Health Assessment of Earthing System (Delhi NCR)

Our O&M service helps prevent and solve electrical problems through testing, preventive maintenance, repair, replacement on either a routine or an emergency basis.

As far as Earthing system is concerned our activity will include the following:

Earth Electrodes

a) Measure soil resistivity at site by Wenner/Schlumberger Palmer method as detailed in IEEE 81 standard. This is essential to determine the resistance that can be expected from a healthy earth pit. The electrode resistance to earth shall be calculated as per formula given in clause no. 9.2.2 of IS3043 &Clause 9.5.3 of BS7430. (Incase of non availability of space within the plant, SR could be measured outside plant area to get representative values)

b) For measuring the resistance of individual isolated electrode for LT and other non-DG/Transformer create a temporary by pass arrangement for the earth pit to be tested by connecting its grounding electrode conductor to the nearest alternative earth pit.

Physical inspection of electrode for its condition to be done before carrying out testing. If damage found like broken neck /collar straightway the electrode shall be replaced with new one.

c) Isolate the earth pit under test and measure its resistance value by fall of potential method/Stakeless method and record the findings.

d) If the measured value is within the value calculated and the electrode is deemed to be healthy. If not, salt water charging of earth pit may be done and measured again after two hours. If the value is still not in limits, earth electrode may have to be redone/replaced with a maintenance free earth electrode.

e) Reconnect grounding electrode conductor and earth grid. Apply petroleum jelly etc. to bolted joints to minimize corrosion.

Equipment grounding conductor and electrode grounding conductor

f) In case the earth strips are totally corroded, recommend replacement.

g) Check for continuity of the equipment grounding conductor from equipment to earth pit.

h) If continuity is not found or loop resistance is very high, check all bolted/welded connections enroute and establish the continuity of the earth conductor.

i) For LV or HV side, it is enough to check the continuity of the equipment grounding conductor (physical).

Meters and Equipment Used

1. Earth resistance/Soil resistivity tester

Make: WACO with higher with variable voltage and variable frequency which are absolutely essential for testing in live installations.

Else stray currents will cause continuous fluctuation making it impossible to determine meaningful values.

2. Continuity Test

3. Good Multimeter

4. Tool set, welding machine/cutter (where necessary and if job being done under shut down).