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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?
arnab ghosh said:why grounding transformers are used with a delta secondary
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: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".
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.
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.
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.
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.
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.