Floods in Sydney? - Page 1
Forum section: electronics / general

author: Excavatoree
author_rank: Frequent Contributor
timestamp: April 22, 2015, 12:58:02 pm
content: Is Dave affected by the flooding or power outages in Sydney? I hear 225,000 people in Sydney are without power, and it looks like many of them won't get power for a while. (Of course, Dave has his own power when the sun shines)(apologies if there is another thread about this that I don't see.)

author: EEVblog
author_rank: Unknown
timestamp: April 22, 2015, 01:19:49 pm
content: I'm fine. My area seems to have been spared the worst.No I don't have power when the sun shines, my inverter relies on the grid in order to work.It's very unlikely that both my lab and home would go down at the same time.Blackouts are fairly rare in my area, only ever had one at the lab in 4 years, for a few minutes IIRC.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: April 22, 2015, 01:29:29 pm
content: Quote from: EEVblog on April 22, 2015, 01:19:49 pmI did wonder about that - if your power system could "bootstrap" itself, or if it required grid power. As you can tell, I know nothing about such things. I'm glad you were spared the worst of it. Sounds bad from what I've read from the other person I know in Sydney via the internet.

author: jhalar
author_rank: Regular Contributor
timestamp: April 23, 2015, 02:22:11 am
content: The storm brought down 2 out of 3 phases coming into my house. The broken cables were removed for safety.Unfortunately the working phase is in the wrong part of the house.Fortunately I was able to run long extension leads to the fridge and other essential items.Hot water at least is working on its booster connection and not its usual cheaper off-peak connection.Early next week is the quoted ETA to fix my power.

author: RJFreeman
author_rank: Regular Contributor
timestamp: April 23, 2015, 02:36:11 am
content: QuoteGrid Interactive Inverters (that feed power from solar panels etc. into the Grid) must have a feature called 'anti islanding' this shuts down the inverter if mains power is lost to stop it feeding power into downed power-lines or power-lines which be being worked on as this would be a hazard to the lines crews working on them.

author: mtdoc
author_rank: Super Contributor
timestamp: April 23, 2015, 02:42:37 am
content: Quote from: RJFreeman on April 23, 2015, 02:36:11 amA bit of clarification of terms. Generally the term "grid interactive inverter" is used to describe inverters which can do both battery back up power and "sell" power back to the grid when the grid is available. Yes, they must have "anti-islanding" circuitry for utility worker safety (meet UL 1741 in the USA)Inverters that are only grid tied (no ability to produce power from batteries) - like Dave's - are not usually referred to as "grid interactive". They also require anti-islanding protection.

author: Zero999
author_rank: Super Contributor
timestamp: April 23, 2015, 07:43:25 am
content: Quote from: jhalar on April 23, 2015, 02:22:11 amI thought the electricity company had to pay the bill as it's their cables?Failing that do you have insurance?

author: Excavatoree
author_rank: Frequent Contributor
timestamp: April 23, 2015, 02:52:10 pm
content: As I said, I'm completely ignorant about these things, but why can't a system simply be disconnected from the grid to eliminate the danger to power line workers? I'd think an "island" would be OK as long as no power were fed to the grid.

author: Galenbo
author_rank: Super Contributor
timestamp: April 23, 2015, 02:59:58 pm
content: Quote from: Excavatoree on April 23, 2015, 02:52:10 pmI worked a few years in that domain. It's more complicated than it seems even for simple unredundant systems.The system opens a relay between grid and inverter, the inverter keeps on delivering energy to devices.For going back to grid, it gets synchronised and then closes the relay again. (simplification)The relay that is put between grid and inverter, is controlled by the inverter, so in the legal block diagram, becomes part of the inverter, wich implies that all devices connected to it, get their energy through that block. A block with 2 power sources. You end up in a spaghetti of regulations here.It already exists a long time but makes inverters/sources more expensive, less efficient, and more complex.Also think of firefighters. Now they shut down electricity in the street and it's (electrically) safe(r) inside.Another spaghetti of regulations here.

author: mtdoc
author_rank: Super Contributor
timestamp: April 23, 2015, 04:37:18 pm
content: Quote from: Excavatoree on April 23, 2015, 02:52:10 pmIn the US, the NEC requires a manual disconnect switch to be accessible to firefighters and utility workers. In addition, signage is required at the utility meter indicating the potential for live wire even when grid power is out.The UL 1741 anti-islanding requirement is, in part, to protect utility workers who may be working somewhere nearby and may not know that there is a home with grid connected PV nearby. I agree the term "anti-islanding" is somewhat confusing.

author: cimmo
author_rank: Frequent Contributor
timestamp: April 27, 2015, 09:50:20 am
content: I've just had the power restored after almost eight days of near medieval living.If I had a multi-thousand dollar grid-tied solar system, I'd be spewing. All that bright sunshine and kilowatts going to waste.I really do not know why these systems can't have a big red switch on the box - throw that switch and all connections to the grid are severed and whatever power your panels are producing goes through your inverter into your house.Sure, you won't have a hot dinner, but at least you can have a hot lunch, cold drinks and frozen meat.And a hot shower, perhaps?

author: EEVblog
author_rank: Unknown
timestamp: April 27, 2015, 10:32:07 am
content: Quote from: cimmo on April 27, 2015, 09:50:20 amRegulations.Grid tied inverters must have "anti-islanding" to prevent line workers getting electrocuted.http://en.wikipedia.org/wiki/IslandingI'd be spewing too if I couldn't use it.AFAIK the only (legal) way to do it is to have local battery storage.I've always wondered if I really had to, how I could bypass this feature and manually power the house. After disconnecting from the grid of course with the main circuit breaker.I wonder if a UPS could be used to kickstart it?

author: SeanB
author_rank: Super Contributor
timestamp: April 27, 2015, 01:04:35 pm
content: Generator or a sine wave UPS, and then the load must be big enough to keep the UPS frequency lower than 50HZ, so the solar inverter will not trip off from the islanding system. Will work but will tend to be unstable as solar power changes and the load stays constant.

author: dexters_lab
author_rank: Unknown
timestamp: April 27, 2015, 01:36:29 pm
content: i recall photonicinduction made himself a similar system, in fact it seems remarkably similar to tesla's idea of selling batteries for home use...