Again, as Es describes a circle while δ varies between 0 and 2π, E2 also describes a circle, as
shown in Figure 10.7. Voltages at any other intermediate points – such as E1 – can be calculated
similarly, using the appropriate k for each location. A somewhat different way of expressing the
same relationships is shown in Figure 10.8.
The apparent impedance seen by a distance relay located at one of the intermediate points (say
at bus 1 in Figure 10.6) is the ratio of the voltage and current at that location. The voltages and
currents produced during a stability swing are balanced. As discussed in Chapter 5, all distance
relays respond to a three-phase fault, or to a balanced condition, in an identical fashion. For example,
the phase and ground distance relays located at bus 1 in Figure 10.6 will see an apparent impedance
Z given by