Excitation Voltage. Excitation system will be wide range stabilized to permit
stable operation down to 25 percent of rated excitation voltage on manual control.
Excitation ceiling voltage on manual control will not be less than 120 percent of rated
exciter voltage when operating with a load resistance equal to the generator field
resistance, and excitation system will be capable of supplying this ceiling voltage for
not less than 1 minute. These criteria, as set for manual control, will permit
operation when on automatic control. Exciter response ratio as defined in ANSI/IEEE
100, Dictionary of Electrical & Electronic Terms, will not be less than 0.50.
Wave Shape. Deviation factor of the open circuit terminal voltage wave will
not exceed 10 percent.
Telephone Influence Factor. The balanced telephone influence factor (TIF) and
the residual component TIF will meet the applicable requirements of ANSI C50.13.
Excitation Systems. Rotating commutator exciters as a source of DC power for
the AC generator field generally have been replaced by silicon diode power rectifier
systems of the static or brushless type.
a) A typical brushless system includes a rotating permanent magnet pilot
exciter with the stator connected through the excitation switchgear to the stationary
field of an AC exciter with rotating armature and a rotating silicon diode rectifier
assembly, which in turn is connected to the rotating field of the generator. This
arrangement eliminates both the commutator and the collector rings. Also, part of the
system is a solid state automatic voltage regulator, a means of manual voltage
regulation, and necessary control devices for mounting on a remote panel. The exciter
rotating parts and the diodes are mounted on the generator shaft; viewing during
operation must utilize a strobe light.
b) A typical static system includes a three-phase excitation potential
transformer, three single-phase current transformers, an excitation cubicle with field
breaker and discharge resistor, one automatic and one manual static thyristor type
voltage regulators, a full wave static rectifier, necessary devices for mounting on a
remote panel, and a collector assembly for connection to the generator field.
Generator Leads and Switchyard
General. The connection of the generating units to the distribution system
can take one of the following patterns:
a) With the common bus system, the generators are all connected to the same
bus with the distribution feeders. If this bus operates at a voltage of 4.16 kV, this