Views: 0 Author: Site Editor Publish Time: 2026-06-16 Origin: Site
When a current-limiting fuse operates under short-circuit conditions, it must rapidly transition the arc gap from a conductive state to an insulating state to withstand the recovery voltage imposed by the power system. The interruption process fundamentally involves a complex arc process from melting to arcing and finally to arc extinction. The arc characteristics during this transient process—particularly under high-current conditions—directly determine the fuse's interrupting capacity and the overvoltages generated during interruption.
2.1 Arc Ignition and Plasma Formation
Upon occurrence of a fault current, Joule heating causes the fuse element (typically silver or copper) to vaporize almost instantaneously, forming metal vapor. This vapor becomes ionized, creating a plasma channel with temperatures reaching 5,000–20,000 K. The arc acts as a low-impedance path that, if uncontrolled, would sustain fault current conduction and release massive thermal energy.
2.2 Arc Suppression Mechanisms
The arc suppression in current-limiting fuses relies on a synergistic combination of physical and electrical mechanisms:
Narrow-Slot Arc Division: The fuse element is designed with multiple variable cross-section sections or narrow-neck arrays, dividing the arc into several short arcs in series. This segmentation increases the total arc voltage and enhances the cooling effect.
Quartz Sand Cooling Effect: High-purity quartz sand (SiO₂ ≥ 99.6%) densely packed around the element creates a "cold wall" effect. Arc energy is absorbed by the sand grains, which undergo phase transformation into silicate glassy slag, effectively cooling the plasma. The sand filling also restricts charged particle movement, increasing arc column resistance by 10³ to 10⁴ times.
Reverse Voltage Establishment: The rapid increase in arc resistance induces a sudden change in current derivative (di/dt), generating a counter-electromotive force (up to several kV) that forces the current to zero before the natural current zero.
2.3 Temporal Evolution of Arc Interruption
The arc interruption process can be divided into distinct stages: initial arcing (0–0.5 ms) dominated by arc division; energy absorption (0.5–2 ms) characterized by quartz sand heat absorption and metal vapor condensation; current chopping (2–5 ms) marked by steep arc resistance rise and forced current zero; and dielectric recovery (beyond 5 ms) involving slag solidification and insulation strength restoration.
3.1 Fundamental Principles
The post-arc dielectric recovery process refers to the transition of the arc gap from a plasma-conducting channel back to an insulating medium capable of withstanding the transient recovery voltage (TRV). The success of interruption hinges on whether the fuse can withstand the TRV without dielectric breakdown after current zero.
The arc gap resistance undergoes a nonlinear increase from very low resistance to very high resistance during the interruption process. Research has shown that post-arc current decays rapidly with time, from which the post-arc resistance can be derived as increasing with time.
3.2 Dielectric Recovery Characteristics
Experimental investigations on fuses rated at 500 VAC have revealed that dielectric recovery speed varies significantly with fault current magnitude. When the fault current is 8 times the rated current, the dielectric recovery speed is considerably slower than at 35 times the rated current. Moreover, the experimental results exhibit significant dispersion under overload conditions, attributed to uneven arcing across series-parallel narrow sections.
Analysis at 100 µs post-current-zero indicates that arc voltage and arcing time are linearly related to dielectric recovery strength—shorter arcing time and higher arc voltage lead to superior dielectric recovery.
3.3 Factors Affecting Dielectric Recovery
Arc Energy: Reducing arc energy effectively improves dielectric recovery capability. Experimental results demonstrate that when arc energy is 3.6 J with a 60 µs dielectric recovery time, the critical field strength reaches 1.5 V/µm; when arc energy increases to 22 J, the critical field strength drops to 0.6 V/µm under identical recovery time.
Current Rise Rate (di/dt): Both dielectric recovery time (t_z) and arc interruption time (t_p) decrease with increasing short-circuit current rise rate, while the peak limited current increases. Optimizing the arc trigger branch inductance can increase t_z to 600 µs, significantly improving current-limiting performance.
Fulgarite Morphology: The post-arc characteristics are closely related to the shape and structure of the residual fulgarite. Studies employing cylindrical models with finite difference methods have analyzed temperature distribution and post-arc resistance.
Recent advances have enabled more detailed diagnosis of arc phenomena. A borescope-integrated spectroscopic system has been developed for single-shot recording of axial distributions of electron density and arc temperature in fuse arcs just before extinction. Combining electron density and temperature data allows identification of fuse arc composition and calculation of axial electrical conductivity distribution under the Chapman–Enskog approximation. This methodology provides superior accuracy compared to previous estimation methods.
The high-current interruption process in current-limiting fuses involves a complex interplay of arc ignition, plasma formation, arc suppression through narrow-slot division and quartz sand cooling, and post-arc dielectric recovery. The nonlinear evolution of arc resistance—from conductor to insulator—is fundamental to successful current interruption. Dielectric recovery strength depends critically on arc energy, fault current magnitude, and current rise rate. Advanced spectroscopic diagnostics are now enabling more precise characterization of fuse arc properties. Continued research into these mechanisms is essential for developing fuses with higher interrupting capacities and improved reliability in modern power systems.
