Excitation system type СВТГ-600/250 УХЛ4

Technical characteristics
Basic set of equipment for the excitation system СВТГ-600/250 УХЛ4 (operating and stand-by sets):
1. Dry converter transformer ТСЗП-240: capacity 400kVA, 6.3kV/0.462kV (supplied with sets of built-in voltage and current measuring transformers on the high side and temperature control sensors)
- 1 pce.
2. Excitation system cubicle ШСВ550/570 (two thyristor bridges, each for 550A, 570V; current forcing up to 1100A with the voltage of 570V during 50sec; two sets of microprocessor system of control, regulation and protection - МПСУ)
- 1 pce.
3. Cubicle for switching devices and auxiliary drives ШКАП (contains switching devices, including devices of insulation control system, initial excitation and field suppression) 
- 1 pce.
4. Spare set (SPTA)  - 1 set
5. Set of instruction manuals - 1 set
Generator characteristics provided by the excitation system:
- nominal rotor current - 550A
- nominal excitation voltage - 225V 
Main parameters for the excitation system СВТГ-600/250:
- nominal rectified voltage - 225V
- nominal rectified current - 550A
- voltage in forcing mode (ratio – 2.5) - 570V
- rotor current in forcing mode (ratio – 2.5) - 1100A
- permissible forcing interval - 50 s
- permissible frequency variations,
                   continuously - +2 Hz/-3 Hz
                   short-time (not more than 20s) -  +40Hz/ -10Hz
- operation mode with rotor current of 1,1Inom = 600А - continuous
- operation mode with rotor voltage of 1,1Unom = 250 - continuous
Main characteristics for the rectifying transformer:
- nominal power - 400 kVA
- nominal line voltage of primary winding - 6300 V
- nominal current of primary winding - 33 A
- nominal line voltage of secondary windings - 462 V
- nominal (phase) current of secondary windings - 450 A
- nominal voltage at output of voltage measuring transformers - 100V
- nominal output current of current measuring transformers - 5 A
- temperature control for transformer windings - provided
The excitation system СВТГ-600/250УХЛ4 provides:
  • functioning of operating and stand-by sets in the following modes:
           - stator voltage regulator (АРН);
           - reactive power regulator;
           - excitation current regulator (РТР);
  • initial excitation for no more than 15s from the 220V DC power supply (an accumulator battery) or from 0.4kV auxiliary station buses;
  • no-load operation;
  • automatic adjustment of the generator voltage to the line voltage and connection to line with precise synchronization method;
  • connection to line by self-synchronization method;
  • maintenance of the generator voltage according to the set value while an aggregate is in the network;
  • operation in integrated and isolated power networks with loads from noncutting to nominal within the range of the generator’s power curve and overloads corresponding to the requirements of GOST 5616-89;
  • stable operation in transient and emergency modes (load surge and shedding, short circuit);
  • bumpless transfer from the АРН mode into PT mode, Q regulator and vice versa;
  • bumpless transfer from the operating regulator to the stand-by one;
  • maintenance of the excitation current at the set level with the precision 1% of the set value in the manual mode;
  • excitation forcing with set duration and voltage and current boosting ratio during disturbances in the network causing decrease of voltage at station buses;
  • de-excitation during disturbances in the network causing increase of voltage at station buses;
  • generator reactive power damping to zero value during scheduled generator’s outage;
  • field suppression in case of protection activation resulting in tripout of the filed suppressing device;
  • line disconnection carried out by an operator or automatically, including protection mode activation.
Short description of the excitation system СВТГ-600/250УХЛ4
A simplified structural diagram for the excitation system СВТГ-600/250УХЛ4 is given in the figure below, where:
ТВ – dry type converter transformer with the capacity of 400kVA, 6.3kV/0.462kV; uk≈ 6%, the valveside windings current 450A. The transformer comprises built-in current transformers at phases and voltage transformers for protection and measuring on the high-voltage side. To provide two-level temperature control the transformer is equipped with a set of Pt100 temperature probes and relays to process output signals.
ШКАП – the cubicle comprises input and output switching units that provide connection/disconnection of inputs and outputs of the exciter’s power part to the power source and load in on-line modes, and also switching off in emergency modes (a field suppression breaker – АГП). The cubicle also includes a generator initial excitation system (a ballast resistor can be a separate unit) and an insulation monitor module.
Also the ШКАП cubicle contains the relay part of the СВТГ control system, a set of switching devices for connection of МПСУ modules and other consumers to sources of operating voltages 3х380V, 50Hz and =220V (=110V if required). The cubicle is supplied with corresponding measuring devices and elements for control, adjustment and indication.
ШСВ – the cubicle contains two sets of the excitation system (operational and stand-by sets). Each set comprises cells of the microprocessor control system (МПСУ) and a three-phase thyristor bridge, to the arms of which two parallels “thyristor-fuse-inductive divider” are coupled.
The cubicle ШСВ is supplied with units monitoring burned fuses (thyristors), necessary elements for control, adjustment and indication and a human-machine interface. МПСУ power supplies forming a set of stabilized supply voltages are made in a form of PWM-sources. The PWM-sources operate both from the three-phase line with operating voltage ~380V and from 220V line (=110V if required).
The power part of the cubicle ШСВ is perfomed on powerful thyristors installed in two airshafts each having a separate fan. The main operation mode of the power part of ШСВ cubicle is with natural air-cooling. 
The cubicle ШСВ comprises all necessary measuring devices and elements for control, adjustment and indication.
Excitation control system
Digital control system
Static excitation systems are equipped with a modern modular-type microprocessor control system of our own design that provides high control accuracy (± 0.5%) and fast response.
The control system is built on the basis of custom-designed, high-performance, digital signal processor TMS320 from Texas Instruments.
Local control
A graphic control terminal is standard for excitation systems and is implemented in the form of stationary (fixed) device located at the door of the control section in the cubicle.
The terminal is used for local control and monitoring of parameters. Besides, the terminal can be used to change parameters of the software. Monitoring and control over parameters of the excitation system can be implemented with the help of a personal computer using one of the common industrial Fieldbus protocols.