DL/T 462-2025 in English

Standard Revision Background and Technological Evolution

DL/T 462-2025, "Technical Conditions for the Use of Series Reactors for High-Voltage Shunt Capacitor Banks," is a comprehensive upgrade and revision of the 1992 edition. This revision fully considers the technological developments in power systems over the past 30 years, particularly the increased requirements for reactive power compensation devices following the construction of ultra-high voltage (UHV) power grids and the large-scale integration of new energy sources. The standard expands the applicable voltage range to 110 kV and adds two new product types: dry-type iron-core reactors and dry-type semi-iron-core reactors, reflecting the diversification trend in reactor technology.

Product Classification and Model Compilation Specifications

The standard classifies series reactors into four categories based on their structure: dry-type air-core reactors, dry-type iron-core reactors, dry-type semi-iron-core reactors, and oil-immersed iron-core reactors. Model compilation uses a systematic coding rule, with letter codes clearly identifying product characteristics. For example, CKDKL-35-1200/2.88-12 represents a single-phase dry-type air-core series reactor with a rated voltage of 35kV, aluminum conductors, a rated capacity of 1200kvar, a rated terminal voltage of 2.88kV, and a rated reactance ratio of 12%.

Key technical requirements and performance indicators

Insulation Level Requirements

The standard provides detailed insulation requirements for different types of reactors, specifically adding insulation requirements for 20kV and 110kV products. Taking a 35kV system as an example, the relative power frequency withstand voltage of dry-type air-core reactors is 100/80kV (dry/wet) relative to ground, and the lightning impulse withstand voltage is 170/200kV, reflecting the high emphasis on equipment operational reliability.

Optimized Loss Limits

The new standard systematically optimizes reactor loss limits, setting differentiated requirements based on different capacity levels. Taking the 1000-3150 kvar capacity range as an example, the loss limit for dry-type air-core reactors is ≤1.1%, for dry-type iron-core reactors is ≤0.8%, and for oil-immersed iron-core reactors is ≤0.7%, reflecting the differences in the technical characteristics of different reactor types. The standard specifies temperature rise limits for oil-immersed and dry-type reactors. For oil-immersed iron-core reactors, the winding temperature rise limit is ≤60K, with the top oil temperature rise ≤55K. Dry-type reactors are categorized by insulation heat resistance grade. Class B has an average winding temperature rise of ≤60K and a hottest point temperature rise of ≤70K, ensuring long-term operational stability.

Selection Configuration and Engineering Application Guide

Equipment Selection Principles

The standard clarifies the applicable places of different types of reactors: Dry-type air-core reactors, dry-type semi-iron-core reactors, and oil-immersed iron-core reactors are suitable for outdoor use. Dry-type air-core reactors should not be stacked in three-phase configuration; dry-type iron-core reactors are suitable for indoor use. When three-phase stacking is necessary, the standard specifies detailed minimum insulation clearance requirements. For example, the minimum insulation clearance between reactors for 35kV outdoor installation is 400mm. Series reactors should be configured according to the reactance ratio specified for the capacitor device. The standard recommends reactance ratio values of ≤1%, 4.5%-5%, and 12%-13%, and emphasizes that the minimum reactance ratio should not be less than 0.5%. When the capacitor branch current may exceed 1.30 times the rated current, the reactance ratio should be adjusted to ensure safe operation of the equipment.

Test Methods and Inspection Rules

The standard categorizes tests into four categories: routine tests, type tests, special tests, and acceptance tests, and specifies the applicable scope and frequency requirements for each test. Routine testing includes 11 items, including visual inspection, winding DC resistance measurement, and reactance measurement, to ensure that every product leaving the factory meets basic requirements. Type testing is conducted at least once every five years to comprehensively assess product design performance.

Detailed Explanation of Key Test Items

Winding Turn-to-Turn Withstand Voltage Test: Routine tests use 2 times the rated terminal voltage, while type tests use 3 times the rated terminal voltage. The test duration is calculated as fN/fS × 120s and must be no less than 15 seconds. This effectively verifies the winding insulation strength.

Environmental Withstand Performance Test: New test items for dry-type reactors are required to meet GB/T 1094.11 Level E2 standards, including condensation and moisture penetration tests, to ensure product reliability in harsh environments.

Weather Resistance Test: Dry-type reactors are required to meet Level C2 standards, verifying their ability to withstand temperature fluctuations through low-temperature storage and thermal shock tests.

Standard Implementation Recommendations and Precautions

Design and Selection Recommendations

Dry-type reactors recommended in the standard should be preferred in engineering design. Especially for indoor installations, dry-type iron-core reactors offer advantages such as compact size, low losses, and maintenance-free operation. For outdoor installations with larger capacities, oil-immersed iron-core reactors remain a reliable choice.

Installation and Operation Precautions

Reactors must be installed in strict accordance with the spacing requirements specified in the standard, especially for three-phase stacked installations, ensuring sufficient insulation clearance. During operation, reactor parameters such as temperature rise and noise should be regularly checked, and any abnormalities should be addressed promptly. For dry-type reactors, special attention should be paid to the surface hydrophobicity to ensure insulation performance.

Maintenance and Inspection Points

Develop a reasonable preventive test plan in accordance with the inspection rules required by the standard and in combination with the actual operating conditions of the equipment. Focus on the changing trends of key parameters such as the winding DC resistance, insulation resistance, and reactance value to promptly detect potential defects. For oil-immersed reactors, the oil level and sealing condition should also be checked regularly.

The implementation of the DL/T 462-2025 standard will effectively improve the technical level and operational reliability of high-voltage shunt capacitor devices, and provide important technical support for the optimization of reactive power compensation and improvement of power quality in the power grid. All relevant units should carefully study the content of the standard and strictly implement the standard requirements in all aspects of equipment selection, engineering design, installation and commissioning, and operation and maintenance to ensure the safe and stable operation of the power system.