Focus on Reactor Technological Innovation: Early Fault Diagnosis of Dry-Type Air-Core Reactors Under Harmonic Voltages and Carbon Neutrality Practices

In the process of the power system transforming towards high efficiency and low carbon, reactors, as core primary equipment, undertake key responsibilities such as limiting short-circuit current, suppressing harmonics, and reactive power compensation. Their safe and stable operation is directly related to grid efficiency and the advancement of carbon neutrality goals. Dry-type air-core reactors are widely used in various power scenarios due to their compact structure and good heat dissipation, but frequent inter-turn short-circuit faults have become a prominent problem restricting their reliability. Especially since early fault characteristics are not obvious, coupled with the impact of harmonic voltage fluctuations in the power system, traditional diagnostic methods are difficult to accurately identify, which may easily lead to serious consequences such as equipment burnout and grid outages, affecting power factor correction effects and low-carbon power supply stability. Combining the latest technical research, this article details the early fault diagnosis scheme for dry-type air-core reactors considering harmonic voltages, helping the power industry improve equipment operation and maintenance levels and consolidate the foundation for carbon neutrality.

Reactor Operation and Maintenance Pain Points: Difficult Early Fault Identification and Harmonic Interference Obstacles

Dry-type air-core reactors are core components for reactive power compensation and harmonic governance in power systems, and their operating status directly affects the accuracy of power factor correction. During long-term operation, affected by internal electromotive force, external environment and other factors, local defects are prone to occur in the inter-turn insulation of reactors, which gradually develop into early arc-type short circuits. If not intervened in a timely manner, they will evolve into mid-to-late stage metal fusion-type short circuits, eventually leading to equipment burnout.

Traditional reactor fault detection mainly relies on relay protection and infrared inspection. Relay protection judges based on a single current threshold, but the current change is extremely small during the early inter-turn short circuit of the reactor. Coupled with grid voltage fluctuations, it is often impossible to respond in a timely manner; infrared inspection can only identify faults in the outer windings. For early faults in the inner windings, it is difficult to provide early warning due to the insignificant change in the surface temperature of the equipment. More importantly, the widespread existence of harmonic voltages in the power system will interfere with the monitoring of reactor electrical characteristics, leading to increased false alarm and missed alarm rates of faults, seriously affecting the effect of power factor correction, and indirectly increasing grid energy consumption and carbon emissions.

Reactor inter-turn short-circuit faults account for more than 60% of their total faults. Power grid outages caused by such faults not only result in huge economic losses but also affect the absorption of new energy due to power supply interruptions, which is contrary to the goal of carbon neutrality. Therefore, breaking through the bottleneck of harmonic interference and realizing accurate diagnosis of early reactor faults have become an urgent technical problem to be solved in the power industry.

Technological Breakthrough: Targeted Diagnostic Schemes to Unlock the Code for Early Reactor Fault Identification

According to the different operating characteristics of series and parallel reactors and combined with the law of harmonic voltage influence, the research team proposed differentiated early fault diagnosis methods to achieve efficient fault identification by accurately capturing core characteristic quantities.

Series Reactors: Current Harmonic Ratio Diagnosis Method to Eliminate Harmonic Interference

Series reactors are mostly used in three-phase shunt capacitor branches, and their terminal voltages are difficult to measure directly, making traditional voltage monitoring-based diagnostic methods ineffective. Studies have found that during the early arc-type inter-turn short circuit of the reactor, the arc resistance shows nonlinear and periodic changes, which will cause significant changes in the current harmonic content, and this change is not affected by harmonic voltages.

By establishing a simulation model of series reactors considering harmonic voltages and analyzing the electrical characteristics under different working conditions, it can be seen that: during normal operation and early faults, the change rate of reactor current amplitude is less than 1%, which is difficult to distinguish; but the difference in total harmonic distortion rate (THDi) of current is obvious, with a change rate of 87.39% under power frequency voltage and 25.31% under power frequency superimposed harmonic voltage. Based on this, the "current harmonic ratio diagnosis method" is proposed: by real-time calculating the reactor current harmonic content and comparing it with the theoretical calculation value under normal working conditions, the influence of harmonic voltage fluctuations is eliminated, and early faults are accurately identified. This method can greatly improve the accuracy of early fault identification of series reactors and effectively avoid the problem of power factor decline caused by equipment faults.

Parallel Reactors: Active Power Ratio Diagnosis Method for Stable Fault Identification

Parallel reactors are directly connected between the high-voltage bus and the ground, and their terminal voltage is equal to the bus voltage, so fault diagnosis can be realized through power monitoring. Studies have shown that during the early inter-turn short circuit of the reactor, a huge current will be induced in the short-circuited turn. According to the active power calculation formula, even if the resistance of the short-circuited turn is small, it will lead to a significant increase in the active power of the equipment, and this change is minimally affected by harmonic voltages.

Simulation analysis shows that during normal operation and early inter-turn short circuit of parallel reactors, the differences in current amplitude and current harmonic content are not obvious, making it difficult to use as a basis for fault judgment; but the active power shows a significant difference under the two working conditions, and this difference remains stable in the harmonic voltage environment. The "active power ratio diagnosis method" constructed based on this can quickly identify early faults by comparing the real-time active power of the reactor with the reference value under normal working conditions, without additional harmonic interference compensation, and is simple to operate and highly reliable. Experimental verification shows that this method can accurately capture the early fault signals of parallel reactors and meet the needs of engineering applications.

Both diagnostic methods have been verified by building physical test platforms, using real grid harmonic voltage data as excitation to simulate reactor normal, early fault and other working conditions. The test results are consistent with the simulation conclusions, proving the effectiveness and engineering applicability of the methods.

Practical Value: Empowering Low-Carbon Operation and Maintenance to Help Reactors Support Carbon Neutrality

The early fault diagnosis method for dry-type air-core reactors considering harmonic voltages not only solves the diagnostic pain points of traditional technologies but also has important practical significance in the fields of power factor optimization and carbon neutrality.

From the perspective of equipment operation and maintenance, this method realizes "early detection and early disposal" of early reactor faults, which can eliminate faults in the bud, reduce equipment maintenance costs and replacement frequency, extend the service life of reactors, and reduce resource consumption and carbon emissions caused by equipment updates.

From the perspective of grid efficiency, the stable operation of reactors can ensure the accuracy of reactive power compensation, improve power factor, and reduce grid losses. The optimization of power factor can reduce energy waste in the process of power transmission, which is equivalent to reducing fossil energy consumption and indirectly reducing carbon emissions. At the same time, it avoids the abandonment of new energy power generation caused by reactor faults, ensures the smooth grid connection and absorption of wind power, photovoltaic and other clean energy, and provides equipment guarantee for the realization of carbon neutrality goals.

In industrial scenarios, this diagnostic method can be widely applied to the operation and maintenance of reactors in substations, new energy power stations, industrial power distribution systems and other scenarios, especially suitable for high-harmonic and high-load operating environments. It helps enterprises reduce electricity costs, improve green production levels, and promote industrial low-carbon transformation.

Conclusion: Reactor Technological Innovation Drives Low-Carbon Transformation of the Power Industry

As the "stabilizer" and "energy saver" of the power system, the reliable operation of dry-type air-core reactors is the key to improving power factor and reducing carbon emissions. The early fault diagnosis method considering harmonic voltages successfully solves the diagnostic problems of traditional technologies by accurately capturing core characteristic quantities such as current harmonic ratio and active power ratio, providing an efficient solution for reactor operation and maintenance.

In the future, with the deep integration of artificial intelligence, big data technology and power equipment operation and maintenance, reactor fault diagnosis will develop in the direction of intelligence and normalization. By building a full-life cycle monitoring system and combining the diagnostic methods proposed in this article, closed-loop management of reactor fault early warning, trend analysis and accurate disposal can be realized, further improving grid operation efficiency.

The power industry is a key field for carbon neutrality. The technological innovation and efficient operation and maintenance of core equipment such as reactors will inject sustained momentum into the construction of low-carbon power grids. It is expected that more enterprises and scientific research institutions will participate in reactor technology research and development, promote equipment performance upgrading and operation and maintenance model innovation, and jointly help the power industry achieve green transformation and contribute to the global carbon neutrality goal.

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