Capacitive Load Switching with Trapped Charge Measurement
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Solution Overview
Problem
Existing methods for controlling capacitive loads, such as capacitor banks and uncompensated vacuum lines, face challenges with inrush currents and overvoltages, particularly when using high voltage circuit breakers with excessive natural dispersion and insufficient rate-of-decay of dielectric strength, and struggle to accurately manage trapped charges due to the need for precise voltage synchronization and knowledge of circuit breaker characteristics.
Innovation Solution
A method and device that measure and memorize trapped electrical charges during opening operations of capacitive loads, allowing for synchronized opening and closing maneuvers based on detected zero crossings with constant voltage slope, enabling controlled arc durations and optimized closing operations to minimize inrush currents and overvoltages, even with circuit breakers having excessive natural dispersion and insufficient RDDS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If zero crossing synchronization is used for closing capacitive loads, then inrush current is reduced, but precise knowledge of circuit breaker characteristics and high RDDS are required
Solution Approach 1:
The patent measures and memorizes the trapped charge value at the capacitive load during opening operations before the closing operation. This preliminary measurement allows the closing operation to be optimized based on actual trapped charge conditions rather than relying on precise circuit breaker characteristics and RDDS, thereby reducing inrush current without requiring high precision circuit breaker characteristics
Solution Approach 2:
The patent implements a feedback mechanism where the trapped charge value measured during opening is stored and used to control the closing operation timing. This feedback loop allows the system to adapt to actual circuit conditions and trapped charge states, eliminating the need for precise prior knowledge of circuit breaker characteristics while still achieving reduced inrush current
2Ease of operation
If insertion resistors are used for controlled switching, then switching control is improved, but cost and reliability deteriorate
Solution Approach 1:
The patent extracts and eliminates the insertion resistor component from the switching system by using trapped charge measurement and memorization to control closing operations. This removal of the insertion resistor simplifies the device, reduces cost, and improves reliability while maintaining switching control through intelligent timing based on trapped charge values
Solution Approach 2:
The patent enables the circuit breaker to control its own switching operations by measuring and using its own trapped charge characteristics. The system uses the trapped charge information from opening operations to optimize closing timing, eliminating the need for external insertion resistors and achieving self-controlled switching
3Productivity
If voltage synchronization with zero crossing is used, then capacitive load management is optimized, but additional instrumentation and precise timing are required
Solution Approach 1:
The patent makes the trapped charge measurement serve multiple functions: it characterizes the capacitive load state, optimizes closing timing, and eliminates the need for separate instrumentation. The same measurement infrastructure used for voltage monitoring is utilized to measure trapped charge, thereby optimizing capacitive load management without adding additional instrumentation
Solution Approach 2:
The patent enables the existing voltage measurement system to serve the additional function of trapped charge measurement and memorization. By using the available voltage sensing infrastructure to detect trapped charge conditions, the system optimizes capacitive load management without requiring additional specialized instrumentation
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A method for operating capacitive loads and a device for implementing the method. Such a load (4) is powered by a three-phase source (2), via a circuit breaker with independent poles (6), carrying out opening and closing operations for each phase, during intentional operations. According to the invention, the method involves measuring one of the voltages of the phases of the source; for each phase, monitoring the sign of a charge trapped at the capacitive load at each opening and taking same into account for the subsequent closing operation.