Description
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3.2 Upgrading of regulators and control systems
For the upgrade of the regulator, the original excitation control system cabinet structure is retained, and the entire system is upgraded by upgrading the board card.
Among them, the CoB main board, MUB measurement board, F10 input and output board, and LCP local control panel were replaced with the PEC800 controller,
CCM measurement control interface board, CIo comprehensive input and output board, and ECT excitation system control terminal in the Unitrol6800 system respectively.
For the upgrade of the power cabinet, since the power of the excitation system will not change during the transformation, the N-1 redundant configuration of the five
UNL3300 rectifier bridges in the original system has not been changed, but the control and measurement parts of the rectifier
bridge have been upgraded. And the fan circuit and power control part of the rectifier bridge have been upgraded. Among them, the signal interface board (PsI) was
changed to the rectifier bridge signal interface board (CsI), the circuit breaker of the rectifier bridge panel was changed from CDP to CCP, and the rectifier bridge control
interface board (CIN) was changed to the rectifier bridge control board (CCI).
For the upgrade of the demagnetization cabinet, the switch control part was mainly upgraded. By adding a CIo board to the switch cabinet and installing a special
power distributor and relay to control the demagnetization switch, the original PsI board was removed. Secondly, in the transformation of the current detection part,
the Hall element in the Unitrol5000 system was replaced by the current relay of the Unitrol6800 system.
For the upgrade of the excitation current measurement part, the rectifier side Hall element of the rectifier bridge was replaced with an AC side CT. Relying on the linearity of the
CT, the current sharing coefficient of the excitation system was increased to 0.98, so that the role of the rectifier bridge can be fully exerted in the system. .
For the upgrade of the fan power supply circuit of the rectifier cabinet, each power cabinet can independently control the power supply of the fans in the
cabinet to avoid the problem that if the power circuit relay fails in the original system, all the fans will not work.
3.3Unitrol6800 functional logic configuration points
The Unitrol6800 system adds PT slow-blow judgment logic, and defines the actions of PT slow-blow as alarm and channel switching. The system PT
slow-blow logic pressure difference is 2% to ensure sufficient sensitivity. Since some external reasons will cause the sequential increase or decrease of magnetic
commands, a special increase or decrease magnetic contact adhesion judgment logic has been added to effectively lock out external causes. At the same
time, it can
avoid the jitter of the relay on the increase or decrease magnetic circuit and ensure the stability of the circuit. The excitation temperature detection is used to
alarm in the system, but it cannot control the system tripping. The tripping intermediate relays K291 and K292 use high-power (≥5w) relays to avoid
the problem of tripping of the excitation system
due to signal interference.
4 Problems discovered during the transformation and their solutions
After upgrading the excitation system from Unitrol5000 to Unitrol6800, since the partition between the regulator cabinets of the original excitation switch
cabinet was removed and the mounting backplate of the regulator was moved forward, the hot air from the excitation switch cabinet will enter the excitation regulator
cabinet, causing the cabinet to be damaged. The internal temperature rises, and sometimes the temperature can even reach 45°C. In order to avoid problems caused
by high temperatures, partitions were added to reduce the temperature inside the switch cabinet and control the
temperature to 30°C.
During the maintenance process, if the grounding carbon brush of the generator is removed, it is easy to cause the rotor grounding relay isoLR275 to
malfunction. Therefore, during maintenance, the power supply of the grounding relay will be disconnected and the large shaft in the magnetic cabinet will be short-circuited.
5 Conclusion
Through the transformation of the excitation system, our company not only meets the needs of increasing the generator capacity, but also
eliminates the safety hazards of ARCnet failure or flat cable damage in the excitation system of the unit. It can find the fault point during maintenance
and prevent the unit from non-stop. event. The new board used in the new excitation system has modular characteristics, which can make online maintenance more
convenient, and because the boards use trigger pulse generation communication and optical fiber redundant communication, the stability of
information transmission is ensured. Avoid communication failures and damage to pulse lines.
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