I believe that this is because of circulating currents; any unbalance may lead to large circulating currents. Hence, we have I^2 R losses and the current that can be used to supply load is limited. Another reason could be the presence of ground which helps to detect the fault.
Transmission lines are not star connected. Transformers are star or delta connected.
I agree with Mr. Adeshara. Furthermore, star or delta connected are generators and motors, capacitors, inductors, all 3ph electrical equipments. You have to notice that star connection decreases the voltage, delta connection decreases the current. For example, LV induction motors are usually in delta connection in order to have lower current. In MV. Alternators and generators are usually star connected. HV applications (pf correction with capacitors) in order to reduce the insulation cost, the connection is star. In LV applications, where non symmetrical loads are present, a neutral line solves the assymetry and offers to the resulted current a way out. In MV or HV, where loads are symmetrical, star connections with neutral line are selected for other reasons. Beyond that, a serious reason for choosing delta or star are the resulting harmonics.
Bro,
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No, Transmission lines are not connected in Star. They are always connected in Delta.
I wrote the answer of this question on Quora, please check below.
Electrical power transmitted at an overhead transmission line is always has a “Delta Connection”.
You have seen most of the time, that the overhead transmission lines OR Transmission towers have 3 cables going through and at the top of the transmission tower, there is another cable which is used for Earthing or protection from lightning strikes etc.
So why use Delta connection??
Because when we transmit power at high voltage (like 11 kV, 22 kV, 33 kV, 500 kV etc.) we don’t need a neutral connection. Because our main goal is to transfer bulk power via transmission lines, so neutral wire has no usage in transmitting the power.
But at the distribution side or at the consumer end (for residential buildings etc.), we need a 3 phase 4 wire system - which is a usually a star connection (As shown in the attached picture). It also provides safety to consumers.
Please check the attached image
As you can see in the above picture that a star connection and delta connection has one major difference. There is no neutral connection (or 4th wire) in Delta.
Using delta connection on transmission lines also reduce the cost of the cable, if we use the star connection, then we additionally need the 4th cable, which will cost us money and we can’t afford it anyway.
Please check another attached image here.
Thanks, Yousuf (Founder of Eliteguide)
@ Yousuf Mahtab Is it always delta connection? (I mean Transmission line). I have seen some of the maths in our books, the transmission line was delta as well as sometimes star connected.