A New Technique And A Comprehensive Intelligence Device For Eliminating Electric Arc And Resonance, And For Interrupting Single-Phase Ground Fault

In a traditional three-phase power grid, single-phase ground fault (SPGF) not only directly results in more than 60% of network breakdowns, but also leads to a significant portion of phase-to-phase faults; and hence the SPGF also indirectly causes some of the other approximately 40% of breakdowns. Resonance is another common fault that breaks down a grid. The total percentage of breakdowns due to a SPGF or a resonance, in a 6kV-66kV, neutral-point, ineffective grounding power grid, is even higher than those in other types of grid systems. Common products for fault protection suffer from low reliability, ineffective protection, or are unfavorable to safe operation of a power grid. It is imperative to develop new techniques and protection systems that are highly reliable and safe, in eliminating or reducing power gird's breakdowns.In this thesis, a new technique is presented for eliminating ground fault due to electric arc, and resonance due to ferromagnetic fields; and for predicting, detecting and protecting against a high-resistance ground fault (HRGF) in the entire power grid. A comprehensive intelligence device that implements the technique is also developed.The major innovation in this thesis includes: 1) developing a new voltage method that eliminates the electric arc 100% by connecting in parallel a reactance between a faulty phase and the ground, clamping down on the voltage of a faulty phase, cutting off arc paths, and 1 diverting all faulty currents; 2) conducting a novel, fault pattern recognition, and designing/coding a computer program to automate an accurate monitoring and protection against possible HRGF; and 3) using a new method to suppress resonance by inserting in parallel a reactance between the generator of the one responsible phase and the ground, destroying resonance points, suppressing over-voltage from a resonance, diverting excited currents, and hence realizing a no-dead-ends, complete protection against resonance.Our protection device has passed a series of tests conducted by relevant government inspection agencies. These tests include an extensive and rigorous electrical and modeling performance test, an electromagnetic compatibility test, a 10kV in situ ground fault detection and protection experiment, and an extended practical running of our equipment in a 10kV three-phase power grid. The new technique and device are shown to be reliable and practical. A national-level new product appraisal was completed and a certification was granted. It is stated in the certificate that "1) the design is novel; 2) the protection is good; 3) the methods for eliminating electric arc, resonance, and for monitoring, detecting and protecting against HRGF are among the state of the art in China; and 4) a mass production of the intelligent protection device is permitted."...