Thanks for the posts, yes there would be a separate 33kV earthing transformer.
Most standard units have equal primary and secondary winding ratings thus reducing loading capacity for the secondary if the tertiary is loaded.
May go for a higher rated primary on any new units to get round this...
Does anyone have any comments on the idea of putting load on the tertiary winding of an autotransformer - in this case a 400/132kV earthed Star autotransformer with a 33kV delta tertiary winding?
It is not uncommon in the UK to have reactive compensation connected to such tertiaries but this...
Do you mean to make a distinction by using the phrase "high voltage" (HV)? In power system terminology transmission is usually referred to as at EHV rather than HV.
A large proportion of urban load is fed from EHV and HV cable networks into cities.. so if you measure the load fed by...
DC remains a good choice for certain transmission tasks.
Not so much in the US and Europe but in developing countries the distances between load centres can mean that AC lines are well beyond their natural loads and expensive line connected compensation is required, making DC more comparable...
Thanks for the background windie, presumably turbines could be protected by overhead earth wires or just higher structures nearby with earth connections - although I havent heard of anyone doing this. Offshore this may make some economic sense given the likely down time from any strikes.
Yes...
Just a few points to consider -
1) Fault levels will vary with voltage so 1/Xs will produce a low result (assumed 1.0 pu voltage) Most standards require at least 1.05 pu.
2) Fault levels can increase with load due to the machines being on higher loadings and therefore having higher excitation...
I suspect the program you are using may have a default assumption that somewhere in the real system between your real generators and this substation where the generation is being modelled there will be a break in the zero sequence path and is therefore not including any zero sequence impedance...
One of the first offshore wind turbines in the UK (at Blyth) has been struck by lightning. It broke one of the blades, I don't know how much info has been made public about it - I know no more about it.
Hi all,
Does anyone know of any manufacturer of MV (33kV) shunt tapped reactors that offers a range down to 0 MVARs (or close). Designs based on a single core apparently limit the devices due to volts/turn limits so the ranges can't be say 0-8 MVAR but only say 4-8 MVAr (4MVAr shunt on minimum...
I think mrg probably meant Ia=Ib=Ic=1 for the unfaulted case.
Are you considering here the currents in an unloaded feeder during a fault on another feeder connected to the same busbar?
Well i've checked references back to Lackey and Edith Clarke (1950s) and not found a clear explanation... so to just expand on my thoughts a little for now :
On the X/R ratio to use :
For a 3 phase fault the DC component is not the same in all 3 phases - it's not a positive sequence current...
I would suggest not trying to apply X/R ratios to sequence networks at all for a couple of reasons :
1) The X/R ratio at the point of fault is only a crude way of trying to assess the DC decrement of a transient current. This transient is a point on wave phenomenon and is not truly comparable...
You may find in practice the limit is determined by the values that equipment manufacturers are willing to specify or warrant their equipment good for. Most check synch relays (transmission) default to 20 degrees with maximum settings of 40 to 60 degrees. Distribution voltages (33kV and below)...
As a last resort ShawPTI may let you have a copy of the source code for the model - if its the actual workings of the model you need to investigate and seeing the Fortran would give you the info you need.
