Tadace na Kirfi na Makaranta na Aiki na Zabe-zabe da Yawanci da Iyakokin Kirkiro

Na takaɗi masu shirya kai da kuma tattaunawa masu shirya a cikin birnin, an yi karfin kayan zafi a 6kV/10kV/35kV masu shirya (gaskiya mafi yawan 10A). Saboda haka masu shirya a wannan kungiyar gida suna amfani da yanayin da ba ake tsara baya, kuma karamin shirya na muhimmanci suka shiga da kyau, babu wurin da ya fi tsara baya, saboda haka karkashin tsakiyar da ke faru ba zai iya inganta da kusa, domin haka ya kamata a taka zuba da IEE-Business. Z-type grounding transformers ta zama na musamman saboda kayan zafin da ba su da shi, amma wasu masana'antu sun buƙatar kayan zafi mai yiwuwa. Idan kayan zafi yana da yiwuwa, ya kamata a yi tushen da za su iya inganta a tattalin daidaito da low zero-sequence impedance grounding transformers.

1. Hanyar Tushen Kayan Zafin Z-Type Grounding Transformer
1.1 Tsarin Tushen

Kayan zuba na high-voltage winding ta Z-type grounding transformer ta shiga da zigzag connection. Karamin shirya ana kawo da karamin shirya mai uku (kamar hakan da aka nuna a Figure 1), kuma suka shiga da karamin iron core columns. Karamin shirya biyu daga karamin shirya mai uku ana kawo da karamin shirya mai uku da karamin shirya mai uku da kyau, wanda ya samu tsarin magnetoelectric coupling structure mai kyau.

Kayan zafi an tushen kamar hakan da aka nuna a equation (1).

A nan, X0 shin kayan zafi, W shi ne karamin turn da karamin shirya (ya'ni karamin shirya mai uku), ΣaR shi ne equivalent leakage magnetic area, ρ shi ne Lorenz coefficient, kuma H shi ne reactance height da karamin shirya.

2 Bincike Kayan Zafin Da Ba Ta Da Yiwuwa

Daga bayanin IEC 60076 - 1 standard, kayan zafin da ba ta da yiwuwa wa grounding transformer ta shahara idan yana cikin ±10%. Daga binciken abubuwan da aka samu a matsayin hundreds of grounding transformers (da ma'ana oil-immersed da dry-type) da aka yi a kananan shekaru, da kuma tsaftace da farkon masu samun da masu tushen kayan zafi, farkon da aka samu zai iya kula da kamar hakan:

• Masu samun da take da yiwuwa da masu tushen: Farko yana cikin yiwuwar. Wannan shine mafi yawan adadin, kuma mafi yawan abubuwan da suka shahara.

• Masu samun da suka fi yiwuwa da masu tushen: Farko yana da yiwuwa da take da. Amma saboda masu amfani suna magana da limitin yakin kawai, babu limitin yaki, don haka shi ne shahara, amma yawan adadin yana da yiwuwa.

• Masu samun da suka fi yiwuwa da masu tushen: Yana da yiwuwa mafi yawa da take da. Wannan yana da yiwuwa mafi yawa, amma yawan adadin yana da yiwuwa.

Saboda farkon da masu amfani suka buƙata da kayan zafi, akwai gwamnati da dama da grounding transformers. Daga cikinsu, 35kV class ta da mafi yawan adadin, kuma 10kV class ta da mafi yawan adadin. Gaskiya, idan ana buƙata da 35kV class grounding transformers, kayan zafi yana buƙata da take da ≤ 120Ω; idan ana buƙata da 10kV class, kayan zafi yana buƙata da take da ≤ 15Ω. Wasu masu amfani sun buƙata da yiwuwa, wasu ba su buƙata da yiwuwa ba.

3 Bincike Abubuwa

Idan a yi tsaftace da abubuwan da aka samu a matsayin multiple grounding transformers, asal da yiwuwar da ba ta da kayan zafi ya shafi da yiwuwar da masu amfani suka buƙata da kayan zafi da ba ta da yiwuwa. Idan yana da yiwuwa ko kuma yana da yiwuwa, zai iya ba aiki da takarda mafi yawa. Idan a nemi bayanin a Equation (1), kayan zafi na da square relationship da karamin turn, wanda yana da muhimmanci mafi yawa a kayan zafi: idan karamin turn yana da yiwuwa, yana da yiwuwa da karamin wire; idan karamin turn yana da yiwuwa, yana da yiwuwa da karamin iron core. Idan kayan zafi yana da yiwuwa ko kuma yana da yiwuwa, zai iya ba takarda mafi yawa.

3.1 Bincike Maidaicin Aiki

A nemi bayanin two batches of small-capacity 10kV grounding transformers don bincike:

• Oil-immersed grounding transformer: Model DKS11 - 125/10.5, babu secondary winding. Masu amfani sun buƙata da kayan zafi da take da < 4&Omega;. Daga bayanin hanyar tushen da aka bayyana, idan a yi tsaftace da manufacturing deviation da kuma reserving a margin, an tushen da design value da take da 2.2&Omega;. Amma a matsayin production process, an samu result da take da yiwuwa, yana da yiwuwa da 3.5 times da design value; don batch of 7 products, kayan zafi yana cikin 7&Omega; - 8&Omega;.

• Dry-type grounding transformer: Model DKSC11 - 125/10.5, design value da take da 2.25&Omega;, kuma an samu finished product da take da 6.8&Omega;, yana da yiwuwa da about 3 times. An fitar da shi daga factory ba a negotiation and permission from the user.

Daga tsaftace, yiwuwar da oil-immersed type yana da yiwuwa da dry-type. Dalilin haka shin, idan a yi tushen da very small zero-sequence impedance, karamin turn yana da yiwuwa, radial size da karamin shirya yana da yiwuwa, kuma height yana da yiwuwa, saboda haka kayan zafin da take da yiwuwa ba zai iya inganta. Idan base value yana da yiwuwa, poor control of the size easily leads to the amplification of the deviation; while the dry-type winding is cast with resin, and the external dimension is easier to control with the help of a mold, so the deviation is relatively smaller.

Bayanin da aka samu ya nuna cewa hanyar tushen da yake da yiwuwa ba zai iya amfani da grounding transformer da low zero-sequence impedance. Daga tsaftace da bayanin da aka samu a matsayin previous products, ana sashe da introduction of a correction factor, and different zero-sequence values correspond to different correction factors: as the zero-sequence value increases, the factor decreases non-linearly; when the zero-sequence value reaches about 10&Omega;, the factor approaches 1.0; after exceeding 10&Omega;, affected by the slight differences in the production process, the factor changes little (there are occasional cases where it is less than 1.0, and the overall deviation is low), and the form of expression is approximately an inverse proportion function in the first quadrant (see Figure 2).

Yana da kyau a duba cewa binciken da aka bayyana yana da damar da 10kV products. Don products above 10kV, since there is no such strict requirement for low zero-sequence impedance, the phenomenon of excessive zero-sequence impedance deviation has not been found so far.

4 Solutions

To address the issue of excessive measured zero-sequence impedance in low zero-sequence impedance grounding transformers, the following optimization measures are proposed based on data collection and analysis:

4.1 Design Optimization Strategy

When users require an extremely small zero-sequence impedance value, the precision of winding dimensions is difficult to ensure, easily amplifying measurement deviations. For products with a required zero-sequence impedance <5&Omega;, a design margin of 2-5 times should be reserved. The smaller the impedance value, the larger the margin needed to ensure measured values meet requirements.

4.2 Manufacturing Control Points

The production process plays a decisive role in ensuring product performance accuracy:

• Mold Precision Control: Manufacture winding molds strictly according to design specifications, ensuring dimensional tolerances are met.

• Winding Dimension Management:

• Precisely control the radial and axial dimensions of windings, as these parameters directly affect zero-sequence impedance after the number of turns is determined. All dimensions must comply with drawing tolerances.

• For low-impedance products using small-gauge enameled wires, interlayer insulation must be laid flat, and windings should be tightly wound.

• Special Processes for Dry-type Products:

• For cast-resin structures, use internal and external molds to accurately control diameter dimensions. The thickness of the mesh cloth laid before winding should be slightly smaller (not larger) than specified.

• Axial dimensions of segmented windings are controlled by inter-segment insulation. Adjust and fix the height and spacing of each segment to prevent collapse during casting.

4.3 Technical Agreement Recommendations

• Prioritize specifying a zero-sequence impedance &ge;5&Omega; in agreements.

• If users insist on <5&Omega;, clearly communicate manufacturing difficulties in advance and establish a consultation mechanism to avoid delivery risks.

5 Conclusion

For low zero-sequence impedance grounding transformers, significant deviations exist between design values calculated by general formulas and actual measurements. It is recommended to evaluate manufacturability at the ordering stage, introduce correction factors during design, and reserve sufficient production margins to enhance product consistency and delivery reliability.