【正文】 ting MMF (NsIs) creates a separate flux, apart from the flux φ0 produced by I0, which links the secondary winding only. This flux does no link with the primary winding and is therefore not a mutual flux. In addition, the load current that flows through the primary winding creates a flux that links with the primary winding only。 thus the induced quantities Ep and Es vary as a sine function. The average value of the induced voltage given by Eavg = turns c h a n g e in flu x in a g iv e n tim eg iv e n tim e （ 32） which is Faraday’s law applied to a finite time interval. It follows that 河南理工大學畢業(yè)設計（論文）說明書 V Eavg = N 21/(2 )mf? = 4fNφm （ 33） which N is the number of turns on the winding. Form ac circuit theory, the effective or rootmeansquare (rms) voltage for a sine wave is times the average voltage。 in phase behind the primary voltage VP. It is this ponent that sets up the flux in the core。 There are nine drawings total, in which four are prepared by hand, others are prepared by puter in which installed the software electrical AutoCAD. From other view, it also can be classified as first part and second part. This is a design of substation for graduation design test. It can strengthen our specified knowledge. Keywords: substation； transformer； Relay protection 河南理工大學畢業(yè)設計（論文）說明書 III TRANSFORMER 1. INTRODUCTION The highvoltage transmission was need for the case electrical power is to be provided at considerable distance from a generating station. At some point this high voltage must be reduced, because ultimately is must supply a load. The transformer makes it possible for various parts of a power system to operate at different voltage levels. In this paper we discuss power transformer principles and applications. 2. TOWWINDING TRANSFORMERS A transformer in its simplest form consists of two stationary coils coupled by a mutual magic flux. The coils are said to be mutually coupled because they link a mon flux. In power applications, laminated steel core transformers (to which this paper is restricted) are used. Transformers are efficient because the rotational losses normally associated with rotating machine are absent, so relatively little power is lost when transforming power from one voltage level to another. Typical efficiencies are in the range 92 to 99%, the higher values applying to the larger power transformers. The current flowing in the coil connected to the ac source is called the primary winding or simply the primary. It sets up the flux φ in the core, which varies periodically both in magnitude and direction. The flux links the second coil, called the secondary winding or simply secondary. The flux is changing。通過本次設計，使我對電氣工程及其自動化專業(yè)的主干課程有一個較為全面，系統(tǒng)的掌握，增強了理論聯(lián)系實際的能力，提高了工程意識，鍛煉了我獨立分析和解決電力工程設計問題的能力，為未來的實際工作奠定了必要的基礎。母線保護和所用變保護設計。 說明書和計算書包括整體概述 。電氣設備選擇 。 一次部分由說明書，計算書與電氣工程圖組成，說明書和計算書包括變電所總體分析 。其設計分為電氣一次部分和電氣二次部分設計。短路電流計算 。 二次部分由說明書，計算書與電氣工程圖組成 。電容器的保護整定計算 。 本變電所設計為畢業(yè)設計課題，以鞏固大學所學知識。 Specifications and putation book include following section: General, The evaluation and calculate of line protection, Transformer protection, capacitor protection, Bus protection and Selfusing transformer protection. Computation book, Electrical engineering drawings and catalogue of drawings are attached in the end。. It is readily seen that the current ponent Im= I0sinθ0, called the magizing current, is 90186。 out of phase with the applied voltage. Since no current flows in the secondary winding, Es=Vs. The noload primary current I0 is small, a few percent of fullload current. Thus the voltage in th