| S.No. | Checkpoint | IS Requirement | Status |
|---|---|---|---|
| A. TEST EQUIPMENT & PROCEDURE | |||
| A1 | Earth megger (earth tester) is used with 3-point or fall-of-potential method; equipment is calibrated Acceptance: Earth megger with 3-point method, calibration certificate within 12 months, frequency 50 Hz | Cl. 8.1.1 — Test equipment specification | OK NC NA HOLD |
| A2 | Three auxiliary electrodes (probe electrodes) are established at 10 m, 20 m distances per 3-point method Acceptance: Probe 1 at 10 m from earth pit, Probe 2 at 20 m, probes in straight line, depth ≥ 0.5 m | Cl. 8.1.2 — Auxiliary electrode placement | OK NC NA HOLD |
| A3 | Test is performed in dry season when soil moisture is lowest; rainfall avoided within 48 hours before test Acceptance: Test in dry season, no recent rain, soil moisture ≤ 10%, test time recorded | Cl. 8.1.3 — Test timing | OK NC NA HOLD |
| A4 | Main switch is OFF; no current is flowing in earthing system during measurement Acceptance: Main switch OFF, isolation confirmed, no load on circuit during testing | Cl. 8.1.4 — System isolation | OK NC NA HOLD |
| B. EARTH RESISTANCE MEASUREMENT | |||
| B1 | First reading taken with probes at 10 m (P1) and 20 m (P2); this is the primary measurement point Acceptance: Reading at P1(10m)-P2(20m) recorded, resistance value noted, stability verified (±5% variation) | Cl. 8.2.1 — Primary measurement | OK NC NA HOLD |
| B2 | Second reading taken with probes at intermediate distance (15 m if possible) to verify consistency Acceptance: Reading at P1(15m) recorded, should be within ±10% of first reading, consistency verified | Cl. 8.2.2 — Verification measurement | OK NC NA HOLD |
| B3 | Multiple readings (minimum 3) taken and averaged; individual readings should not vary by >±10% Acceptance: Minimum 3 readings taken, mean calculated, standard deviation ≤ 10% of mean value | Cl. 8.2.3 — Multiple readings | OK NC NA HOLD |
| B4 | Final earth resistance calculated as average of valid readings; value documented with units (Ohms) Acceptance: Mean earth resistance calculated, documented in Ohms (Ω), recorded in table | Cl. 8.2.4 — Result documentation | OK NC NA HOLD |
| C. ACCEPTANCE CRITERIA FOR BUILDING TYPES | |||
| C1 | For buildings (residential/commercial): Earth resistance ≤ 5 Ω is acceptable; ≤ 3 Ω is preferred Acceptance: Measured resistance ≤ 5 Ω (acceptable), ≤ 3 Ω (preferred), APPROVED if within limit | Cl. 8.3.1 — Building limit | OK NC NA HOLD |
| C2 | For substation/power distribution: Earth resistance ≤ 2 Ω is required; testing per utility standards Acceptance: Measured resistance ≤ 2 Ω for substations, documented and approved by utility authority | Cl. 8.3.2 — Substation limit | OK NC NA HOLD |
| C3 | If measured resistance > 5 Ω: remedial measures taken (additional electrodes, backfill treatment, chemical injection) Acceptance: If > 5 Ω: additional electrode added, backfill improved, or chemical treatment applied, re-tested until ≤ 5 Ω | Cl. 8.4.1 — Remedial action procedure | OK NC NA HOLD |