battery chargers, etc. If the load taken off the tertiary is large enough to upset the transformer
differential, it must be connected into the differential CTs, as shown in Figure 8.20. Protection of
the 13.8 kV leads presents other problems that are discussed in Chapter 7. The difficulty arises first
from the very large phase-to-phase fault currents that are present and then from the fact that this
is an ungrounded circuit and must use a ground detector scheme as discussed in section 7.2.