Question: There is an old 1000kVA transformer with a current load of about 200kW. If approximately 600kW of new load is added, can this transformer handle it?

This question involves understanding the relationship and difference between kVA and kW. kVA is a unit of apparent power, while kW is a unit of active energy. Besides apparent and active power, there is also reactive power, measured in kVA.

The capacity of a transformer is rated in kVA, whereas the power consumption of electrical equipment is rated in kW. The difference lies in the power factor that needs to be considered when calculating the equipment power in kW. This means that a 1000kVA transformer can only output 1000kW of power at a power factor of 1, which is practically unattainable in real applications.

A certain margin must be left in design, typically calculated at 90% utilization for economic and practical reasons. Thus, 1000 × 0.9 = 900kVA. If we use power compensation to improve the power factor to 0.95 or above, then the transformer can output 900 × 0.95 = 855kW of active power.

Note: The power company requires the power factor to be above 0.9, otherwise, there will be penalties. However, the power factor cannot exceed 1, as it would increase the system voltage, affecting normal operation.

The 1000kVA transformer initially supplies 200kW of electrical load in the given scenario. Adding another 600kW of load brings the total active power consumption to 800kW, which is still within the calculated value.

Therefore, the 1000kVA transformer, initially supplying 200kW, can indeed handle an additional 600kW load, as long as we can improve the power factor to the required level. Under these conditions, the transformer can operate safely and reliably for the long term.