 - Selection of Earthing Conductors
Clause 21 - Measurement of Earth Resistivity
Clause 22 - Measurement of Earth Electrode Resistance