Earthing, also known as grounding, is a fundamental safety measure in electrical systems. It’s a method that connects the neutral points of a system to the earth, providing an alternative path for electrical energy to discharge safely during a fault. This prevents dangerous potential build-ups in exposed conductive materials. A well-designed earthing system has low impedance, which ensures sufficient current can flow through safety devices and disconnect from the supply during a fault. This safeguards both people and electrical devices from electrical hazards and current leakage. In this blog we will understand the the concept of Types of Earthing, focusing on Plate Earthing, Diagram of Plate Earthing, it’s procedure and applications.
Now, let’s delve deeper into the concept of Plate Earthing, one of the types of earthing systems.
What is Plate Earthing?
Plate Earthing is a method where a plate made of galvanized copper or iron is buried vertically at least 3 meters below ground level. This plate connects all conductors to the earth, providing a path for electrical discharge. The Diagram of Plate Earthing typically illustrates this setup, showing the plate’s position in relation to the ground level and the conductors it connects.
The Plate Earthing Diagram also often includes the dimensions of the plate. For instance, a copper plate used in this method typically measures 600mm x 600mm x6.35mm. The plate’s size and material can vary based on specific requirements, but the principle remains the same, to provide a safe path for fault current to the earth.
Plate Earthing Diagram’s Explanation
The diagram of plate earthing shows a plate electrode, which is either made of galvanized iron or steel (with a minimum thickness of 6.3 mm) or copper (with a minimum thickness of 3.15 mm). The plate should be at least 60 cm by 60 cm in size.
The plate is buried in the earth, surrounded by alternating layers of charcoal and salt. The charcoal layer is used to retain moisture, which helps to maintain a low earth resistance.
A galvanized iron strip is connected to the plate and extends above the ground. This strip is used to connect the plate to the electrical system that is being earthed.
A pipe is also shown in the diagram, which is used for watering the earth around the plate. This helps to maintain the moisture levels around the plate, ensuring effective earthing.
Finally, an inspection chamber is built around the earth pit. This chamber allows for regular inspection and maintenance of the earthing system.
Plate Earthing Procedure
The procedure for Plate Earthing involves several steps, often illustrated in a Diagram of Plate Earthing:
- Earth Pit: An earth pit is excavated at a suitable location in the substation, with a minimum size of 900mm x900mm and a depth of 3m below the surface.
- Plate Electrode: A GI plate of minimum size 600mm x600mm and thickness of 6.3 mm is used. If a copper plate is used, a minimum thickness of 3.15mm is required. The plate is surrounded by alternating layers of charcoal and salt.
- Earthing Connection: Galvanized Iron strips are fixed and welded to the plate at two different locations. Loose earthing can adversely affect the electrode system resistivity, so these connections are made strong.
- Water Connection: A pipe is fixed at the top to maintain moist conditions around the earth plate. The pipe is covered with a wire mesh, and water is poured through it. The excavated pit is then filled with stone-free soil.
- Inspection Chamber: A brick chamber is built over the earth pit on a P.C.C layer. The top cover is placed with cast iron hinges to a CI frame.
Other Types of Earthing
Apart from Plate Earthing, there are other types of earthing systems as well. These include Pipe Earthing, Rod Earthing, and Chemical Earthing. Each of these methods has its unique characteristics and applications, but all aim to provide a safe path for electrical discharge.
Pipe Earthing: This involves burying a galvanized steel perforated pipe vertically, connecting all electrical conductors to the ground. The depth of the pipe depends on soil conditions. This is a cost-effective earthing method. Read our blog to know more about Pipe Earthing.
Rod Earthing: Here, a copper rod or galvanized steel hollow section is buried vertically at least 2.5 meters deep. This method reduces the earth’s resistance to the desired value, similar to pipe earthing.
Chemical Earthing: This method involves applying a chemical compound to layers of charcoal and salt, which are then buried. The procedure is similar to pipe earthing. Read our blog to know more about Chemical Earthing.
The choice of earthing type depends on various factors such as safety requirements, equipment maintenance, economic considerations, and the need for supply continuity at different voltage levels.
Standards for Earthing Systems
Earthing systems adhere to various standards, including IS 2309- 1989 (protection against lightning)
IS 3043 (Code of Practice for Earthing)
Indian Electricity Rules 1956
Central Electricity Authority Regulations (CEAR).
These standards ensure the safety and effectiveness of the earthing systems. Also, Megger for testing the resistivity of earth, welding tool kit, excavator for earth pit excavation, copper wires, pipe, coke/ charcoal and salt, PVC wires, cement, bricks, funnel and, wire mesh are the materials used for earthing.
Applications of Plate Earthing
Plate earthing is used in various applications, including telecommunications, power generation, transformer neutral earthing, lightning arrester earthing, and more. It’s a versatile method that can be adapted to different environments and requirements.
In conclusion, electrical earthing is a vital safety measure in electrical systems. It minimizes the danger of electrical current discharge and improves lightning protection systems. Plate earthing, in particular, can prevent static charges and stray current accidents, protecting central communication, electronic, and AC power systems. The Diagram of Plate Earthing provides a clear visual representation of this method, aiding in understanding and implementation.
At AXIS, we test our products following major international standards such as IEC, BS EN, UNE, and UL & IS. We also provide design solutions including proprietary risk assessment software complying with IEC 62305 -2.
This article is part of our series of articles on Lightning Protection, Surge Protection & Earthing, you can read more with the following links:
Introduction to the basics of Lightning Protection and Earthing and the Standards (IEC 62305 and UL 467)
Surge Protection Devices (SPD)
Lightning Protection Zones and their Application to SPD Selection
How does a Lightning Arrester work?
Thank you for reading the blog, Axis is a leading manufacturer and supplier of Electrical Components to over 80+ Countries. Talk to our industry expert and visit our contact us section. You can also watch our videos by our experts – click here.