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MCQ
101. The effect of corona is-
increased energy loss
increased reactance
increased inductance
all of above
ব্যাখ্যা: The phenomenon of ionisation of surrounding air around the conductor of transmission line due to which luminous glow with hissing noise is rise is known as the corona effect.
102. The line voltage on the LT side of a distribution transformer is--
400V
230V
11KV
33kV
ব্যাখ্যাঃA LT (Low Tension) line is a low voltage line and ITT (High Tension) line is a high voltage line. In LT supply is of 400 volt for three-phase connection and 230 volt for single-phase connection. High tensione HT supply is applicable for bulk purchase who need 11 kilo-volt (kV).
103. How many electricity distribution utilities are there in Bangladesh?
4
6
5
none
ব্যাখ্যা: বাংলাদেশে বিদ্যুৎ বিতরণকারী প্রতিষ্ঠান হলো ৬টি, যথা- BREB, BPDB, NESCO, WZPDCL, DESCO, DPDC
104. Dhaka Power Distribution Company Limited distributes power to-
Dhaka City and Narayanganj
Dhaka City and Saver
Dhaka City and Tongi
All of the above
105. Corona is observed on--
ac transmission lines only
dc transmission lines only
both a & b
none
ব্যাখ্যা: Corona is observed on AC transmission line only Because in AC transmission line there is focx associated
106. Which of the following statement is true?
at higher voltage cost of transmission is reduced
at higher voltage cost of transmission is increased
at higher voltage efficiency is increased
all of these
ব্যাখ্যা: At higher voltage, volume of conductor is reduced. Area of conductor AI/V Where V. Supply voltage. So that material requirement is reduced and hence cost of the material and transmission reduced.
107. What is to be added in an electric line to increase voltage?
Capacitor
Resistor
Inductor
All
ব্যাখ্যা: Increase the total working voltage of two capacitors by connecting them in series.
108. The distribution transformer is generally connected in--
Delta/Delta
Star/Delta
Star/Star
Delta/Star
ব্যাখ্যা: The distribution transformer is generally connected in deta/star. In secondary side, star connection is required which has neutral point. From this star connection. Voltage is used by consumers.
109. Under the condition of maximum power transfer, the efficiency is --
100%
50%
75%
25%
ব্যাখ্যা: The power efficiency is 50% at maximum power transfer (Other 50% is dissipated at source impedance
110. For a single circuit 3 phase line the inductance per phase per km is of the order of--
1mH
0.2mH
10 mH
0.1 mH
111. When a load of leading pf the full load secondary voltage of a transformer is-its no-
load voltage.
equal to
greater than
less than
ব্যাখ্যা: ফুল-লোড ভোল্টেজ যখন নো-লোড ভোল্টেজ অপেক্ষা বেশি হবে তখন লোডের পাওয়ার ফ্যাক্টর হবে লিডিং এবং ভোল্টেজ রেগুলেশনের ঋণাত্মক মান পাওয়া যাবে।
112. ক্যাবল বা কোরের প্রতি একক দৈর্ঘ্যের রেজিস্ট্যান্স জানা থাকলে যে টেস্ট উপযোগী, তা-
সাবস্টিটিউট টেস্ট
র‍্যাভিয়ার টেস্ট
মারি লুপ টেস্ট
ভারলি লুপ টেস্ট
113. Corona occurs between when they-
two transmission lines are closely-spaced
are widely-spaced
high-potential difference
carry d.c power
ব্যাখ্যা: The phenomenon of ionisation of surrounding air around the conductor due to which luminous glow with hissing noise is rise is known as the corona effect. Corona occurs between two transmission lines when they have high potential difference.
114. The transmission lines generally use-
copper
all aluminium conductor
ACSR conductor
none
ব্যাখ্যা: These cables are formally known as All Aluminium Conductor (AAC). These overhead aluminium conductors are used as power transmission.
115. Which of the connections is best suited for 3-phase 4-wire service?
Δ-Δ
Y-Y
Δ -Y
Δ-Υ
116. As compard to overhead system, the maintenance cost of underground system is--
very high
very low
same
none above
ব্যাখ্যা: As compared to overhead system, the maintenance lost of underground system is very low. In underground system, there is less possibility to occur fault as compared to overhard system. If any fault is occured at a specific place the fault point should be maintained which is low cost.
117. Objectives of power system is/are-
cost of electrical energy per kWh is to be minimum
rated voltage and frequency has to be supplied to the consumers
both a & b
neither a or b
ব্যাখ্যা: (i) Cost of electrical energy per kWh is to be minimum (il) Rated voltage and frequency has to be supplied to the consumers. (iii) Reliable power has to be available. (iv) Effective protection system has to be used for isolating the faulty section and keeping other sections healthy. (v) More stable generators are to be used, so that it should not lose synchronism under faulty condition. (iv) Flexible power has to be available.
118. How many electricity transmission utilities are there in Bangladesh?
4
01
6
65
119. Ferranti effect will not occur in which of the transmission lines?
long transmission line
short transmission line
medium transmission line
all of these
ব্যাখ্যা: Ferranti effect occurs in case of no load or light load condition of medion and long transmission lines due to copacitance effect of the transmission lines. In case of short transmission lines, the cuparitance effect is negligible. Therefore, Jerranti effect will not occur in short transmission lines
120. Advantages of higher transmission voltage is/are-
power transfer capability of the transmission line is increase
transmission line losses are reduced
area of cross section and volume of the conductor is reduced
all of those