Earth Pit Preventive Maintenance

Earth Pit

An “Earth pit” in electrical systems is a hole that is dug out and filled with common materials (charcoal or salt).

Earth pits are often utilized as a short circuit protection measurements.

It serves as a reference point for many electric power sources as well. Since the early days of commercial power, Earth Pits have been utilized as reference sites because they are simple to construct and maintain.

An underground enclosure used in earthing systems to provide access for the inspection, testing, & maintenance of the earth electrodes & other earthing system components is called an earth pit, often referred to as an earth pit chamber or inspection pit.

Earth Pit Preventive Maintenance

Earth Pit Preventive Maintenance is a regular practice used to guarantee the effectiveness and long-term reliability of the grounding system. 

It includes inspecting, cleaning, measuring earth resistance, and taking remedial procedures to avoid corrosion, loose connections, or excessive resistance that might jeopardize electrical safety. 

Regular maintenance will ensure personnel protection & equipment safety during fault conditions & lightning surges.

Purpose

The primary objective of this post is to develop an organized procedure for the Preventive Maintenance of Earth Pits. 

Earth pits serve a key part in maintaining secure earthing systems that protect both equipment & workers from electrical failures and surges.

Regular maintenance makes sure the earth resistance stays within permissible limits & that the system remains functional and dependable.

Scope

This technique applies to all earthing pits built throughout the plant or substation site. 

The scope includes the regular inspection, testing, & maintenance operations necessary to guarantee the health and effectiveness of each earth pit. 

It involves inspecting the physical state of the pit, assessing earth resistance, and assuring correct bonding & moisture levels in the surrounding soil.

References

The preventative maintenance operations  are in accordance with relevant international standards & management systems to guarantee compliance and best practices. This includes:

1. ISO 9001:2008, Clause 5.4.2: Quality Management – Establishing quantifiable targets and programs to assure product and service conformance.
2. ISO 14001:2004, Clause 4.3.3: Environmental Management, identifies and updates legal and other environmental obligations.
3. OHSA 18001:2007 – Clause 4.3.3: Occupational Health and Safety Management – Identification of risks, risk assessments, and identification of appropriate controls.

These references guarantee that earth pit maintenance follows quality, safety, & environmental protection requirements.

PPM Procedure

PPM is a planned preventative maintenance procedure that is scheduled on a yearly basis. 

Any equipment PPM schedule may be created in accordance with his nature and characteristics. 

This action is carried out to keep the equipment in good working order.

There are two types of PPM schedules: quarterly and annual. This scheduled action checks every component of the earth pit, including the 

1. Electrode, 
2. Electrode connection, and 
3. Earth resistance value.

Earth Megger Testing

• Ensure the required permit/clearance as per the WPS.
• Connect the C1 and P1 terminals of the earth megger and a lead from them to earth electrode “E” under test.
• Keep shorting lead as short as possible as this resistance will be included in testing.
• Attach one test spike to the P2 terminal’s lead and another to the C2 terminal’s lead. The test spikes are known as current electrode C2 & potential electrode P2
• Install the test spikes by driving it to a depth of 30 cm in the ground.
• The distance between the 2 test spikes / electrodes is enough that the current electrode C2 is 30 to 50 meters away from the electrode under test “E”. the potential electrode P2 should be put at 61.896 % of distance in a straight line with the remaining two.
• As mentioned above, connect the instrument to the suitable test equipment. 
• Set the range selection switch to the maximum range, if applicable.
• Rotate earth megger handle to the required speed and watch the ohmmeter deflection.
• Move the range selection switch to the next lower range if the ohmmeter’s deflection is very small. 
• Rotate earth megger handle & note the reading shown by the meter’s deflection.

Stakeless Earthing Resistance Measurement

• The resistance paths need to be coupled in a series-parallel manner. You might use a temporary jumper lead to make a loop if there isn’t one to measure.
• The measured result will be more in line with the electrode’s actual earth resistance the more parallel pathways they exist.
• Without unplugging the electrode from the system, testing is possible.
• To test, there’s no need to drive auxiliary test spikes.
  Whether the measured value has many parallel lines or just a few in series with it, the stake-less tester can quickly identify a bad electrode.
• Include the resistance measurement technique and record the test report in specified document format.
• Check for any loose parts or connections. Tighten as necessary. Check the jointing nut and bolt condition and replace as necessary.
• If necessary, clear the unwanted plants from the earth pit.

Quarterly PPM Procedure

• Following earth wire isolation from the earth electrode & other safety measures, a quarterly ppm of earth pit is conducted.
• Verify that the earth pit resistance value is not less than 2Ω.
• Fill the earth hole with the salt solution if the resistance value is more than 2Ω.
• Fill the charcoal & salt type earthing pit with water using a funnel to increase the moisture content if the resistance value is less than 2Ω.
• Use emery paper and CRC to clean the corroded electrode terminal point.
• On the earth electrode termination, apply grease.

Yearly (or) Annual PPM Procedure

• Following earth wire isolation from the earth electrode & other safety measures, a yearly ppm of the earth pit is conducted.
• Verify that the earth pit resistance value is not less than 2Ω.
• Fill the dirt hole with salt water if the resistance value is more than 2Ω.
• Fill the charcoal salt type earthing pit with water using a funnel to increase the moisture content if the resistance value is less than 2Ω.
• Use emery paper and CRC to clean the corroded electrode terminal point.
• On the earth electrode termination, apply grease.

Verification, Correction, & Preventive Action

To maintain the dependability & safety of the earthing system, the Head of the Department is responsible for overseeing the effective execution of the Earth Pit Preventive Maintenance procedure. 

Routine inspections and planned maintenance operations must follow the authorized checklist and standard criteria. 

Any deviations from the established protocol, such as missing inspection sites, excessive earth resistance values, corrosion, (or) physical damage to pit components, must be handled quickly.

Upon finding a non-conformance, necessary remedial activities (such as cleaning, tightening of connections, chemical recharge, or replacement of components) should be done to return the earth pit to its ideal state. 

In addition, preventative activities must be designed and recorded to avoid the risk of recurrence. 

This may involve enhancing inspection frequency, building protective barriers, or changing the maintenance approach depending on detected difficulties.

A follow-up verification should be done post-action to guarantee efficacy.

The purpose is to have a low-resistance, steady grounding system to assure safety & equipment protection during faults or lightning strikes.

Documentation

To preserve traceability and guarantee compliance, all preventative maintenance actions conducted on the earth pits must be documented & recorded consistently.