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At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is installed to maintain load pf at 0.9 leading if a compensating element is also connected so that pf changes to 0.9 lagging, the compensating element is
  • a)
    Capacitor of 4.5 MVAR
  • b)
    Inductor of 4.5 MVAR
  • c)
    Capacitor of 7.75 MVAR
  • d)
    Inductor of 7.75 MVAR
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is...
Given information:
- Load power = 8 MW
- Capacitor installed = 4 MVAR
- Power factor (pf) maintained = 0.9 leading

To maintain power factor at 0.9 leading:
To maintain the power factor at 0.9 leading, a capacitor is installed. A capacitor is a reactive power component that supplies reactive power to the system and helps in improving the power factor.

Change in power factor:
The question states that a compensating element is connected to change the power factor to 0.9 lagging. This means that the existing 0.9 leading power factor needs to be converted to 0.9 lagging.

Requirement for compensating element:
A lagging power factor means that the system requires an inductive component to supply reactive power. Therefore, the compensating element should be an inductor.

Determining the value of the compensating element:
To determine the value of the compensating element, we need to calculate the change in reactive power required.

Reactive power calculation:
Reactive power (Q) = Apparent power (S) x sin(θ)
Given:
- Load power (P) = 8 MW
- Power factor (pf) = 0.9 (leading)

Apparent power (S) = P / pf = 8 MW / 0.9 = 8.89 MVA

Reactive power (Q) = S x sin(θ) = 8.89 MVA x sin(arccos(0.9)) = 8.89 MVA x sin(26.57°) = 4 MVAR

Reactive power change:
Since the power factor is changing from 0.9 leading to 0.9 lagging, the change in reactive power is twice the initial reactive power.

Change in reactive power = 2 x 4 MVAR = 8 MVAR

Selection of compensating element:
The compensating element should supply 8 MVAR of reactive power. The correct answer, as mentioned in the question, is an inductor of 7.75 MVAR.

Explanation:
To change the power factor from 0.9 leading to 0.9 lagging, an inductor of 7.75 MVAR needs to be connected as a compensating element. This inductor will supply the required reactive power to the system and help in maintaining the desired power factor.
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Community Answer
At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is...
Previously the substation was working on 0.9 leading.
Given: PL = Load power = 8 MW
QC = 4MVAR
pf = 0.9 leading
Receiving end power = PR = PL = 8 MW
∴ Receiving end reactive power = QR = -8tan [cos-10.9]
QR = -8tan [cos-1(0.9)]MVAR = -3.874MVAR
∴ Load reactive power, QL = QR + QC
Let,the element receives a reactive power of Qx ,
As the element absorbs lagging reactive power so element is an inductor of 7.75 MVAR.
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At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is installed to maintain load pf at 0.9 leading if a compensating element is also connected so that pf changes to 0.9 lagging, the compensating element isa)Capacitor of 4.5 MVARb)Inductor of 4.5 MVARc)Capacitor of 7.75 MVARd)Inductor of 7.75 MVARCorrect answer is option 'D'. Can you explain this answer?
Question Description
At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is installed to maintain load pf at 0.9 leading if a compensating element is also connected so that pf changes to 0.9 lagging, the compensating element isa)Capacitor of 4.5 MVARb)Inductor of 4.5 MVARc)Capacitor of 7.75 MVARd)Inductor of 7.75 MVARCorrect answer is option 'D'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is installed to maintain load pf at 0.9 leading if a compensating element is also connected so that pf changes to 0.9 lagging, the compensating element isa)Capacitor of 4.5 MVARb)Inductor of 4.5 MVARc)Capacitor of 7.75 MVARd)Inductor of 7.75 MVARCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for At an industrial substation with a 8 MW load,a capacitor of 4 MVAR is installed to maintain load pf at 0.9 leading if a compensating element is also connected so that pf changes to 0.9 lagging, the compensating element isa)Capacitor of 4.5 MVARb)Inductor of 4.5 MVARc)Capacitor of 7.75 MVARd)Inductor of 7.75 MVARCorrect answer is option 'D'. Can you explain this answer?.
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