160 kVA Oil-Immersed Transformer for Industrial Applications: Performance Guide

Overview

The S11 and S13 series fully sealed oil-immersed transformers are designed for AC 50 Hz systems at an operating voltage of 20 kV and below. They are widely applied in the petroleum, metallurgy, chemical, textile and light industries, including environments with significant dust, where the sealed tank is a decisive advantage because airborne contamination cannot reach the oil. The 160 kVA class is a common service-transformer rating for production lines, auxiliary power and site distribution.

Core and Winding Design

The core is built from cold-rolled grain-oriented silicon steel (CRGO) with high magnetic permeability. It uses full oblique (step-lap) joint stacking with a multi-step circular core column, and the iron yoke and core limbs have consistent cross-sections, which reduces no-load loss, excitation current and noise. The windings are concentric coils with corrugated oil channels that improve heat transfer; a no-paint dipping process and tight tape binding keep the coils rigid and quiet. The high-voltage winding carries tap connections to an off-circuit tap changer mounted on the tank cover, allowing voltage adjustment before the transformer is energized.

Safety and Monitoring Devices

Pressure relief valve on ratings from 30 kVA to 2000 kVA, protecting the tank from internal fault pressure.

Gas (Buchholz) relay with alarm and trip contacts, available on request for enhanced protection.

Glass thermometer pocket extending 120 +/- 10 mm into the oil at the top of the tank; ratings of 1000-2000 kVA add an outdoor signal thermometer for remote temperature monitoring.

Oil level gauge, sampling valve and drain valve as standard fittings.

Tank and Cooling

The tank has a corrugated wall with a dust-sprayed surface and a robust paint film. The corrugated panels act as cooling fins and flex to compensate oil volume changes - the breathing function - while the fully sealed structure keeps the oil and insulation away from atmospheric moisture. This design needs no conservator, breather or desiccant maintenance.

Performance and Standards

The S11 and S13 loss classes follow GB/T 6451, with S13 offering lower no-load loss than S11 for the same rating. Design, manufacture and testing comply with IEC 60076-1/-2/-3 and the GB 1094 series. The unit is suitable for indoor or outdoor installation under the working conditions of the series, including the dusty industrial environments typical of cement, mineral processing and chemical plants.

Application Guidance

For dusty industrial environments, the fully sealed design is the main protection against contamination. For harmonic-rich loads such as variable-frequency drives and rectifiers, confirm the additional heating with the manufacturer and specify derating or a suitable harmonic rating. Routine maintenance consists of annual oil sampling and dissolved gas analysis per IEC 60422, inspection of bushings and protective devices, and periodic checks of the pressure relief device and thermometer.

Frequently Asked Questions

What is the difference between S11 and S13?

S11 and S13 are loss classes defined in GB/T 6451. S13 has a lower guaranteed no-load loss than S11 for the same rating, which reduces idle energy consumption; the purchase decision is usually made by comparing capitalized loss cost against first cost.

Why is a fully sealed tank important in dusty plants?

Because a sealed tank never breathes, dust and moisture cannot enter the oil. In conventional transformers, breathing draws humid air in as the oil cools, accelerating oil aging and reducing insulation life.

What protection devices are standard?

Standard fittings include a pressure relief valve, oil level gauge, thermometer and drain and sampling valves; a gas relay with alarm and trip contacts is available on request.

Can the tap changer be operated under load?

No. It is an off-circuit (de-energized) tap changer: the transformer must be disconnected before changing the tap position. Specify an on-load tap changer separately if voltage regulation under load is required.

What maintenance schedule is recommended?

Annual oil sampling with dielectric strength, acidity and dissolved gas analysis per IEC 60422, plus visual inspection of bushings, tank, thermometer and protective devices. Fully sealed units need no conservator or breather care.

Can this transformer supply VFD or rectifier loads?

Yes, but harmonic currents increase winding and core heating, so the load must be derated or the transformer specified with a harmonic rating; state the expected harmonic content when ordering.