Dear all,
is there any negative impact of operating one circuit of a double circuit overhead line at a lower voltage than its rating.
For example having double circuit 225 kV line and operating one circuit at 225 kV and the other at 33 kV.
From my perspective since it is a lower voltage there...
Dear all,
concerning the current carrying capability of three-single core cables in trefoil in 9 way (3 x 3) duct bank and following the procedure in IEC 287 - 1 -1 and 287 - 2 - 1
when we are calculating T4 = T'4 + T"4 + T"' 4
T'4 is according to 287-2-1 2.2.7.1
T"4 is according to 287-2-1...
Dear all,
all manufacturers has a certain upper limit or maximum rating for the circuit breakers that they manufacturem, i.e. feeder rating. For example some manufacturer would have for 33 kV rated breakers a maximum current rating of 2500 A. In other words if I am to serve a load from a...
Dear members,
when considering a substation in the following configuration:
HV 380 kV breaker and half switchgear with 2500 A rating
2 transformers 380/115 kV each 500 MVA
HV 115 kV breaker and half switchgear with 3150 A
is it correct to say that at 380 kV i can only serve a load of sqrt(3) x...
Dear members,
for the above mentioned installation conditions for underground cables a thermal calculation is usually recommended. However in case we want to make a rough estimation of the cable amapcity derating what is the recommended factor to be used? According to available references from...
Dear all,
is there any considerable problems of paralleling generators' GSUs with OLTC to the same busbar.
will there be any problem if operating the OLTC action is delayed from the first generator on the busbar to the last one?
This question is concerning thermal power plants with several...
Dear all,
I went through the forum to see the input regarded the control strategies and installation requirements for the generator ste-up unit transformer tap changer and I found some indications. However I would appreciate if anyone can provide some literature regarding this topic whether in...
Dear all,
is there any literature regarding recommendations for transformer replacement (time-line).
The transformers installed currently are 13.8/0.22 kV and serving a residential area (about 1000 units with different ratings). These are being replaced becausee the utility is changing the low...
Dear all,
I am aware that this topic has been discussed in many previous threads however none of the threads I saw has indication for de-rating of cables with SI cross-sections i.e. mm.sq.
Any reference? or is it valid to directly transform from AWG\kcmil to mm.sq.
Thank you
Dear all,
I searched in the forum concerning this question but I did not find a comprehensive answer since some implications were scattered in other queries.
When having a certain load\customer to be connected to an electrical network with different voltage levels available (transmission...
Dear all,
in an installation the utility is the changing the low voltage distribution system voltage from 208 V to 380 V to cope with international standards.
Anybody has any literature or recommendations concerning the change of the distribution system assets to cope with this change.
Thank you.
Dear all,
in all literature from manufacturers it is always recommended to consider the virtual current chopping phenomena when dealing with switching off loads connected to converter transformers (ex. motors through Variable Speed Drives) using a vacuum circuit breaker.
These recommendations...
Dear all,
I've been performing transient over-voltage studies which involve vacuum circuit breakers (VCB).
In order to simulate the actual phenomena that the VCB causes (mainly high frequency re-igntions), a high frequency model of all the equipment should be included.
I am having a problem...
Dear all,
i took a look at the FAQ references list but i could not find much references for topics such as :
- integration of renewable energy (photovoltaics and wind)
- dynamics of renewable energy sources
- DC network analysis (HVDC links, fault identification and interruption in DC...
Dear all,
I am doing a transient study for which the transofmer data from the manufacturer is not easy to provide.
Concerning that issue i have two questions:
1- are there any recommended values of the transformer capacitances (transformer is 40 MVA YYN0 132/33 kV). I will be calculating...
Dear all,
i am designing a wind-generation grid connected system with battery system.
Are there any pointers about the size of the battery?
the load is stable and doesnt have a lot of change. The battery should cover a portion of the load and minimize export to the grid.
Any literature...
Dear members,
i am designing a system for a building which recieves its main supply from a wind turbine.
The building is still connected to the grid in order to provide a stable operation for the wind turbine (IG).
The utility however prevents injecting active power into the grid.
Other than...
Dear Members,
I am doing a dynamic study which involves load shedding system and a number of filters that remains connected to the network after the bulk of the load is disconnected due to under-frequency. The filters are then disconnected due to overvoltage settings.
During the period of...
Dear members,
I would appreciate if i can some suggestions regarding literature and publications or examples related to the modelling of networks for switching overvoltages.
Thank you.
Dear members,
i am trying to simulate the calculations done by the line drop compensator of a tap changer in order to estimate the voltage at the end of a 110 kV 120 km line based on local measurements of voltage, current and current phase angle.
The supplier of the tap changer insists that...
