Kilovar Supply in Bulk-Power Transmission Systems

The principal results of this study are shown in Figs. 5-7. The data as presented permit a broad range of application as far as system operating voltages are concerned, since circuit kw loading is expressed in per-unit of 2.5 (kv)2, where kv is the actual operating voltage in kv at the sending-end of the transmission line. For reference, 1.0 per-unit circuit kw load for several operating voltages is shown in Table I. Approximate economic kvar transmission limits are shown in each figure as a function of circuit kw loading for several transmission distances as well as fox two different values of transformer impedance, i.e., 10 and 15%. For convenience, optimum kvars are expressed as a ratio of kw load received. Figs. 5, 6, and 7 apply to conductor sizes of 1,272-, 636-, and 266.8-MCM ACSR respectively. Also, Figs. 5(A), 6(A), and 7(A) apply to future design cases where differences in transformer kva, generator reactive capacity, and power and energy loss are evaluated. Data for existing facilities, where only energy and power demand differences are considered, are given in Figs. 5(B), 6(B), and 7(B). Indications of the normal peak-load generator power factors and receiving system load-bus voltages which correspond to the economic kvar transmission limits are also given in Figs. 5-7. It should be clear that the load-bus voltages are expressed in per cent as seen from the highvoltage sending-end bus, and reflect the actual operating turns ratio of the receiving-end step-down transformer.