The paper presents a power approach for the analysis of the interaction between switched reactors and their supply network with special application for the TCRs. It proves analytically that for a system containing a switched reactor an active power occurs: it "absorbs" active power at the network operating frequency that is fully returned as harmonic active powers, the sum of which represents the overall harmonic losses. The influences of different factors (as the TCR rated VAR, its location or the thyristor conduction angles) on these harmonic active powers are investigated by means of simulation on the IEEE 14 bus-balanced system. For the studies lied on power interactions between the TCR and the supply network the power factor is found irrelevant. On the other hand the displacement factor seems to be more appropriate for such a goal. Finally it is proposed a new quantity, namely the specific power losses of a switched reactor, as the ratio of the total harmonic active power injected in the network by the TCR and its rated reactive. Merely computable based on the displacement factor, it allows to compute the losses price of a switched VAR for specified location and operating condition of the switched element.