Just curious......
Does anyone have any experience/knowledge of how quickly a GE system reacts to a grid power failure? I'm just wondering if it is slow enough to reduce the impact of grid-borne brownouts, on equipment attached within my household?
Thanks,
Chris
ToothyChris I think @TheDragon (GivEnergy) has EPS which does not disconnect on grid disconnection, but you will have to think about how much you want to power by EPS.
Tim
Thanks Tim,
I wasn't thinking about the EPS outputs, just the regular power to the house.
If there is a small delay in the system reacting to a grid power outage, then a very short power outage (i.e. a brownout) in the grid may not be experienced within the house.
Perhaps it depends on whether the household load is being supplied by the grid, or battery/solar, at that instant in time.
All my computers and network are on UPS's (Or laptops with batteries!) - so don't have the issue - anything else will just have to sort themselves out!
As Tim says though if you happen to be on the battery at the time it may take up the slack.
If the inverter tried to take up the slack, it'd be backfeeding to all the other houses on that phase from the substation. Not going to work.
ToothyChris Sorry, but the GE inverter is "grid tied", which means that if the grid supply is lost, it basically switches off, except for the EPS output.
So if you were expecting it to carry on feeding the house during any supply interruption, your expectations will be dashed!
Given there is an EPS function, it must therefore disconnect from the grid to be able to supply the EPS circuits until grid is restored - so logically a brownout could be covered - given they last very short periods of time.
Perhaps - but only on those circuits which the EPS supplies, which won't be the whole house. I am still unsure if the EPS actrs like a UPS - some documentation seems to indicate that in the event of grid failure, the EPS takes 30 seconds or so to restore output, others say that is not so and it is, in effect, a UPS. Since I have never tried it myself, I can't be sure!
In any event, what is the definition of a "brownout"? Is it a short term voltage dip, or a total cessation of supply for however long?
wilfleek A brown out is where the power is reduced but not lost (According to what I have just read anyway!) - so would cause lights to flicker and some stuff to fail if its a voltage loss as apposed to current.
A black out is loss of voltage.
So in theory the inverter would still have a sync signal.
Must admit I always thought it was a very short loss. - Like a main generator goes down and the loss is taken up by a standby - usually Dinorwig in Wales if the loss in in England or Wales - which always has one generator spinning in standby and is designed to cover any one single generator loss on the gird. Also hence the max size of generators allowed on the grid.
anglefire A black out is loss of voltage.
We all have experienced power cuts where all power is lost to our house for a period of time. A brownout is where the grid system is stressed and is struggling to supply the load. This manifests itself as reduced voltage (you can't have current without voltage) which leads to some devices switching themselves off (very helpfully) as they detect low voltage. A brownout can be caused by many factors but typically is because of the failure of a system interconnector or a transformer or some other source of energy to the area. If the grid is stressed sufficiently, then devices further afield will automatically disconnect the whole area in an attempt to protect the network from any damage in the short term and maintain supplies further afield. Reconnection is usually automated and happens within a few seconds but if the problem still exists, the protection will eventually stop attempting to restore power and you have a blackout. It is feasible to have such a disruption (or cyber attack) which causes all the power in the country to disconnect. In this case, there are a number of power plants which train and practice a "cold start" or "black start" to provide energy for other power plants to restart.
My understanding is that all generators (including inverters) are configured to automatically disconnect and shut down if grid supplies are lost even if for a fraction of a second. This isn't Givenergy's whim, it's a fundamental electrical design principle. The "cold start" plants mentioned are chosen because those generators can be configured to set the grid frequency and voltage for all other generators (and inverters) to follow.
The EPS (according to @TheDragon (GivEnergy) if I remember correctly) does not disconnect when grid is lost (although I had read that it did disconnect and restart after a few seconds) because it feeds separate circuits isolated from the rest of the domestic supplies.
Tim The UPS option can be turned on by GE on request.
Otherwise standard EPS will activate 5 seconds after power loss.
Circuits on the EPS output will come back on after 5 seconds.
Mine switches immediately tested in multiple scenarios.
Slightest flicker seen on an LED lamp, using a osciloscope it's around half a cycle switch time so 1/100 second..
ToothyChris impact of grid-borne brownouts, on equipment attached within my household?
The Givenergy inverter datasheets suggest an operating range of 180-280Vac and a frequency of 50, 60Hz+/- 5%. Looking at the voltage, I'd expect the inverter to follow grid voltage and continue in operation while the grid voltage varied as a result of stress on the system. I'd expect it to switch itself off only if it detected a grid disconnection (or maybe a voltage below 180V?). Looking at frequency, and assuming that it either operates at 50Hz or 60Hz, in the UK, while voltage can vary by up to 10% of the nominal value, frequency has a much tighter band of 0.5%.
I'm not sure how quickly the inverter output ramps up and down but it is only a few seconds. I'm guessing that your inverter would lag behind the voltage swings during a brownout but wouldn't prevent you from experiencing it.
Thanks all for your comments and feedback. I was specifically not talking about the EPS output - sorry if that was not clear.
I was just interested to know if the system would act as a buffer against those fast, partial losses of mains voltage, which would normally result in a single lamp flicker.
It won't act as a buffer as such on the non EPS side, it's designed to follow the grid so will follow your voltage down with it.
The inverter is type tested to the ENA register and therefore follows the specific G98/99 limits for both power quality and voltage. It should be noted that these limits far exceed the standard well known DNO limits before a trip primarily because what you really don't want (particularly in an undervoltage condition on your network) is to cause a cascade of generation tripping out which just compounds the problem.
As such you can get down to as low as 185V and as high as 270V for a few seconds.
Should you wish to geek out on figures an example from a Solax inverter tested to the same standard is here
The grid side is a bit more complicated.
As above the blackout in 2019 was due to incorrect trip settings between Hornsea windfarm and Little Barford compounding together to cause local grid collapse. The grid isn't daft though so it will cut off a limb to save the host and in that case it severed as planned. This is annoying but not as annoying as having to do a full scale black start.
Which brings me to:
Yes you can spin Dinorwig turbines on air ready to roll but it's expensive (the air has to come from somewhere) and given you now have a few more toys in the toolbox like FFR contracts, Batteries and also the new Synthetic Inertia plants now running I doubt they do that (with those tools you can prop the grid up long enough for Dinorwig to get rolling)
A lot of plants are Black Start capable should the worst happen and we do do test runs - starting an entire 4GW plant essentially from a car battery in a series of increasing power cascades from generators, GTs to aux boilers onwards isn't a walk in the park but it is a well understood / rehearsed process)
Dinorwig - at least when I was there in about 1986 had one turbine sat spinning on the water down the hill, not air which I didn’t think I suggested? It would spin to full load in something like a second.
Another turbine could be pumping up the hill and do a reverse to full generation in less than 30seconds.
They have slam shut valves on the inlets that close in a couple of seconds - watched one do it when we were there.
Ok, lets add some detail. Dinorwig did and does have one or more machine spinning in air most of the time (more or fewer depending on expected need). This means that the units are motoring in the generating direction with the water supply cut off and the turbines running in air. Since the unit is already rotating and synchronised, there is no need to bring it up to speed when needed. 330MW per unit on standby is available merely by opening the penstocks. Less than 10 seconds.
The same response can be produced if one or more units are pumping to re-fill Marchlyn Mawr. In that case, the operators can shut the penstocks and vent the turbine to eliminate the pumping load.
It takes longer to go from pumping to generating because the units run in oposite directions for the two purposes. It was intended that the operators could, actually do this by careful opening of the penstocks to brake and re-accelerate the unit. Then synchronising it for generation.
My learned knowledge is some decades out of date and first hand experience was limited to taking the CEGB Barnwood inspectors around the fabrication shop when the generator pole piece endplates were being welded on and working next to the modified boring machine where the rotor shafts were being leveled and balanced. I was pretty exiting for a young man though. 😀
mrand31 I'm trying to rack my brains for the details of my visit - I am struggling though! Though I do admit somethings that I said earlier may well be wrong! Though I thought the standby unit was flooded? I say that because when you put your had on the turbine casing it was warm to the touch caused by the water spinning in the case with the penstock closed I assume (I don't remember!).
anglefire I cant vouch for whatever they were doing in the 80s (i wasnt around) but Dinorwig was partly to help out with the inflexibility of our Gen 1 Nuclear that was a bit all or nothing so they may have kept one in service like that i guess for "reasons"
Cant see anything about them doing that now, mostly stood still or on Sync in air.
I'll ask them, given i track this stuff another contact on the list wouldnt hurt (although the reply may be a while, took Ripple a month just for a simple yes/no answer!)
hoggy Sync in air
The units are synchronised to the grid with the impellor casing filled with compressed air and the penstocks closed to prevent water from flowing from the upper reservoir. The whole machine hall is below the level of the lower reservoir and so the impellor casing is filled with compressed air to force back the water from the lower reservoir. The impellor motoring in compressed air uses much less energy than motoring in water which would cause cavitation and erosion damage to the impellor and casing. Picking up load can be done very quickly by opening penstocks and letting the water flow down and literally flush the air through the pipework. An amazing feat of engineering.
Tim Is that how it was always done? Because I do remember that the casing was warm to the touch and as I said thought flooded. The ones generating or pumping had condensation on them.
At the time the 4th one was out of service due to the breaker not tripping correctly and single phased the one generator before the third phase finally opened - but because the cores were ali and air insulated, and plasmerised blew all the oxide into the motor. Was not a cheap fix!
anglefire casing was warm to the touch
I don't know the state of plant when you were there but (from memory), it's the vertically-mounted motor/generator which you can see on the operating floor, the impellor and casing being below. If you put your hand on the casing, it would probably be of the motor/generator which would likely be warm whether motoring or generating.
This is seriously derailing now (do we have a General Interesting stuff thread anywhere?) but before the old portal demise the login page used to have some arbitrary feelgood gauge along the lines of "trees saved"
The code behind that was a lot more interesting though such that figures about GEs install base were shown. Back in March installed battery capacity as a whole was >50MWh and you could also extrapolate from the cumulative MWh of PV Gen a rough Live PV output from everyone which again was a good few MW.
At some point it would be nice to have enough kit in localised areas to be able to offer the grid response services & collect the fee (like Dinorwig but on a smaller scale) but we aren't quite there yet to be able to swing the local demand "needle" enough for it to be taken seriously.
hoggy I think that what you're alluding to is what @GribinIsaf higlighted on this thread.
Tim no it was definitely the turbine casing. We were in the chamber with the motor above us. It wasn’t a normal visit it was arranged by the polly I was at as part of the electrical engineering course. So very much back of house.
I have done a normal punter one and that didn’t go anywhere really interesting!
We have just experienced a brownout, which reset my amplifier speaker relay, and re-booted our cordless phone and WiFi routers. So it seems the answer to my original question is: No, a solar/battery/inverter system does not appear to offer any mitigation against grid-borne brownouts (assuming it was grid-borne, and not my system itself having a hick-up).
At the time, the house was running on power from the battery/inverter/solar - we were not importing power.
Tim I'd expect the inverter to follow grid voltage and continue in operation while the grid voltage varied
I think that what you experienced is expected behaviour of the inverter; it follows grid voltage but won’t prop it up.
ToothyChris my inverter remains alive regardless of grid. Router and important stuff like all the PoE IT kit all on the EPS which for me, requested to GE is UPS. Zero drop outs, regardless of what grid does