Muri,Earthing 23.07.2024 2 nd group.pptx

Earthing

1. ELECTRICAL EARTHING BY BB NAYAK DATE-26.07.2024

2. INDEX What is grounding Different Type of grounding Earth testing and treatment Safety Earthing System Earthing & Different types Step potential and touch potential Earth Mats Case Study

3. WHAT IS GROUNDING 1. Grounding (in US) or Earthing (in UK) is a process of connecting electrical systems, appliances and metal enclosure to ground. 2. Here, ground refers to the physical connection to Earth which acts as a reference point and also a return path for current. 3. THE MAIN PURPOSE OF GROUNDING IS TO PROVIDE A LOW RESISTANCE PATH FOR ELECTRICITY TO FLOW. We can implement the connection to ground with the help of a grounding electrode. This way, we can keep all the non-current-carrying conductors such as metal frame/housing of a computer, washer, drier, electric drill etc. at 0V potential.

4. What is Grounding ? Grounding is the process of connecting a conductor or an electrical device to the earth, effectively providing a safe and stable path for excess electricity to escape. What is Earthing ? Earthing is the process of connecting some specific areas of an electric power system with the earth through low resistance wire for safety purposes .  

5. Parameter Grounding Earthing Definition It protects the entire power system from malfunctioning. It protects human life from electrocuted. Types It is of three types such as Solid, Resistance, and Reactance grounding. It is of five types such as Pipe, Plate, Rod earthing, tap earthing, and strip earthing. Location It is placed between the neutral of the equipment and ground. It is placed between the equipment body and earth and kept under the earth’s surface. Potential It does not possess any zero potential. It contains zero potential. Example It is in use as a neutral generator and power transformer and connected to the ground. It is in use in transformer, generator, and motor for connecting to the earth. Applications Grounding provides the return path to the current. It is mainly in use for unbalancing when the electric system overloads. Earthing discharges the electrical energy to the earth. It is mainly in use to avoid shocking the humans.

6. RELATION BETWEEN ELECTRICITY & EARTH 1. Earth behaves as a vast reservoir or electricity & is at zero potential * All unwanted/unsafe electric energy can be guided to Earth. 2. COMPOSITION OF EARTH

7. WHAT IS THE DIFFERENCE BETWEEN EARTHING AND GROUNDING? Earthing: Earthing can simply be defined as the process of protecting against unwarranted spikes and bouts of electricity that can cause damage to life and property. Therefore it is important to remember these key differences between the two. One needs to understand that they both are referring to the same process. Grounding: Grounding is similar to Earthing, which achieves insulation against accidental currents. The main live wire is connected to a power supply to power an appliance. However, the other portion of the wire is led under the earth. This is done in case of an accidental cut in the circuit to avoid overloading and other dangerous side effects.

8. What are step and touch potentials? * When a fault occurs or lightning strikes the grid, an individual that touches a substation instrument creates a touch potential, and an individual walking in the substation creates a step potential. * Both touch potential and step potential are important considerations in electrical safety and are addressed through proper grounding techniques and equipment design to minimize the risk of electric shock to individuals.

9. STEP POTENTIAL: Voltage between the feet of a person When current is flowing from the tower to the earth ground, the ground potential rises at the tower and a voltage gradient will occur based on the resistivity of the soil, resulting in a potential difference between two points on the ground. This is called a Step Potential as it can cause voltage between a person’s feet. TOUCH POTENTIAL: Voltage between energized object and feet of a person If the ground connection between the tower and the soil is high resistance (common with some soil conditions), the tower itself (and any conductive item touching the tower) can be energized. Touch potential is the voltage between the energized object and the feet of a person in contact with the object.

10. Touch Potential Touch potential is a potential difference between the fingers of a raising hand touching the faulted structure and the feet of the person standing on substation floor. The person should not get a shock even if the ground structure is carrying fault current, i.e.; the touch potential should be very small. Step Potential Step potential is the potential difference between the feet of a person standing on the floor of the substation,  with 0.5 m spacing between the one step, during the flow of fault current through the ground system.

11. How To Avoid Step and Touch Potential Touch Potential : To avoid touch potential, never touch anyone or anything that may be in contact with a source of electricity. If you do, you will become a victim, as well. Wait until the electricity is turned off before attempting a rescue. Step Potential : To avoid step potential near an energized, grounded object, shuffle away with small movements, keeping your feet close together and on the ground at all times. Keeping your feet together ensures that the voltage remains the same between them, minimizing the electrical potential.

12. Transfer Potential Definition : The term transferred earth potential refers to the voltage-to-earth of grounding systems that will appear on conductors as a result of the source system grounding electrode being above normal earth potential.  The larger voltages are usually developed by ground fault currents returning to their source through earth. A common example is a ground fault of a conductor, which is supplying a substation transformer primary, to the station ground grid that is used for grounding of the transformer secondary neutral.  If this grounding grid is not connected to the high-voltage source system ground, there can be a significant voltage rise above earth as the fault current flows into the earth.  

13. Neutral Grounding Factor The grounding factor is the rise ratio of the values ​​of the phase-to-ground voltages of the healthy phases in the ground fault case to the phase-to-ground voltage in faultless condition. In the isolated network, we had shown that the voltage of the healthy phase is raised stationary to 1.73 times the value before an earth fault occurs.

14. EARTHING Reference Standard I:S 3043-2018 IEC-62305(2007)

15. 1. Relation Between Electricity & Earth Earth behaves as a vast reservoir or electricity & is at zero potential * All unwanted/unsafe electric energy can be guided to Earth. 1. What is earthing ? * Earthing is a critical aspect of electrical installation. It provides a safe path for the dissipation of fault currents to earth reducing risk of electric shock protecting equipment from damage. * Guiding unbalance current through neutral to earth in a 3 phase star system To protect i ) People ii) Equipment iii) Stability of electrical system .

16. Earth Resistance Testing and Treatment Three-Terminal Method (Fall of Potential Method) This method is the most commonly used for measuring earth resistance and is based on the IEEE 81-2012 standard. It’s suitable for transmission line structures and calculates earth resistance using Ohm’s law. The fall of potential method is reliable and especially suitable for large grounding systems.

17. Four-Point Method (Wenner Method ) For Measurement of Soil Resistivity Similar to the fall of potential method, the Wenner method utilizes four electrodes driven into the ground along a straight line at equal intervals. The current flowing into the earth produces an electric field proportional to its density and the resistivity of the soil, providing an efficient measure of earth resistance. Soil Treatment 1.Maintain the moisture content of the earth: Regularly water the earthing point to maintain soil resistivity. 2.Increase the contact area of the electrode: You can maintain earth resistance by increasing the thickness or surface area of the rod used for earthing. 3 .Increase the depth of the electrode: Earth resistance can be reduced by placing the earth electrode at a greater depth. 4 .Use of an earthing compound: The application of compounds like salt, coal, marconite , and bentonite can help maintain soil resistivity.

18. 3. Key objective of earthing Safety: (Human Safety) * Human safety --- Earthing provide low resistance path for fault current to earth. *Fault current flow through earthing system instead of passing through a person or equipment *Minimize risk of shock or damage to equipment *Important in construction site, Industrial plant etc.

19. B. Voltage stabilization : *It is important for voltage stabilization where there is fluctuation in power supply By providing low resistance path to ground ,earthing helps to limit voltage transient , over voltage that can cause damage to electric and electronic equipment C. Lightening Protection : *Lightening strikes can cause significant damage to building & electrical system By providing a path of lighting current to flow to earth, it protects electrical system & building D. Corrosion protection: *Prevents corrosion in metal structure & pipes. When metal structure are not properly earthed they can develop stray currents that can cause corrosion & damage to metal. Earthing helps to prevent build up of stray currents and risk of corrosion

20. E. Signal reference: *In electrical circuit a common reference point is required for signals to be properly transmitted and received By providing a common ground reference by earthing. It helps to ensure that signal are transmitted correctly

21. F. Electro-magnetic compatibility *In electrical system, when electrical equipment is not properly grounded it can cause electro-magnetic interference ,that can disrupt the operation of other electrical equipment in that area. *Earthing helps to reduce electro magnetic interference.

22. 4. IMPORTANCE OF EARTHING *Protection against electrical shock . A. Equipment protection *Protects equipments from damage caused by fault currents B. Reduced risk of fire *Providing a path for lightening and fault current to earth reduces risk of fire. C. Improved Power quality *It helps to maintain stable voltage level reduce electro magnetic interference (EMI) and improves over all quality distribution system.

23. Different Types of Earthing

24. A. Pipe Earthing: Pipe earthing involves running a metal rod into the ground, usually at least 3 meters deep, and connecting it to your electrical system with an electrical conductor. Although pipe earthing is quite commonly used earthing system, it has many  disadvantages. Corrosion Leads to Poor Electrical Conductivity:  One of the most serious concern in this type of earthing system is that the pipes can corrode over time, leading to a decrease in their electrical conductivity. This can result in problems ranging from erratic circuit operation to an increased risk of electric shock hazards. Stray Current:  In addition, depending on the surface and soil surrounding the pipe, there may be an increased risk of stray current contamination. In cold weather climates, ice can block the pipe, which reduces its effectiveness and can potentially lead to system failures. Maintenance:  Lastly, pipe earthing may require frequent maintenance due to displacement caused by seasonal changes in ground levels which could increase costs over time.

25. B. Plate Earthing: Plate earthing is an earthing system where a metallic plate usually made of copper or galvanized steel is distanced at 3 meters from the earth and horizontally placed in the ground pit.The scale is connected to the earth electrode of the electrical installation. While plate earthing is a popular choice for grounding systems, it has many  disadvantages . Limited Effectiveness:  Plate earthing may not be effective in areas with high soil resistivity. In such cases, a deep-earth grounding system may be required to provide a low-impedance path to Earth. Large Surface Area:  Plate earthing requires excavating a large soil surface area to install the metal plate. This can be problematic in urban areas where space is limited. Environmental Impact:  The excavation of soil for plate earthing can have a negative impact on the environment, as it disturbs the natural vegetation and can cause erosion. Maintenance:  While plate earthing requires minimal maintenance, it can become ineffective if the metal plate becomes corrupted or damaged. Regular inspection of the grounding system is required to ensure it is functioning properly.

26. C. Chemical Earthing Chemical earthing is a method of grounding electrical systems using chemical compounds that have the ability to conduct electricity. The chemical compounds, which are usually in liquid form, are poured into the ground around the grounding system to create a low-resistance connection to the earth. This method is typically used in areas where the soil is not conductive enough to provide the necessary grounding for electrical systems. The chemical earthing system has several  disadvantages  which one must consider before opting for it. Environmental impact:  The chemicals used in chemical earthing, such as copper sulfate, are potentially harmful to the environment. These chemicals leech into the soil causing pollution to soil and underwater bodies. Maintenance cost:  Chemical earthing requires periodic maintenance to ensure its effectiveness. The cost of maintenance can add up over time and can be a major disadvantage compared to other types of earthing systems that require zero maintenance .

27. Soil conditions:  Chemical earthing is less effective in certain types of soil, such as rocky or sandy soil, which may make it unsuitable for some locations. Corrosion:  Chemical earthing may lead to corrosion of the earthing system and the associated infrastructure over time due to the chemical reactions that occur. Conclusion: The best electrical earthing system to use will depend on the specific requirements of your electrical installation, soil conditions at the site, budget constraints, and any local regulations or standards that need to be followed. It is recommended to consult with a qualified electrical engineer or an earthing expert to assess your specific needs and determine the most suitable earthing system for your application.

28. PIPE EARTHING

29. DIFFERENT TYPES OF EARTH ELECTRODE Definition:- The conductor buried in ground to make connections to the mass & the earth is called earth electrode. Types of Earth Electrode 1. Rod Electrode a) GI Rod Earth Electrode b)Copper Rod Electrode c)Copper Bonded Rod Electrode 2. Pipe Electrode 3. Plate Electrode

30. COPPER BONDED EARTH ELECTRODE

31. *The process of transferring an unintended electrical energy directly to the earth through a low resistance wire is called electrical earthing. *It refers to the connection of a noncurrent-carrying part of the equipment or neutral of supply system to the ground, which represents the zero potential. *The leakage current chooses the simple low resistance path to flow. *Thus, the electrical system and equipment are protected from damage. Safety Earthing

32. *System grounding refers to the limit of the defined values the voltage has to the ground in every part of the electrical system. *It connects the current-carrying point of the electrical system to the ground, i.e., the neutral of transformers and rotating equipment as well as lines. System Earthing

33. Solid Earthing A power system is said to be effectively grounded or solidly grounded when the neutral of a generator, power transformer or grounding transformer are directly connected to the ground through a conductor of negligible resistance and reactance.

34. The resistance of the earth electrode to the current flow into the earth is known as earth resistance. The resistance between the earth and the earthing plate is measured through a potential fall method. Numerically, it is equivalent to the ratio of the earth electrode potential to the current disappeared by it. 2. Resistance Earthing

35. Peterson coil is an iron core reactor connected between transformer neutral and ground. It is used for limiting the capacitance earth fault current which is flowing when the line ground fault occurs in the line. The coil is provided with the tapping so that it can be adjusted with the capacitance of the system. 3. Peterson coil Earthing

36. EARTH MAT *It is a network of conductor buried beneath the ground inter connecting the metallic non-current carrying parts of equipments and structures. *These system provide a electrical connection to earth *Earth mat is formed by joining, number of rods in vertical and horizontal direction. *It is largely used where large fault current to be experienced. *It is a type of electrical grounding system. *It is a closely placed bare conductors iron or copper forming like net or mesh inter connected with each other by wielding.

37. Lightening Arrester                                 DEFINITION - A Lightning Arrester is an Electrical Device to protect Electrical System/ Equipment from Transient Over voltage caused by Lightening Strikes . Over voltage is detrimental to Power distribution , Electrical equipments, Electronic  devices. Importance of  Lightening Arrester-    It is a first line of Defense  against Lightening induced Over vol tage

38. WORKING PRINCIPLE   1- Voltage Response Characteristics Metal Oxide  Arrestors Exhibit non-linear voltage characteristics At very high voltage , Metal oxide offer a very low Resistance  path to Ground But under normal voltage they offer very high Resistance path to ground.                     EARTHING  OF LIGHTENING ARRESTER Earthing System -                       1- Air Termination Net work                       2- Down conductor                       3- Earth pit with Earth Electrode

39. Recommended Values of Earth Resistance 1) Earth Resistance of Power Station 0.5 ohms (2) Earth Resistance of EHT Sub-station 1.0 ohms (3) Earth Resistance of 33 KV Stations 2.0 ohms (4) Earth Resistance of D/t Structure 5.0 ohms (5) Tower Foot Resistance 10.0 ohms IEEE standard 142-2007 IS 2309: 1989, Cl 12.3.1 Page 32 and BS 7430:1998