If a transmission line rated at 400 MVA carries a load of 300 MW and 200 MVAR, is it operating above its rating?

To determine whether the transmission line is operating above its rating, it's essential to analyze both the real power (MW) and reactive power (MVAR) loads and how they combine to create the apparent power (MVA).

The apparent power (S) can be calculated using the formula:

S = √(P² + Q²)

where P is the real power in MW and Q is the reactive power in MVAR.

In this case, we have:

• P = 300 MW

• Q = 200 MVAR

Using the formula:

S = √(300² + 200²)

= √(90000 + 40000)

= √130000

≈ 360.55 MVA

Next, we compare the calculated apparent power (approximately 360.55 MVA) to the transmission line's rating (400 MVA). Since 360.55 MVA is less than 400 MVA, this indicates that the line is operating within its capacity.

Thus, the correct conclusion is that the transmission line is not operating above its rating because its apparent power consumption is below the rated capacity of 400 MVA.