Power Transmission Essays - Electric Power, Electrical Engineering

Power Transmission Essays - Electric Power, Electrical Engineering Power Transmission CHAPTER 1. GRID SYSTEM Power Transmission in a country is usually done through what is known as a Grid System. The Grid System consists of extensive interconnected transmission network supplying the whole country. Its supply from a small no. of very large and highly effective power stations. The basic network is usually 132kHZ. For a very high industrialised nation they use 275,475,800,1250 kV. Most consumers receive supplies from medium voltage distribution system of 3.3kV, 415V, 240V. For heavy industry consumer they may be supplied with 11 or 33kV. The generators produce electrical power at 11kV / 25kV and it is stepped up by using a step- up Transformer (X?mer) to a value of 132kV before it is transmitted. The receiver station will step - down the voltage to a value of 33kV at various distributions centres. Generating station 11kV / 25kV Step up X?mer 25kV / 32kV Sending station. Step down X?mer 132kV / 33kV Receiving station. Step down X?mer 33kV Heavy Industry. Step down X?mer 11kV Light Industry Step down X?mer 3.3kV Substations Step down X?mer 415V/ 240V Consumer fig. 1, Single Line Diagram . THE PURPOSE OF THE GRID SYSTEM. The purpose of the grid system is to maintain a secure supply of electricity at a standard voltage and frequency to consumers throughout the country. Having stated its purpose, we can now list several advantages that have resulted from its introduction: 1. security of supplies; 2. standardisation of frequency and voltages; 3. economy; 4. the ability to transmit very large loads for considerable distance without loss; and 5. the ability to transfer electricity to and from different parts of the country and to step up / down the voltages using X?mers (Transformers). 6. Easy way to convert A.C to D.C but the reverce is expensive FUNCTION OF THE GRID SYSTEM. In order to fill its purpose, The grid system must function in the following way. The National Grid Control Centre in association with the various grid control centres around the country, estimates the load required in different areas each day. This information is then used to arrange to purchase the countries power depending on the demand. In this way stations are used to their maximum efficiency, which in turn reduces the cost of generation. Due to the fact that the system is interconnected, bulk supply points can be fed from other areas, should a failure of the usual supply occur. DISADVANTAGES OF A.C TRANSMISSION:- 1. Skin effect - cable losses. 2. Heavy losses hence efficiency is reduced. 3. For high voltage higher harmonics are produced, hence it interferes with communication lines. SYSTEM LAYOUT OF A GRID. 3- f (PHASE), 4 WIRE SYSTEM . Vph = phase voltage VL = Line Voltage IL = Line Current Iph = Phase Current FOR STAR CONFIGURATION ( Y). VL= 3 Vph IL = Iph OB = 3 . OA 2 OB = OA 3 2 ? OC ? should be twice the value of ? OB ? , Hence OC = 2 x OA 3 2 OC = OA 3 VRY = OA 3 VL = 3 Vph FOR DELTA CONFIGURATION ( ) IL = 3 Iph VL = Vph If 3 loads are identical in every way i.e impedance and phase angle. Then the current in the 3 lines would be identical the resultant current returning down the neutral would therefore be zero. The load in this case is know as a balanced load. In actual practice its hard to find it exactly balanced. Hence the neutral wire is left to carry the leftover current. The advantages of this system compared with both a single phase and 3 phase 6 wire system is like this. Suppose 3 identical loads are to be supplied with 200A each. The 2 lines for a single phase would carry a total of 600A.. This conductor (C.S.A) would only need to be 1/3 that of single phase system but being 6 lines it would still be the 50mA current of conductor material. Hence the conductor saves an increase in the 2nd case where in the 1st case if the proper cable selection is not used overheating of the cable occurs, this will later result in a short circuit. POWER DISSIPATION IN STAR AND DELTA 3 - PHASE CONNECTION. P = VI Pph = Vph.Iph Pph = Vph . Iph [ Cos q] P3 - f = 3 Vph Iph Cosq

Seven Ways to Build Up Your Writing Confidence

Seven Ways to Build Up Your Writing Confidence Seven Ways to Build Up Your Writing Confidence Seven Ways to Build Up Your Writing Confidence By Ali Hale Do you ever worry that your writing isn’t good enough? Maybe you’re scared to let anyone read your latest short story. Or perhaps it’s worse than that – you find yourself agonising over every email that you write. You’re not alone. Most writers – even those who make a living from their craft – lack confidence at times. Writing is, after all, a daunting thing to do: you’re putting down your thoughts on the page and hoping that they’ll be worthy of someone else’s time and attention. A lack of confidence, though, can be crippling. It leads writers to give up before they’ve even begun – or to fret for hours over the simplest of writing tasks. Whether you’re struggling to get to grips with grammar or preparing to launch your third novel, you can become more confident. Here’s how. #1: Practice Writing – Regularly As a child, I had piano lessons. I didn’t much like having to practice – but I knew that if I didn’t, I wouldn’t get any better. It’s the same with writing. Some people love writing, others find it tedious: but either way, you’ll find that the more you practice, the more you’ll improve. That could mean: Spending ten minutes free-writing every morning Working through different writing exercises, so you get experience in several forms Deliberately working on the elements of writing that you find hard (e.g. if you write fiction, practice dialogue or description; if you write for work, practice those difficult emails) Writing a weekly post for your blog – no excuses! Write from a prompt (a word, phrase, question or image that inspires you) Your writing exercises might be for your eyes only – or you might choose to develop them into something more. Author E.J. Newman’s From Dark Places is a book of short stories that started as pieces written from prompts sent in by her â€Å"story of the month club†. #2: Read Widely You’re probably already reading a lot in your chosen genre or area – but try dipping into a book, magazine or blog that’s very different from what you’d normally choose. You’ll come across authors who are: Journalistic and factual, giving you the details without making any judgements about them Extremely personal and introspective, writing based on their own experiences Unconventional and creative with their use of language, perhaps coining new words and so on. There’s no one â€Å"correct† way to write a book, a blog post, or an article – and the more you read, the more you’ll realise that lots of different styles can be effective. You’ll learn new techniques, and you’ll also get a better feel for your own voice and style (look at what resonates with you – and what turns you off completely). #3: Take Time Over Your Writing If you don’t like writing, or if you find it anxiety-provoking, then you might be tempted to get it over with as quickly as possible. That’s not a great way to build your confidence. No writer – not even Shakespeare! – can produce a perfect piece of work in just one draft. By taking a little extra time to edit your work, you’ll realise that you can: Spot clumsy or ambiguous sentences and correct them Change words that aren’t quite right Fix any typos or spelling mistakes that have crept in I often advise writers to write a basic plan then produce a quick first draft, without worrying too much about quality: that way, they don’t get bogged down trying to perfect the first paragraph. After that, though, it’s important to edit rigorously. You’ll feel more confident about your work when you know you’ve given it enough time and attention. #4: Learn About Writing I’ve been writing with serious intent (i.e. hoping to get published!) for thirteen years now – half my lifetime. I’ve read dozens of books and ebooks about writing, I’ve subscribed to a writing magazine, I’ve taken several online courses, and I’ve completed an M.A. in Creative Writing. Obviously, I wouldn’t have progressed very far at all if I didn’t actually write (see #1!) – but I learnt a lot about the theory and practice of writing from all these resources. Whether you’re a brand-new writer or an old hand, there’s something you can learn. Look out for: Blogs on writing (like this one) – a great place to start learning for free. Books about your specific area or genre – try your library Specialised ebooks and ecourses – you might want to start with 100 Writing Mistakes to Avoid Writing conferences where you can attend lectures and workshops Degree programs – a big investment of time and money, but a great way to study writing in a thorough and rigorous way, alongside other students #5: Ask For Feedback This one requires a bit of bravery but it’s a great way to give your writing confidence a real boost. Ask someone for feedback. Ideally, pick a writer or tutor who you know and trust – you want them to be honest but also thoughtful. Get them to tell you what you’re already doing well (because there’ll be plenty of good things in your work!) And ask them what you could improve on. I know it can be quite daunting to have your work critiqued but once you’ve edited a piece based on feedback, you’ll be able to have real confidence in it. #6: Share Your Work With an Audience One great way to boost your confidence is to have appreciative readers for your work. But where do you find them? The Web 2.0 era has made publication accessible to anyone with an internet connection. Sites like Blogger.com are free and extremely easy to get started with, and allow you to publish your writing online. (If you start getting serious about blogging, I’d recommend using WordPress and hosting the blog on your own domain, for maximum control over your work. For all things blogging-related, check out Daily Writing Tips’s sister blog, Daily Blog Tips.) You might even choose to put together an ebook for people to download and read. You can create this using a word processing program (like Open Office or Microsoft Word) and then convert it to a .pdf file, which can be read on any type of computer and on many devices like Tablet computers and ebook readers. #7: Submit Your Work for Publication One of the best ways to achieve publication is to send a guest post to a big blog. This can be a pretty daunting thing to do but it’s a huge confidence boost if you get your post accepted. Follow the tips above and make it as good as you can before sending it in – and make sure you follow any submission guidelines. You might think that you have to already be a big â€Å"name† in the writing or blogging world in order to get published, but this simply isn’t true: editors care about the quality of your writing and the professionalism of your approach. If you’re a fiction writer, try entering competitions – winning a prize, or even being shortlisted, is a great validation of your work. And if you’re aiming to write for magazines as a freelancer, try sending in fillers or letters to the editor – a great first step in making contact and seeing your name in print. Keep Moving Forwards – However You Feel Maybe it seems like other writers have far more confidence than you. You see them chatting away at conferences, or you look at their work on big blogs or you read their prize-winning competition entries and you think if only I was as confident as them. Perhaps you already are. Maybe they spent a week screwing up their courage to send in that competition entry, or they had to take a deep breath and conquer their nerves before striking up a conversation with a stranger at that conference. As you write more (regardless of how you feel) and as you put your work out there in the world, you’ll find that you gradually become more confident and comfortable with your writing. What one step could you take today to help boost your writing confidence? Pick something from the list above – or add your own ideas in the comments! You can find Ali Luke posting all over the blogosphere – but her home base is on her own blog, Aliventures. If you want to get more writing done, check out her post How to Write Thousands of Words Every Single Week and follow the eight simple steps there. Want to improve your English in five minutes a day? Get a subscription and start receiving our writing tips and exercises daily! Keep learning! Browse the Writing Basics category, check our popular posts, or choose a related post below:7 English Grammar Rules You Should KnowDisappointed + PrepositionEbook, eBook, ebook or e-book?