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Chapter 1 Equipment Overview GEH-6632 EX2100 User’s Guide
System Overview
The exciter is a flexible modular system that can be assembled to provide a range of
available output currents and several levels of system redundancy. These options
include power from a potential, compound, or auxiliary source. Single or multiple
bridges, warm backup bridges, and simplex or redundant controls are available. An
overview of the turbine generator excitation s ystem is shown in Figure 1-1.
Power for the exciter is drawn from a power potential transformer connected to the
generator terminals, or from an excitation transformer connected to an auxiliary bus.
Generator line current and stator output voltage are the primary feedbacks to the
exciter, and dc voltage and current is the controlled output to the exciter field.
The architecture supports Ethernet LAN (Unit Data Highway) communication with
other GE equipment including the GE Control System Toolbox (toolbox) for
configuration, the turbine control, the LCI Static Starter, and the HMI (operator
interface).
Figure 1-2 is a simplified one line diagram of the exciter showing the power source,
generator current and voltage measureme nts, control module, power conversion
module (PCM), and protection circuits. In the potential source system, the secondary
of the PPT is connected to the input of a 3-phase full-wave inverting thyristor bridge.
The inverting bridge provides both posi tive and negative forcing voltage for
optimum performance. Negative forcing provides fast response for load rejection and
de-excitation.
Either simplex or redundant
control is available.
Excitation control results from phase controlling the output of the SCR bridge
circuit. The SCR firing signals are generated by digital regulators in the controller.
In the redundant control option (Figure 1-2), either M1 or M2 can be the active
master control, while C monitors both to determine which should be the active and
which the standby controller. Dual independent firing circuits and automatic tracking
is used to ensure a smooth transfer to the standby controller.