A generator synchronization panel is dedicated to the synchronous grid connection of generators or busbars with the power system.
It monitors the voltage, frequency and phase of the power system, the incoming generator and the busbar. Meanwhile, it can adjust parameters in automatic, manual and semi-automatic modes, so that all parameters between the incoming side and the operating system become identical or within the allowable deviation range, realizing fast and reliable grid connection.
What is a Generator Synchronization Panel?
Most generators adopted are synchronous generators. For a synchronous generator to be connected and operated in parallel with the power grid, the following conditions must be met:
The generator voltage shall be equal in magnitude and identical in phase to the grid voltage;
The generator frequency shall be the same as the grid frequency;
The phase sequence of the generator shall be consistent with that of the power grid.
Minor deviations are permissible for the first two conditions, while the third must be strictly satisfied. Before grid connection, the generator forms an independent power system separate from the external distribution network. Synchronization is required prior to parallel operation, mainly considering three deviations: voltage difference, phase difference and frequency difference. The ideal synchronization point has zero deviation for all three parameters, which is practically unattainable. Therefore, grid connection permission is issued as long as the voltage, phase and frequency deviations are within allowable limits, enabling safe and reliable paralleling of the generator set.
The smaller the deviations, the lower the inrush current and system reactive power demand, as well as the less impact on the external power grid. The generator synchronization panel functions to implement and control the whole synchronization process.
Composition of Generator Synchronization Panel
The panel consists of CPU module, analog module, LCD touch screen, quasi-synchronization controller, manual synchronization device, synchro-check relay, three-phase voltage transmitter meter, synchronous voltmeter, synchronous frequency meter, cabinet body and other switching components.
Features of Generator Synchronization Panel
It integrates automatic and manual quasi-synchronization control functions. The automatic quasi-synchronization operation is simple and precise.
By pressing the Auto Quasi-Synchronization start button, the device automatically compares the voltage and frequency of the line side and the generator side. It automatically adjusts the thyristor excitation system and turbine digital electro-hydraulic governing system to match the voltage and frequency between the two sides. When the phase difference also meets the setting requirement, the automatic quasi-synchronization device sends a closing command instantly, and the generator outlet breaker parallels with the power grid immediately.
The panel features simple operation and high accuracy. The manual quasi-synchronization serves as the backup mode; it can be used for grid connection when the automatic device fails, ensuring continuous normal power production.
The panel supports synchronization for multiple circuits. Multi-circuit parallel synchronization can be realized simply by switching the selector switch on the operation panel.
Reserved interfaces for thyristor excitation panel and digital electro-hydraulic governor are all led to terminal blocks for easy connection. It can realize linkage control of the excitation system and electro-hydraulic governing system on the synchronization panel, including tripping the de-excitation switch, regulating generator terminal voltage (or reactive power), and adjusting turbine speed (or generator active power). It displays frequency and voltage of both the generator side and system side, as well as excitation current and excitation voltage.
It outputs standard 4–20 mA industrial analog signals to the integrated control system of hydropower stations, facilitating HMI configuration and parameter monitoring, mainly including excitation current, excitation voltage and other key signals.
The cabinet is made of 2 mm thick aluminum-zinc coated steel plate, featuring corrosion resistance and long service life.
For convenient operation and commissioning, the synchronization panel is usually installed side by side with the generator protection panel, unit LCU panel and common LCU panel in the central control room.
Precautions for Operation of Synchronization Panel
All signal circuits and external wiring terminals connected to the synchronization panel must be carefully checked repeatedly to ensure correct operation and prevent major accidents caused by asynchronous paralleling.
Before synchronization testing, the PT signals introduced into the panel must be verified with a phase sequence meter to ensure consistent phase sequence between the generator side and the system side.
Push the generator circuit breaker to the test position, then conduct automatic and manual synchronization tests. Before testing, the normally open contact signal of the circuit breaker must be temporarily disconnected from the DEH system; otherwise, turbine speed runaway may occur instantly upon grid connection.
Only after the test verifies correct performance can the generator circuit breaker be switched to the working position, and the breaker normally open contact signal be reconnected to DEH for actual formal synchronous grid connection.
