Dear,
How can I measure the grid frequency.
In Node red I can select multiplus II AC/OUT/L1/F , but resolution is very bad 0.128Hz!
AC/ActiveIn/L1/F is even worse.
Is there a way to measure frequency in mHz resolution?
ESS relies on phase angle rather than absolute frequency. Accurate meassurement seems only for DNO and grid redispatch important. To read the value in NodeRed accurate, I am using the Ziehl UFR / EFR relais. Both models are available with Ethernet, have http server included and communicate by Modbus TCP. On the other hand, there are some free internet service. Hier for the european grid. Unfortunately, those pages stop operation after about one hour and you have to pay subscription for receiving reliable data.
Be aware, no to buy the UFR from Victron. They do not offer the version with ETH interface. This is model UFR1002 IP only. EFR is more expensive but good if you like to have accurate grid currents. Frequency resolution is 2 digits absolute accurate for all Ziehl models.
A much cheaper version is the turkish Tense EM07 instrument. But this is cheap and inaccurate. Only one digit behind the comma is useless. Interface is Modbus UDP only.
A cheap and accurate solution is the Murata DMR20. Unfortunately no interface and no acces by NodeRed. What you pay is what you get.
Alternatively, you can go the DIY way. See Alexander Mumm - Netzfrequenzmessung und Diagramme for an example of how it can be done and also for current data, including raw data from yesterday.
Online view of european data: Aktuelle Netzkennzahlen
I would like to know the net frequency to check if it would be possible to charge/ discharge on the frequency.
Or if virtual inertia would be possible to implement.
It depends on where you live if this would be feasible at all. The European grid generally is extremely stable and thus the frequency is not suitable for control purposes. The recent blackout in Spain not withstanding, and to avoid that, there would have to be regulatory changes first. Single small solar generators are too weak to have any impact there, and anti-islanding requirements conflict with grid stabilization goals.
A lot of decentral storage isn’t weak at all, the question is how should it act to avoid net instability.
The net frequency is the predictor if there is to much or to less energy in the grid.
And phase voltage is a parameter of cable load, maybe smart charging based on those 2 parameters could stabilize the grid,…
Recently I read my ABB grid counter. Its easily available in Victrons GridMeter Node and accurate for 10mHz or two digits behind comma. Cannot speak for Carlo Gavazzi and others.
How about a P1 meter, do they measure frequency?
What ABB module do you use?
I think I just have enough space to install an EM540 meter.
According the manual it has an resolution of 0,001Hz, can someone conform that this resolution is also seen in venus OS?
Any advice on the 315 ma fuse, what fuse holder can I use for this?
Can confirm. At least for Node-Red the resolution is 0,001Hz. In VRM though the visible resolution is only 0,1Hz.
On the Cerbo screen, the frequency is not visible.
As for the fuse holder: you could use this Phoenix Contact fuse holder and mount that next to the EM540 on the DIN rail. But there are also other brands that carry similar products.
Thanks!
Now installed EM540.
In node red I only get 49.984 Hz, and sample interval is 5 seconds!
Seriously,…
Can this be clanged in next venus os version?
This is what I get,
Every 5sec fixed 49.951Hz from grid meter EM540.
Multiplus II AC out jumps between 50.07692337036133 and 49.948848724365234 Hz
and Multiplus II AC IN fixed 50.10256576538086 Hz
How do I get access of the 100ms interval 0.001Hz resolution value send by the EM540 grid meter???
Doubt the last digit is anything valid. This are simply rounding errors converting the integer into IEEE 754 float format by node.js
Here is a photo of my ABB. Photo shows RS485 where A and B are not always inverted and non inverted signal or plus and minus. Every manufacturer counts different. But both digits behind comma are exactly same between Murata offline instrument, ABB and Ziehl EFR. For the Ziehl I polled with a frequency of 1 Hz by Modbus TCP using Sunspec register 40096. Anyhow, NodeRed is not sufficient to show long term diagrams. After several minutes data amount gets too high for a Cerbo and needs to be transfered to anything like InfluxDB, SQL to Grafana.
The 0,01 Hz diagrams were pretty in center of 50 Hz. Some full hours we can recognize a peak of about 100mHz up or down for 2-3 minutes before compensated
I know last digit isn’t reliable, but I don’t see any change at all.
Communication is working do see the grid meter in Remote Console.
On EM540 display I also see frequency changes in 0.01 digits, but they don’t appear in node-RED.
None of the parameters grid AC/frequency, multiplus AC/out/l1/f or AC/ActiveIn/L1/F seems to work or do have a very bad resolution.