AC Grounding System with Switch-Controlled DC Blocking
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Solution Overview
Problem
Current solutions for protecting electrical equipment from geomagnetic-induced currents (GIC) and high-altitude electromagnetic pulses (HEMP) are either costly, unreliable, or require adjustments to power system relay settings, lacking a reliable and low-cost protection circuit compatible with existing power delivery systems.
Innovation Solution
A continuous uninterruptable AC grounding system with a switch-controlled DC blocking mechanism, using a DC blocking component in parallel with the switch assembly to block DC currents and harmonics, maintaining a standard grounding path under normal conditions and switching to a protective mode upon detection of high DC or harmonic levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If capacitive circuits are used to block DC currents, then DC blocking is achieved, but the system requires expensive electronics and switching devices
Solution Approach 1:
The patent replaces expensive electronic DC blocking components with a simple, inexpensive resistive element that can be easily installed and maintained. The resistor serves as a disposable-like component that provides reliable DC current limitation without requiring complex electronics or switching devices.
2Object-affected harmful factors
If fixed value resistors are used to reduce DC current, then DC current reduction is achieved, but the resistor must have high resistance value and only reduces rather than eliminates DC current
Solution Approach 1:
The patent employs a dynamically controllable resistance element that can adjust its resistance value based on operating conditions. This allows the system to provide low resistance during normal operation for optimal grounding, and high resistance during GIC events for DC current blocking, thereby achieving both DC current elimination and reliable operation across different conditions.
3Object-affected harmful factors
If switch-controlled DC blocking is implemented, then DC current blocking is achieved, but the system may have unintentionally open grounding connections
Solution Approach 1:
The patent introduces a normally-closed switch as an intermediary component in the grounding path. This switch is designed to fail-safe in the closed position, ensuring that the grounding connection remains intact under normal conditions. The switch provides controlled interruption only when actively commanded by a control system detecting GIC events, thereby maintaining reliability while enabling DC blocking when needed.
4Object-affected harmful factors
If continuous active components are used to reduce GIC events, then GIC protection is achieved, but the system requires expensive power electronics and constant operation
Solution Approach 1:
The patent implements a control system that activates DC blocking only periodically or event-driven, rather than continuously. The normally-closed switch remains conductive during normal operation and is opened only when a control system detects GIC events, thereby providing protection when needed while avoiding the costs and complexities of continuous active component operation.
5Reliability
If standard grounding connection is used, then reliable grounding is achieved, but the system is vulnerable to transformer saturation from DC currents
Solution Approach 1:
The patent modifies the electrical parameters of the grounding path by introducing a controllable resistance element and switch. During normal operation, the grounding path maintains low resistance for reliable grounding. During GIC events, the control system changes the resistance parameter by opening the switch, thereby blocking DC currents and preventing transformer saturation while maintaining AC grounding functionality.
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 system effectively blocks DC and quasi-DC currents, preventing transformer saturation, overheating, and harmonic generation, thus protecting power systems from damage and preventing power grid instability without requiring changes to existing relay settings or incurring high costs.
Implementation Method 1
A first class of solutions uses a capacitive circuit to simultaneously provide the AC grounding path and a block for the induced DC currents
Implementation Method 2
a switch assembly connected between a neutral grounding connection of a transformer and a ground, the switch assembly having an open position and a closed position, the open position disrupting the path through the switch between the electrical connection and the ground connection
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A continuous grounding system for use in an alternating current system including a transformer is disclosed. The system includes a switch assembly connected between a transformer neutral of a transformer and a ground, the switch assembly having an open position and a closed position, the open position disrupting the path through the switch assembly between the electrical connection and the transformer neutral, and the closed position establishing a path connecting the electrical connection to the transformer neutral through the switch assembly, wherein in normal operation of the alternating current electrical device the switch assembly remains in a closed position. The system also includes a DC blocking component positioned in parallel with the switch assembly and connected between the transformer neutral and the ground. The system further includes a control circuit configured to control the switch assembly, the control circuit including a sensor configured to actuate the switch assembly to an open position upon detection of a predetermined harmonic signal threshold at one of the transformer phases or a predetermined threshold of DC current between the transformer neutral and ground.