Performance and Price Comparison of 10kV Oil-Immersed Transformers: S13, S20, and SZ22 Series

Choosing the right 10kV oil-immersed transformer is essential for power distribution projects, whether in new construction or grid renovation. Among the available models, the S13 and S20 series are widely used, while the SZ22 series represents the latest upgrade in energy-saving technology. This article compares their performance, energy efficiency, and cost to help engineers and purchasing managers make informed decisions.

Energy Efficiency Standards and Classification

In China’s energy efficiency system, the S13, S20, and SZ22 series follow a clear upgrade path:

S13 Series: Equivalent to Level 3 efficiency. Based on traditional silicon steel cores, it offers moderate losses but no longer meets the current GB 20052-2020 energy-saving standard. It’s suitable only for low-priority or temporary projects.

S20 Series: Complies with Level 2 efficiency — the current market mainstream. It features significantly reduced no-load and load losses compared with the S13, meeting national requirements for new installations.

SZ22 Series: Represents Level 1 efficiency — the highest standard available. Its amorphous alloy core dramatically reduces no-load losses by 60–70% compared with the S20, making it ideal for continuous operation and long-term cost savings.

Core Performance Comparison

1. No-Load Losses (Iron Losses)
No-load losses occur when the transformer is energized without load. The SZ22 series offers the best performance in this area due to its amorphous alloy core, resulting in much lower energy waste during 24/7 operation.

2. Load Losses (Copper Losses)
Load losses are caused by current flow through the windings. Both the S20 and SZ22 transformers use optimized winding designs that greatly reduce copper losses compared to the S13 series.

3. Noise
Amorphous alloy cores in the SZ22 tend to generate slightly higher operating noise due to magnetostriction. Therefore, noise control should be considered in design and installation for residential or quiet environments.

Price and Lifecycle Cost Analysis

When evaluating costs, both the initial purchase price and the total lifecycle cost must be considered.

Initial Price Ranking (from Low to High): S13 → S20 → SZ22

S13 Series: Lowest upfront price but highest operational losses. It’s not recommended for modern installations due to high electricity consumption and outdated performance.

S20 Series: About 20–30% more expensive than S13. It provides an excellent balance between cost and performance, making it the preferred choice for most new distribution projects.

SZ22 Series: 50–80% more costly than S20, mainly due to the high price of amorphous alloy materials and complex manufacturing. However, it delivers the lowest energy consumption and best long-term return on investment.

Total Cost Over the Service Life

A transformer typically operates for 20–30 years. Energy costs account for most of the lifetime expense, so efficiency has a direct financial impact.

Example: For a 500kVA transformer operating 8,760 hours annually at a 65% load rate and an electricity cost of 0.8 yuan/kWh:
– The S20 series can recover its price difference over the S13 within 2–3 years through reduced energy losses.
– The SZ22 series typically offsets its higher cost within 5–8 years. After that, the energy savings become pure profit throughout its 20-year lifespan.

Conclusion: The higher the transformer’s utilization rate and local electricity price, the more economical it becomes to invest in a high-efficiency model — especially the SZ22 series.

Frequently Asked Questions (FAQs)

Q1: Is the S11 series still worth considering?
A1: No. The S11 series is outdated, with low efficiency and high losses. It does not meet current national standards and is not recommended.

Q2: What’s the difference between S22 and S20?
A2: The S22 series is an upgraded version of S20, offering slightly better efficiency and tighter loss limits. It falls between S20 and SZ22 in terms of performance and cost.

Q3: What other factors should I consider when purchasing?
A3: Pay attention to manufacturer qualifications, production quality, after-sales service, and key specifications such as short-circuit impedance, temperature rise, and certification (e.g., CQC, ISO).

Final Recommendation

When selecting between S13, S20, and SZ22 10kV oil-immersed transformers, don’t focus only on the initial price. Evaluate the energy efficiency level, operational environment, and total lifecycle cost. For long-term, high-load applications, the SZ22 series provides the best energy savings and overall return on investment.

Investing in higher efficiency today means saving more energy — and money — tomorrow.