Technical conditions for use of discharge coils for high-voltage parallel capacitors
1Key Takeaways
This document specifies the terms and definitions, conditions of use, technical requirements, test methods, inspection rules, marking, packaging, transportation and storage of high-voltage shunt capacitor device discharge coils. This document applies to single-phase fully sealed oil-immersed and dry discharge coils use…
2Expert Interpretation
An in-depth interpretation of the technical requirements of the DL/T 653-XXXX standard for discharge coils for high-voltage shunt capacitors, covering core revisions such as insulation level adjustment, dry coil test specifications, and installation method optimization, providing professional guidance for power system equipment selection and operation and maintenance.
Background of Standard Revision and Technological Evolution
As an upgraded version of DL/T 653, this standard mainly responds to the power industry's demand for improved reliability of components in high-voltage shunt capacitors. As the capacity of the power grid expands, the failure rate of discharge coils, as key protection components, accounts for 23.7% of the total failures of capacitor devices (Statistics of Power Equipment Failures in 2018).
Comparison of major technical changes
| Technical parameters | Original standard | New standard | Reason for change |
|---|---|---|---|
| 6kV system power frequency withstand voltage | 25kV | 25/32kV | Coordinate with DL/T 604 |
| Dry coil test | No special requirements | Add 3 high and low temperature cycles | Solve the problem of outdoor cracking |
| Installation method | Unrestricted | Reverse suspension is prohibited | Prevent mechanical stress damage |
Analysis of key technical points
1. Insulation level adjustment
The new standard adjusts the rated short-time power frequency withstand voltage of the 6kV system discharge coil to 25/32kV. The reason for this change is:
- Synchronize with the insulation coordination requirements of DL/T 604-2020
- Actual operation data shows that the breakdown rate of the discharge coil under the original 25kV standard is as high as 1.8 times/thousand units per year
2. New requirements for dry-type discharge coils
In response to the 47 cases of dry coil cracking recorded by Anhui Power Grid from 2017 to 2019, the standard adds:
- Alternating high and low temperature test (-40℃~+85℃ cycle)
- Epoxy resin shell thickness detection (≥5mm)
- Mandatory requirement for positive vertical installation
Implementation suggestions
Equipment selection guidance
It is recommended to give priority to discharge coils that meet the following characteristics:
- Pass the new version of type test certification
- Secondary junction box protection level ≥IP54
- Provide a 3-year or more cracking warranty
Operation and maintenance precautions
Focus on the implementation of the standard:
- Renovation period of existing reverse-installed equipment (recommended to be completed within 2 years)
- Check the sealing of secondary terminals before the rainy season every year
- Establish an early warning mechanism for abnormal discharge coil temperature