Apparent Impedance Swing Circle

This page plots the apparent impedance seen at the machine terminals as the internal machine angle δ changes with respect to the system equivalent.

One-line diagram

Source Magnitudes

|E|, internal machine voltage (pu).
|V|, system voltage reference (pu).

Impedance Base

Z_base — R-X plot scaling. Impedances entered in pu; plot axes in pu × Z_base.

Generator Impedance Z_G

R_G: X_G:

GSU Impedance Z_T

R_T: X_T:

System Equivalent Z_S

R_S: X_S:

Initial Angle

Initial angle of E in degrees.

Direction of δ Deviation

Increasing (generator accelerating)
Decreasing (generator decelerating)

Plot PRC-026-2 Lens Full Shape

Include Z_app at GSU high-side

Show equal EMF line

Scale (top figure only)

COMTRADE Export (terminal 3ϕ V/I)

Swing Rate (deg/sec):

# of Swings:

Voltage Format: Wye Delta

Nominal Frequency: 60 Hz 50 Hz

Initial Conditions (pu)

V_T (terminal voltage)	=	—
I (current into system)	=	—
Z_app (app Z)	=	—
S = V_T x I*	=	—

Apparent impedance swing circle

Impedance Summary (@ machine terminal)