- #1
arnab ghosh
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Just curious about why grounding transformers are used with a delta secondary . What would happen if I connect a phase to ground load to the secondary of a star delta transformer without adding a grounding transformer?
Why Grounding Transformers Used w/Delta Sec. Transformer?
- Thread starter arnab ghosh
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In summary, a grounding transformer is used with a delta secondary to eliminate neutral currents and to keep the voltage potentials within known space.
- #2
Hesch
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arnab ghosh said:
A Δ/Y-coupled transformer cannot transfer a neutral current (no neutral on the Δ-side). In a power-line no power is transferred due to the neutral current as 0V*1000A = 0W, so the neutral current only results in ohmic losses (P=I2*R.Therefore we want to eliminate the neutral current so that the phasecurrents: Ia + Ib + Ic = 0 (KCL). Of course these phase-currents also result in ohmic losses, but they result in a power-transfer as well.
So Δ/Y-transformers are inserted to minimize losses. The grounding on the Y-side is used to keep the voltage potentials within some "known space".
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- #3
arnab ghosh
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Yes that is okay . That is the use of inserting Y-D transformers . But I wanted to know why Grounding Transformers(see the figure) are used with the secondary of a Y-D transformer when we need to connect single phase-ground loads. Is it because it completes the circuit and avoids voltage surges?Hesch said:
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- #4
Windadct
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There can be a couple reasons - but the one that comes to mind is that a Grounded circuit may be required for safety and code purposes (created by the grounding transformer), but the Delta secondary is needed due to phase shift. -- Each Y-D or D-Y transformer creates a phase shift, in doubly ( or more) fed systems it may be necessary to match the phase shift - in another source.
- #5
Windadct
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Oh -- In your diagram I do not feel this is for the connection of neutral loads. -If it is for connection of loads I do not like the naming of this a grounding transformer - we connect loads to neutrals, and not to ground in AC Systems. This if it is for a neutral load, I suspect for a relatively small percentage of the main transformers capacity. In an industrial setting the bulk of the load could be a large motor or system, yet the controller may need the neutral point connection.
There is also the issue of filtering the - transformer in this case would pass the 3rd ( and 3 multiple) harmonics. ( are there solid state loads ??)
There is also the issue of filtering the - transformer in this case would pass the 3rd ( and 3 multiple) harmonics. ( are there solid state loads ??)
1. What is the purpose of using a grounding transformer with a delta secondary transformer?
The purpose of using a grounding transformer with a delta secondary transformer is to create a neutral reference point for the system. In a delta secondary transformer, the secondary winding does not have a neutral point, which can cause imbalances in the system. The grounding transformer provides a path for fault currents to flow to ground, protecting the system from damage.
2. How does a grounding transformer work with a delta secondary transformer?
A grounding transformer works by connecting the secondary winding of the transformer to ground. This creates a neutral reference point for the system and allows fault currents to flow to ground in the case of a fault. The primary winding of the grounding transformer is typically connected in parallel with the secondary winding of the delta secondary transformer.
3. What are the benefits of using a grounding transformer with a delta secondary transformer?
Using a grounding transformer with a delta secondary transformer helps to protect the system from damage in the case of a fault by providing a path for fault currents to flow to ground. It also helps to balance the system by creating a neutral reference point and reducing the potential for voltage imbalances.
4. Are there any drawbacks to using a grounding transformer with a delta secondary transformer?
One potential drawback of using a grounding transformer with a delta secondary transformer is the cost. Grounding transformers can be expensive to purchase and install, and they also require regular maintenance. Additionally, the added impedance from the grounding transformer can reduce the overall efficiency of the system.
5. Is a grounding transformer always necessary for a delta secondary transformer?
No, a grounding transformer is not always necessary for a delta secondary transformer. In some cases, the system may already have a grounded neutral point, and a grounding transformer may not be needed. However, in systems where there is no neutral point or the neutral point is not grounded, a grounding transformer is necessary to provide protection and balance to the system.
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