A reactor rated at 100 MVAR is operating at 90% voltage. How many MVAR is it absorbing from the system?

To determine how much reactive power (measured in MVAR) a reactor absorbs when operating at a specific voltage level, we need to understand the relationship between the rated capacity of the reactor and the voltage at which it operates.

In this case, the reactor has a rated capacity of 100 MVAR, which is the maximum reactive power it can absorb when operating at its rated voltage (assumed to be 100%). When the reactor operates at a lower voltage, such as 90%, its ability to absorb reactive power diminishes proportionately to the square of the voltage ratio.

To calculate the actual MVAR absorbed, you can apply the formula for reactive power adjustment based on voltage:

1. Calculate the voltage ratio: 90% = 0.9.

2. Square the voltage ratio: 0.9^2 = 0.81.

3. Multiply the rated capacity by this squared voltage ratio to find out the absorbed MVAR:

• 100 MVAR * 0.81 = 81 MVAR.

Thus, at 90% voltage, the reactor absorbs 81 MVAR from the system. This value aligns with choice B.

This approach illustrates how the voltage level impacts the reactive power capacity of equipment