Inverters as Feeder Circuit Source
Inverters as Feeder Circuit Source
(OP)
We are working with an experimental 5MVA battery storage system that is to be connected to one of our 13kV feeder circuits. While it will generally be in parallel with the normal source, it may be possible to island the circuit and supply it from the batteries.
Does anybody have any experience with things of this type? In particular I'm concerned about what happens when there is a fault out on the circuit while the inverters are the only source. The inverters won't produce enough fault current to blow a tap or transformer fuse, nor will they produce enough current for an overcurrent relay at the point of connection to detect the fault and separate the inverters from the system. The inverters should shut down, but controls aren't protection.
If anybody's worked with something similar, what have you done to detect and clear faults?
Does anybody have any experience with things of this type? In particular I'm concerned about what happens when there is a fault out on the circuit while the inverters are the only source. The inverters won't produce enough fault current to blow a tap or transformer fuse, nor will they produce enough current for an overcurrent relay at the point of connection to detect the fault and separate the inverters from the system. The inverters should shut down, but controls aren't protection.
If anybody's worked with something similar, what have you done to detect and clear faults?






RE: Inverters as Feeder Circuit Source
The test ensures that at least 10% of nominal voltage remains and which allows the inverter to feed into a load with an X to R ratio of 2.5. The onus would be on the utility to protect itself and other customers from the detrimental effects of islanding.
Do you have enough oomph to operate the relays if you apply dual settings groups which invoke alternative settings or functions in the event of an islanding condition? If not then the only safe approach may be to accept that the operation of an island is likely to be only an occasional event, and the likelihood of occurrence of a subsequent fault within the island is very remote, and consider it appropriate that the entire island can be tripped on fault, without need for normal discrimination.
Regards
Marmite
RE: Inverters as Feeder Circuit Source
RE: Inverters as Feeder Circuit Source
RE: Inverters as Feeder Circuit Source
For example a commerical UPS should not shut down in case of overload, but supply sufficient fault current to blow fuses or trip breakers in downstream distribution. Take a look into the related IEC Standard IEC 62040.
Also inveters for feeding renewable energy to the grid are required to stay on the grid during a fault and to contribute to fault current (islanding is usually not desired in this case). This requirement is usually referred as LVRT (Low voltage ride through).
As these converters all contain output filters, these requirements can be met by properly sized semiconductors (usually IGBT-modules) and suitable control and modulation.
RE: Inverters as Feeder Circuit Source
Let us know what you learn. We have a similar situation with a wind farm that has generators with full inverters. We've made repeated requests to the manufacturer for information on fault performance of the generators, but so far, they have not come up with any meaningful data.
dpc
RE: Inverters as Feeder Circuit Source
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Inverters as Feeder Circuit Source
RE: Inverters as Feeder Circuit Source