So now I have a solar PV system how do I make the most of it???

Martyn1981

Ich wrote: »

The maximum permitted is 253V and parts of the network will be running close to this as a legacy of when the declared voltage was 240V, it will be particularly evident near to substations as the higher voltage at the feed end is in part to maintain voltage at remote ends of cables.
The actual difference in a typical installation is about 5 volts (we measured and recorded this recently).

So if the voltage is within limits at, say, 250V adding 5 takes it out of limits. Fine we can reduce the voltage, and do but it does risk low volts for other customers.

Cheers, I appreciate the info. What is the time limit that any part of the grid is allowed to run at 253V? I've got '10 minute average' in my head, but have no idea where that came from, so may be total rubbish.

Also, at 253V or even 255V inverters should still be able to run, so isn't the problem that parts of the supply are running above these levels before PV is added (or in this case not added, given the problem!)?

Ich wrote: »

As for what the installation companies can do, perhaps measure the voltage at the survey stage and flag it up the DNO then, rather than complete an installation and leave it to the customer to discover that the invertor keeps tripping and they have to start the process.

Apologies, I thought you meant that the installers could or should have done something to sort the problem, as opposed to just reporting the issue to help start the process of getting it fixed.

Ich wrote: »

As one of my colleagues commented recently that he wondered how many consumers are not checking the system is exporting and have paid out for a system that is not working.

We are now in the position on some parts of the network where we cannot reduce the voltage any further as we have transformers on the lowest setting. Of course this means that in poor weather customers might then start getting low volts!

Am I right in thinking that if the problem is the 253V limit being exceeded before PV input, then responsibility for sorting this (and subsequent costs) fall on the DNO?

Mart.

Ich_2

Cheers, I appreciate the info. What is the time limit that any part of the grid is allowed to run at 253V? I've got '10 minute average' in my head, but have no idea where that came from, so may be total rubbish.

Also, at 253V or even 255V inverters should still be able to run, so isn't the problem that parts of the supply are running above these levels before PV is added (or in this case not added, given the problem!)?

The limits are 230V +10% or -6%. When the declered voltage was 240V it was +/- 6%

There is no time limit as such, the only real limit is that once a voltage complaint is proved we have 6 months to correct the issue, this allows for the case of major alterations being required.

From what we are seeing invertors are tripping out above about 254V, I would actually see this as correct as any higher puts us (as we are discussing) in breech of regulations, as this could and does affect the supply to other customers we have to take action, which (though the politics would be interesting) could include disconnecting the customer causing the supply issue! Obviously we seek to lower the system voltage to deal with this, but as I commented above this could lead to low voltage issues elsewhere.

Generally we are seeing that without PV, voltages are within limits though towards the top, it is only the addition of the PV that takes it outside limits. Again we can see this with the reduced voltages at night which without PV is usually the time voltage is highest.

Am I right in thinking that if the problem is the 253V limit being exceeded before PV input, then responsibility for sorting this (and subsequent costs) fall on the DNO

Prior to the "explosion" in PV we were seeing no more that a handfull of justified high voltage issues a year, now we are seeing these in a month but all caused by PV as without it volts are within limits

Any case where the voltage is above limits, even if caused by PV, falls on the DNO to correct.

Ich_2

Regarding the question about costs

An I right in thinking that over voltage means the consumer is paying for extra unneeded watts every time he uses his on switch for an appliance - the worst examples being appliances using motors?.

http://www.flameport.com/electric/savings/useless_savings.cs4

KevinG

EricMears wrote: »

There are devices you can add to your consumer unit to control voltage at lowest possible working level. However, they're not cheap and I really can't see them as an economic advantage.

Just in case anyone was interested:

http://www.vphase.co.uk/

There are others.

zeupater

Ich wrote: »

.... Prior to the "explosion" in PV we were seeing no more that a handfull of justified high voltage issues a year, now we are seeing these in a month but all caused by PV as without it volts are within limits ....

Hi

Surely the increase in frequency of the high voltage issues are more likely a result of general awareness of overvoltage due to the continuous measurement of voltage by the inverters and inverter 'tripping' than increased voltage due to pv ?

Until a few years ago I had absolutely no idea what the actual supplied voltage was in our property, it was only after buying a plug-in monitor to check appliance usage that I noticed that it was quite high and varied considerably throughout the day. Even before the 'explosion' in pv installations (well there are around half-a-dozen within a mile now ) our voltage was regularly noted as being around/over 250V and that was without continuous monitoring for voltage 'spikes' which would likely trip inverters.

HTH
Z

Martyn1981

zeupater wrote: »

Hi

Surely the increase in frequency of the high voltage issues are more likely a result of general awareness of overvoltage due to the continuous measurement of voltage by the inverters and inverter 'tripping' than increased voltage due to pv ?

HTH
Z

Which came first the voltage or the PV?

And if it was the voltage, why did it cross the road?

Sorry Z, silly Thursday afternoon going on here.

Mart.

Ich_2

Surely the increase in frequency of the high voltage issues are more likely a result of general awareness of overvoltage due to the continuous measurement of voltage by the inverters and inverter 'tripping' than increased voltage due to pv ?

As I commented, measurements clearly show in all the cases we have dealt with that without the PV system in use the voltages are within legal limits, though towards the upper end which is perfectly acceptable.
On any system voltage varies with load so it is usually at it's highest at night when loads are low and conversely lower during the day when load is high.
PV has effectively reversed it in that voltages are at the highest during the day at that customer's premises and lower at night when the PV is not generating (we proved it further with one customer who switched the system off for a day which saw the normal variance return.
It is not that we have an issue with PV just the way systems are installed and commissioned, the customers are generally not being advised there could be an issue which should show at the commissioning stage (especially as the electrician should be including te measured voltages as part of their testing).
The first the customers know is when the inverter starts tripping out and then involves us.

As for the plug in monitor, I'm sure it does have a calibration certificate to attest to it's accuracy as all our equipment does

zeupater

Ich wrote: »

As I commented, measurements clearly show in all the cases we have dealt with that without the PV system in use the voltages are within legal limits, though towards the upper end which is perfectly acceptable.
On any system voltage varies with load so it is usually at it's highest at night when loads are low and conversely lower during the day when load is high.
PV has effectively reversed it in that voltages are at the highest during the day at that customer's premises and lower at night when the PV is not generating (we proved it further with one customer who switched the system off for a day which saw the normal variance return.
It is not that we have an issue with PV just the way systems are installed and commissioned, the customers are generally not being advised there could be an issue which should show at the commissioning stage (especially as the electrician should be including te measured voltages as part of their testing).
The first the customers know is when the inverter starts tripping out and then involves us.

As for the plug in monitor, I'm sure it does have a calibration certificate to attest to it's accuracy as all our equipment does

Hi

Well, AIUI all users pay a levy within their electricity bills for the DNOs to maintain and upgrade the grid, it's just that the amount raised by the levy seems to have exceeded the upgrade expenditure for a number of years, therefore it looks like shareholders will have their(/our) dividends adjusted for a few years whilst the DNOs play catchup on what they should have been doing as a requirement for their operating license for a number of years ....

As for the monitor, it's not a calibrated unit as I'm an end user not a business which needs certificated instruments, however, as I also have a digital multimeter and an inverter and they are all from different manufacturers and they all read the same voltage to one decimal place .... I reckon that's good enough to reasonably believe that they are accurate ...

HTH
Z

zeupater

Martyn1981 wrote: »

Which came first the voltage or the PV?

And if it was the voltage, why did it cross the road?

Sorry Z, silly Thursday afternoon going on here.

Mart.

.... I guess the answer must be the voltage (as most had volts before pv) and it crossed the road, as is usual, to get to the other side (where the houses are !) ....

How did it cross the road ? ... well that's simple ... either in underground conduit or via overhead cables ....

Martyn1981

Ich, can I ask a question, and I hope it's not too general, nor too stupid. But why does some of the grid run as high as 250+?

I appreciate you explained earlier that voltages will vary with location, especially if it needs to be high at the start to 'pump' it to the end. But is this completely normal and correct, or does it reflect the condition of the UK grid?

Do we have a reasonably good quality grid, and these things are normal, or are there ways to level out supply? Be patient here with me, but can cable upgrades/sizing and local transformers be used (I appreciate at a cost) to bring voltages down. If not to 230V, then at least closer to the mark. Should these issues be addressed anyway, or is it widely accepted/approved to be running near the 253V limit?

Apologies for all the questions, but we're supposedly never too old to learn.

Cheers.

Mart.