200 kVA Solar Photovoltaic Low-Loss Oil-Immersed Transformer
Nov 04, 2025
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A 200 kVA solar photovoltaic low-loss transformer is a three-phase, oil-immersed distribution transformer designed for photovoltaic power plants and distributed generation systems. This article focuses on the S13-M type, a fully sealed unit with non-excitation voltage regulation that combines low no-load loss with reliable outdoor operation, and explains its technical data, insulation levels, and typical applications.
What Is the S13-M 200 kVA Transformer?
The S13-M series is a three-phase, fully sealed oil-immersed distribution transformer. In the model designation, S indicates a three-phase transformer, 13 refers to the loss level, which is lower than that of S11 units, and M means that the tank is fully sealed so that the insulating oil does not contact the atmosphere. The transformer is built with premium silicon steel laminations and oxygen-free copper windings to achieve low loss, low noise, and high efficiency under continuous solar duty cycles.
Photovoltaic arrays generate power during daylight hours and their output fluctuates with irradiance, so the transformer must handle frequent partial loading with low no-load losses. The low no-load loss of the S13-M design directly reduces the energy consumed overnight and during cloudy periods, which improves the overall energy yield of the plant.
Technical Data of the S13-M 20 kV Series
The following table shows reference values for the S13-M series with a 20 kV high-voltage winding and a 0.4 kV low-voltage winding at 50 Hz.
| Rated Power (kVA) | No-load Loss (W) | Load Loss (W) at 75 C | Impedance (%) | No-load Current (%) |
|---|---|---|---|---|
| 50 | 100 | 1010/960 | 5.5 | 1.9 |
| 100 | 150 | 1730/1650 | 5.5 | 1.5 |
| 200 | 140 | 3000/3860 | 5.5 | 1.2 |
| 315 | 340 | 4210/4010 | 5.5 | 1.0 |
| 500 | 480 | 5940/5660 | 5.5 | 0.9 |
| 630 | 570 | 6820 | 6.0 | 0.8 |
| 1000 | 830 | 12000 | 6.0 | 0.6 |
| 1600 | 1170 | 15950 | 6.0 | 0.5 |
| 2500 | 1640 | 22220 | 6.0 | 0.4 |
Values are reference data published by the manufacturer; the exact figures for a specific order depend on the voltage combination, impedance, and accessory configuration.
Insulation Levels
| Voltage Grade (kV) | Maximum Operating Voltage (kV) | Power-frequency Withstand (kV/min) | Lightning Impulse Full Wave (kV peak) | Lightning Impulse Chopped Wave (kV peak) |
|---|---|---|---|---|
| 0.4 | 0.46 | 5 | 75 | 85 |
| 10 | 12 | 35 | 75 | 85 |
| 20 | 23 | 55 | 125 | 140 |
Why Low-Loss Transformers Suit Solar Plants
Low no-load loss reduces energy consumption during the night and in low-irradiance periods.
Stable performance under fluctuating output from photovoltaic arrays.
Oil-immersed, fully sealed construction is suitable for outdoor installation in solar fields.
Sealed tank design minimizes maintenance and prevents moisture ingress.
Mineral oil or eco-friendly ester fluids can be selected according to the site requirements.
Applicable Standards
The design and testing follow GB 1094.1 for power transformers, GB/T 6451 for technical parameters of three-phase oil-immersed power transformers, GB 2536 for transformer oils, and IEC 60076 for power transformers. Load guidance follows GB/T 15164, and model designation follows JB/T 3837. The latest editions of these standards apply.
Typical Applications
Photovoltaic power plants and rooftop commercial solar systems.
Distributed generation and energy storage collection stations.
Utility distribution networks and rural electrification projects.
Industrial facilities and commercial buildings with solar power input.
Frequently Asked Questions
Q1. What does S13-M mean in the model name?
S stands for three-phase, 13 is the loss level designation, and M indicates a fully sealed oil tank. The series is designed for low no-load loss and low maintenance.
Q2. Why is a low no-load loss important for a solar transformer?
Solar plants generate power only during daylight hours. When the plant is idle at night, the transformer still consumes no-load power, so reducing no-load loss directly improves the energy yield and operating economy of the plant.
Q3. What voltage levels are available?
The series is commonly supplied with a 10 kV or 20 kV high-voltage winding and a 0.4 kV low-voltage winding. Other combinations can be arranged according to the local grid code.
Q4. Can ester fluid be used instead of mineral oil?
Yes. Synthetic or natural ester fluids can be specified for projects with higher fire safety or environmental requirements. The tank and accessory design must be adapted accordingly.
Q5. How is the transformer cooled?
The standard cooling method is ONAN, oil natural and air natural. The oil circulates by convection and the heat is dissipated through the tank surface.
Q6. What tests are required before delivery?
Routine tests include ratio and vector group verification, winding resistance, insulation resistance, no-load loss and current, load loss and impedance, and dielectric withstand tests in line with IEC 60076.