Phase-splitting Operation Technology Of Drop-out Fuse And System Safety Control
The phase-splitting operation characteristic of High Voltage Fuse is its core function to realize selective protection in three-phase power system. Its operation logic needs to meet multiple requirements such as electromagnetic transient control, mechanical linkage constraint and insulation coordinated recovery. Based on the operation characteristics of 10-35kV distribution network, this paper systematically analyzes the technical principles and engineering practice specifications of phase-splitting operation.
1. The physical mechanism of phase-separated operation
Asymmetric effect of three-phase system
During phase-splitting operation, the undisconnected phase will generate an induced electromotive force. Measured data show that after single-phase disconnection, the remaining two-phase voltage vector angle shifts by 8°-12°, and the phase-to-phase voltage fluctuation range reaches 15%-20%. The middle phase priority disconnection strategy can reduce electromagnetic coupling interference by more than 40%.
... Split-phase operation requires the arc energy to be controlled within the range of 18-22kJ. Copper tungsten contacts (CuW50) are combined with longitudinal magnetic field design to make the arc rotation speed reach 120m/s, effectively avoiding local overheating of the melting tube. Tests at a 110kV substation showed that if the phase separation time difference is controlled within 80ms, the reignition rate can be suppressed to below 0.3%.
2. Standard phase splitting operation specifications
Three-phase opening timing sequence Three-phase opening timing sequence (1) Fault phase priority: Based on the SCADA system positioning signal, the fault phase is removed first
(2) Load balancing control: non-fault In this state, select the operating phase according to the phase current deviation>15%
(3) Environmental factor adaptation: Prioritize operation in the upwind phase to reduce the impact of arc product diffusion
(1) Opening speed: 0.65±0.05m/s, contact separation time ≤3ms
(2) Operating torque: using a special insulating rod (J≥120kN·m), force angle 55°-65°
(3) Status indication: triggered when the fuse droop angle ≥88° Mechanical locking, deviation tolerance <1.5°
3. Intelligent phase control technology
The application of a coastal wind farm shows that this method reduces the peak value of the closing inrush current from 5.6kA to 1.8kA.
... The permanent magnet motor drive system (25N·m torque) cooperates with the FPGA controller to realize the dynamic adjustment of the opening speed curve. When contact adhesion is detected (pressure sensor>200N), the secondary impact program is automatically triggered, and the impact energy is set to 130% of the nominal value.
4. Special working conditions operation strategy
Capacitive load handling
The capacitor bank is operated by a phase-selective tripping device (action time error <0.3ms), which is forced to disconnect 25° before the current passes zero. The matching RC absorber (C=0.22μF, R=33Ω) can limit the operating overvoltage to within 2.2p.u.
Adaptation to high-altitude cold environment
In an environment of -25°C, the melting tube needs to be preheated to above -5°C before operation (infrared heating power 2.5kW)
Lubricant should be replaced with low-temperature silicone grease (viscosity index > 180)
Operation interval extended to 150% of the standard value
... ... 24kV100A load-type drop-out fuse-silicone rubber support with arc extinguishing cover device-Enbimei
Six. Direction of technological evolution
Digital twin applications
... Develop a vacuum-assisted arc extinguishing chamber (pressure 0.8-1.2Pa) and use it with CF3I mixed gas to reduce the greenhouse effect index (GWP) to 1/23 of SF6. Experimental data show that the design can withstand a short-circuit current shock of 42kA/4s.
VII. Conclusion
The split-phase operation of drop-out fuses is a key link in the refined control of distribution networks, and it is necessary to establish an intelligent control system of "state perception-strategy optimization-dynamic execution". Therefore, Enbima will focus on improving three core capabilities: mechanical state diagnosis based on vibration spectrum analysis (0-10kHz), adaptive operation parameter adjustment based on meteorological data, and full-dimensional digital recording of the operation process (sampling rate ≥ 1kHz). At the same time, split-phase operation simulation training should be carried out regularly, focusing on improving the personnel's cognitive level of multi-phase coupling effects, and ensuring that the pass rate of split-phase operation reaches more than 99.98%.
