Triggered Vacuum Gap Circuit for Riding Through Current Zeroes
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Solution Overview
Problem
Existing TVG devices used in pulse testing for fault detection in power systems face challenges with premature current interruption due to high frequency current zeroes, which can lead to unreliable synchronized closing operations.
Innovation Solution
A TVG device with two triggering electrodes and a triggering circuit that includes a high voltage impulse source and a low voltage unidirectional current source to sustain a cathode spot on the main electrode, preventing premature extinction of the vacuum arc and ensuring continuous conduction through high frequency current zeroes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a TVG device is used for synchronized closing operations, then the switching speed and precision are improved, but the device is susceptible to premature current interruption due to high frequency current zeroes
Solution Approach 1:
A low voltage unidirectional current source is activated before the expected high frequency current zeroes occur to sustain the cathode spot on the main electrode. This preliminary action ensures that when the high frequency current zeroes arrive, the cathode spot is already established and can be maintained continuously, preventing premature arc extinction and ensuring reliable current conduction throughout the switching operation.
2Speed
If a high voltage impulse source is used to break down the triggering gap, then the triggering speed is improved, but the complexity of the triggering circuit increases
Solution Approach 1:
The triggering circuit is segmented into two independent sources: a high voltage impulse source responsible for rapid breakdown of the triggering gap, and a low voltage unidirectional current source responsible for sustaining the cathode spot. This segmentation allows each source to be optimized for its specific function without compromising the other, achieving fast triggering while maintaining circuit manageability through functional separation.
3Reliability
If a cathode spot is sustained through high frequency current zeroes, then continuous conduction is achieved, but additional current control circuitry is required
Solution Approach 1:
A low voltage unidirectional current source is introduced as an intermediary element between the power system and the TVG device. This intermediary provides the necessary current to sustain the cathode spot during high frequency current zeroes without requiring complex modification of the existing power system control circuitry. The unidirectional current source acts as a buffer that simplifies the overall control architecture while ensuring reliable continuous conduction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution enables the TVG device to ride through high frequency current zeroes without interrupting main gap current, ensuring successful synchronized closing operations in power systems by maintaining the vacuum arc and preventing premature current interruption.
Implementation Method 1
When a sufficiently high triggering voltage impulse is applied to the main electrode and the triggering electrode across the triggering gap, the triggering gap breaks down and a plasma cloud is created
Implementation Method 2
a low voltage unidirectional current source that supplies current to the first triggering gap to sustain a cathode spot on the main electrode and, thereby, to prevent premature extinction of the vacuum arc
Implementation Method 3
two stationary main electrodes positioned within a vacuum chamber, where a main vacuum gap is defined between the electrodes
Data Source
AI summary
A triggered vacuum gap (TVG) device that has application as a closing switch for synchronized closing in distribution and transmission power systems. The TVG device controllably sustains a current arc in the device through initial current zeros created by power system transients and, thereby, prevents premature interruption of the closing operation. The TVG device includes main electrodes defining a vacuum gap therebetween and a triggering electrode providing a triggering gap between one main electrode and the triggering electrode. The TVG device also includes a triggering circuit having a high voltage impulse source that supplies a fast rising impulse voltage to the one main electrode and the triggering electrode for creation of a plasma to provide an initial breakdown of the triggering gap and a low voltage unidirectional current source that supplies current to the one main electrode and the triggering electrode once the first triggering gap breakdown has occurred.