Explicit current transformers (CTs) are used to measure the currents at power transformers, but these efforts are often saved for the voltage measurements. However, even if there are no dedicated voltage transformers (VTs) attached at the power transformer itself, the voltages at the buses will be measured somewhere. By using Sampled Values, the voltage measurements can be easily delivered to any protection function that requires them. The time synchronised measurements can be simply aligned and processed by the protection algorithms. Transformer differential protection works with Sampled Values just as well as with classical secondary currents. However, with the availability of both the voltages and currents at the transformer, some experiments can be made. Not only Kirchhoff's law for the currents applies, but also the conservation of energy, so the power flow through the transformer must also be balanced. With all the measurements available, the power balance from all terminals is easily observed, vector groups need not be taken into account. In a simulation, the power system quantities are produced as Sampled Values and recorded. Power measurements during the course of power systems faults are compared and the feasibility of such a concept is discussed.