Shadowing Practice: 17E058 - Back to Back Stations - Learn English Speaking with Video
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119 משפטים
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Hello everyone, I am Monika.
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I am here to present back -to -back stations.
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Let's see.
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What is back -to -back?
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Generally, in electronics and power electronics, if two bipolar components are connected in series with opposite polarity, then this pair is known as back -to -back system.
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As same as in electrical, rectifiers and inverters are identical
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and connected in series is known as back -to -back system from this diagram here rectifier
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and the inverter are connected in series via a hvdc link
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and it is also a hvdc back -to -back link a back -to -back hvdc link the hvdc system
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which transfers energy between two ac buses at the same location is called as back -to -back system
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or an hvdc coupling system in other words the converters
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and rectifiers are installed and operates on high voltage DC in the same stations.
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Hence there is no DC transmission line.
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So it reduces the overall conversion cost and improve the reliability of the DC system.
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Such type of system is designed for bipolar operation.
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This picture shows the bipolar link of a back -to -back link.
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A bipolar link has two conductors.
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One is positive and the other one is negative.
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This link has two converter stations at each end.
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The midpoint of the converter station is connected to the air through the electrodes.
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Next, we are going to see about the construction of back -to -back HPDC link.
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The main components are converter station, converter unit, converter vaults, converter transformer,
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filters, high frequency filter, reactive power source, smoothening reactors and then system port.
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What do you mean by converter walls?
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There are two types of converter walls.
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One is the sending end converter and then receiving end converter.
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The sending end converter act as a rectifier which converts AC into DC.
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The receiving end converter act as a inverter which converts DC into AC.
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What are converter transformers?
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These are transformers
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which are used before the rectification of ac in the hvdc system filters filters may be ac
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or dc what is the use of high frequency filters these
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are provided to suppress the high frequency currents what do you mean by smoothening reactors smoothening reactors are those
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which is used on the dc side to smoothen the dc current as well as the production purposes
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This shows the simple block diagram of back -to -back HPDC link.
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From the system 1, AC current is converted into DC by means of rectifier
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and current DC is supplied via DC link
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and it is converted back again to AC by means of inverter and then distributed to the different grids.
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It shows the simple block diagram.
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Working principle of back -to -back link.
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Two independent neighboring transmission systems with incompatible electrical parameters such as frequency
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or voltage level or short -circuit power level are connected via a DC link.
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The basic principle operation of HPDC linking system is based on the conversion of AC to DC
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and vice versa by means of converter volts power from two
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or more system is first converted into dc by means of power rectifier system
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and then summed up after summing of the resultant power is
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again converted into ac with the help of power inverter
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and then supplied to different grids the process involved in here is simple only by theoretical
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but in practical it is very much complex as it involves high voltages
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and power semiconductor devices what are the needs for back -to -back stations we all know
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that high voltage ac is used to transmit the electrical power for reducing power transmission losses
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in a transmission system different grids are interconnected but sometime it might happen
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that one or more grids or power systems may not be in synchronization with other grids
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or there exist a weak link between different power systems due
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to various factors to overcome these problems hvdc back -to -back system is created it also can be used
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when two asynchronous ac system need to be interconnected for a bulk power transmission
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and also for the stabilization processes these are the some examples of back -to -back stations mcnell hvdc back -to -back station,
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HVDC back -to -back link commissioned between India and Bangladesh, Chandrapur HVDC back -to -back station, Vaisak back -to -back station, Windyashal back -to -back station.
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We will see them one by one in the following slides.
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McNeil HVDC Back -to -Back Station A back -to -back station
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is a series of HVDC interconnectors between the unsynchronized eastern and western AC systems of United States and Canada.
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It connects the power grids of Canadian provinces at Alberta and Saskatchewan.
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The station was built by Geck -Alstom,
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was commissioned in 1989, with the power capacity about 150 megawatt at a DC voltage of 42 kilovolt.
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This picture shows the back -to -back station at Alberta.
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Mechanical station was notable for operating with low short -circuit ratio.
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What do you mean by short -circuit ratio?
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Short -circuit ratio is a measure of how strong or weak the connected AC system is.
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Most of the HVDC schemes uses line commutated converters with SCR about 3,
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but McNeill's scheme was designed to operate with an effective SCR which is even less than 1 .0 on the SASCAT7 side.
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So hence it was the only SCR with the lowest value
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ever achieved with the line commutated hvdc converter it is also
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considered as the first hvdc station to use three phase four winding converter transformer the transformer
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which are connected at the 138 glow volt at alberta side
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and 230 glow volt on the saskatchi one side the number of poles used in this link is about only one Next,
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we are going to see about Indo -Bangladesh link, a SVDC back -to -back link commissioned between India and Bangladesh.
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This Indo -Bangladesh link was commissioned by Siemens.
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Here, two back -to -back links are installed.
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The block one is in operation since 2013 with a capacity of 500 megawatts.
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Siemens recently announced that in June 2020, it fully commissioned the second block of hvdc back -to -back
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line in barhamara at bangladesh to connect the electricity supply network to india
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and bangladesh with the transmission capacity of 500 megawatts hence a total capacity is up to 1000 megawatt
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which is the highest reliable power capacity in bangladesh Siemens is a world leader in HVDC technology,
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which has installed more than 55 projects worldwide with an overall capacity of 94 GW.
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This picture shows the back -to -back stations at Biramara at Bangladesh.
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This is the map which shows the back -to -back HVDC link between India and Bangladesh.
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Here, from Biramara, at the western border of Bangladesh,
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a 230 kV grid of the country will be connected via substation and OH lines to India's 400 kV grid,
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which is located at Baharampur.
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Next, we are going to see about Chandrapur back -to -back HVDC station.
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It is a back -to -back HVDC connection between western and southern regions in India located close to the city of Chandrapur.
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Its main purpose is to export power from the Chandrapur Super Thermal Power Station to the southern regions of Indian National Grid.
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This picture shows the power station at Chandrapur.
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It was owned by Power Grid Corporation of India and the installer for the substation is Gek Alstom and commissioned in 1997.
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7 with a power capacity of 500 megawatts at a dc
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voltage of 205 kilo volt at each pole next we are
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going to see about why is a back -to -back hvdc
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station why is a back -to -back hvdc station is a back -to -back hvdc station connection between the eastern
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and southern regions in india located close to the city of Viswagapatnam in the state of Andhra Pradesh.
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It was owned by Power Grid Corporation of India.
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It has two substations namely VISAG -1
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and VISAG -2 commissioned in 1999 by Alstom
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and the latter in 2005 by ABB
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which has a power capacity of 500 megawatts
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and a DC voltage of 205 kilovolt at ysac 1 and 176 kilovolt at ysac 2.
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It consists of two independent poles.
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The station is no longer required for its original purpose of linking eastern and southern grids,
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although it can be still used as an embedded power flow device to help control power flow within the AC system.
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Next, we can see recent developments.
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Power Grid Corporation of India has chosen Siemens to upgrade India's oldest HVDC link,
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which is the India's oldest HPDC link.
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Any guess, Vintiachal back -to -back HPDC link is the India's oldest link.
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And Siemens has been chosen by Power Grid of India to modernize it.
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Next, we can see some of the advantages of back -to -back HPDC link.
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Power can be upgraded to desired frequency then two asynchronous systems can be joined successfully without loss of stability
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stability of the system is increased as well as power flow can be maintained within the limits
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more active power can be added where the ac system is
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already at the limit of short circuit capability then it also
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helps in the stabilization of weak ac signals weak ac links thank you
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אוצר מילים והערות הגייה לשיעור הזה
שיעור הדיבור הזה ברמה C2 מבוסס על הסרטון “17E058 - Back to Back Stations”. המילים שחוזרות הכי הרבה: link, station, hvdc, converter, grid. בסרטון הזה יש 119 משפטים ו-1512 מילים לתרגול Shadowing. הדיבור נמשך 11:21. הדובר שומר על קצב יציב של כ-133 מילים בדקה, קצב נוח לתרגול Shadowing. רק 76% מהמילים נמצאות בין 3,000 המילים הנפוצות ביותר באנגלית, כך שאוצר המילים מאתגר.
אוצר מילים מרכזי בסרטון הזה
11 המילים המתקדמות ביותר בסרטון, עם ההגייה והמשמעות שלהן:
| מילה | הגייה | משמעות |
|---|---|---|
| voltage שם עצם | /ˈvəʊltɪd͡ʒ/ | מֶתַח, ווֹלטָג׳ |
| transformer שם עצם | /tɹænsˈfoɹməɹ/ | שַׁנַּאי, טְרַנְסְפוֹרְמָטוֹר |
| volt שם עצם | /vəʊlt/ | ווֹלְט |
| reactor שם עצם | /ɹiˈæktɚ/ | כּוּר |
| diagram שם עצם | /ˈdaɪ.ə.ɡɹæm/ | תַּרְשִׁים |
| electrode שם עצם | /əˈlɛk.tɹəʊd/ | אֶלֶקְטְרוֹדָה |
| kilogram שם עצם | /ˈkɪləɡɹæm/ | קִילוֹגְרָם |
| semiconductor שם עצם | /ˌsɛmikənˈdʌktə/ | מוֹלִיךְ לְמֶחֱצָה |
| distribute פועל | /dɪˈstɹɪbjuːt/ | חילק |
| conductor שם עצם | /kənˈdʌktɚ/ | מְנַצֵּחַ, מנצחת |
| vault שם עצם | /vɑlt/ | כִּיפָּה |
דקדוק בסרטון הזה
המבנים שהדובר משתמש בהם הכי הרבה, עם המילים המדויקות מהסרטון:
| מבנה | בסרטון |
|---|---|
| סביל (Passive voice) be + past participle — הדגש הוא על מה שקורה, לא על מי שעושה את הפעולה | are connected · is known · is called |
| הווה מושלם (Present perfect) have/has + past participle — פעולה שקרתה בעבר ועדיין יש לה חשיבות או השפעה עכשיו | has installed · has chosen · has been chosen |
הגייה ששווה לשים לב אליה
- הצלילים של “th”: smoothen /ˈsmuːðən/, theoretical /ˌθi.əˈɹɛt.ɪ.kəl/
- הצלילים של “sh” ו-“zh”: substation /sʌbˈsteɪʃən/, stabilization /ˌsteɪ.bəl.ɪzˈeɪ.ʃən/, rectification /ˌɹɛktɪfɪˈkeɪʃən/
- מילים ארוכות — שימו לב להטעמה: asynchronous /eɪˈsɪŋ.kɹə.nəs/, interconnect /ˌɪn.tə.kəˈnɛkt/, stabilization /ˌsteɪ.bəl.ɪzˈeɪ.ʃən/, incompatible /ˌɪŋkəmˈpætɪbəl/, polarity /pəˈlæɹɪti/
צלילים שדוברי עברית מתקשים בהם:
- /æ/ — פתוח יותר מה-“אֶ” העברית, לא כמו “a” ב-“cup”: transformer /tɹænsˈfoɹməɹ/, reactor /ɹiˈæktɚ/, diagram /ˈdaɪ.ə.ɡɹæm/, incompatible /ˌɪŋkəmˈpætɪbəl/, kilogram /ˈkɪləɡɹæm/
- /r/ — הלשון לא נוגעת בשום מקום, לא ה-“ר” הגרונית: converter /kənˈvɜɹtɜɹ/, rectifier /ˈɹɛktɪfaɪɚ/, transformer /tɹænsˈfoɹməɹ/, reactor /ɹiˈæktɚ/, diagram /ˈdaɪ.ə.ɡɹæm/
- עיצור קולי בסוף מילה — /b/, /d/, /g/, /z/, /v/ בלי להפוך אותם לאטומים: voltage /ˈvəʊltɪd͡ʒ/, electrode /əˈlɛk.tɹəʊd/, modernize /ˈmɑdɚnaɪz/, reactive /ɹiːˈæktɪv/, provinces /ˈpɹɔv.ɪns.ɪz/
איך לתרגל עם הסרטון הזה
- הקשיבו לכל הסרטון פעם אחת בלי לדבר, ורשמו את המילים שאתם לא מכירים.
- תרגלו Shadowing משפט אחר משפט במהירות רגילה, וחזרו על כל משפט עד שהקצב שלכם תואם את הדובר.
- הקליטו את עצמכם והשוו למקור, תוך תשומת לב למילים כמו voltage, transformer, volt.
מהי טכניקת השאדואינג?
שאדואינג היא טכניקת למידת שפה מבוססת מדע שפותחה במקור להכשרת מתורגמנים מקצועיים ופופולרית על ידי הפוליגלוט ד"ר אלכסנדר ארגואלס. השיטה פשוטה אך עוצמתית: אתה מקשיב לאודיו באנגלית ילידית וחוזר עליו בקול רם מיד — כמו צל העוקב אחרי הדובר עם עיכוב של 1–2 שניות בלבד. בניגוד להאזנה פסיבית או תרגילי דקדוק, שאדואינג מכריח את המוח והשרירים בפה לעבד ולשחזר דפוסי דיבור אמיתיים בו זמנית. מחקרים מראים שזה משפר משמעותית את דיוק ההגייה, האינטונציה, הקצב, הדיבור המחובר, הבנת השמיעה ושטף הדיבור — מה שהופך אותו לאחת השיטות היעילות ביותר להכנה לIELTS Speaking ולתקשורת באנגלית בעולם האמיתי.