Paghulagway sa Prototipo sa 20 kV Single-Phase Distribution Transformer

1. Pagdisenyo sa 20 kV Single-phase Distribution Transformer

Ang mga sistema sa distribusyon nga 20 kV kasagaran molambo og mga linya sa cable o mixed cable-overhead line networks, ug ang neutral point kasagaran gipahigayon pinaagi sa usa ka gamay nga resistance. Kini nga sitwasyon wala mobati og problema nga ang phase voltage mohimo og dako pa sa √3 beses sama sa caso sa single-phase fault sa 10 kV system. Busa, ang single-phase distribution transformer sa 20 kV system mahimong magamit ang tipo sa pagpahigayon sa dulo sa coil. Kini makapadami sa main insulation sa single-phase distribution transformer, nang ang volume ug cost sa 20 kV single-phase distribution transformer dili na mubo sa 10 kV.

2. Pagsangpot sa Impulse ug Test Voltages

Alang sa basic impulse level (BIL) ug insulation test level sa 20 kV single-phase distribution transformer, ang mga konsiderasyon mao ang mosunod:

Ang American National Standard ANSI C57.12.00—1973 (IEEE Std 462—1972) nagbutang nga ang basic impulse level (BIL) sa high-voltage side (20 kV) adunay 125 kV; ang rated voltage sa high-voltage component adunay 15.2 kV, ug ang AC withstand voltage (60 Hz/min) adunay 40 kV.

Ang insulation test nagbutang nga ang applied voltage test wala kinahanglan, apan ang induced voltage test kinahanglan ma-implementar. Sa panahon sa test, human sa pagpuyo og voltage sa outgoing terminal sa usa ka winding, ang voltage sa tanang high-voltage outgoing terminal ngadto sa ground mao ang 1 kV plus 3.46 ka beses sa rated voltage sa transformer winding. Bisan, sa induction test (frequency-doubled and voltage-doubled test), ang high-voltage mao ang:

2.1 Low-voltage Side (240/120 V)

• Basic Impulse Level (BIL): 30 kV

• AC Withstand Voltage (60 Hz/min): 10 kV

2.2 Sumala sa China’s National Transformer Quality Supervision Test Regulations

• High-voltage side:

• Basic Impulse Level (BIL): 125 kV (full wave), 140 kV (chopped wave)

• AC Induced Withstand Voltage (200 Hz/min): 40 kV

• Low-voltage side:

• Applied Voltage (50 Hz/min): 4 kV

3. Struktura ug Features sa 20 kV Single-phase Distribution Transformers

Duha ka specifications (50 kVA ug 80 kVA) gi-prototype, parehas nagamit ang outer-iron structure. Aron mapugos ang main insulation, gi-add ang end-insulation structure. Usa ka bushing gigamit alang sa lead-out. Ang dulo sa high-voltage coil gipahigayon ug giconnect sa tank. Ang low-voltage winding adunay single-coil structure.

3.1 Teknikal nga Performance Comparison Tali sa Prototyped 20 kV ug 10 kV Single-phase Distribution Transformers

• Loss comparison tali sa 20 kV ug 10 kV (gi-take ang 50 kVA ug 80 kVA isip ektsemplo) makita sa Table 1.

• Weight comparison tali sa 20 kV ug 10 kV (gi-take ang 50 kVA ug 80 kVA isip ektsemplo) makita sa Table 2.

4. 20 kV∥10 kV Single - phase Dual - voltage Distribution Transformer

Ang pag-upgrade sa 10 kV ngadto sa 20 kV distribution system involbari sa pagbag-o sa key equipment sama sa mga distribution transformers. Ang mataas nga kos sa pagbag-o ug power outages nga moguba sa produksyon nagbutang sa design sa dual-voltage (10 kV/20 kV) single-phase transformer isip solusyon aron malabtan ang mga suliranin.

4.1 Design

Batasan sa 10 kV wound-core single-phase distribution transformer, kini nga dual-voltage variant gi-basehan sa 20 kV = 2×10 kV relationship, gi-gamit ang series-parallel primary coils. Ug duha ka parallel high-voltage coils, duha ka core columns adunay high-voltage/low-voltage windings (high-voltage coils parallel). Duha ka low-voltage coils series sa “mid-point” output ±220 V-ground para sa duha ka users. Hayaay W₁ (high-voltage turns) ug W₂ (low-voltage turns). Sa parallel, U₁/U₂ = W₁/W₂ = 10 kV/220V, ug total high-voltage current doubles a single coil’s. Sa series, ang high-voltage input current equal sa coil current.

4.2 Switching Application

Ang capacity consistent para sa 20 kV o 10 kV high-voltage inputs. Sa 20 kV input, ang duha ka high-voltage coils in series mean each bears 10 kV. Ug high-voltage current I₁, capacity S₁ = I₁×20 = 20I₁(kVA). Switched to 10 kV, parallel high-voltage coils give 2I₁ input current, so S₁ = 2I₁×10 = 20I₁ (kVA). Thus, S₁ = S₂).

4.3 Structure

• Structure matches the single - phase wound - core transformer (patent No. 4612429).

• 10 kV/20 kV voltage - switching uses a reliable contact strip tap - changer.

• Insulation meets IEC 20 kV transformer standards (rated impulse voltage: 125 kV).

• Noise complies with IEC and relevant power company technical specs.

4.4 Advantages of Single - phase Dual - voltage Transformer

• Energy Conservation：The line loss of the 20 kV distribution system is 25% of that of the 10 kV distribution system, achieving a 75% energy savings. By adopting the single - phase wound - core technology in this design, the no - load loss of the transformer is 30% lower than that of the currently used S11 - type distribution transformer.

• Construction Cost Savings：During the upgrade from 10 kV to 20 kV, only a changeover switch is needed to switch the voltage. This reduces the power outage time, and the entire operation process can be completed within just a few minutes.

5. Conclusion

• Most neutral points of the 20 kV system are grounded through a small - resistance system. Therefore, it is easier to handle the main insulation of single - phase transformers at the 20 kV level compared to the 10 kV level.

• The load loss of 20 kV - class single - phase transformers is at the same level as that of 10 kV - class ones; their weight is also at a comparable level. In terms of no - load loss, 20 kV is lower than 10 kV. Regarding impedance, the 20 kV single - phase transformer is 20% higher than the 10 kV one.

• The 20 kV single - phase transformer is relatively economical. Its price will not differ significantly from that of 10 kV - class single - phase transformers.

• The 20 kV∥10 kV single - phase dual - voltage distribution transformer can be used in both 10 kV and 20 kV distribution systems. When upgrading a 10 kV system to a 20 kV system, there is no need to replace the transformer; simply switching the changeover switch suffices. It is a relatively economical and convenient method.