Sunday, 5 April 2015

Before giving the power some tests must be done.

In my previous post, I have discussed about the instruction of wiring. Now, suppose you have made the wiring complete and going to power it up. Stop one second, are all the connections tested?
Before giving the power some tests must be done.
1.   Insulation resistance test
This test is done to know whether there is any leakage in the conductors. There are mainly two types of leakage.
(a)between phase and neutral, (b)between conductors and earth.
For the first part of the test, the main switch should be opened and all electrical appliances removed from the circuit. All controlling switches should be closed. The resistance between phase and the neutral conductors is measured with a 500 volt megger.

 Resistance of each circuit should not be3 less than 10MegaOhm.
For second part of the testing between conductor and earth, all controlling switches should be closed, all lamps put in position, all fuses provided and phase and neutral conductors short circuited at the main switch. The insulation resistance between conductors and earth is then measured. This value should not be less than 5ohm.
2.   Continuity Test
In this test, all the fuses and links are provided and switches closed. All outlets are shorted one by one and continuity checked. The resistance between phase and neutral is measured with a 500v megger at the main switch. the value shouls be nearly zero.
3.   Polarity test
4.   This test is done to ensure that switches are controlling the phase wires and not the neutral wires. One terminal of the megger is connected to the phase and main switch and the other to the terminal of the control switch. the megger in this condition should read zero, otherwise it indicates that the switches are controlling the neutral wire.     
5.   Earth Resistance Test
For this, one terminal of earth tester is connected with the earth to be tested and two other terminals with two earthing  electrodes placed at distances of 22.5m and 45m respectively. the tester is run with constant speed for about a minute. The value of resistance should not be more than 2ohms for good condition.  

Hope you have enjoyed the post . thank you for coming to my blog.
For any enquiry you can contact with me
Whats app- 9641977195 (india)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

Saturday, 4 April 2015

যে ভাবে পাওয়ার এসে পৌছয় আপনার সাধের কম্পিউটার এ

কেমন আছেন সবাই? আজ অনেকদিন পর আবার লিখছি,
বিদ্যুৎ ছাড়া আমাদের এক মুহুত চলে না
দশ মিনিট পাওয়ার কাট হলেই যেন হাপিয়ে  উঠি। কিন্তু কখনো ভেবে দেখি কি এতো পাওয়ার আসে কোথা থেকে? কি ভাবেই বা আসে? আবার মাঝে মাঝেমাঝে ই বা চলে জায় কোথায়? এই সব প্রশ্নের উত্তর নিয়েই আজকের পোস্ট।
ফিজিক্স বলে অনেক পদ্ধতি তেই বিদ্যুৎ শক্তি উতপন্ন করা সম্ভব। কিন্তু তাদের মদ্ধে সবথেকে এফিসিয়েন্ট পদ্ধতি হল তড়িৎ চুম্বকীয় আবেশ এর মাধ্যমে তইরি বিদ্যুৎ। কথায় কিথায় চলে এল জেনারেটর এর কথা। এই যন্ত্র টির মূলনীতি সেই আবেশ।
এটাকে কোনোভাবে ঘোরাতে পারলেই হল।ব্যাস বিদ্যুৎ শক্তি তইরি। এবার সুধু প্লাগ লাগিয়ে সুইচ অন করলেই হল। আপনার পিসি চালু।ব্যাপারটা শুনতে এত সহজ লাগলেও আসলে কিন্তু এত সাদামাটা না।
এখন এই জেনারেটর ঘুরিয়ে বিদ্যুৎ বানানোর জন্য বসে আছে পাওয়ার প্ল্যান্ট। হাত দিয়ে তো আর টারবাইন ঘুরানো সম্ভব না। তাই এরা ব্যবহার করে শক্তির প্রাকৃতিক উতস কে। কেউ ব্যবহার করে কয়লা,কেউ প্রাকৃতিক গ্যাস, কেউ পরমাণু শক্তি। কয়লা থেকে বিদ্যুৎ সবথেকে বেসি প্রচলিত। কয়লা পুড়িয়ে তাপ, সেই তাপ জল কে পরিণত করে বাস্পে, সেই বাস্পের চাপেই ঘোরে টারবাইন এর চাকা। বেশিরভাগ প্লান্ট এ জেনারেটর ভোল্টেজ তইরি করে কিলো ভোল্ট রেঞ্জে।

এইবার ঘটে একটা বিশেষ ঘটনা। থিওরি বলে কোনো পরিবাহীর মধ্যে বিদ্যুৎ অপচয় তার মধ্যে দিয়ে জাওয়া কারেন্টের বরগের সমানুপাতিক।  তার মানে কারেন্ট যত বেশি হবে লশ ও তত বেসি হবে। অপচয় কেইবা করতে চায়? কিন্তু এদিকে প্রয়োজনিয় পাওয়ার তো পাঠাতেই হবে। তা হলে উপায় কি?
আমরা জানি টোটাল পাওয়ার হল ভোল্টেজ আর কারেন্ট এর গুনফল।তাই মোট পাওয়ার ঠিক রাখতে ভোল্টেজ বাড়িয়ে কারেন্ট কমিয়ে দিলেই হয়। হয় তো ভালোকথা, কিন্তু সেটা করা হবে কি ভাবে। এখন দরকার পড়ে ট্রান্সফরমার এর। এটা জেনারেটরে তইরি কিলোভোল্ট কে পরিনত করে কয়েকশো মেগাভোল্টে। এরপর লম্বা ট্রান্সমিশন লাইন ধরে বিদ্যুৎ এর যাত্রা শুরু।
এরপর আসে পাওয়ার গ্রিড। বিভিন্ন প্ল্যান্ট এর সব লাইন গিয়ে জমা হয় এখানে।এখানেই ঠিক হয় কে যাবে কোনদিকে। আবার যাত্রা শুরু।

এরপর গিয়ে থামে আবার সাবস্টেশনে। এখানে আবার বিদ্যুৎ কে মেগাভোল্ট রেঞ্জ থেকে নামিয়ে আনা হয় কিলোভোল্ট এ। এরপর চলে জায় ডিস্ট্রিবিউশন সেকশনে। এখানে প্রয়োজন অনুযায়ী ৪৪০ ভোল্ট এ ভোল্টেজ নামিয়ে আনা হয়। এতদূর অবধি পাওয়ার আসে থ্রি ফেজ সিস্টেমে। ছোটোখাটো কলকারখানা গুলো চলে ৪৪০ ভোল্টে।কিন্তু আমাদের বাড়ির সাপ্লাই হল ২২০ ভোল্ট। ছোট ছোট পোল ট্রান্সফরমার দিয়ে থ্রি ফেজ ৪৪০ ভোল্ট কে নামিয়ে আনা হয় ২২০ ভোল্টে। এর তিনটে ফেজ দিয়ে পাওয়ার সাপ্লাই করা হয় তিনটে এলাকায়। তাই একই ট্রান্সফরমার দিয়ে সাপ্লাই হলেও একটি এলাকায় বিদ্যুৎ থাকলেও অন্যটিতে নাও থাকতে পারে।
 বিদ্যুত তো আপনার বাড়িতে পৌছে গেল।  কিন্তু আপনার পিসি সরাসরি ২২০ ভল্ট এসি  তে চলে না। একটি বিশেষ যন্ত্র যাকে বলে সুইচ মোড পাওয়ার সাপ্লাই।

  ইটা ২২০ ভল্ট কে প্রয়োজন মত ডিসি  ভোল্টেজ এ পরিনত করে।  এখান থেকে ক্যাবল দিয়ে পিসির বিভিন্ন অংশে পাওয়ার সেওয়া হয়।  তাহলে একটা পিসি চালাতে কত পরিশ্রম করতে হয় কত মানুস কে ভাবতেই অবাক লাগে।
পারলে  আসতে পারেন আমার ব্লগ

Friday, 3 April 2015

Make a wiring installation for a small residential building

Make a wiring installation for a small residential building
Hello, friends how are you. Thanks for coming to my blog.
Today , I am going to discuss  how you can prepare estimate for a wiring of a small residential building.  I first did the wiring in my own home. All the connection was very simple. But various type of problems appeared when I switched on the appliances.   A heater or an induction heater draws a larger current from the supply,. As a result a large voltage drop appears in the line. By mistake I connected a light bulb very near to the induction oven. As a result the bulb dims.
So, it is not so easy that you are thinking. For a big building it becomes more complex and complicated. There are several rules to be followed by an electrician according to the Indian standard.
You must carry out these steps during the project first you must study the plan of the building
2.then you calculate the total load for the building
3.make a survey of the building and then decide where you want to install the electrical distribution points
4.calculate all the required specification of the instruments like main switch, conduct pipe, earth wire3, distribution board, conductor sizes etc.
5. then draw the wiring diagram and estimate the material required and it’s cost.

1.make a lay out plan of the building which comprises various types of rooms like offices, lecture rooms, drawing halls, workshops etc. lay out plan of the4 building, a single line circuit diagram will show all the  electrical points. can  use any of the following types of wiring. (a)wood casting wiring. (B)batten wiring, (c)rigid steel wiring, (d) pvc sheathed wiring.
4. make separate two different lines. One is for light fans, and another for high current appliances like pump, heater, motor etc. meters should be place in a easily accessible place.
6. use the circuit breakers of proper value. And place them in human reach. So one can easily exchange it.
7.use colour codes in the connecting wires. For three phase live line should be red , yellow, blue in colour and the neutral should be black.
8.all switches must be installed on live not in neutral.
9.all portable appliances must be earthed using three pin plug.
10. After the main switch, supply should  brought to the distribution boards  for lighting and power circuits separately. Branch distribution boards should be provided with a fuse on the live conductor of each circuit while neutral conductor of each circuit should be connected to a common link capable of being disconnected individually for testing purposes. One spare circuit of adequate capacity should be provided on each branch of the distribution board.

11. lights and fans may be connected in the same circuit. Each sub-circuit should have not more than a total of 10 points including light fans and 5amp socket outlets. The load on each sub-circuit should not be more than 800 watt. If a separate circuit is installed for fans only, the number of fans in the circuit should not exceed 10. In each house at least two lighting sub circuits may be provided so that in case of fault in one sub-circuit the whole house is not plunged into total darkness.
12. if the load on any power sub circuit exceeds 3000watt , the wiring for that sub circuit should be done in consultation authorities.
13. lighting arrangement is a very important thing in house wiring.  The need of illumination is different for different purposes . here I give you a chart which will help you to choose a proper lighting arrangement.
Illumination level in lux
Supply workshop
Table games
Dressing rooms
Dining room
Living room
Play ground
14. always provide a switch at the entrance for lighting purposes.
15. two  way switches should be provided in case of large hall room and stairs.
16. in bedroom locate some switches near the3 bed for lighting and emergency purposes.
17. switches for bathroom must be located outside.
18.3-pin, 5amp socket outlets should be provided for all lights and fans and 15amp socket for power circuit.
19. A voltage drop happens when a electrical equipment is connected to line. This voltage drop must not exceed 3% for general equipment and 5% for power equipment.
The minimum size of aluminium cable is 1.5 sq mm for lighting circuits and 205sq mm for power circuits. For determining the load in amperes, in a particular circuit, distance of load centre from distribution board should be calculated. Size of the conductor can be calculated by the following formula
Size in square mm= (2*K*L*I)/(permissible voltage drop)
K= resistivity in ohm mm^2/m
L= distance of load centre from distribution board.
Value of the K , may be taken 0.03for aluminium and 0.02 for copper conductor.
These are the basic instruction. After installation is over some testing must be done before powering. I will discuss about that in my next post. Keep visiting my blog.
Thank you very much, have a nice day.