Earthing. PRESENTATION BY: Farid Momminzadah Droni Guha

Transcription

1 Earthing PRESENTATION BY: Farid Momminzadah Droni Guha

2 آرتی چیست What Is Earthing The process of connecting metallic bodies of all the electrical apparatus and equipment to huge mass of earth by a wire having negligible resistance is called Earthing. پروسه که زمین انتقال تمام بدنه های فلزی تجهیزات ارت میشود تا لیکیج برق به بدنه فلزی داده شده سبب حفاظت جان کارکنان و تجهیزات شود آن را آرتی میگوید. به

3 Provide an alternative path for the fault current to flow so that it will not endanger the user تهیه مصیر احتیاطی به خاطر جریان عارضه و بیخطر ساختن برای استفاده کننده ها Ensure that all exposed conductive parts do not reach a dangerous potential مطمعن بودن ازقطعات هادی که در محدوده خطر واقع نشوند Maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the appliances or equipment. نگه داشتن سطح ولتاژ در مقدار نومینال آن به خاطر جلوگیری از اضافه جریانی و لتاژ های اضافه که سبب تخریب وسایل میشود.

4 Purposes of Grounding Grounding system has three main purposes: Overvoltage protection Lightning, line surges or unintentional contact with higher voltage lines can cause dangerously high voltages to the electrical distribution system wires. Grounding provides an alternative path around the electrical system of your home or workplace minimizes damage from such occurrences. Voltage stabilization There are many sources of electricity. Every transformer can be considered a separate source. If there were not a common reference point for all these voltage sources it would be extremely difficult to calculate their relationships to each other. Current path in order to facilitate the operation of over current devices مقصد آرت یا گروند کردن حفاظت اضافه ولتاژی از اثر الماسک,جرقه ها ویا سهوآ تماس لین های ولتاژ بلند باعث ولتاژ اضافه در سیستم های توزیعی یا وایرنگ میگردد.سیستم گروند یک مسیر مصنوی جریان را بوجود آورده این خطرات را کاهش میدهد ثابت ساختن سظح ولتاژ هرگاه چندین منبع برق داشته باشیم طورکه هرترانسفارمر درآن جداگانه کار کند.هرگاه ما یک ریفرنس مشترک نداشته باشیم نمیتوانیم یا بسیار مشکل خواهد بودتا ارتیاطاط آنرا محاسبه نمایم.زمین یگانه هادی مشترک میباشد. مصیر جریان به خاطر عمل کردن وسایل اضاف جریانی عرگاه یک عرضه واقع شده باعث تماس جریان به بدنه وسیله میکند.چون بدنه به آرت وصل است کمک میکند تا وسایل اضافه جریان زودترعمل کرده باعث قطع جریان گردد.

5 Qualities Of Good Earthing 1. Material of electrodes and earth wire. 2. Size of electrode and earth wire. 3. Temperature of the soil. 4. Moisture of the soil. 5. Depth to which it is embedded. 6. Quantity of coal and charcoal مواد الکترود و وایر آرتی اندازه الکترود و سایز وایر درجه حرارت خاک رطوبت خاک عمق نقطه که نصب میگردد مفدار إغال و چونه in the earth electrode pit. 7. مقاومت آن پایینتر از محدوده آن باشد 7. Must be of low electrical resistance مقاوم دربرابر کروژن )شریده گی,خورنده گی (باشد.8 9. توانایی داشته باشد تا جریان اعظمی عارضه را.8 Must be of good corrosion resistance همیشه از خود عبور دهد. 9. Must be able to dissipate high fault current repeatedly

6 Type of Earthing There are three different main earthing arrangements explained in international standard IEC : T : Direct Connection to the Earth N : Direct Connection to the Neutral I :No Connection to the Earth کنکشن مستقیم در نقطه نقطه آرت کنکشن مستقیم در نقطه نیترال کنکشن نکردن در نقطه آرتی T N I

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14 Methods of Conventional Earthing روش های معمولی سیستم آرتی 1. Plate Earthing 2. Pipe Earthing 3. Rod Earthing 4. Strip Earthing آرت صفحه یی پیپ آرتی راد آرتی آرتی تسمه یی

15 Plate Earthing In this type of earthing plate either of copper or of G.I. is buried into the ground at a depth of not less than 3 meter from the ground level. The earth plate is embedded in alternative layer of coke and salts for a minimum thickness of about 15cm. The earth wire(copper wire for copper plate earthing and G.I. wire for G.I. plate earthing) is securely bolted to an earth plate with the help of bolt nut and washer made of copper, in case of copper plate earthing and of G.I. in case of G.I. plate earthing. درین نوع آرتینگ از صفحه مسی ویا آهن گلونایز شده استفاده میشود.طور که آنرا در یک عمق مناسب که کمتر از 3 متر نباشد صفحه متذکره با یک قشر ذغال ونمک طور که ضخامت آن از 15 سانتی متر کمتر نباشد استفاده شود وایر آرتی توسط نت و بولت مسی در صورت صفحه مسی ودر صورت گلونایز از نت و بولت گونایز استفاده شود.

16 PLATE EARTHING

17 Pipe earthing Pipe earthing is best form of earthing and it is cheap also in this system of earthing a GI pipe of 38 mm dia and 2meters length is embedded vertically in ground to work as earth electrod but the depth depend upon the soil conditions, there is no hard and fast rule for this. The earth wire are fastened to the top section of the pipe with nut and bolts. The pit area arround the GI pipe filled with salt and coal mixture for improving the soil conditions and efficiency of the earthing system. It can take heavy leakage current for the same electrode size in comparison to plate earthing. The earth wire connection with GI pipes being above the ground level can be checked for carrying out continuity test as and when desired, while in plate earthing it is difficult. In summmer season to have an effective earthing three or four bucket of water is put through the funnel for better continuity of earthing. آرتی پیپ نیز یکی از انواع آرتی میباشد که به قیمت بسیار کم تهیه میشود درین سیستم از پیپ با قطر 38 ملی متر و طول 2 متر استفاده میشود.. وایر آرتی توسط نت و بولت وصل میشود. اطراف پیپ توسط نمک و ذغال پر شود. پیپ میتواند عین جریان که از صفحه مسی عبور میکند از خود عبور دهد کنکشن آن در سطح زمین صورت میگیرد درتابستان ها زمان که زمین خشک میشود باید به آن آب عالوه شود.

18 PIPE EARTHING

19 Earthing Electrode The resistance of a ground electrode has 3 basic components: A) The resistance of the ground electrode itself and the connections to the electrode. B) The contact resistance of the surrounding earth to the electrode. C) The resistance of the surrounding body of earth around the ground Electrode. It consist of three basic components: 1. Earth Wire 2. Connector 3. Electrode واریر آرتی کلمپ یا بست راد آرتی.1.2.3

20 STRIP OR WIRE EARTHING In this system of earthing strip electrod of cross section not less than 25mm into 1.6mm of copper or 25mm * 4mm of GI or steel are burried in horizontal trenches of minimum depth of 0.5m If round conductor are used their cross sectional area shall not be smaller than three if copper is used and 6mm2 if GI or steel is used. The length of burried conductor shall be sufficient to give the required earth resistance (about 0.5Ωto 1.5Ω) It shall however be not less than 15 m The electrod shall be as widely distributed as possible in a single straight or circular trenches radiating from a point This type of earthing is used in rockey soil earth bed because at such places excavation work for plate earthing is difficult درین نوع آرتی تنها از پطره آرت طور استفاده میشود که مقطع آن 25mm X 1.5mm

21 Standard Pipe & Plate Type Earthing Design for the 15 Kv. System Equipments, Distribution Transformer Centers, L.T. Distribution System Equipments Design Details : 1. Earthing Pit : Size 1000 X 1000 X 1800 mm Depth.M.S. / C.I. Plate : 500 X 500 X 8 mm Thick. 2. Electrode Assembly : 40 mm Ø GI / CI Perforated pipe duly fitted or welded with base plate and 50 X 6 mm flat termination taken on top for equipment earthing as shown in drawing.

22 Standard Pipe & Plate Type Earthing Design for the 15 Kv. System Equipments, Distribution Transformer Centers, L.T. Distribution System Equipments 4. Mixture - I : Homogeneous mixture of black soft soil 0.3 CMT. approx. 5. Mixture - II : Homogeneous mixture of common salt 25 Kgs. + wood charcoal pieces 25 Kgs. + Black soft soil 1 CMT. Approx. 6. Crushed Rock pieces Gravel Size 50 X 35 mm 0.1 CMT. Approx. 7. Arrangement for earthing lead terminations from equipment body, and connection for main earthing Grid.

23 Typical arrangement for Pipe electrode earthing pit (Bore Type) Design Details : mm thick RCC Cover mm Ø 6000 mm deep (Approx. 20 ft.) bore in the earth mm Ø 6000 mm long (Approx 20 ft.) G.I. pipe electrode. Forged at the top up to 75 mm length and 12 mm hole provided for taking earthing connection. 4. A homogeneous mixture of 50 kgs. wooden coal pieces + 50 kgs. common salt 5. Water pouring purpose at the time of routine maintenance

24 How to Measure soil Resistivity اندازه گیری مقاومت خاک

25 Soil Resistivity S. NO. Type of Soil Resistivity in Ω c.m. 1. Morshy ground Ω c.m. 2. Clay Ω c.m. 3. Brick clay Ω c.m. 4. Chalk ,000 Ω c.m. 5. Sand ,000 Ω c.m. 6. Sandy gravel 30,000-50,000 Ω c.m. 7. Rocky mountain area 50,000-1,00,000 Ω c.m.

26 How to Measure the earthing Resistance اندازه گیری مقاومت آرتی

27 Max. Value of Earth Resistance to be achieved Equipment to be Earthed Large Power Stations 0.5 Major Substations 1.0 Small Substations 2.0 Factories Substations 1.0 Lattice Steel Tower 3.0 Industrial Machine and Equipment Max. Value of Earth Resistance to be achieved in Ohms 0.5 * The Earth Resistance depends upon the moisture content in the soil.

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