NECESSITY OF MAINTENANCE FREE EARTHING SOLUTION – Challenges
A good earthing system and earthing maintenance is an essential element of any electrical system, required for safety and reliability reasons. Good earthing systems are important for safety of human and animal life, limiting damage to electrical equipment in case of fault/lightning, and timely operation of protective devices.
The resistance of an earth electrode purely depends on the soil resistivity and type of electrode used. Conventionally, a cast iron plate/GI pipe is used as an electrode filled with soil mixed with salt and charcoal. The conduction of current in the conventional electrode is electrolytic. Hence, regular watering and charging of the earth pit with salt is very essential to maintain low earth resistance.
Regular Maintenance is Becoming a Challenging Preposition Due To:
- A typical installation requires 4 types of Earthing (Safety, System, Electronic & Lightning)
- In many commercial projects in the cities, the earthing is possible only in basements
- In projects where the open area is used for earthing, landscaping is done, completely sealing/hiding the earth electrodes
- Even where the electrodes are accessible, willingness to maintain is either lacking or not happening
India being a tropical country, where close to 9 months is dry season, a single earth pit needs around 4000 liters of water just to raise moisture content to 5% — which is impossible to provide with so much scarcity. The salt provided also dissolves over time due to rain (in many places, within 2-3 years), causing resistance to rise and the earthing to become useless.
Limitations in Conventional Earthing System
- No standardization — neither in electrode nor in backfill
- Commercial grade Cast Iron plate/GI pipe is used as electrode in most cases
- The backfill (SALT) reacts with the electrode and causes corrosion
- The salt dissolves in water and conductivity dips over time, increasing resistance
- Not suitable for places with high water table, flowing water etc.
- Residual current flowing through the electrode due to harmonics and imbalance in loads aids corrosion
Why Soil Treatment?
The technology to achieve good earthing mainly depends on the Backfill compound as it influences the critical area around the electrode as mentioned in IEEE 142. The type and quality of Backfill compound determines the long-term reliability. The advanced latest Maintenance free earthing system shall comply with all leading international standards like IS 3043, BS 7430, IEC 60364/62561, IEEE 80 (clause 14.5D), ANSI/NSF 60. The system generally comprises of steel-cored copper-bonded electrodes with carbon-based conductive concrete backfill compound having Resistivity of less than 0.1 Ohm meter (when tested as per IEC 62561-7).
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