EARTHING STANDARDS

• EARTHING SHALL CONFORM TO I.S. 3043 / 2018 AND IS 732:2019.

• NGR USED FOR HV GENERATOR/ TRANSFORMER SHALL BE RATED FOR 10 SECONDS.
• IF THE ACTUAL FAULT LEVEL IS LESS THAN 150MVA, THE EARTHING DESIGNS MUST ASSUME A MINIMUM
FAULT LEVEL AT THE 11 KV SIDE OF 150MVA.

• CALCULATE THE NECESSARY NUMBER OF EARTH ELECTRODES BASED ON THE FAULT CURRENT AT THE HV
SIDE. A 1.2M × 1.2M PLATE'S CURRENT LOAD CANNOT BE GREATER THAN 1300A. (I.S. 3043 - CL.14.2.1)

• DURATION OF FAULT CURRENT SHALL BE TAKEN AS 3 SEC FOR EARTHING DESIGN AT HT INSTALLATIONS AND
1 SEC FOR EHT INSTALLATION.
• ALL EARTH ELECTRODES SHALL BE INTERCONNECTED USING THE CONDUCTORS OF LARGEST SIZE IN THE EARTHING
SYSTEM.
• MAXIMUM EARTH RESISTANCE AT HT PREMISES SHALL BE LIMITED TO 1 OHM.(IS 3043, CLAUSE 25.1)
• EARTH MAT SHALL BE PROVIDED AT EHT PREMISES FOR LIMITING STEP VOLTAGE AND TOUCH VOLTAGE TO
TOLERABLE VALUES ACCORDING TO IEEE 80.
• ALL NON-CURRENT CARRYING METAL PARTS OF ELECTRICAL EQUIPMENT'S SHALL BE EARTHED AND IF VOLTAGE OF
EQUIPMENT EXCEEDS 250V, IT SHALL BE CONNECTED IN DUPLICATE(CEA (MR&ES) REGULATION – CL. 41(XII))
• TRANSFORMER AND GENERATOR NEUTRAL SHALL BE CONNECTED IN DUPLICATE. ONE DIRECT CONNECTION FROM
NEUTRAL TO AN EARTH ELECTRODE SHALL BE PROVIDED FOR NEUTRAL EARTHING. LINKS SHALL ALSO BE PROVIDED
IN NEUTRAL EARTHING CONDUCTOR. GENERATOR NEUTRAL SHALL BE EARTHED AT CONTROL PANEL
• LIGHTNING ARRESTOR SHALL BE DIRECTLY CONNECTED TO AN EARTH ELECTRODE USING NO. 6 SWG CU. THE L.A.
EARTH ELECTRODE MAY BE INTERCONNECTED WITH OTHER EARTH ELECTRODES.
• ACCORDING TO IS 3043-2018, THE FOLLOWING ALLOWANCES IN THE CROSS-SECTION AREA OF THE EARTHING
CONDUCTOR ARE ADVISED WHEN USING STEEL CONDUCTORS FOR EARTHING IN ORDER TO ACCOUNT FOR THE
EFFECTS OF CORROSION.
• A NUMBER OF RODS OR PIPES MAY BE CONNECTED IN PARALLEL, AND THE RESISTANCE IS THEN PRACTICALLY
PROPORTIONAL TO THE RECIPROCAL OF THE NUMBER EMPLOYED SO LONG AS EACH IS SITUATED OUTSIDE THE
RESISTANCE AREA OF ANY OTHER. IN PRACTICE, THIS IS SATISFIED BY A MUTUAL SEPARATION EQUAL TO THE
DRIVEN DEPTH. LITTLE IS TO BE GAINED BY SEPARATION BEYOND TWICE THE DRIVEN DEPTH. A SUBSTANTIAL GAIN
IS AFFECTED EVEN AT 2 M SEPARATION. A SEPARATION OF TWO METER BETWEEN PLATE ELECTRODE IS SUFFICIENT
TO GET THE EARTH RESISTANCE VALUE WITH 20% VARIATION. (IS 3043:2018 CL.14.2.2)
• A MINIMUM OF 1.5 METERS MUST SEPARATE THE GROUND ELECTRODE FROM THE NEARBY CIVIL CONSTRUCTION.
• IN LOCATION OF SBS, DBS ETC. SUB EARTH BUSES OF 25X3MM2 COPPER OR 32*6 MM2 GI MAY BE PROVIDED.
• ALL COPPER JOINTS IN EARTHING CONDUCTORS SHALL BE PROPERLY TINNED.
▪ FOLLOWING GUIDELINES SHALL BE ADHERED TO WHEN GI EARTHING IS ADOPTED.
• (A) GI STRIPS USED FOR EARTHING SHALL BE MINIMUM 6MM THICK AND HOT DIP GALVANIZED.
• (B) THE GI SHALL HAVE A MINIMUM CROSS-SECTIONAL AREA OF 50 SQ.MM.
• (C) TO PREVENT ELECTROLYTIC ACTION, JOINTS WHERE A COPPER CONDUCTOR IS TO BE CONNECTED TO GI SHOULD BE TINNED.
• (D) JOINTS MUST ALWAYS BE MADE BY WELDING, EXCEPT FOR THOSE SITES WHERE INTERMITTENT DISCONNECTION OF JOINTS IS
REQUIRED FOR TESTING, THE EARTHING CONNECTION TO THE BODY OF EQUIPMENT, ETC.
• (E) BARIUM CHROMATE OR ZINC DICHROMATE TREATMENT SHOULD BE DONE AT THE WELDS. JOINTS
SHOULD BE PROVIDED WITH COATING ALTERNATIVE LAYERS OF RED OXIDE AND ALUMINUM. JOINTS ARE TO
BE COVERED WITH HOT BITUMEN. ALSO, JUTE BAND COVERING OF ADEQUATE THICKNESS IS TO BE MADE ON
THE PORTION OF EARTHING SUSCEPTIBLE TO HIGHER CORROSION AND ENVIRONMENTAL INFLUENCE.
• (F) WHEN CALCULATING THE AREA OF DISSIPATION FOR THE FAULT CURRENT, THE STRIP ELECTRODE AREA
COVERED WITH BITUMEN AND JUTE SHOULD NOT BE TAKEN INTO ACCOUNT.
• (G) IN PLACES WHERE THE RESISTIVITY IS VERY HIGH AND ATMOSPHERIC CORROSION IS NOT SIGNIFICANT
EVEN ORDINARY STEEL CONDUCTORS SHALL BE PERMITTED.
• (H) EARTHING SYSTEMS WITH GI CONDUCTORS SHALL UNDERGO A COMPLETE PHYSICAL INSPECTION
AFTER TEN YEARS, AND ADJUSTMENTS SHOULD BE MADE IF THEY ARE DISCOVERED TO BE NECESSARY.
• (I) JOINTS USING GI CONDUCTORS SHOULD BE WELDED AS FAR AS POSSIBLE AND KEPT SEPARATED FROM
AIR BY A THICK COATING OF TAR OR SIMILAR NON-HYGROSCOPIC MATERIALS. IN CASE BOLTED JOINTS
CANNOT BE AVOIDED, THERE SHOULD BE A MINIMUM OF 2 BOLTS FOR SIZES UP TO 25MM X 6MM, 3 BOLTS
FOR SIZES UP TO 31MM X 6 MM AND ZIG ZAG BOLTING FOR LARGE SIZES.
➢FOLLOWING GUIDELINES SHALL BE ADHERED TO WHEN COVERED ALUMINIUM IS USED FOR EARTHING
• (A) BARE ALUMINUM SHOULD NOT BE USED FOR FINAL UNDERGROUND CONNECTIONS TO EARTH
ELECTRODE.

• (B) ALUMINUM SHALL BE USED BELOW GROUND ONLY IF EFFICIENTLY PROTECTED OR SHEATHED AGAINST
CONTACT WITH SOIL AND MOISTURE. PVC COVERING SHALL BE ALLOWED.
• (C) TO PREVENT ELECTROLYTIC ACTION, JOINTS CONNECTING A COPPER CONDUCTOR TO AN ALUMINUM
CONDUCTOR SHOULD BE TINNED.
• (D) USE A BENDING MACHINE TO CREATE THE SHARP BENDS NEEDED IN ALUMINUM STRIP.
• (F) TUNGSTEN INERT GAS ARC OR METAL INERT GAS ARC PROCEDURES MUST BE USED TO ARC WELD
ALUMINUM TO ALUMINUM CONNECTIONS ON STRIP CONDUCTOR. ADDITIONALLY, WELDING OR BRACING
USING OXY-ACETYLENE GAS IS PERMITTED.

• (F) ROUND AND RECTANGULAR CONDUCTORS CAN BE JOINED WITH BOLTED CLAMPS. RECTANGULAR
CONDUCTORS CAN BE JOINED OR TERMINATED BY DRILLING AND BOLTING.
• (G) GREASE OR AN APPROVED JOINTING COMPOUND SHOULD BE APPLIED IMMEDIATELY TO BOTH MATING
SURFACES WHEN CREATING A BOLTED TYPE JOINT. THE ALUMINUM STRIP'S SURFACE SHOULD BE CLEANED
COMPLETELY WITH A WIRE BRUSH. AFTER THAT, BOLTS SHOULD BE TIGHTENED, AND ANY LEFTOVER GREASE
OR COMPOUND SHOULD BE WIPED OFF AND THROWN AWAY.
• (H) WHEN CONNECTING ALUMINUM CONDUCTORS TO EQUIPMENT, IT IS PREFERABLE TO DO SO VERTICALLY.
THE ALUMINUM SHOULD BE SURFACE-PREPARED, AND THE JOINT SHOULD BE MADE AS PREVIOUSLY
SPECIFIED. BITUMASTIC PAINT NEEDS TO BE APPLIED TO PROTECT THE FINISHED JOINT.
• NOTES
• PERMISSIBLE CURRENT DENSITY (FOR 3 SECONDS) FOR EARTHING CONDUCTORS. A) COPPER =118A/MM2
B) ALUMINUM =73AMM2 C) STEEL(GI) =46A/MM2
• MAXIMUM CURRENT PER METER OF ROD LENGTH FOR THE TOTAL ROD SYSTEM SHOULD NOT EXCEED THE VALUES AS DETERMINED
BY EQUATION

• I = (1140XD) ⁄ √( Ρ X T ) WHERE I = MAXIMUM CURRENT IN AMPS/METER D = ROD DIAMETER IN MM Ρ = EARTH RESISTIVITY IN

OHM-CM T = TIME IN SECONDS (TYPICALLY ONE SECOND ) IF GROUND CURRENTS OF HIGH MAGNITUDE AND LONG DURATION ARE
ANTICIPATED, THE SYSTEM MUST COVER A RELATIVELY LARGE AREA AND EMPLOY ENOUGH ELECTRODES AND ELECTRODE
CONNECTIONS. THIS WILL KEEP THE CURRENT DENSITY IN THE EARTH TO A LOW VALUE.
• PROTECTIVE EQUIPOTENTIAL BONDING SHALL BE CARRIED OUT IN ALL BUILDINGS AS SPECIFIED IN IS 3043/IS 732.

• EARTH FAULT PROTECTION AT EVERY LT CONSUMER PREMISES SHALL BE ACHIEVED BY THE FOLLOWING A) THE EARTH FAULT LOOP
IMPEDANCE HAS TO BE LOW ENOUGH TO ALLOW ADEQUATE EARTH FAULT CURRENT FLOW TO CAUSE AND OVER CURRENT
PROTECTIVE DEVICE (FOR EXAMPLE, A FUSE OR CIRCUIT BREAKER) IN THE FAULTY CIRCUIT TO OPERATE IN A SUFFICIENTLY SHORT
TIME : OR B) WHERE IT IS NOT POSSIBLE TO ACHIEVE A LOW ENOUGH EARTH FAULT LOOP IMPEDANCE, DISCONNECTION MAY BE
ACHIEVED BY FITTING A RESIDUAL CURRENT DEVICE (RCD) OF 30MA SENSITIVITY (IS 3043:2018, CLAUSE 23.1)