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Asked By :  sampit dravid
Answers1

This question is about transformer connection a why are

This question is about transformer connection
a) Why are transformers generally connected in parallel at a substation?
b) What conditions must be met for two transformers to be paralleled?
c) Draw the phase relationship and clearly labelled connection diagram for Dd0 connection and Yy6





Answers :

0

Sure, let's tackle each part of your question about transformers in detail:

a) Why are transformers generally connected in parallel at a substation?

Transformers are generally connected in parallel at a substation for the following reasons:

  1. Increased Capacity: Parallel connection of transformers increases the total capacity of the system, allowing it to handle larger loads than would be possible with a single transformer.
  2. Redundancy and Reliability: If one transformer fails, the others can continue to supply the load, thus improving the reliability of the power supply.
  3. Flexibility: It provides operational flexibility, allowing some transformers to be taken offline for maintenance without interrupting the power supply.
  4. Load Sharing: Multiple transformers can share the load demand, reducing the stress on individual units and possibly extending their operational life.
  5. Reduced Voltage Drop: Parallel connections can help in reducing the voltage drop across the network due to better load distribution.

b) What conditions must be met for two transformers to be paralleled?

For two transformers to be paralleled, the following conditions must be met:

  1. Same Voltage Rating: The primary and secondary voltage ratings should be the same to ensure proper voltage levels in the system.
  2. Same Phase Sequence: The phase sequence must be identical to avoid phase shift issues and possible short circuits.
  3. Same Phase Angle: The phase shift between the primary and secondary windings should be identical.
  4. Same Polarity: The polarity of both transformers must be the same to avoid circulating currents and possible damage.
  5. Impedance Matching: The percent impedance of the transformers should be within a certain range (commonly within ±10%) of each other to ensure proper load sharing.

Failure to meet these conditions can result in inefficiency, excessive circulating currents, or even damage to the transformers and connected equipment.

c) Draw the phase relationship and clearly labelled connection diagram for Dd0 connection and Yy6

Dd0 Connection (Delta-Delta, 0º Phase Shift)

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

Yy6 Connection (Wye-Wye, 180º Phase Shift)

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!


Answered By

Steven Wallace

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