The swing equation is given byWhere δ is electrical power angle; H is per unit inertia constant; Pm is per unit mechanical power; Pe is per unit electrical power and f0 is frequency.

• A. \({P_e} - {P_m} = \frac{{180{f_o}}}{H}\frac{{{d^2}\delta }}{{d{t^2}}}\)
• B. \({P_m} - {P_e} = \frac{H}{{180{f_o}}}\frac{{{d^2}\delta }}{{d{t^2}}}\)
• C. \({P_m} - {P_e} = \frac{{180{f_o}}}{H}\frac{{{d^2}\delta }}{{d{t^2}}}\)
• D. \({P_e} - {P_m} = \frac{H}{{180{f_o}}}\frac{{{d^2}\delta }}{{d{t^2}}}\)