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In the paper G. Gross et al. (see ibid., vol.17, no.2, p.283-9, May 2002) the analysis on the reactive support cost is addressed to specify the so-called "dominant component" of variable cost. It is the opportunity cost consequent to the obligation given by the ISO to the producer to curtail part of the real power production (revenue losses) when the generator hits the capability limits in order to satisfy additional reactive power requirements. The authors put in evidence the dominant position of the ISO in posting decision consequent to his definition of the system operating security constraints. Our comments are related to the role of the ISO in the voltage and reactive power control and to the computational tools it can employ for the definition of a nondiscriminatory reactive support.