外文翻譯--變壓器的類型及結(jié)構(gòu)(文件)
【正文】 時過流繼電器通過電流整定使它們作為負(fù)載母線或負(fù)載設(shè)備故障的后備保護(hù)。要達(dá)到這個目的，我們可在斷路器 B 和 D 上裝設(shè)方向繼電器，該方向繼電器的聯(lián)接應(yīng)保證只有當(dāng)通過它們的電流方向?yàn)殡x開母線時才起動。我們觀察通過斷路器 B 或 D 的電流方向是隨故障點(diǎn)發(fā)生在哪一條線路上變化的。例如，故障點(diǎn)在靠近斷路器 D 的線路端， D 跳閘應(yīng)比 B 快，反之， B 應(yīng)比 D 快。對該系統(tǒng)配置合適的斷路 器后，當(dāng)一回線發(fā)生 故隨時，仍可對負(fù)載供電。在系統(tǒng)發(fā)生故障后，把用戶切換至任一條正常的線路。第二種專門設(shè)計(jì)的變壓器設(shè)計(jì)成為用來提供比一次側(cè) 的電流要小的多的二次側(cè)電流，且使二次側(cè)的電流與一次側(cè)的電流成比例。 第一種專門設(shè)計(jì)的變壓器是用來采樣電壓，并產(chǎn)生一個低的二次電壓，該電壓與所采樣的電壓成正比。在輸電線另一端，將電網(wǎng)電壓降至配電電壓的變壓器稱為降壓變壓器。 在實(shí)際的變壓器中，一次繞組和二次繞組一個在另一個的外面，低壓繞組在最里面。另一類是由三個分支的鋼片疊A C B D G 5 成，繞組繞 在中間的一個分支上。如有第三個繞組，稱之為第三繞組。它由兩個或多個繞 在鐵氧體上的繞組構(gòu)成．通常，繞組之間不直接相連，它們是通過鐵芯內(nèi)部的主磁通相連接的。 the difference between a potential transformer and a power transformer is that the potential transformer is designed to handle only a very small current. The second type of special transformer is a device designed to provide a secondary current much smaller than but directly proportional to its primary current． This device is called a current transformer. The Directional Protection Basis Early attempts to improve powerservice reliability to loads remote from generation led to the dual1ine concept． Of course， it is possible to build two 1ines to a load， and switch the load to whichever line remains energized after a di51urbance． But better service continuity will be available if both lines normally feed the load and only the faulted line is tripped when disturbances occur． shows a sing1egenerator，two1ine,singleload system with breakers properly arranged to supply the load when one line is faulted． For the arrangement to be effective it is necessary to have the proper relay application． Otherwise， the expensive power equipment will not be able to perform as p1anned． Consider the application of instantaneous and/or time delay relays on the four the type of the relay cannot coordinate for a11 1ine faults． For example, a fault on the line terminals of breaker tripping should be faster than B, however , the condition reverses and B should be faster than D. It is evident that the relay protection engineer must find some characteristic other than time delay if relay coordination is to be achieved． 3 The magnitude
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