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MCQ
4581. 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
4582. 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.
4583. 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).
4584. 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
4585. The most severe unsymmetrical fault is-
single line-to-ground fault
line-to-line fault
double line-to-ground fault
none of the above
ব্যাখ্যা: Symmetrical three phase fault is the most severe kind at the transmission lines, while for faults occurring very close to the generating station or synchronous generator, single line to ground fault is the most severe.
4586. 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
4587. 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.
4588. 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
4589. 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.
4590. A line which connects distributor to substation is called--
service mains
distributor
feeder
infinity
4591. 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।
4592. Dhaka Power Distribution Company Limited distributes power to-
Dhaka City and Narayanganj
Dhaka City and Saver
Dhaka City and Tongi
All of the above
4593. Modern high-voltage lines are designed with a safety factor of about --
1.5
2
3
4
4594. 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.
4595. 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.
4596. The ring main system is used in power distribution because it--
is reliable for continuity of supply
gives better voltages regulation
results in less feeder losses
all of the above
ব্যাখ্যা: There are less voltage fluctuations at consumer terminals. The system is very reliable as each distributor is fed via two feeders. In the event of fault on any section of the feeder, the continuity of supply is maintained
4597. In de transmission, the skin effect is-
large
zero
small
depends on voltage
4598. For a distortionless transmission line --
R/L = G/C
RG=LC
RL= GC
RLGC-0
4599. 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
4600. 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.