function Gyreactive(p)

global DAE

if ~p.n, return, end

DAE.J21(p.bus,:) = 0;
DAE.J22(p.bus,:) = 0;
DAE.J12(:,p.bus) = 0;
DAE.J22(:,p.bus) = 0;
DAE.J22(p.bus,p.bus) = DAE.J22(p.bus,p.bus) + speye(p.n);