Sure, let's tackle each part of your question about transformers in detail:
Transformers are generally connected in parallel at a substation for the following reasons:
For two transformers to be paralleled, the following conditions must be met:
Failure to meet these conditions can result in inefficiency, excessive circulating currents, or even damage to the transformers and connected equipment.
In the Dd0 connection, both primary and secondary windings are connected in delta configuration, and there is no phase shift between the primary and secondary windings.
Primary Side (Delta):
A B C
\ / \ / \
\ / \ / \
\ / \ / \
\ / \
\ / \ / \
\ / \ / \
\ / \ / \
\ / \
A B C
Secondary Side (Delta):
a b c
\ / \ / \
\ / \ / \
\ / \ / \
\ / \
\ / \ / \
\ / \ / \
\ / \ / \
\ / \
a b c
In the Yy6 connection, both primary and secondary windings are connected in wye configuration, with a 180º phase shift between the primary and secondary windings.
Primary Side (Wye):
A
|
/ \
/ \
/ \
B C
Secondary Side (Wye):
a'
|
/ \
/ \
/ \
b' c'
In the phasor diagrams for the Yy6 connection, each secondary phase would be 180º out of phase with the corresponding primary phase.
These diagrams are simplified and you should use proper electrical engineering diagrams when working in practice.
If you have any further questions or need additional clarification, feel free to ask!
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