There are many different types of faults that synchronous generators may experience and,
therefore, many different types of protection. All generators will not have the same level of
protection, however. As a general rule, the larger, more expensive machines will have the
greatest number of different protective systems simply because serious damage of these units
is very costly, both in terms of the repair and also the cost due to the unavailability of the
unit. Nearly all generators will have basic protection against stator short circuits, but not
all generators will have all of the other protective measures described in this chapter. For
example, there are some differences in the protection provided to machines located in attended
stations and those in unattended locations. Generally, those machines in unattended
locations must have protective devices to shut down the unit for precautionary conditions
where an operator might be able to keep the unit on line by changing its operating conditions.