110kV SSZ11 Series Three-Phase Three-Winding Oil-Immersed Power Transformer with On-Load Tap-Changer

1. Product Overview & Model Definition

The 110kV SSZ11 series three-phase three-winding oil-immersed power transformer with on-load tap-changer is an energy-saving upgraded model developed from the SZ11 two-winding transformer.

Its core features include three-winding independent power supply and on-load voltage regulation without power interruption. It can output three voltage levels (high, medium and low voltage) at the same time, well suited for multi-voltage power grids and multi-load scenarios. It is a key equipment in 110kV power transmission and distribution systems featuring multi-voltage output, energy saving and voltage stabilization.

This product complies with:

GB 1094.1-2013, GB/T 6451-2015, GB 20052-2020 and IEC 60076 standards, reaching China’s Class 2 energy efficiency or higher.

It is widely used in 110kV key substations, regional power supply centers, large industrial parks, urban distribution network upgrading, new energy collection stations and other places requiring high power supply reliability, voltage stability and multi-voltage output.

Model Explanation

• S: Three-phase oil-immersed power transformer

• S: Three-winding structure

• Z: On-load tap-changer

• 11: Low-loss series (no-load loss ≥30% lower than S9)

• 110kV: Rated high voltage

Typical model: SSZ11-50000/110

• 50000: Rated capacity 50000 kVA

• 110: High voltage 110 kV

• Typical voltages: MV 38.5kV, LV 10.5kV

• Tap range: ±8×1.25%

2. Core Technical Parameters(Customizable)

2.1 Basic Parameters

• Rated capacity: 31500, 40000, 50000, 63000, 80000 kVA

  Capacity ratio: 100% / 100% / 100%

• Rated voltage:

  HV: 110/115/121 kV (±8×1.25% or ±10×1%)

  MV: 35kV / 38.5kV

  LV: 10.5kV / 6.3kV / 6.6kV (customizable)

• Connection group: YNyn0d11 (standard), YNyn0yn0 (optional)

• Frequency: 50Hz (60Hz export version available)

• Short-circuit impedance:

  HV–MV: 10.5% (31500–50000kVA), 12% (63000kVA+)

  HV–LV: 17%

  MV–LV: 6.5%

2.2 Loss & Energy Efficiency

• No-load loss: ≥30% lower than S9 series

• Load loss at 75℃: Meets GB/T 6451

• No-load current: ≤0.5%–0.6%

• Energy efficiency: Class 2 or above (Class 1 customizable)

2.3 On-Load Voltage Regulation

• Regulation type: On-load tap changing (without power outage)

• Tap range: ±8×1.25% (17 steps) or ±10×1% (21 steps)

• Switching time: ≤5 seconds per step

• Tap-changer: Oil-immersed type

• Mechanical life: ≥300,000 operations

• Electrical life: ≥100,000 operations

• Control: Manual / automatic / remote

2.4 Other Key Parameters

• Insulation level:

  HV: Lightning impulse 450kV, withstand voltage 200kV

  MV: Lightning impulse 200kV, withstand voltage 85kV

  LV: Lightning impulse 75kV, withstand voltage 35kV

• Cooling: ONAN / ONAF (OFAF for large capacity)

• Noise: ≤65–68 dB(A) under ONAN

• Partial discharge: ≤100 pC

• Ambient temperature: -30℃ ~ +45℃

• Altitude: ≤1000m (up to 4000m customizable)

• Design life: ≥30 years

• Transformer oil: 25# environmental oil

3. Structure & Technical Features

3.1 Core

• High-permeability grain-oriented cold-rolled silicon steel (0.27–0.30mm)

• Multi-step step-lap joint, 3-limb structure

• Hole-free binding, low vibration and noise

• Phosphating and painting for anti-moisture and anti-corrosion

• Wound core available for lower noise and loss

3.2 Three-Winding Structure

• High-purity oxygen-free copper conductors

• HV: multi-layer cylindrical winding

• MV: cylindrical type

• LV: spiral or continuous type

• Balanced ampere-turns, excellent short-circuit withstand capability

• Vacuum drying and impregnation, low partial discharge

• End reinforcement for high mechanical strength

3.3 On-Load Tap-Changer

• Double transition resistor, arcless switching

• Silver alloy contacts, long service life

• Integrated sealed structure

• Manual & automatic control, remote monitoring supported

• Built-in overcurrent, overheating and short-circuit protection

3.4 Tank & Sealing

• High-quality Q235B steel plate, ultrasonic inspection

• Corrugated or radiator-type tank

• Capsule or diaphragm fully sealed structure

• Anti-oxidation, oil-isolated from air

• Three-layer primer + one top-coat painting, long anti-corrosion life

3.5 Insulation & Protection System

• Composite insulation: pressboard, oil, epoxy parts

• Insulation class A (105℃)

• Standard protections:

  Buchholz relay, pressure relief valve, oil level gauge, thermometer

• Optional: DGA online monitoring, lightning protection, tap-changer monitor

3.6 Cooling System

• ONAN: natural cooling, low noise

• ONAF: fan-assisted, high overload capacity

• Intelligent temperature control, automatic fan control

4. Core Product Advantages

1. Three-winding multi-voltage output

   Simultaneous HV/MV/LV output; reduces equipment quantity and space.

2. On-load voltage regulation without outage

   Stable voltage, strong adaptability to grid fluctuation, high power quality.

3. Ultra-low loss & high efficiency

   No-load loss ≥30% lower than S9; obvious power saving; short payback period.

4. Low noise & eco-friendly

   Noise ≤65–68 dB(A); environmental oil; fully sealed, no leakage or pollution.

5. Strong short-circuit withstand capability

   High mechanical strength, rigid clamping, stable and reliable operation.

6. Fully sealed & maintenance-free

   Long oil service life; no frequent oil replacement or testing; maintenance cost reduced by over 60%.

5. Application Scenarios

1. Power grid: 110kV key substations, regional power supply, urban grid upgrading

2. Large industry: metallurgy, chemical, mining, cement, large industrial parks

3. Urban construction: commercial areas, residential quarters, subway, airport, railway stations

4. New energy: PV and wind power 110kV collection & boosting stations

5. Special environments: plateau, low temperature, coastal salt-fog, corrosive areas

6. Installation, Operation & Maintenance

6.1 Installation

• Level, firm concrete foundation

• Reliable earthing (earth resistance ≤4Ω)

• Proper lifting, anti-shock during transportation

• Correct wiring for three windings and tap-changer control

• Full insulation and function tests before commissioning

6.2 Operation

• Real-time monitoring of oil temperature, level, current, voltage

• Avoid long-term overload

• Regular cleaning of radiators

• Stable tap-changer operation; no rapid continuous switching

6.3 Maintenance

• Routine inspection: oil level, temperature, sealing, cooling system

• Periodic tests: oil analysis, insulation, partial discharge

• Tap-changer inspection every 3–5 years

• Long-term outage: periodic operation to prevent moisture