What is Earth Electrode?

Earth Electrode

What is Earth Electrode?
The term electrode means "a way in or a way out for electricity". The bare copper conductor plate or strip or water pipe or gas pipe or any other conductors are used for earth electrodes.The electrode must be an underground, cold water, metal piping system. The earth electrode is the way into the earth for the electrons. In general we use the one or more electrodes in earthing system for efficient earthing purpose. A good earth electrode is that to maintain a good contact with the earth. The one responsibility of earth electrode is that it maintains zero potential between ground and the non-current carrying metal parts of electrical equipment and enclosures. The earth continuity conductor in an electrical installation must be connected at the main intake to an earth electrode which affords a path of low resistance to the earth. Generally in domestic wiring system, we use a mains, water pipe as an earth electrode and a factory or commercial premises (over 12kv) have a its own individual electrode.
The main purpose of an electrode is to provide and maintain good continuity with earth at all times. The following are the types of electrodes such a 'copper plates, copper rods, and strips.

Pipe Earthing:
In Pakistan generally for earth electrode G.I pipe and copper plates are used. A Galvanized iron pipe of minimum 40mm diameter and minimum length of 2.7m is buried in the earth. It may be more in case of dry and rocky soil. The pipe is provided with the tapped casing at the lower end so that it can be driven into the soil easily. Alternate layers of salt and charcoal are placed around the pipe up-to 2 meter from the bottom end and 15cm around the pipe. The layer of salt and charcoal increases the resistance. An arrangement is made to pour water into the pipe periodically so that soil remains moist. Another pipe of 1.9em diameter is connected at the top of that pipe through a reducing socket. water pipes offer good conductance to earth. The actual resistance usually a fraction of an ohm. The low resistance of such systems is due to their size and the fact that the pipes, are in contact with a great volume of earth.

Rod Earthing:
Artificial grounding electrodes should also be used. Such electrodes may be rods, pipes, plates or conductor embedded in the earth. They should be of no-corrosive metal, such as copper or copper bearing steel. Copper electrodes are widely used as electrode. It is made in a range of diameters from (1/2in) to (1in). These copper rods are available to many parts length. The minimum length of copper rod at 8 feet with a minimum diameter of 1/2 inch. The driven grounds consist of rods driven into the ground deeply enough so that they are in contact with perpetually moist soil. A G.I-steel rod or copper rod is driver into the ground. The rod should be driven until the top end is 4 to 6 inch below the ground level. If driving is difficult, a bar may be used to make the hole before the rod is driven.
A person can accommodate a rod at any length, as the driving hammer slides over the rod. If many ground rods have to be driven, a power hammer can be used. After the rod is driven in place, connection is made with the ground wire. A bronze clamp is used for connection. The clamp is placed over the ground rod and end the round wire end.
The sectional grounding rods are also used. The section are threaded at each end. The usual section length is 8, 10 or 12ft. The installation procedure of sectional ground rods is as follows. The coupling and driving stud are screwed on the top end of the sectional rod. The assembly is then driven until the coupling on the rod reaches the ground level, and then driving stud is removed coupling. Another coupling is screwed onto the top end of the second sectional rod and then driving stud is screwed into the second coupling. And finally, the driving is now continued until the second section reaches ground level.

Plate Earthing:
The plate is also used for electrode. The electrode plate is installed below water level. The plate should be installed in vertical position and completely surrounded by a bed of at least 1ft of charcoal mixed with lime, salt, charcoal, chalk power etc. This mixture increases the size of plate and also maintains moisture surrounded by the plate. The electrode plate is buried at least 1ft below of the water level. If we use double earthing, then the distance both two plates in 20 to 30ft.
In Pakistan two types of earthing plates are commonly used. A copper  plate, which is 2 feet in length and fraction width, the thickness of copper plate, is 1/8 inch (600*600*3). The other plate which is used for electrode is iron made. The thickness of this plate is 6mm. The Plate is connected to a G.I pipe of 12.7mm diameter for pouring water around the plate. The earth wire is either bolted or welded to plate and is taken out along with G.I pipe.

Strip Earthing:
A copper strip (25mm*1.6mm) and (25mm*4mm)in case of G.I are buried horizontally in trenches of sufficient depth (8m or higher). This type of earthing is most suitable for places having rocky soil.