On voltage instability caused by static bifurcation at OLTC node

This paper investigates power system voltage instability in the presence of an on-load tap-changer (OLTC). The sensitivity of load voltage to tap position, dv/dn ( Delta I), is investigated associated with the static bifurcation at the OLTC node. It is shown, through an eigenvalue analysis, that the points I=+or- infinity correspond to the static bifurcation condition which is caused by the dynamics of the load at the bus controlled by the OLTC.