The Auxiliary Switch is a critical precision component in electrical switchgear, whose core function is to accurately convert the position status of the main contacts into electrical signals. These signals form the foundation for the safe and correct execution of commands in secondary protection, interlocking, and remote monitoring (telemetry) circuits. Therefore, the synchronous accuracy and reliability of signal output are paramount to power grid operation. The assurance of this performance relies heavily on the component source; selecting a certified auxiliary switch supplier is the first critical step in guaranteeing the high quality and manufacturing precision necessary for survival in extreme dynamic environments.
However, in many applications, such as Vacuum Circuit Breakers (VCB) utilizing high-speed operating mechanisms (especially Disc Spring mechanisms), the operation process—spanning only a few tens of milliseconds—generates massive mechanical shock and acceleration. This extreme dynamic environment poses the most severe challenge to the millisecond-level synchronous accuracy of the auxiliary switch, directly impacting the success of protection interlocking. It is against this backdrop of high-speed and high-dynamic operation that analyzing how high-speed operating mechanisms become the source of signal synchronization error, and determining the core design elements required to achieve millisecond-level precision, becomes the primary task for enhancing auxiliary switch reliability.
Criticality of Millisecond Synchronization in Protection Circuits
The signal synchronization accuracy of an auxiliary switch is a crucial indicator for assessing the overall reliability of the switchgear. In power systems, precise synchronous signals are fundamental to enabling the following functions:
-
Protection Interlocking: Ensures that the next level of protection or interlocking operation can only be executed after the main switch is fully open or closed, preventing live operation errors, which is essential for equipment and personnel safety.
-
Condition Monitoring and Diagnostics: Accurate time stamps of closing and opening signals are invaluable data sources for monitoring the mechanical characteristics and diagnosing faults in switchgear, used to analyze contact wear and mechanism performance degradation.
-
Grid Control (SCADA): Provides reliable real-time status to the SCADA/dispatch system, preventing misjudgment by the upper-level system due to signal delay or error, thus ensuring grid stability and operational efficiency.
Design Barriers: Mitigating Dynamic Shock and Jitter in High-Speed Operation
Taking Vacuum Circuit Breakers (VCB), which are widely used in the medium-voltage sector and known for their high speed, as an example, they typically employ high-speed operating mechanisms, such as the exceptionally fast Disc Spring mechanism. The closing and opening actions of this mechanism complete within tens of milliseconds, and its instantaneous high-speed movement is the main source of the “synchronization error” in the auxiliary switch.
The following table summarizes the primary technical challenges posed by high-speed operating mechanisms to the auxiliary switch:
| Mechanism Characteristic | Technical Challenge Analysis | Key Requirements for Auxiliary Switch |
|---|---|---|
| High Acceleration and Shock | The enormous mechanical impulse from the mechanism's operation can cause instantaneous bouncing or chatter of the auxiliary switch contacts, leading to false signals. | High mechanical stability; contact design must be anti-vibration and anti-chatter. |
| Extremely High Operating Speed | A time delay (latency) exists in the mechanical transmission and electrical switching of the auxiliary switch after the main contacts have completed their position change. | Extremely low inertia and transmission clearance to ensure synchronized action. |
| Accumulation of Mechanical Tolerances | Manufacturing and assembly tolerances in the transmission linkages between the mechanism and the auxiliary switch affect the repeatability and precision of the auxiliary switch's operating point. | Precision mechanical coupling design to eliminate transmission backlash (dead zone). |
The challenges posed by the high-speed operating mechanism to the auxiliary switch’s synchronous accuracy are concentrated in three key error mechanisms: Mechanical Inertia, Shock, and Transmission Clearance. The high-speed motion’s mechanical inertia and the cumulative clearance in the transmission chain together lead to Latency in the signal output, meaning the contact switching does not synchronize with the main contact’s position. Simultaneously, the severe shock and vibration generated by the high-speed operation can cause momentary Jitter or bouncing of the auxiliary switch contacts during or immediately after switching. This momentary loss of contact can produce erroneous signal sequences, directly compromising the reliability of the secondary circuit. Furthermore, long-term mechanical tolerances and wear can lead to Drift in the signal’s operating point, causing the signal output to lose its precise repeatability, which is a core issue affecting long-term operational reliability.
Related reading: Auxiliary Switches in Vacuum Circuit Breakers
Achieving Sub-Millisecond Accuracy: Core Design Principles
To achieve millisecond-level signal synchronization in a high-speed operating environment, the design must revolve around three core principles aimed at overcoming the challenges mentioned above:
-
Zero Latency Response: The design objective must be to minimize the time lag (latency) between the main switch’s mechanical movement and the auxiliary contact’s electrical response. This requires the transmission chain to possess extremely low inertia and eliminate all transmission gaps that could cause delay, ensuring signal switching occurs almost simultaneously with the main contact position change.
-
Structural Anti-Vibration and Signal Purity: The overall structure of the auxiliary switch must possess high rigidity and anti-shock capabilities to completely suppress the violent vibrations generated by the high-speed mechanism. The core is to ensure that the contacts do not experience any form of bounce or chatter during the switching moment or in the stable state, providing a stable and pure signal output.
-
Long-Term High Repeatability and Stability: Ensures that the auxiliary switch’s operating point and synchronous accuracy do not drift even after tens of thousands or hundreds of thousands of high-speed mechanism operations. This requires all transmission and contact components to have excellent wear resistance, fatigue resistance, and self-locking stability, guaranteeing the long-term consistency of the signal output.
These three principles collectively form the design paradigm for high-precision auxiliary switches operating under high-speed mechanisms. They are not only the theoretical foundation for overcoming mechanical inertia and shock but also the key requirements for upgrading the auxiliary switch from a traditional mechanical component to a millisecond-level timing sensor, ensuring the absolute reliability of the secondary protection and interlocking circuits.
Conclusion and Outlook
In the contemporary evolution of power switchgear towards higher speeds and greater capacities, the high-speed operating mechanism imposes extremely stringent design requirements on the auxiliary switch’s signal synchronization accuracy. This precise capture of millisecond-level timing is a crucial design element for ensuring the safety of the secondary circuit interlock and preventing operational errors. Therefore, overcoming the challenges posed by high mechanical shock and rapid movement is a rigorous test of precision mechanical engineering design.
High-performance auxiliary switches, by employing zero-clearance transmission and low-inertia designs, effectively compress the action error into the microsecond range, thus becoming the critical data gateway for achieving switchgear digitalization and intelligent diagnostics. Moving forward, the high-precision auxiliary switch will be upgraded from a traditional accessory to an indispensable high-precision timing sensor in the smart grid, continuously empowering grid stability and reliability.
English
Russian