What is Electrical earthing?
The process of transferring the immediate discharge of the electrical energy directly to the earth by the help of the low resistance wire is known as the electrical earthing. The aim of earthing in electrical installations and circuits is to enhance the safety of the installation by reducing the level of danger inherent to fault currents. Fault currents may be caused by different factors. Therefore, it is very important to design an earthing system according to the installation’s characteristics.
Generally in any earth system (or earth pit) measures are taken to ensure the good conductivity with low earth resistance. For this purpose water/humidity, retaining compounds like salt, charcoal, etc are used in the earth pit along with various metallic parts.
Types of Electrical Earthing
The electrical equipment mainly consists of two non-current carrying parts. These parts are neutral of the system or frame of the electrical equipment. From the earthing of these two non-current carrying parts of the electrical system earthing can be classified into two types.
- Neutral Earthing
- Equipment Earthing.
In neutral earthing, the neutral of the system is directly connected to earth by the help of the GI wire. The neutral earthing is also called the system earthing. Such type of earthing is mostly provided to the system which has star winding. For example, the neutral earthing is provided in the generator, transformer, motor etc.
Such type of earthing is provided to the electrical equipment. The non-current carrying part of the equipment like their metallic frame is connected to the earth by the help of the conducting wire. If any fault occurs in the apparatus, the short-circuit current to pass the earth by the help of a wire. Thus, protect the system from damage.
Earthing at PV Plants
- Involves exposed conductive parts and the live parts of the PV power plant.
- Exposed conductive parts include a metal frame of the PV modules and other parts of the power plant that, even though should be isolated, could have current circulating through them by a fault event (e.g. metal racks and module mounting structures).
- It is important to differentiate between the AC side and the DC side.
- Earthing should be in compliance with IS 3043: Code of practice for earthing.
Common points of earthing in a Solar PV Power Plant
- Solar Inverter
- PV Modules Frames
- Module Mounting Structures
- Combiner Box/Junction Box
- Interconnection Panel Box
- Energy Meter Box
- Lighting arrestors
- Any other AC conductor or electrical enclosure
Earthing equipment specifications
- Multifaceted proactive earthing protection
- Ensure maximum conductivity
- Contains a highly conductive compound (HOC) to protect the main earth electrode in the soil
- High rust resistive, good conductive & Corrosion free
- Least variation in ohmic value
- Large surface area to carry large fault current
- Control Radio Frequency Emissions & Electromagnetic interferences
- Provide stable reference potentials for instrument accuracy.
- Soil Resistivity Improvement Powder compound should be used as it is a conductivity improver, Non-corrosive, absorbing & retaining the moisture and reduces the soil resistivity.
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