ELECTRIC, WITH AN EDGE

The Complete Guide to a Three-phase Combined Power Transformer

This guide indicates the terms and definitions, operating conditions, product models, basic parameters, structural requirements, and technical requirements of three-phase combined power transformers with a rated capacity of 4000KVA and above, a nominal system voltage of 110kv~500kv, and a rated frequency of 50Hz. , Nameplate, allowable deviation, inspection rules and methods, lifting, packaging, transportation, installation, and storage.

Pad-mounted Transformer

We can provide you single phase and three phase pad mounted transformer

Dry-type Transformer

Type:Cast resin; Rated Capacity: Up to 25MVA; Rated Voltage: Up to 36KV;

Pole Transformer

TypeCSP type Frequency: 50/60Hz; Rated Power: 5~167kva

Dry-type Transformer

Frequency: 50/60Hz Rated voltage:10kv, 20kv,30kv Rated Power: 400~2500kva

Table of Contents

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What is a three-phase site-combined power transformer?

The three-phase site-combined power transformer refers to a three-phase site-combined power transformer that will share one oil tank and install three units on the same foundation through pipelines.

What is the operating environment of the three-phase combined power transformer?

The three-phase combined power transformer is applied to the climate and environmental conditions at different altitudes, as shown in Table 1.

For transformers scheduled to be installed at a certain altitude, the environmental parameters can be negotiated between the supplier and the buyer with reference to Table 1.

Top Electricity Transformer Manufacturers and Suppliers in The USA
NoEnvironmental parametersAltitude m
010002000300040005000
1Air pressure/kpaThe annual average101.39079.570.161.754
2Air humidity/°C°Clowest9787.277.5686052.5
Highest45.445.435302520
Highest daily average35、3035、3025201510
The annual average2020151050
lowest(+5、-5、-15、25、-40、-45
Maximum daily temperature difference/K15、25、30
3Relative humidity/%The wettest month has the smallest monthly average (monthly average maximum temperature/°C)95.9 (25)95.9 (25)90 (20)90 (15)90 (10)90 (5)
The driest month has the smallest monthly average (monthly average maximum temperature/°C)20 (15)20 (15)15 (15)15 (10)15 (5)15 (0)
4Absolute humidity/(g/m2)The annual average117.65.33.72.71.7
Annual average minimum3.73.22.72.21.71.3
5Maximum direct solar radiation intensity/(W/m2)100010001060112011801250
6Maximum custom/(m/s)s)25、30、35、40 
7Maximum precipitation (continuous 10min)/mmmm15、30 
8Maximum soil temperature (depth 1m)/°C302520201515

What is the three-phase transformer specification?

The rated capacity, voltage combination, tapping range, connection group number, no-load loss, load loss, no-load current, and short-circuit impedance of the 110kvthree-phase site-combined power transformer should meet the requirements of Table 2~Table 6.

Table 2~Table 6 are applicable to transformers with hierarchical insulation for high-voltage windings (the rated insulation level of the neutral point segment is: the RMS value of the rated applied to withstand voltage is 95kv, and the peak value of the rated lightning impulse withstand voltage is 250kv).

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Tab2: 40000kva~180000kva dual winding three-phase site-combined power transformer

For step-up transformers, a tapless structure should be adopted, and taps can be set if there is a requirement for operation.

Rated Capacity kvaVoltage combination and tapping rangeConnection group labelNo-load loss kWLoad loss kWLoad current%Short-circuit impedance%
High voltage kvLow voltage kv
40000110±2 X 2.5%  115±2 X 2.5%  121±2 X 2.5%6.3   6.3   10.5YNd11331480.4510.5
50000391750.42
63000462080.38
7500013.8  15.75  18     21522380.3312~14
90000602730.3
120000763390.27
150000884010.24
1800001004600.2

Tab3: 40000kva~180000kva three winding three-phase site-combined power transformer

The capacity of the high, medium, and low voltage windings are allocated as (100/100/100)%.

According to user needs, the medium voltage can choose a voltage value different from that in the table, and the capacity exceeds 90000kva. It is not suitable to set up taps for medium voltage.

For step-up transformers, a tapless structure should be adopted, and taps can be set if there is a requirement for operation.

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Rated Capacity kvaVoltage combination and tapping rangeConnection group labelNo-load loss kWLoad loss kWLoad current%
High voltage kvMedium  voltage kvLow voltage kv
40000110±2 X 2.5%  115±2 X 2.5%  121±2 X 2.5%36     37    38.56.3   6.3   10.5    21YNyn0d11411790.45
50000482130.42
63000562560.38
90000743350.3
120000924160.27
1500001094920.24
1800001255650.22

Tab4: 40000kva~180000kva dual-winding on-load voltage regulating three-phase combined power transformer

On-load tapping transformers, temporarily providing step-down structure products.

According to user requirements, other voltage combination products can be provided.

Rated Capacity kvaVoltage combination and tapping rangeConnection group labelNo-load loss kWLoad loss kWLoad current%Short-circuit impedance%
High voltage kvLow voltage kv
40000110±8 X 1.25%  6.3   6.6   10.5  21YNd11381560.4512~18
50000441940.42
63000522320.38
90000683040.3
120000853780.27
1500001004470.24
1800001165130.22

Tab5: 40000kva~180000kva three winding three-phase site-combined power transformer

On-load tapping transformers, temporarily providing step-down structure products.

The capacity of the high, medium, and low voltage windings are allocated as (100/100/100)%.

According to user needs, the medium voltage can choose a voltage value different from that in the table or set traps, and the capacity exceeds 90000kva. Taps are not suitable for medium voltage.

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Rated Capacity kvaVoltage combination and tapping rangeConnection group labelNo-load loss kWLoad loss kWLoad current%Short-circuit impedance%
High voltage kvMedium  voltage kvLow voltage kv
40000110±8 X 1.25%  36     37    38.56.3   6.3   10.5    21YNyn0d11441790.45high-midium  17.5~18.5  high-low 10.5   midium-low 6.5
50000522130.42
63000612560.38
75000682920.38
90000803350.3
120000994160.27
1500001164920.24
1800001335650.22

Tab6: 40000kva~180000kva dual winding three-phase site-combined power transformer

For step-up transformers, a tapless structure should be adopted, and taps can be set if there is a requirement for operation.

Rated Capacity kvaVoltage combination and tapping rangeConnection group labelNo-load loss kWLoad loss kWLoad current%Short-circuit impedance%
High voltage kvLow voltage kv
40000110±2 X 2.5%  115±2 X 2.5%  121±2 X 2.5%36   37  38.5YNd11381560.4510.5
50000421940.42
63000492320.38
75000552650.3812~14
90000643040.3
120000793780.27
150000934470.24
1800001045130.22

How to lift a three-phase power transformer?

Three-phase power transformers should be hoisted in units.

Each unit should have a lifting device to withstand the total weight of the unit.

The body, mailbox, radiator, or cooler of each unit should be equipped with lifting devices.

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How to pack a three-phase power transformer?

The package of the disassembled components and parts of the three-phase power transformer (such as gas relay, quick-acting oil pressure relay, bushing, pressure release valve, temperature measuring device and fasteners, etc.) should be transported and stored without damage before installation. And free from dampness.

The main body of each unit and the disassembled large components (such as radiator or cooler, oil purifier and oil conservator, etc.) can be transported without packing, but it should be guaranteed not to be damaged or damp.

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three-phase power transformer’s Package
three-phase power transformer’s Package

How to transport three-phase power transformers?

Three-phase power transformers are usually transported in units. The internal structure of each unit should remain unchanged relative to each other after passing through normal railways, highways, and shipping, and the fasteners should not be loosened.

The structure and location of the components and parts of the three-phase power transformer shall not hinder the transportation and fastening and positioning.

Each unit of a three-phase power transformer is usually transported without oil.

It must be filled with dry gas during transportation (the dew point is lower than -40°C), and the type of inflation must be clearly marked.

A seal test should be carried out before transportation to ensure a good seal when filled with gas at a pressure of 20kPa~30kPa.

The gas pressure in the mailbox should be maintained at a positive pressure during transportation and after reaching the site of each unit subject, and a pressure gauge should be used to monitor it.

If the transportation conditions permit, it can also be transported with oil.

Three collision recorders should be installed during transportation, and the transportation shock acceleration that each unit can withstand is 3g (monitored during transportation).

All components and parts of the three-phase power transformer (such as oil conservator, bushing, valve, radiator or cooler, etc.) should be protected from damage and moisture during transportation.

transport three-phase power transformers
transport three-phase power transformers

How to install a three-phase power transformer?

The installation base of the three-phase power transformer should be firm and flat, and the mailbox should take into account unfavorable factors such as ground subsidence and deformation.

The units of the three-phase power transformer should be combined strictly in accordance with the layout drawings provided by the manufacturer and the requirements of the installation and operation instructions.

During the installation of the three-phase power transformer, moisture-proof, dust-proof and pollution-proof work should be done well.

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How to store three-phase power transformers?

Each unit of the three-phase power transformer is divided into temporarily not installed storage and temporarily not put into operation storage after installation.

When not installed, the gas pressure in the tank of each unit should be monitored regularly. Ensure that the gas is not less than 10kPa. Protect all components and parts of the three-phase power transformer from damage and moisture.

When not put into operation after installation. The moisture absorber of the oil conservator should be installed in time after the vacuum oil filling (the oil conservator that does not need a moisture absorber should be sealed with all flanges).

This can prevent the three-phase power transformer from getting wet, and the oil level should be monitored regularly.

About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.

Custom Three-phase Power Transformer

When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.

We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.

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