If you need oil-immersed transformers, please contact us. We are a Chinese manufacturer.The model parameters of an oil-immersed transformer encompass a series of technical specifications crucial for selecting the appropriate transformer, system design, installation, and maintenance. Below are the core parameters and their meanings.

I. Core Model Identification (Usually included in the model name)

1. Product Category Code:

S: Three-phase

D: Single-phase - Less common for large power transformers.

2. Phase Number:

S: Three-phase

D: Single-phase

3. Cooling Method:

J: Mineral-oil-immersed, self-cooled - Relies on natural heat dissipation through tank radiators.

F: Mineral-oil-immersed, fan-cooled - Fans mounted on radiators for forced air cooling.

S: Mineral-oil-immersed, water-cooled - Uses circulating cooling water to cool the oil. Less common.

FP: Forced-oil, forced-air cooled - Uses an oil pump to force oil circulation and fans to cool the radiators.

SP: Forced-oil, water-cooled - Uses an oil pump to force oil circulation and cooling water to cool the oil.

4. Structural Feature or Winding Material:

F: Fan-cooled (sometimes used to distinguish cooling methods)

Z: On-load tap changer

L: Aluminum winding - Omission usually implies copper winding.

R: Wound core - Distinguished from laminated core.

H: Amorphous alloy core

5. Design Sequence Number:

A number indicating the generation of design improvements or a specific series.

6. Rated Capacity:

Unit: kilovolt-ampere (kVA) or megavolt-ampere (MVA). E.g., 500, 1000, 50000 (50MVA).

7. High-Voltage Winding Voltage Level:

Unit: kilovolts (kV). E.g., 10, 35, 110, 220.

8. Special Operating Environment (Optional):

TH: Tropical humid

TA: Tropical arid

W: Anti-pollution type

Model Examples

S11-M-1000/10:

S: Three-phase

11: Design sequence number (may represent energy-efficient type or specific loss level)

M: Fully sealed (usually refers to corrugated tank or expansion-type radiators, no conservator)

1000: Rated capacity 1000 kVA

/10: High-voltage side rated voltage 10 kV

(Implied: Oil-immersed self-cooled J, Copper winding)

SFSZ11-50000/110:

S: Three-phase

F: Fan-cooled

S: Three-winding

Z: On-load tap changer

11: Design sequence number

50000: Rated capacity 50000 kVA (50 MVA)

/110: High-voltage side rated voltage 110 kV

SZ11-20000/35:

S: Three-phase

Z: On-load tap changer

11: Design sequence number

20000: Rated capacity 20000 kVA (20 MVA)

/35: High-voltage side rated voltage 35 kV

(Implied: Oil-immersed self-cooled J, Copper winding, Two-winding)

II. Key Performance Parameters

Usually detailed in technical specifications or nameplate

1. Rated Capacity: The apparent power (kVA or MVA) the transformer can continuously deliver under rated conditions. This is the most fundamental parameter.

2. Rated Voltage:

High-Voltage Side Rated Voltage (U1N): The voltage applied to the primary winding or the primary winding terminal voltage under no-load conditions (kV).

Low-Voltage Side Rated Voltage (U2N): The voltage on the secondary side when the primary side is at rated voltage and the secondary side is open-circuited (kV).

Voltage Ratio: U1N / U2N.

3. Rated Current:

High-Voltage Side Rated Current (I1N): Calculated from rated capacity and high-voltage rated voltage (A).

Low-Voltage Side Rated Current (I2N): Calculated from rated capacity and low-voltage rated voltage (A).

4. Rated Frequency: Usually 50 Hz or 60 Hz.

5. Vector Group Symbol: Indicates the connection method of HV and LV windings (Star Y, Delta D, Zigzag Z) and their phase relationship (clock notation). E.g., Dyn11, Yyn0, YNd11.

6. Short-Circuit Impedance (Uk%):

The percentage of the voltage applied to one winding at rated frequency, required to circulate rated current in that winding when the other winding is short-circuited, relative to the rated voltage of that winding.

Crucial! Affects short-circuit current, voltage regulation, and parallel operation. Typical range: 4% - 24% (increases with voltage level and capacity).

7. No-Load Loss (P0):

The active power loss (kW) of the transformer at rated frequency and rated voltage with the secondary side open-circuited. Primarily caused by hysteresis and eddy current losses in the core.

Important energy efficiency indicator.

8. Load Loss (Pk):

The active power loss (kW) of the transformer at rated frequency when rated current flows through one set of windings (with the other side short-circuited). Primarily caused by resistance losses (I²R) in the windings.

Important energy efficiency indicator and basis for temperature rise calculation.

9. No-Load Current (I0%):

The current flowing in the primary winding under rated frequency and rated voltage with the secondary side open-circuited, expressed as a percentage of the rated current.

Reflects magnetizing characteristics.

10. Temperature Rise Limit:

The maximum allowable temperature rise (°C) above ambient temperature for various parts when the transformer operates at rated capacity and under rated cooling conditions.

Key parts: Winding (commonly 65K for oil-immersed), Top oil (commonly 55K or 60K). Based on insulation material life.

11. Cooling Method: Clearly stated, e.g., ONAN (Oil Natural Air Natural), ONAF (Oil Natural Air Forced), OFAF (Oil Forced Air Forced). See Part I.

12. Insulation Level:

Rated Power-Frequency Withstand Voltage (AC, kV): Power frequency withstand test value.

Rated Lightning Impulse Withstand Voltage (LI, kV): Lightning impulse withstand test value.

Values specified separately for HV side, LV side, and neutral (if applicable).

13. Tap Changer:

Tap Range: E.g., ±5%, ±2x2.5%.

Number of Taps: E.g., 5 steps, 9 steps.

Tap Changing Method:

Off-circuit tap changing: Requires de-energization for tap changing.

On-load tap changing (OLTC): Can change taps under load (model often includes Z).

14. Weight:

Core and Coil Weight: Total weight of core and windings (kg or t).

Oil Weight: Weight of transformer oil (kg or t).

Total Weight: Total shipping weight of the transformer (kg or t).

15. Overall Dimensions: Length x Width x Height (mm).

16. Oil Quantity: Total volume of insulating oil required (L or m³).

17. Protection Class: Degree of protection provided by enclosure against dust and water (IP code), e.g., IP20, IP23, IP54.

18. Sound Level: Noise level (dB(A)) during operation under rated conditions and specified measurement conditions.

19. Efficiency: Ratio of output active power to input active power (%). Usually calculated based on specific load factor (e.g., 50% load) and specific loss levels.

III. Other Factors to Consider During Selection

Application Site: Indoor, outdoor, special environments (high altitude, heavy pollution, severe cold, humid heat, etc.).

Overload Capability: The transformer's ability to handle short-term or periodic overload operation.

Service Life: Design expected lifetime (typically 20-30 years).

Environmental Requirements: Oil type (mineral oil, silicone oil, natural ester), recyclability, noise, etc.

Compliance Standards: Such as IEC, IEEE, GB, etc.

Summary

When selecting an oil-immersed transformer, the model provides basic identification and structural information, while the detailed technical parameters (rated capacity, voltage, current, losses, impedance, temperature rise, insulation level, etc.) are key for evaluating its performance, efficiency, compatibility, and cost. Always refer to the manufacturer's detailed specifications and nameplate information, and consider the specific application requirements (such as load characteristics, system short-circuit capacity, energy efficiency requirements, installation environment) comprehensively.

If you have a specific model or application scenario, I can help interpret the meaning of particular parameters or provide more targeted advice.