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Chapter 4 Electrical connections
4.1 General
Electrical connections are made after the mechanical installation and alignment
procedures. The electrical connections include the connection of main and
auxiliary cables, earthing cables and possible external components. In order to
determine proper actions, see
Annex 3. Main Connection Drawing, Annex 4.
Connection Instructions, Annex 10. Option Connection Drawing
and
Annex 11. Layout of connection.
For optional PMG-unit, see
Annex 9. Permanent
Magnet Regulator (PMG) User's Manual.
NOTE: When making holes or threads through the terminal box, check always
that no components will be damaged. Metal particles can be hazardous
for the electrical components.
4.2 Automatic Voltage Regulator
4.2.1 General
AVR (Automatic Voltage Regulator) is a device that continuously monitors the
voltage at the voltage regulating point of the system and automatically initiates
corrective actions to maintain the terminal voltage of the generator. AVR also
controls that the synchronous generator operates within pre-set limits.
An auxiliary winding supplies the excitation power to the field winding of the
shaft driven by a three phase exciter under the control of the AVR. A voltage
feedback is supplied by the voltage transformer and a current feedback is provided
by the current transformer. The transformers are installed in the generator.
Operational limits, such as over and under excitation, machine voltage and
Volts/Hz, are implemented in the AVR. Static reactive power compensation in
parallel operation and several other software functions are also available. The
AVR is equipped with the PC software for the AVR.
More detailed information about the AVR used in the specific generator can be
found in the AVR manual, see
Annex 6. Automatic Voltage Regulator User’s
Manual
and in
Annex 8. Technical Specification.
4.2.2 Configuration
The voltage regulator with actual value reading and set point formation is active
in the automatic mode. The limiter functions which protect the machine against
excessive loads are also active in the automatic mode. In addition to the actual
voltage regulator function, reactive power or power factor regulators are also
available. Reactive power and power factor regulators can be switched on and off.
NOTE: Reactive power and power factor regulators are not available in island
systems.
In the manual mode the actual value is formed from the measurement of the
excitation current and passed with the set-point value to the excitation current
regulator. The output from the regulator is passed to a switch which is used to
select the corresponding mode. This mode is only used for test purposes and as an
