Comprehensive QDTB Transformer and Electrical Equipment Selection Guide
Selecting the right electrical equipment at the design stage is the critical factor determining investment efficiency, operational reliability, and lifetime maintenance costs. This guide details the QDTB product portfolio — from high-efficiency oil-immersed transformers to smart compact substations — complete with technical specification tables and decision-making processes to support engineers, EPC contractors, and investors.
Every QDTB product line is designed and manufactured to international standards (IEC/IEEE/GB), undergoes rigorous quality inspection, and has been successfully deployed in over 120 countries worldwide.
1. Oil-Immersed Transformers — S11, S13, S20 Series
Oil-immersed transformers are QDTB's flagship product line, widely used in distribution systems from low voltage to medium voltage. This product family includes three generations with progressively higher efficiency:
S11 — Standard Efficiency: The most economical line, suitable for general infrastructure, residential distribution, and light industrial applications. Meets IEC 60076 and GB/T 6451. Capacity: 30–1,600 kVA, primary voltage up to 35 kV.
S13 — Low-Loss: Higher-grade silicon steel and advanced core stacking reduce no-load losses by ~30% vs S11. Suitable for energy-efficiency projects meeting Class 2 per GB 20052 or IE2 per IEC 60076-20.
S20 — Ultra-High Efficiency: Premium grain-oriented silicon steel (Hi-B/domain-refined), optimized flux design, high-grade copper conductors. No-load losses reduced 40–50% over S13. Meets GB 20052 Class 1 and IEC IE3/IE4. Payback: 3–5 years.
Oil-Immersed Transformer Specifications
| Parameter | S11 | S13 | S20 |
|---|---|---|---|
| Rated capacity | 30–1,600 kVA | 30–2,500 kVA | 50–3,150 kVA |
| Primary voltage | ≤ 35 kV | ≤ 35 kV | ≤ 35 kV |
| No-load loss (500 kVA) | 770 W | 540 W | 290 W |
| Load loss (500 kVA) | 5,410 W | 5,010 W | 4,610 W |
| Noise level (≤1,000 kVA) | ≤ 45 dB(A) | ≤ 45 dB(A) | ≤ 42 dB(A) |
| IEC efficiency class | IE1 | IE2 | IE3/IE4 |
| GB 20052 class | Class 3 | Class 2 | Class 1 |
| Payback (vs S11) | — | 4–6 years | 3–5 years |
| Design lifespan | ≥ 30 years | ≥ 30 years | ≥ 30 years |
2. Dry-Type Transformers — SCB, SCBH Series
Cast resin dry-type transformers are optimal for indoor installations with stringent fire safety. QDTB offers two lines:
SCB — Cast Resin Dry-Type: LV winding encapsulated in epoxy resin, HV winding in glass-fiber-reinforced epoxy. F1 fire safety per IEC 60076-11, self-extinguishing, no toxic gas emission. Ideal for commercial buildings, hospitals, data centers, and basements.
SCBH — Amorphous Core: Amorphous metal core reduces no-load losses 60–70% vs standard SCB. Perfect for highest-efficiency indoor applications where oil-immersed units cannot be used.
Dry-Type Transformer Specifications
| Parameter | SCB (Class F) | SCB (Class H) | SCBH (Amorphous) |
|---|---|---|---|
| Rated capacity | 30–2,500 kVA | 30–2,500 kVA | 30–1,600 kVA |
| Primary voltage | ≤ 35 kV | ≤ 35 kV | ≤ 20 kV |
| Insulation class | Class F (155°C) | Class H (180°C) | Class F (155°C) |
| Permissible winding rise | 100 K | 125 K | 100 K |
| Protection (enclosure) | IP00–IP31 | IP00–IP31 | IP20–IP31 |
| Fire safety | F1 | F1 | F1 |
| No-load loss (800 kVA) | ~1,750 W | ~1,900 W | ~550 W |
| Typical applications | Buildings, malls, hospitals | Metallurgy, chemicals, marine | Green buildings, data centers |
3. Compact Substations — ZBW, ZGS Series
ZBW — European-Type: Three-compartment (MV–transformer–LV) design. Transformer up to 800 kVA (oil) or 1,600 kVA (dry). On-site installation time is 1/3 vs. conventional substations.
ZGS — American-Type (Pad-Mounted): Sealed two-compartment design on concrete pad. Ideal for outdoor distribution, residential areas, solar farms. SCADA-ready.
4. Switchgear — MV and LV Cabinets
- KYN28A-12: Withdrawable circuit breaker for 12kV. IEC 62271, IP4X. For intermediate substations and industrial distribution.
- XGN15-12: Fixed ring main unit (RMU) for 12kV. Compact, economical, for distribution and wind substations.
- GCS/GCK/MNS: LV drawout distribution cabinets, modular. IEC 61439, for MCC and main distribution.
Product Selection Process
Step 1: Define Input Parameters
- Required capacity (kVA/MVA) and load profile
- Primary and secondary voltages, including tap range
- System frequency (50Hz or 60Hz)
- Installation conditions: indoor/outdoor, altitude, ambient temperature
- Energy efficiency requirements (IE class, DOE level, GB class)
- Applicable standards: IEC, IEEE, GB, or combination
- Certification requirements: CE, UL, CSA, CCC
- Investment budget and expected operating costs
Step 2: Selection Matrix
| Application | Recommended Product | Notes |
|---|---|---|
| Outdoor distribution ≤1,600 kVA | S11/S13 oil-immersed | IE1/IE2, fast payback |
| Highest efficiency distribution | S20 oil-immersed | IE3/IE4, 3–5 year payback |
| Indoor, fire safety critical | SCB dry-type | F1 fire rating, zero oil risk |
| Indoor, maximum efficiency | SCBH amorphous | 60–70% lower no-load loss |
| Urban, quick deploy | ZBW compact | Factory-tested, 1/3 install time |
| Residential outdoor | ZGS pad-mounted | Compact, SCADA-ready |
| Solar/wind generation | S13/S20 renewable-grade | Harmonic-resistant design |
| Data center / critical load | K-factor transformer | K-13 or K-20 |
Step 3: Customization
QDTB offers special voltage ratios, tropical climate designs, high-altitude derating, seismic-rated construction, and multi-standard certification documentation. Contact our engineering team for project-specific solutions.