I'm working on the software modelling of a regional grid in India and I would really appeciate some help regarding my below queries,
1) Why is YNd1/YNd11 the most common vector groups for power transformers even though the generators are generally star-connected? Why isn't the primary winding delta-connected that way? Which is more common-YNd1 or YNd11?
2) What are the usual vector groups of inter-connecting transformers in a grid?
3) What are the typical resistance values (in p.u) for a power transformer and an inter-connecting transformer?
4) What vector groups are followed in step-up transformers in wind turbines?
5) In DigSilent PowerFactory, there are options of choosing a 'YN' or a 'Y' connection in generators or transformer modelling. What is the difference between the two?
Thanks in advance.
1) The delta part blocks flow of zero sequence currents thereby traps harmonics
Also the delta is able to supply atleast 58.4% voltage with one phase faulty unlike in star
2) Am not sure but I would expect the YNYd1
3) It depends on the rating of transforme (r & inverter ) otherwise 5 to 6 % is common for transformers rated 0.5 to 1.1 MAC
5) YN means grounded are point and Y means ungrounded
1.Using transformer generator would not be connected directly with system and could be protected being a costliest equipment in system.2.Economical and efficient transmission of power would be achieved with needed HV with step up, using transformer.3.As transmitted power is a balanced(no neutral current flow, to balanced voltage) secondary delta on sending and primary delta on receiving side is economical and convenient.
The earthed neutral at the generator gets a circulating current flow path at the power transformer with a YNd1/11 configuration. The delta connection on the transmission side prevents passing of the zero sequence currents to the secondary side of this transformer, and supplies more power even if a line is lost and also is a better economic option since one conductor is saved over long distances.
Isn't it normal for the grid (transmission) side to be YN, with the neutral point solidly grounded (earthed)? Overvoltage issues are more common on HV systems.
There are two reasons that come to mind:
1) Economically, the Wye-configured winding is smaller, i.e., ~ 58% of what the Delta- configured winding requires!
2) Additionally, location of integral tap-ratios are easier to implement!
Phi Corso
From the earthing perspective The HV and LV systems will often be seperated to avoid transfer of potentials and faulkt currents. The DY or YD transformer allows separation of the two systems relative to earth. Especially important when transmission over large distance.
From the earthing perspective The HV and LV systems will often be seperated to avoid transfer of potentials and faulkt currents. The DY or YD transformer allows separation of the two systems relative to earth. Especially important when transmission over large distance.
From the earthing perspective The HV and LV systems will often be seperated to avoid transfer of potentials and faulkt currents. The DY or YD transformer allows separation of the two systems relative to earth. Especially important when transmission over large distance.
From the earthing perspective The HV and LV systems will often be seperated to avoid transfer of potentials and faulkt currents. The DY or YD transformer allows separation of the two systems relative to earth. Especially important when transmission over large distance.
From the earthing perspective The HV and LV systems will often be seperated to avoid transfer of potentials and faulkt currents. The DY or YD transformer allows separation of the two systems relative to earth. Especially important when transmission over large distance.
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