DL/T 1998-2019 in English
VALIDTechnical specifications for inductive filtering transformer equipment
- Issued on:2019-06-04
- Implemented on:2019-10-01
- File Format:PDF
- Delivery:Via email within 5 business days
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Introduction
Analysis of the core content of the standard
This standard systematically regulates the technical system of the complete set of induction filter transformers for the first time, and innovatively proposes the zero impedance design principle of the induction filter winding. Its core is to achieve local harmonic control through the principle of electromagnetic induction. Compared with traditional passive filtering technology, the harmonic filtering rate is increased to more than 90%.
Comparison of key technical parameters
| Indicators | Traditional transformer | Induction filter transformer |
|---|---|---|
| Harmonic filtering rate | 60-75% | ≥90% |
| Power factor | 0.85-0.92 | 0.98-0.99 |
| Equivalent short-circuit impedance | Conventional design | ≤0.1% |
Equipment composition and working principle
The complete set of equipment includes three core components:
- Induction filter transformer (iFT): adopts a special winding structure, and the equivalent impedance of the filter winding is close to zero
- Tuning and reactive power compensation device (iTVC): fully tuned LC filter branch, the quality factor must meet the requirements of Table 1
- Monitoring system (iFC): integrated harmonic monitoring, AVC/AGC control functions
Through the electromagnetic induction principle described in Appendix B, a harmonic current short-circuit loop is formed to achieve harmonic magnetomotive force cancellation.
Test verification system
The standard establishes a five-level test system:
- Routine test: Short-circuit impedance measurement requires the calculation of power frequency equivalent current according to formula (1)
- Type test: Temperature rise test requires consideration of additional harmonic losses
- Special test: Short-circuit withstand capability verification
- Takeover test: Harmonic measurement is carried out in accordance with GB/T 17626.7
- Field test: Condition maintenance test is carried out in accordance with DL/T 393
Typical application case
After a certain electrolytic aluminum project uses a three-winding induction filter transformer (35kV/10kV):
- The 5th harmonic current is reduced from 19.33A to 1.42A, with a filtering rate of 92.65%
- The harmonic loss of the transformer is reduced by 13.775kW (a decrease of 15%)
- The reactive loss of the system is reduced by 185kW
Implementation suggestions
Design steps according to Appendix C:
- Accurately measure the load harmonic spectrum
- The filter winding adopts D connection (when both high and low voltages are Y-connected)
- Preferably select auto-coupling structure to improve material utilization
- The monitoring system needs to integrate the harmonic monitoring function required by GB/T 19862
Note: The rated capacity of the complete set of equipment is based on the transformer capacity, and the filter winding capacity should be ≥1.2 times the iTVC fundamental capacity.
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