To convert a per-unit impedance from "old" to "new" base values, the equation to be used is

(a) \(Z_{\text {p.u.new }}=Z_{\text {p.u.old }}\left(\frac{\mathrm{V}_{\text {baseold }}}{\mathrm{V}_{\text {basenew }}}ight)^{2}\left(\frac{\mathrm{S}_{\text {basenew }}}{\mathrm{S}_{\text {baseold }}}ight)\)

(b) \(Z_{\text {p.u.new }}=Z_{\text {p.u.old }}\left(\frac{\mathrm{V}_{\text {baseold }}}{\mathrm{V}_{\text {basenew }}}ight)^{2}\left(\frac{\mathrm{S}_{\text {basenew }}}{\mathrm{S}_{\text {baseold }}}ight)\)

(c) \(Z_{\text {p.u.new }}=Z_{\text {p.u.old }}\left(\frac{\mathrm{V}_{\text {baseold }}}{V_{\text {basenew }}}ight)^{2}\left(\frac{\mathrm{S}_{\text {baseold }}}{\mathrm{S}_{\text {basenew }}}ight)\)