Delta-Delta Connection
In this type of connection, both the three phase primary and secondary windings are connected in delta as shown in the Figure 1:
The voltages on primary and secondary sides can be shown on the phasor diagram (Figure 2):
This connection proves to be economical for large low voltage transformers as it increases number of turns per phase.
Key points
- Primary side Line Voltage = Secondary Side Line Voltage.
- Primary side Phase Voltage= Secondary Side Phase Voltage.
- No phase shift between primary and secondary voltages.
Advantages of Delta-Delta Transformer Connection
Sinusoidal Voltage at Secondary
In order to get secondary voltage as sinusoidal, the magnetizing current of transformer must contain a third harmonic component. The delta connection provides a closed path for circulation of third harmonic component of current. The flux remains sinusoidal which results in sinusoidal voltages.
Carry 58% Load if One Transfer is Faulty in Transformer Bank
If there is bank of single phase transformers connected in delta-delta fashion and if one of the transformers is disabled then the supply can be continued with remaining tow transformers of course with reduced efficiency.
Economical for Low Voltage
Due to delta connection, phase voltage is same as line voltage hence winding have more number of turns. But phase current is (1/√3) times the line current. Hence the cross-section of the windings is very less. This makes the connection economical for low voltages transformers.
Absent of Third Harmonic Voltage
Due to closed delta, third harmonic voltages are absent. The absence of star or neutral point proves to be advantageous in some cases.
Disadvantages of Delta-Delta Transformer Connection
Due to the absence of neutral point it is not suitable for three phase four wire system. More insulation is required and the voltage appearing between windings and core will be equal to full line voltage in case of earth fault on one phase.
Application
- Suitable for large, low voltage transformers.
- This type of connection is normally uncommon but used in some industrial facilities to reduce impact of SLG faults on the primary system.
- It is generally used in systems where it need to be carry large currents on low voltages and especially when continuity of service is to be maintained even though one of the phases develops fault.
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Jignesh Parmar
Electrical Middle management professional having more than 22 years rich and dynamic experience in Project Execution / Project Management / Designing / Maintenance diversifies from Electrical Power Transmission (400KV/220KV/66KV)- Distribution(11KV/220V) to Lifts-HVAC-Ventilation-Fire Fighting-Fire Alarm-Lifts-CCTV-Stack Parking Works (High Rise Buildings, Townships, Shopping Complex, Commercial Complex, School, Temple).Profile: Jignesh Parmar
Respected Sir,
I have been visiting your website to gather knowledge. It is very helpful. I appreciate your thoughts in sharing your knowledge. I have a question. What is delta feedback? How will this impact surge arrestor calculations. Please let me know. Appreciate your help on this question.
Thank you
Sincerely,
Annie
dear Mr. Parmar,
would you please explain that in Japan delta-delta transformer they put S line secondary side direct grounded, the voltage between phase keep the same. I still cannot find this theory.
X^2+9X+14=0 X^2+2X+7X+14=0 X(X+2)+7(X+2)=0 (X+2)(X+7)=0 X+2=0 or X+7=0 X=-2 or X=-7
I have a delta delta transformer , 480 volts primary 230 volts secondary has worked fine until yesterday , have very low voltage on one phase of secondary , 230 volts a phase 230 volts b phase , and about 15 volts on c phase . can you tell me what is happening verified all in coming voltages they are good .
Hello,
I am having a doubt with the first advantage of the delta-delta connection, when you say sinusoidal voltage at secondary.
im puzzled. We have 3phase supplies 480Vac but when i measured from ground or neutral one phase reads 415 volts. The other line measured 238 vac. What is the reasons
Dear Sir,
Please Give me i am usage Dd0 Transformer 11 kv Primary Side And Secondary Side 220V
MLTP Panel Side APFC Relay Not Working Actually I am Connected 220 Voltage Between Phase and Neutral but my TRF not Coming neutral
Please give me advise Whicj type APFC Relay in MLTP Panel
For DC Drives Siemens 6RA22 Synchronisation supply used is through Synchronisation PT 33KV/110V, Delta/Delta connection.
My question is can we use PT 33KV/110V star/star connection? Or can we use 415V/110 V LT Delta/delta PT ?
On the secondary side of a delta/delta transformer with 240 volt between phases, what will the voltage be should phase A become grounded?
When onboard a ship during my Navy years, I remember we were using this type of connection and wiring.
Transformer rating 2.5MVA,6.6KV/0.69KV, Dd0 (Delta/Delta) vector Group Transformer.
6.6KV HV Side CT Ratio=250/1 Relay Type-REF615 ABB make
KV LV Side CT Ratio= 3200A ACB with static release Schneider make
Pl advise the Protection Philosophy in Overcurrent and Earth fault. Especially earth fault considering the delta winding on HV & LV side.
LV side being unearthed, Current operated protection will not sense.
HV side source being earthed, Earth fault current will be dependent on source earthing type & NGR. Hence, current operated earth fault protection will be effective.
Should it have any protection against harmonics [due to delta-delta transformer and APFC load
delta connection in lv wdg what is the formula for vt
If we connect a load on secondary of delta delta transformer, which demands harmonic what will happen ?
What is the difference between a Starr-star Transformer connection and a Delta-delta transformer connection?
A Delta Delta is a 3-phase connection without a neutral you’re going the same voltage on the primary to the same voltage of the secondary but it’s used for high current applications like stated in this article. Your star star would be the same type of system except now you’re driving a neutral at the center point of the three phases. It would most likely be used to block fault current and voltage is from the primary or secondary side to not have a substantial impact on your load.
Power supply transformer connection is preferred
Jayesh, we can use separate transformer to change voltage for single phase load
what will be voltage in secondary of delta-delta transformer if single phase supply is applied?
Depending on the voltage you have present it probably be just 208 or 480 that’s what we have in the US anyway. You would just be missing voltage on that third leg if you didn’t have a voltage present On the third leg of your primary. Or there’s a possibility of also seeing an induced voltage on your third leg of your secondary but it may not be as large as the other two legs.
Limit the extend of damage by providing a credible path to ground and using this to interrupt and take a Transformer out of service during a fault