Types of earthing material. This topic explains choice of material, common earthing material, earth electrodes, earth bus, jointing methods for earth conductor. This screen shows the different kinds of materials for earthing. Copper, copper-clad and copper-plated steel, aluminum and steel. Copper is a common material used for grounding systems as it has high conductivity. Copper is used extensively as earth mat in overseas. Copper-clad and copper-plated steel are common materials used for grounding systems especially where theft is a problem. Use of copper clad-steel electrode is commonly adopted in overseas installation. Aluminum may be subject to corrosion in certain soils. Corroded aluminum layer is non conductive. Galvanized steel or stainless steel conductors and ground rods may be used in applications where the soil conditions may be detrimental to copper. Suitable design margin shall be included to account for corrosion of steel. Stainless steel earthing material is used normally in high corrosive and saline environment. Hot dip galvanized steel or conductors is commonly used for earth mat and earth electrodes. Hot dip galvanizing means mild steel material will get uniformly coated with zinc when dipped in hot molten zinc bath. Use of galvanized steel is common in India. Some of the common earthing materials are shown on screen. Bare copper tape, tinned copper tape are used as earth mat. Usage of aluminum tape is not common in India. Bare copper conductor is used as earthing lead about ground applications. Yellow green PVC insulated stranded copper conductor is used as earth mat and earth leads. Some earthing electrodes are GS pipe, copper clad steel rod, mild steel rod, 40 MMS rod is used as earth mat and electrode. Galvanized steel tape, 75 to 10 MM is used as earth mat in India. Earth electrode, it may be of solid copper rod, copper bonded steel rod, stainless steel rod, mild steel rod, and GS pipe. Usually, electrodes are of three meters long. Copper bonded steel earth rods are the preferred choice in several countries. Electrolytic copper is molecularly bonded to low carbon steel rod to produce copper bonded steel. Copper bonded steel rods are highly resistant to corrosion and they can be driven by power hammers directly into the ground. The solid copper earth rods offer greater resistance to corrosion. They are used in highly corrosive soil such as high salt content soils. They are physically not strong for driving from the Earth's surface. Stainless steel rods are used to prevent galvanic corrosion which takes place between dissimilar metals. They are highly resistant to corrosion. MS rod is common in India. MS rod can be directly driven in virgin soil. Galvanized steel pipes having diameter from 38 to 50 millimeters are very common in India. However, they are subject to corrosion. Electrodes may be installed inside pit or without pit, which may be treated or untreated. Electrodes may be direct driven into the virgin soil. They may also be installed in excavated pits with filling of a select material around electrodes. Filling materials may include salts and charcoal, very common in India, bentonite, cement powder, concrete filling as concrete is known to retain moisture. Brick built or precast housing is usually provided for all earth electrodes. Directly when electrodes may or may not be provided with the housing based on local practices. PVC insulated copper conductors are used generally for above ground earthing for providing connection from equipment earning terminal domain or thin conductor. This will be color-coded yellow green with PVC insulation. PVC installation is used to prevent corrosion of the conductor. It is also a general practice to use PVC insulated copper conductor as buried earth mat in oil and gas industry. Earth bus is a convenient way of providing a common earth point. See from the picture, assuming connections at the end or reserved for connecting earth mat, earth bus facilitates connection of individually leads for the earthing of equipment body and other metalics. This earth bus can be provided with integral disconnecting links if required to facilitate easy isolation and testing purposes. Recall the crimping type lug used for cables as studied in cables module. Similarly, for grounding conductors, the crimping type connectors can be used. Some common types of connectors are bolted, crimping, bracing or welding, and thermoweld connectors. The bolted connection can be used above ground only. Crimping type can be used above ground and below ground. Bracing or welding can also be used both above and below ground and the thermoweld is mostly used for below ground installations. The typical thermoweld earth joints appear on screen, cable to rod connection, cable to tape or strip connection, copper cable or steel connection, steel to tape or strip connection, earth rod to earth rod connection, strip to earth rod connection, copper tape to rebar connection, copper cable to rebar connection, earth rod to rebar connection, rebar to rebar connection, earth rod to steel connection. References for earthing related information appear on screen. Here's a quick recap of what you've learned thus far. Copper is commonly used for grounding systems. Copper-clad and copper-plated steel are common materials used for grounding systems, especially where theft is a problem. Aluminum is rarely used for ground grids. Galvanized steel or stainless steel conductors and ground rods may be used in applications where the soil conditions may be detrimental to copper. Some common types of connectors are bolted, cramping, bracing or welding, and thermoweld connectors. PVC insulated copper conductors are used generally for above ground earthing for providing connection from equipment, earthing terminal to main earthing conductor. Earth bus is a convenient way of providing a common earth point and can be provided with integral disconnecting links if required to facilitate easy isolation and testing purposes.
