dry type air core reactor

Dry-Type Air-Core Series Reactor

I. Product Overview

The Dry-Type Air-Core Series Reactor is a core special supporting equipment in the field of reactive power compensation and power quality governance in power systems. It is mainly applied to the loop of 10kV and 35kV high-voltage shunt capacitor banks, forming a "capacitor-reactance" compensation branch in series with capacitors. Its core functions are to limit the closing inrush current of capacitor banks, suppress grid harmonic amplification, reduce switching overvoltage, and protect capacitors and switching appliances. It fundamentally solves the electrical impact problems during the switching of capacitor banks and ensures the long-term safe and stable operation of the reactive power compensation system.

Breaking through the technical limitations of traditional iron-core reactors, this product adopts a fully dry-type structural design of coreless, air-core winding and overall vacuum casting with epoxy resin, using air as the insulation and cooling medium. It completely abandons the oil leakage and explosion risks of oil-immersed equipment, and also avoids the pain points of iron-core reactors such as magnetic saturation, magnetic flux leakage heating and excessive noise. With excellent electrical performance, extremely high mechanical strength, environmental protection, safety and reliability, and extremely low operation and maintenance costs, it is widely adapted to various scenarios such as substations, industrial park distribution stations, wind power/photovoltaic new energy stations, metallurgical and chemical enterprises, rail transit power supply systems, and urban distribution network reactive power compensation projects. It is a key equipment for power quality optimization in the construction of modern smart grids.

The product is designed and manufactured in strict accordance with national and international standards such as GB/T 1094.6 Power Transformers - Part 6: Reactors, GB/T 17004 Dry-Type Reactors and IEC 60076-6 Power transformers - Part 6: Reactors. It has passed all type tests of the National Power Equipment Testing Center, with complete qualification certification and testing reports, and can be seamlessly compatible with capacitors, reactive power controllers and switching switches of mainstream brands at home and abroad.

II. Core Structure and Working Principle

(I) Core Structure Composition

This product adopts a modular integrated design, and its core components are composed of six core parts: vacuum cast winding, upper and lower star frame, high-strength support insulator, terminal assembly, grounding system and outdoor protection components (optional). The structural layout is scientific, and both mechanical strength and electrical performance are optimized:

Vacuum Cast Winding: The core functional component, wound by multiple strands of oxygen-free copper stranded wire, the conductor surface is coated with high-temperature resistant insulating paint, and forms an overall cured insulating cylinder through the vacuum epoxy resin casting process. The winding adopts a multi-layer segmented structure with heat dissipation air passages between layers, which not only ensures insulation performance but also realizes efficient natural heat dissipation.

Star Frame: Welded by high-strength aluminum alloy profiles, the surface is treated with anodic oxidation and anti-corrosion, with light weight, high strength and corrosion resistance. The frame is used to fix the end of the winding and disperse the short-circuit electrodynamic force, ensuring that the winding will not deform or displace under short-circuit impact.

Support Insulator: Selected from high-strength rod-shaped epoxy glass fiber insulators, with an insulation grade of ≥Class H and a mechanical bending strength of ≥12kN. It is used to support the winding and frame, realize high and low voltage isolation, and bear the weight of the winding and short-circuit electrodynamic force.

Terminal Assembly: Made of tinned red copper with a contact resistance of ≤50μΩ, equipped with high-strength insulating shields. The wiring method is flexible (bolt crimping/clamp connection), adapting to high-voltage cables and busbars of different sections.

Grounding System: Including grounding bolts, grounding copper bars and star frame grounding terminals, it realizes reliable grounding of the whole equipment, eliminates induced voltage and ensures the safety of operation and maintenance personnel.

Outdoor Protection Components (Optional): Outdoor products are equipped with UV-proof and rain-proof covers, anti-water accumulation bases at the bottom, and the cabinet is made of 304 stainless steel with a protection grade of IP54, adapting to harsh outdoor open-air environments.

(II) Working Principle

In the loop of high-voltage shunt capacitor banks, the dry-type air-core series reactor is connected in series with the capacitor, and three core functions are realized by using the inductive reactance characteristics of the reactor:

Current Limiting Effect: An inrush current of several times to tens of times the rated current will be generated at the moment of closing the capacitor bank. The reactor limits the peak value of the inrush current through its own inductive reactance (usually the inrush current can be limited to within 5 times the rated current), avoiding damage to equipment such as circuit breakers and capacitors caused by the inrush current.

Filtering Effect: By selecting an appropriate reactance rate (such as 4.5%, 6%, 12%), the "capacitor-reactance" branch presents low impedance to specific harmonics (3rd, 5th, 7th), introduces harmonic current into the branch to realize harmonic suppression, and prevents overheating and damage of capacitors caused by grid harmonic amplification.

Voltage Regulation Effect: Switching overvoltage will be generated when the capacitor bank is switched. The inductive reactance of the reactor can dampen the rising speed of overvoltage, reduce the overvoltage amplitude, and protect the insulation of electrical equipment in the loop.

III. Specifications and Parameters (Full Coverage & Customizable)

Parameter Category Core Specifications Detailed Explanation

Rated Voltage 10kV, 20kV, 35kV (66kV customizable) Adapts to the mainstream high-voltage distribution network voltage grades in China; customized models meet special power grid needs

Rated Frequency 50Hz (60Hz customizable) Complies with the power frequency grid standard; 60Hz models are suitable for export projects and special industrial scenarios

Rated Current 50A～1000A (full range coverage) Precise matching according to the compensation capacity of capacitor banks, supporting single unit customization and batch standardized production

Reactance Rate 1%, 4.5%, 5%, 6%, 7%, 12%, 14% 1% for pure current limiting; 4.5%/6% for suppressing 5th and 7th harmonics; 12%/14% for suppressing 3rd harmonics

Rated Inductance 0.1mH～100mH Precise calculation according to rated voltage, current and reactance rate, linearity error ≤±3%

Insulation Grade Class F (155℃), Class H (180℃) Standard with Class H insulation for high-temperature environments; Class F insulation meets conventional scenarios with higher cost performance

Structural Form Dry-type air-core, overall vacuum casting with epoxy resin Coreless, oil-free, air insulation and cooling; outdoor type with special protective structure

Cooling Method Natural air cooling (AN), forced air cooling (AF, optional) Standard with AN cooling for most scenarios; AF cooling for high-load and high-altitude special scenarios

Loss Grade Standard loss, low loss (customizable) Low loss type has 15%～25% lower loss than standard type, more energy-saving for long-term operation

Noise Level ≤45dB (rated condition, 1m away) No core magnetostriction noise, much lower than iron-core reactors (≤65dB), suitable for silent scenarios

Short-circuit Resistance Withstand short-circuit current impact of 20 times rated current for 2s The winding is integrally cured with high mechanical strength; no deformation or insulation damage after short circuit

Protection Grade Indoor type IP30, outdoor type IP54 (IP65 customizable) IP30 prevents foreign object intrusion; IP54 is rain and dust proof; IP65 adapts to extreme environments such as coastal salt fog and heavy rain

Working Environment Temperature: -40℃～+85℃; Humidity: ≤95% (no condensation); Altitude: ≤4000m (high altitude customizable) Adapts to various harsh environments such as severe cold, high temperature, humidity, high altitude and salt fog

Service Life ≥30 years Epoxy resin insulation layer is anti-aging and UV-resistant; oxygen-free copper winding is corrosion-resistant; service life exceeds 30 years under normal operation and maintenance

Implementation Standards GB/T 1094.6, GB/T 17004, IEC 60076-6, DL/T 840 Fully complies with national, industry and international standards, with controllable and traceable quality

IV. Core Product Advantages

(I) Excellent Electrical Performance, Precise and Stable Operation

No Magnetic Saturation, Extremely High Inductance Linearity: Adopting a coreless design, it completely eliminates the magnetic saturation phenomenon of iron-core reactors. The inductance value remains stable within the range from rated current to short-circuit current (linearity error ≤±3%), and the current limiting and filtering effects do not attenuate with the change of current, ensuring that the compensation system is always in the best working state.

Low Loss, High Energy-saving Efficiency: The winding is wound with multiple strands of oxygen-free copper stranded wire to reduce skin effect loss; the vacuum epoxy resin casting process ensures the denseness of the insulation layer and reduces dielectric loss. The total loss of the product is much lower than the national standard, which can greatly reduce power loss during long-term operation, with both economic and environmental benefits.

Strong Harmonic Suppression Capability: It can accurately match the reactance rate according to the grid harmonic content, targetedly suppress characteristic harmonics such as 3rd, 5th and 7th, effectively prevent overheating and breakdown of capacitor banks caused by harmonic amplification, and ensure the compatibility of the reactive power compensation system and the grid.

(II) Outstanding Mechanical Strength, Extremely Strong Impact Resistance

Integral Curing of Winding, Short-circuit Electrodynamic Force Resistance: Vacuum epoxy resin casting makes the winding form an overall rigid structure. Combined with the support of the aluminum alloy star frame, it can withstand the impact of short-circuit electrodynamic force of 20 times the rated current for 2 seconds. After short circuit, the winding has no deformation, no displacement and no cracking of the insulation layer, and the equipment can continue to operate normally.

Seismic and Wind Resistance, Adapting to Complex Terrain: The overall structure is light in weight and low in center of gravity, equipped with a special seismic base. It can resist external impact of magnitude 8 earthquake and grade 12 typhoon, and is suitable for complex installation scenarios such as mountainous areas, hills and coastal areas.

(III) Environmental Protection, Safety and Reliability, No Operation Hidden Dangers

Fully Dry-type Design, Fireproof, Explosion-proof and Pollution-free: Using air as insulation and cooling medium, it is oil-free, non-flammable medium-free and non-toxic gas-free, completely eliminating the risks of oil leakage, explosion and environmental pollution of oil-immersed equipment. Even under extreme faults, there will be no combustion or explosion, making it the first choice for scenarios with high fire protection requirements such as substations, factories and residential areas.

Low Noise Operation, Adapting to Silent Environments: No low-frequency noise generated by core magnetostriction, the noise is ≤45dB under rated conditions, which is only equivalent to normal conversation. It can be directly installed in noise-sensitive scenarios such as distribution stations, hospitals and schools next to residential areas.

Excellent Insulation Performance, Aging and Corrosion Resistance: The epoxy resin insulation layer is vacuum cast and cured at high temperature, with strong UV resistance, aging resistance, salt fog resistance and chemical corrosion resistance. The insulation performance does not attenuate in the extreme temperature range of -40℃～+85℃, adapting to various harsh climate environments.

(IV) Convenient and Efficient Operation and Maintenance, Low Whole Life Cycle Cost

Maintenance-free Design, Reducing Operation and Maintenance Costs: No oil pillow, no on-load tap-changer, no vulnerable moving parts. Under normal operation, there is no need for regular oil filling, overhaul and maintenance. Only an annual appearance inspection and grounding test are required, which greatly reduces the workload and cost of operation and maintenance personnel.

Flexible Installation, Strong Adaptability: Small in size and light in weight, it supports four installation methods: indoor cabinet installation, indoor floor installation, outdoor pole installation and outdoor floor installation. No special machine room and cooling system are required, and the construction period is short (only 2～4 hours for single unit installation), adapting to different site conditions.

Optional Intelligent Monitoring, Smarter Operation and Maintenance: Customizable installation of on-line temperature monitoring, current and voltage monitoring, and fault alarm modules, which can be connected to the grid monitoring system through RS485/Modbus communication protocol, realizing real-time monitoring of equipment operation status and remote alarm of abnormal conditions, helping the operation and maintenance of smart grids.

V. Application Scenarios (Full Scenario Coverage)

(I) Current Limiting for Supporting High-voltage Shunt Capacitor Banks

This is the core application scenario of this product. It is widely used in reactive power compensation devices of 10kV and 35kV substations and distribution stations, connected in series with high-voltage shunt capacitors to limit closing inrush current, suppress harmonics, protect capacitors, vacuum circuit breakers, disconnectors and other equipment, and ensure the safe switching of the reactive power compensation system.

(II) Power Quality Governance of New Energy Stations

In wind power, photovoltaic and light storage integrated power stations, the volatility and intermittence of new energy power generation are easy to lead to increased grid harmonic content and voltage fluctuation. This product is connected in series with capacitor banks to form a filter compensation branch, suppress harmonics generated by new energy power generation, stabilize grid voltage, and help the smooth grid connection of new energy power.

(III) Harmonic Governance and Reactive Power Compensation for Industrial Enterprises

Industrial enterprises such as metallurgy, chemical industry, mining, rail transit and precision manufacturing have a large number of nonlinear loads such as frequency converters, electric arc furnaces and rolling mills, which generate a lot of harmonics and large reactive power loss. This product can customize reactors with different reactance rates according to the harmonic characteristics of enterprises, and form a special filter device with capacitor banks, which not only compensates reactive power and improves power factor, but also suppresses harmonics and protects production equipment.

(IV) Urban Distribution Network Upgrading and Reconstruction Projects

The urban old distribution network has problems such as aging lines, dense loads and large voltage fluctuations. In the upgrading and reconstruction of the distribution network, this product is used in the newly built or reconstructed reactive power compensation stations to solve the problems of switching inrush current and harmonics of capacitor banks, improve the power supply quality of the distribution network, and reduce the risk of damage to user electrical appliances.

(V) Special Environment Special Power Supply System

In special environments such as high-altitude areas, coastal salt fog areas, severe cold areas and chemical corrosion areas, traditional oil-immersed and iron-core reactors are difficult to operate stably for a long time. This product can operate reliably for a long time in these special environments through customized design (such as high-altitude insulation enhancement, coastal stainless steel protection, severe cold low-temperature insulation adaptation), ensuring the stability of the power supply system.