53 minutes ago, Ironman said:

they absorb changes in current, similarly to how a capacitor absorbs changes in voltage.

Well, something along those lines, but I'll restate differently:

The reactance portion of impedance, call it:  XL

XL = 2*Pi* inductance*frequency.

Lets give 2*PI* Inductance a fixed value, let's say 1, that won't change.

However, for straight DC the frequency is 0Hz, so the reactance component of the wire's impedance is zero.  So the only losses in the wire are because of resistance, which if you done your sums right should be 3% or less.

Now, along come lightening with a rise time, of lets say a nano or maybe a micro -second. (Lets call it a micro-second to give the lightning a fair chance).

That's in the order of a 1MHz, so that adds 1Mohm worth of impedance to those PV wires.

So I wouldn't say it absorbs current, it just lets less through because of Ohm's law.

Its all about showing the lightning the way you want it to go, and making it not want to go the way you don't want it to go.

Incidently, the times I am talking about are too fast for your surge arresters, I would parallel your surge arresters with 30kW transil diodes to earth.

( The 30kW rating is only for the first 10 micro-seconds, if I remember rightly).

Then your surge arresters can kick in.

And I would also put suitably voltage rated (say 150V'ish) bi-directional transil diodes between + and - of your DC coming from your panels.

Transil diodes are supposed to conduct in a pico-second (source: Wikipedia), although how anyone managed to measure this is beyond me.

If I remember, last time I worked it out, light only travels about 9 inches in a pico-second.

 

 

 

Edited October 14, 20196 yr by phil.g00

New issue: Clothes iron is driving me mad!  It has an bimetal strip temp control - 11 seconds on (1500W) , 11 seconds off.

It takes about 6 seconds for the 112ET meter -> Multiplus II feedback loop to settle on the grid setpoint.  The kwh used for that 6 seconds is about 25% of the total cycle time, which means we pay COJ for using the first 25% when the iron switches on, and another 25% when the iron switches off (and we are sending that power back to the grid) - that adds up to about half of the iron's normal energy cost. It happens much faster than can be seen on the graph that just samples every minute, but you still get a good idea:

Help me think of a solution - is there a light switch dimmer that will work if I put it in line with the iron?  Let's say I set the dimmer to 50% - the Iron will just heat up to 50%, and the bimetal strip will be always on...?  The light dimmers use a switching mechanism which kind of distorts the AC waveform because it can be leading edge or trailing edge dimmers.

EG for a trailing edge dimmer - the triac will switch on at the AC zero crossing, and switch off at max voltage (for 50% power).  This means every cycle will see a lot more current on every leading edge of the AV waveform.  Will the Victron MPII be ok with that? @plonkster ?

 

 

Edited October 15, 20196 yr by Ironman

Something like this: https://www.communica.co.za/products/dgm-ac-speed-dimmer-contrl-2000w

 

2 hours ago, Ironman said:

about half of the iron's normal energy cost

So how many hours per day do you spend ironing? 😛

I suppose it depends on how close you are to 100% self consumption. Since I'm nowhere near that (closer to around 45%) I simply don't care about those small amounts taken from the grid, all I care about is that I use as much as possible of the PV, in other words, the balancing act for me is making sure the batteries don't get full prematurely (but that they do get full every few days). I'm going to buy half my electricity from the grid anyway... who cares that a small portion of that is while ironing.

I don't know about dimmer switches. I've used a heat gun on the test bench Multi, and I'm told that at half-power those things use a diode to cut half the waveform. That is technically one of the worst things you can do to your AC waveform... and it seems fine.

Edited October 15, 20196 yr by plonkster

21 minutes ago, plonkster said:

So how many hours per day do you spend ironing? 😛

His handle is Ironman 😀

😂

Yes, yes - the pun works - good.  I am Ironman because my real surname is Stark.

I just ordered two of these 2000W dimmers from Communica.  I hope to smooth out some of these current push-pull situations.

 

30 minutes ago, Thunderdolt said:

His handle is Ironman 😀

Dude! Not only did I miss that... I now have to clean my monitor. And get more coffee...

21 hours ago, Ironman said:

Help me think of a solution - is there a light switch dimmer that will work if I put it in line with the iron?  Let's say I set the dimmer to 50% - the Iron will just heat up to 50%, and the bimetal strip will be always on...? 

Not necessarily, 50% of the volts might result in extending the time it takes to heat up to the point where the bi metal strip breaks the circuit. It would be interesting to see the results of your test though. Please update the results once you have conducted the tests. 

So I received the 2kw dimmers (bought two from Communica @ R50 each!) and built a short dimmer-extension. Tested with a double toaster and it looks like it will work. Tuesday is the next full ironing day.  I will inspect the grid curves and report back. 

On 2019/10/15 at 10:59 AM, Ironman said:

New issue: Clothes iron is driving me mad!  It has an bimetal strip temp control - 11 seconds on (1500W) , 11 seconds off.

You can look at a steam iron - that's the one everybody uses anyway.

And keep us informed please. My wife has a collection second to none of irons. lol

Oh, I can see problems when the iron remains cold .....

I neva eva interfere in that department, unless repairs are called for.

Edited October 22, 20196 yr by Johandup

Feedback on the clothes iron - dimmer.  The iron' bi-metal temperature regulator still switches off - every time when you put the iron down and there is nothing cooling the plate.  So the waveform still look horrible, but with a smaller altitude.

The ESS system still sends spikes through to the council, but they are about 800W, where they were 1600W before the dimmer. 

The spikes look more random.  I had a look at the ET112 readings while the dimmer was used and it looked like the dimmer "confused" the ET112 - the watts reading jumped around a lot - and thus the poor MPII had to try to increase or decrease power output continuously.

 

Edited October 23, 20196 yr by Ironman

[sarcasm] Why is it that days with high power consumption correlates with cloudy days - and a serious loss of PV power - battery depleted by 11pm;

while days with low power consumption correlates with no cloud cover and perfect PV power?