GB/T 24843-2018 in English
VALIDTechnical specification of 1 000 kV single phaseoil-immersed auto-transformer
- Issued on:2018-07-13
- Implemented on:2019-02-01
- File Format:PDF
- Delivery:Via email within 5 business days
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《GB/T 24843-20181000kV单相油浸式自耦电力变压器技术规范》由524（中国电力企业联合会）归口，TC569（全国特高压交流输电标准化技术委员会）执行，主管部门为中国电力企业联合会。
Introduction
1. Standard Background and Overview
GB/T 24843—2018 replaces the old standard GB/Z24843—2009, and is mainly applicable to single-phase oil-immersed autotransformers with rated capacities of 1000MVA and 1500MVA. This standard comprehensively upgrades the performance parameters, structural requirements and test methods of transformers in response to the needs of UHV transmission systems.
2. Comparison of standard frameworks
| Dimensions | Old standard (GB/Z24843-2009) | New standard (GB/T24843-2018) |
|---|---|---|
| Term definitions | The definitions of main transformer and voltage regulating and compensating transformer are not specified in detail. | New key terms such as main transformer and voltage regulating and compensating transformer are added, and the requirements for their sub-box layout are clarified (see Table 1). |
| Insulation level | The design standard for short-time induced voltage at neutral point is not clarified. | The newly added neutral point short-time induced voltage design is carried out according to 185kV, and a comparison of the rated insulation levels of UHV transformer windings in various countries is provided (see Appendix B). |
| Test requirements | The requirement for separate testing of bushing partial discharge is not included. | A new bushing partial discharge test is added, and all tests are required to be completed before leaving the factory (see Section 7.5). |
3. Interpretation of key technologies
3.1 Improvement of performance parameters
The new standard puts forward higher requirements for the no-load loss of transformers. The no-load loss of 1000MVA main transformers shall not exceed 185(1+15%)kW. At the same time, the efficiency index is improved to ≥99.8% (under rated conditions), reflecting the energy-saving design concept.
3.2 Winding and insulation requirements
The performance of the winding insulation material must match the short-circuit withstand capability verification result. The common winding and low-voltage winding use self-adhesive wires to ensure reliability under asymmetric operating conditions (see Section 6.2).
3.3 Cooling system optimization
The cooling device uses a low-noise fan and is equipped with a backup cooling system to meet the heat dissipation requirements under overload conditions (see Section 6.5).
4. Implementation recommendations
4.1 Implementation recommendations for manufacturers
- Strictly follow the rated voltage regulation range requirements of the tap changer (see Table 1) to ensure the long-term reliability of the off-excitation and on-load tap changers.
- In bushing design, focus on the requirement that the creepage distance is not less than 25mm/kV, and conduct a separate partial discharge test (see Section 6.6).
- Complete all factory tests before transportation, especially the ACLD and ACSD tests, to ensure that the insulation performance of the transformer meets the standard requirements.
4.2 User purchase recommendations
- Select the appropriate voltage regulation method (off-excitation or on-load voltage regulation) according to the actual grid conditions, and specify the rated values under special use conditions.
- Propose possible DC bias current values at the inquiry stage to ensure that the manufacturer fully considers its impact at the design stage (see Section 4.3).
- A calculation report on the relationship between the transformer's allowable continuous load and the number of operating cooling devices is required (see Section 5.9).
4.3 Maintenance and servicing recommendations
- Regularly monitor the dissolved gas content in the insulating oil to ensure that the acetylene and total hydrocarbon content is less than 10μL/L (see Section 6.7).
- Check whether the contact temperature rise of the tap changer meets the requirements, especially under high load conditions.
- Regularly clean and calibrate the gas relay to ensure its normal operation.
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