S11 630 kVA Oil-Immersed Transformer: Fully Sealed Design

Introduction to the S11 630 kVA Oil-Immersed Transformer

The S11 630 kVA oil-immersed transformer is a three-phase distribution transformer with a fully sealed tank. Unlike conventional designs with a conservator, the tank cover is equipped with a trinity device combining oil filling, oil level indication, and pressure relief. During packaging, a vacuum oiling process completely removes moisture from the transformer. After sealing, the insulating oil no longer contacts air, which effectively prevents oxygen and moisture from entering and causing performance degradation such as material aging and oil oxidation.

Fully Sealed Construction and Maintenance-Free Operation

Because the oil is isolated from the atmosphere, routine oil sample testing is not required and the oil does not need to be replaced during normal service life. The corrugated fin tank performs two functions simultaneously: it radiates heat, and its elastic walls compensate for oil volume changes caused by temperature variation, acting as the breathing element of the unit. The sealed tank cover and rim are bolted or welded to isolate oil from air, so the insulation never becomes damp, greatly slowing insulation aging and extending service life. The compact structure operates with low noise, and the absence of an oil storage tank makes the unit lower in height than comparable designs.

Technical Specifications

Insulation Levels by System Voltage

For a 10kV system, the S11 630 kVA unit provides 35kV power-frequency withstand voltage and 75kV lightning impulse voltage. For a 20kV system, the values are 50kV and 125kV respectively. For a 35kV system, the power-frequency withstand voltage is 70kV and the lightning impulse voltage is 170kV.

Applications

The S11 630 kVA transformer powers normal industrial factories, mines, and large buildings; distributes electricity in public utility networks for homes and businesses; supports infrastructure projects such as airports and tunnels; and is installed in compact transformer stations to step high voltage down to a usable distribution level. The vacuum filtration and oil injection process used at packaging removes residual moisture, and because the interior is sealed, insulation performance is maintained throughout the service life.

Frequently Asked Questions

Q: What does S11 mean in the model designation?

A: S denotes a three-phase oil-immersed transformer and 11 indicates the loss level series. The S11 series achieves lower no-load and load losses than the older S9 series, improving energy efficiency over the unit's life.

Q: Does the fully sealed transformer require oil replacement?

A: No. Because the corrugated tank isolates the oil from air, oxidation and moisture ingress are effectively prevented, so no oil change is needed during normal service life.

Q: How does the corrugated fin tank compensate oil expansion?

A: The elastic corrugated sheets expand and contract with oil temperature changes, absorbing the oil volume variation without drawing in outside air, which is why no conservator is required.

Q: Which vector group should be selected?

A: Dyn11 is the most common for distribution networks because it provides a stable neutral and good performance with unbalanced loads. Yyn0 is available where the local grid code requires it.

Q: What is the typical service life of this transformer?

A: With sealed construction preventing insulation dampness, the unit typically provides 25 to 30 years of service under normal operating conditions.

Q: Can the voltage ratio be customized?

A: Yes. Primary voltages from 2.4 kV to 34.5 kV and secondary voltages such as 400/230 V or 480/277 V can be configured to match the local grid, and the insulation level is adjusted accordingly.

To receive a quotation and delivery schedule for the S11 630 kVA oil-immersed transformer, contact our sales team with your voltage ratio, vector group, and installation details.