transformer types

[Hameedulla-Ekhlas]

Greeting all,

I am reading a topic regarding to transformer types. I know the below types except the red line type.

power transformers
distribution transformers
auto transformers
zig zag transformers
earthing transformers
current transformers
voltage transformers and etc

1- Can any body give me some information regarding to zig zag and earthing transformers.

2- What is the difference between distribution transformer and power transformer.

 

[cpal]

you can start here http://www.transformerpower.net/zigzaggroundingtransformer.html

 

[SG-1]

An earthing transformer is a transformer intended solely for establishing a neutral earth connection on a three phase system. The transformer is usually of the star-delta or interconnected-star ( zig-zag ) arrangement.

The zig-zag transformer has a very high phase to phase impedance & a very low phase to earth impedance. It can be used to serve neutral loads or just establish a ground fault return path.

A simple CPT ( Control Power Transformer - usually 15KVA ) is used in medium voltage for high resistance grounding. The simplest example is taking a solidly grounded system and intentionally placing an impedance in the neutral to earth connection. The neutral is brought to the H1 terminal of a CPT. H2 is connected to the ground bus. The secondary side of the CPT is connected to a grid resistor. The impedance of the resistor is used to control the current through the primary winding of the transformer and thus establish the primary impedance to ground.


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[SG-1]

I think the main difference in Power & Distrubution Transformers is the standards of operation & practices regarding the application.