Answer / prr

an open delta can continue to supply power,when one of the
transformer, out of 3,is disabled or removed for
maintenance ,even thiugh with reduced capacity ie 57 %.

Answer / dwi tjahjono

Open delta connection (for PT as protection) usefull to detect the shifting voltage during normal and faulty condition.
We can use this to set the directional relay

Answer / prasad@clp

Open delta used in inter turn fault protection of generator

Answer / rman

its very cheap because you only need 2 transformers. but the total capacity of these 2 transformers cannot be used remembering that the rating of each transformer is multiplied by a factor of sqrt(3) which is only 1.73

i.e. two transformers rated at 50kVA to be open delta.
the total is 2(50kVA) which is 100kVA but the transformer can only carry 1.73(50kVA) which is only a total of 86.5kVA

Answer / t.govind

this open delta using protection for generator stator earth fault .
95 % stage ths cald residual voltage
third core of the PT secondary is connected delta connection when the fault accur in the stator voltage will came fr exmple 5o v . normaly it was 0 volt
exm : PT secn 3a 3n 3a 3n 3a 3n ..
frst 3a and last 3n fr out put vltg measrn at this poit only
other connection fst 3n to secnd 3a .second 3n to thrd 3a . & 3rd 3n .

Answer / manoj

for ungrounded system only we are using open delta for
finding earth fault.

Answer / ahmed abdel fattah

هذه المشاركة ذات صلة بملتقى المهندسين العرب :
http://www.arab-eng.org/vb/t205463.html#ixzz1b3W23GT1

The open delta transformer connection can be made with only
two transformers instead of three (figure below). This
connection is often used when the amount of three phase
power needed is not excessive, such as a small business. It
should be noted that the output power of an open delta
connection is only 87% of the rated power of the two
transformers. For example, assume two transformers, each
having a capacity of 25 kVA, are connected in an open delta
connection. The total output power of this connection is
43.5 kVA (50 kVA x 0.87 = 43.5 kVA).
Figure : Open Delta Connection

Answer / shajina

Advantages of open delta are :
• power supply can be continued in balanced condition but with lesser rating ie, derated operation.
• very useful in mining industry where continuing is needed.
•maintenance and repair work can be done on one of the transformer while power is supplied to the consumers.
•cost is less for open delta connection.
•flexibility of power supply at 2 different levels.

Answer / hey now

Cheap metering, bottom line.

Answer / oarhe ize

It can carry more loads.

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