What is the main purpose of Neutral Grounding transformer in power transformer?

[SamHans05]

Hi Everyone,

Good day to all. I just want to have more detail what is the main purpose of Neutral Grounding transformer instead of using neutral grounding resistor?

Hoping to receive a clear feedback. thanks

 

[mesutphen]

A neutral grounding transformer offers low resistance. So, you would use it when you want your neutral to be at ground potential, and ground current doesn't matter as much. If ground current is an issue, you would use a neutral grounding resistor to minimize the ground current.

 

[waross]

A special transformer connection may be used to provide a ground point on an ungrounded system.
A transformer and a resistor or impedance may be used in place of a grounding resistor to lower the voltage on the resistor. If a 13800:240 Volt transformer and a resistor is used in place of a resistor alone to ground a 13,800 Volt system there will only be a maximum of 240 volts across the grounding resistor. It will be safer and may be cheaper.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

There are two distinct types of neutral earthing transformer, the zig-zag or inter-star type which behaves as mesutphen has described, or a single phase transformer with a resistive burden on the secondary connected between the star point and earth as Bill has described.

Perhaps the OP could clarify which variety he is considering?

 

[waross]

A star delta transformer or transformer bank may be used in place of the zig-zag transformer. One advantage is that standard distribution transformers may be used for the initial installation and for replacement. These are usually off the shelf items. A zig-zag transformer may be a special order. Another advantage is that a lower voltage current limiting resistor may be connected inside the delta.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[DTR2011]

Some information available online
High Resistance Grounding

High Resistance Grounding Application

 

[Abdul435]

Neutral grounding is generally preferred to resistor grounding for system reliability.
Neutral resistor blocking is effective in blocking dc neutral currents due to changing earth magnetic field or stray dc currents in the transformer.
however during a fault condition,the earth is to provide a low resistance path for fault current to flow.
With resistor present,there are challenges like maximum resistor overvoltages,transient overvolatges,effect on protection systems,transient and continuos thermal rating, and other factors.
Due to the above mentioned challenges and the potential effects its may have on system reliabilty in case of a fault,neutral grounding is preferred over neutral resistor groundind.

 

[SamHans05]

Thanks to all your inputs. Appreciate it.