**Steady State Frequency Deviation Calculation**

To calculate the steady state frequency deviation, we need to consider the change in load and the corresponding change in frequency.

**Given Data:**
- Total load = 2000 MW
- Load variation: 3% for every 1.5% change in frequency

**Step 1: Calculate Load Change**
First, we need to determine the load change caused by the tripped load of 250 MW. Since the total load is 2000 MW, the load change can be calculated as follows:

Load change = Tripped load / Total load = 250 MW / 2000 MW = 0.125 or 12.5%

**Step 2: Calculate Frequency Change**
Next, we calculate the corresponding change in frequency using the load variation per unit frequency change. Given that the load variation is 3% for every 1.5% change in frequency, we can set up a proportion:

Load change / Frequency change = Load variation / Frequency variation

Substituting the values we have:
0.125 / Frequency change = 3% / 1.5%

Now, we can solve for the frequency change:

Frequency change = (0.125 * 1.5%) / 3% = 0.0625% or 0.000625

**Step 3: Calculate Frequency Deviation**
Finally, we can calculate the steady state frequency deviation using the frequency change. The steady state frequency deviation is the difference between the nominal frequency (50 Hz) and the new frequency after the load trip.

Steady state frequency deviation = Nominal frequency - Frequency change

Steady state frequency deviation = 50 Hz - 0.000625% = 50 Hz - (50 Hz * 0.000625) = 50 Hz - 0.03125 Hz = 49.96875 Hz

Therefore, the steady state frequency deviation after the 250 MW load trip is approximately 49.96875 Hz.