1.Introduction: context and meaning
1.1 Current status of harmonic pollution in the electricity grid
With the rapid development of industrial automation and new energy technologies, the prevalence of nonlinear loads (e.g. frequency converters, rectifiers, electric arc, etc.) in power grids has increased significantly. These devices generate substantial harmonic currents during operation, causing voltage waveform distortion, voltage fluctuations, flicker and three-phase imbalance. According to statistics, harmonic pollution accounts for over 30% of industrial equipment failures, causing direct economic losses of billions of yuan each year.
1.2 Core Position of High-Voltage Series Reactors
High-voltage series reactor is a key equipment to solve harmonic pollution and improve power quality by using the principle of series resonance to suppress harmonic series. Its application can significantly reduce the total harmonic distortion, stabilize voltage amplitude, increase power factor and prolong equipment lifespan. It conforms to 519-2014 "Recommended Practice for Harmonic Control of Power System and China's GB/T 14549-1993"Power Quality-Harmonics.
2.Working Principle of High-Voltage Series Reactors: Analysis of Series Resonance Suppression Technology
2.1 Basic Theory of Series Resonance
When an inductor (L) and a capacitor (C) are in series, the total impedance is given as follows:
Source: Principles of Circuit Analysis (Li Hansun)
2.2 Harmonic Suppression Mechanism
By designing reactor parameters (such as inductance value L) to match the resonant frequency fr to the target harmonic series (for example, the resonant frequency of the fifth harmonic is 250 Hz), a a low-impedance path is created for the fifth harmonic to prevent its flow into the power grid. Measured data show that after reactor installation, 5 harmonic current the attenuation rate can exceed 70%, the THD can be reduced from 8% to less than 3%.
Reference: Study on the Application of Series Reactors in Harmonic Suppression (Thesis of Electrical Electronics Technology)
3. Type and Selection of High-Voltage Series Reactors: Matching Different Grid Solutions
3.1 Comparison of Structural Types
TypeOil-Immersed ReactorDry-Type ReactorHeat Dissipation Performance
Excellent (oil circulation cooling)
Difference (dependent on air convection)
Capacity range
Large (suitable for high voltage and high current situations)
Small (for medium-and low-voltage scenarios)
Suitable Environment
Outdoors (explosion proof design required)
Indoors (environmentally demanding scenes)
Repair costs
High (regular oil changes and testing of oil quality are required)
Low (maintenance-free)
Reference: Siemens and ABB Reactor Technical Manuals
3.2 Key Parameter Selection
Reactance Rate (%): selected in harmonic order. For example, suppression of five harmonics requires a 5% reactance and suppression of seven harmonics requires a 7% reactance.
Rated current and temperature rise: must match load capacity to avoid overheating and failure. IEC 60076-6 sets a temperature rise limit of 100K (ambient temperature 40°C) for reactors.
Source: IEC 60076-6 Power Transformers and Reactor
4.Core Role of High-Voltage Series Reactors in Harmonic Suppression
4.1 Harmonic Suppression Case Study for Nonlinear Loads
For example, after the installation of the reactor, the harmonic spectrum produced by frequency converters is mainly 5 and 7 harmonics:
The fifth harmonic current decreased from 120A to 35A with a attenuation rate of 70.8%.
The 7th harmonic current decreased from 80A to 20A with a an attenuation rate of 75%%.
Source: Field Test Report of harmonic suppression project of a steel mill
4.2 Effects of reduction on Total Harmonic Distortion
Through PSCAD/EMTDC simulation, the changes in THD values before and after reactor installation were as follows:
Scene before installation Scene after installation InstallationImprovement RateIndustrial Park Grid
7.8%
2.9%
62.8%
New energy plants Grid Connection
6.5%
2.1%
67.7%
Source: PSCAD/EMTDC simulations
V. Comprehensive Enhancement of Power Grid Power Quality by High-Voltage Series Reactors
5.1 Voltage fluctuation and flicker suppression
The reactor stabilizes voltage amplitude by absorbing reactive power. For example, in an energy-efficient renovation project in an industrial park, after the installation of a reactor:
voltage fluctuation range decreased from ±8% to ±3%.
Compliance with GB/T 12326-2008 Power Quality-Voltage Fluctuation and flicker requirements.
Source: Energy audit report of an industrial park.
5.2 Improvement of Power Factor and Extension of Equipment Lifespan
The reactor reduces reactive power loss and improves line transmission efficiency. Measured data show:
The power factor was increased from 0.75 to 0.95 and the line losses was reduced by 36%;
Transformers, cables and other equipment have a reduced risk of overheating and an average lifespan of 5 to8 years.
Source: report a Substation energy-saving renovation project.
6. Installation and Maintenance of High-Voltage Series Reactors: Key to Securing Long-term and Stable Operation
6.1 Installation Location and Wiring Specifications
Location Selection: Installed near the nonlinear load side, shortening harmonic propagation path;
Wiring Method: Star connection (Y) is suitable for three-phase equilibrium load and delta connection (Δ) is suitable for suppression of third harmonic.
Reference: GB 50227-2017 Shunt Capacitor Devices Design Specification
6.2 Routine inspection and Fault Handling
Inspection Points: Temperature rise monitoring (≤100K), insulation resistance testing (≤ 100M), noise anomaly investigation (≤65dB);
Common Faults: Coil short circuits (40%%), aging insulation (30%%), requiring regular preventive maintenance.
Source: TBEA Reactor Repair Guide
7. Conclusions and outlook
7.1 Irreplaceability
High-voltage tandem reactor uses the principle of series resonance to suppress harmonics accurately, which becomes the core equipment to improve power grid power quality and ensure safe operation of the equipment. The technology has high maturity and remarkable value for money. It is widely applied in industry, new energy and rail transportation.
7.2 Future Trends
Intelligent monitoring: Integrated IoT technology to realize real-time data collection and fault warning;
New material applications: development of high-temperature superconducting reactors to reduce losses and increase capacity.
References:
519-2014 Recommended Practice for Harmonic Control of Power Systems
GB/T 14549-1993 Power Quality-Harmonics
"Principles of Circuit Analysis" (Li Hansun)
Siemens and ABB Reactor Technical Manuals
Field Test Report on Harmonic Control Engineering of a Steel Plant