Electricity transmission congestion is a condition of the electrical grid that prevents the accepted or forecasted load schedules from being implemented due to the grid configuration and equipment performance limitations.
Lately the newspapers here (NL) report about measures that electricity transmission system operators are taking to deal with electricity transmission congestion.
Because of the increased transport of electricity (heating pumps, electric cars, solar panels etc.) the electrical grid gets overloaded in certain areas. Transmission system operators can prevent damage by ‘playing’ with the net voltage.
One way to do that is to send out 253V (instead of 230V), thus triggering the electrical inverters of solar panels, so that they will switch off. Another way is by using undervolt.
Could it be that this playing with the grid voltage is causing damage to our dCS (and other) equipment?
Appliances manufactured to European Standards are built to withstand very short duration voltage rises up to 2000 volts. Rises such as this are a normal part of the operation of a supply distribution network and can be generated by customers’ electrical equipment and also as a result of lightning or switching operations. Modern appliances are normally fitted with internal protective devices to limit damage to electronic components. All appliances sold in Europe are designed to operate safely and efficiently within the statutory voltage limits.
Manufacturers usually allow a further margin of safety and, if the voltage does occasionally fall outside these limits, there should be no adverse effect on your appliances. In the UK, the declared voltage and tolerance for an electricity supply is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2 volts to 253.0 volts.
Thanks, that is clear. But it also means that in certain areas here the voltage periodically is stationery at its max tolerance of 253V (+10%). If fluctuations then occur, it might go over 253V.
Perhaps @Phil could chime in with the view of dCS on this matter?
Our national grid operator states they are monitoring the following, thus guaranteeing the voltage quality:
Voltage phenomena
The voltage quality at a connection point is characterized by various voltage phenomena. The main phenomena are slow voltage variation, fast voltage variation, voltage asymmetry, harmonic distortion and voltage dips. They all in their own way distort the basic waveform characteristic of the mains voltage.
Monitored Voltage phenomena
Below is a brief explanation of the most important voltage phenomena. The grid operators monitor these phenomena within the Voltage Quality in the Netherlands project:
Slow voltage variation: In the Netherlands, requirements are set for the maximum and minimum value of the voltage. For the low-voltage network, it is determined, among other things, that the voltage at a connection point must be between 207 and 253 volts. If this is not the case, equipment may not function properly or not at all. Voltage variation is, for example, caused by sustainable and decentralized energy generation, such as solar panels.
Rapid voltage variation: Rapid voltage variation is known as ‘flicker’ and is caused by the frequent switching on and off of appliances that require a lot of power, such as welding equipment, copiers, irons, washing machines, dryers, ovens and large coffee makers. This phenomenon can cause flickering light, which can be annoying for you when reading.
Voltage asymmetry: The electricity grid in the Netherlands consists of three phases and a neutral conductor. We talk about voltage asymmetry when the phase voltages are not equal. Asymmetry is caused by an incorrect distribution of loads or generators over the phases. In practice, for example, an illegal connection of cannabis growers can cause an imbalance. Asymmetry can cause malfunctions in three-phase equipment.
Harmonic distortion: So-called harmonics are generated during power control in, for example, computers, microwave ovens and energy-saving lamps. As a result of these harmonics, the waveform of the 50 Hertz mains voltage is distorted. This can lead to additional energy losses, overload or equipment failure.
Voltage dips: These are short-term reductions in the voltage at your connection point. Voltage dips are characterized by a depth and a duration. The cause is often a short circuit in the electricity grid, for example as a result of a broken cable. Switching large loads on and off, such as a very large motor in a factory, can also lead to voltage dips. Most voltage dips do not bother you because they are limited in scope due to the security settings of your grid operator.
Hmmm, strange terminology. Electricity “Transport” or “Transmission” is classically associated with how Electricity is carried over the power grid. Whereas devices like Heating pumps and Electric cars “transport electricity”, consume it (not “transport” it).
Congestion management on Electric transmission typically has to do with dynamically increasing/decreasing power sources, it’s not really about manipulating the Voltage levels which has to adhere to the standards.
Thats the IEC standards; +/- 10% (for 95% of the time) for the Voltage variation, and +/-1% (for 99% of the time) for frequency variation. Albeit, some countries have much stricter standards - the Energy Authorities in Japan and Singapore for example have a standard of +/- 6% for Voltage fluctuations.
Generally, all electrical appliance are built to the IEC standards and must be able to handle those variations, as I’m sure dCS equipment.
The Council of European Energy Regulators has published an interesting benchmarking report on the quality of electricity (and gas) supply (2022).
One of their recommendations is:
RAISE AWARENESS AND UNDERSTANDING OF VOLTAGE QUALITY (VQ).
As was recommended in the previous Benchmarking
Report, education and awareness on how VQ issues might
affect the network and consumers will contribute to
reducing inconveniences due to voltage disturbances. It
is recommended that more countries increase awareness
and education on VQ to be better prepared to deal with
VQ issues.
That is my whole point: they actually DO actively manipulate the Voltage level. When it is very sunny, the Voltage gets pumped up from 230V to 253V (+10%), just within the specs, to trigger the solar panel inverters, so that they will automatically switch off, in order to mitigate the congestion on the grid.
I think that this might need a dCS response from @Phil as to tolerances in practice.
Of course the actual standards adopted in Member States are set by the local authorities. These have conform with the EU Directive but this does not publish these standards as, like all Directives, is written to allow the principle of subsidiarity to apply ( the Directive’s principles are observed but the manner of application is left to the Member State).
The important point is the the EU standard of 230v is really only notional as it was set as part of the Internal Market to harmonise the standard to allow trading of electrical goods across the EU where most ( all?) continental EU Member States had 220v systems but the UK and Ireland 240v systems. Those tolerances are there, not to allow for or codify voltage fluctuations, but to provide a single standard voltage for all Member States without the need for any to actually change their local standards. Hence the reality is that NL keeps to 220v and UK/Ireland to 240v. NL seems to have has found a way of using the tolerances to meet its heavy load issue however.
I wonder what the provenance of the figures is though? Has the newspaper journalist taken the 10% increase at face value and calculated 10% increase to 230v ( 253v) whereas the reality is an increase on 220v ( 242v)?
In 1989 it was decided in NL to go from 220 to 230V, and this transition actually happened in 15 years, so nominal it is now 230V here, with a +/- 10% margin.
Thats interesting if they actually do that. Is it stated somewhere publicly?
I’m not sure I understand. Solar panel inverters are Power generators that convert DC from the Solar Panels to AC to power private homes and/or supply extra power to the grid.
(a) Why would “they” want to shut that down, and
(b) Solar panel inverters supply power, not consume it. How would increasing the grid voltage shutdown the solar panel inverters?
(a) The power grid here is being used at it maximum capacity. Until its infrastructure is made more robust, they need to be able to control the solar panels on the roofs of consumers. In NL about 30% of all consumers have their own panels. In fact, in NL alone there are more solar panels than in the entire continent of Africa. We produce 24,4 gigawatt at the moment, and that will be gradually expanded to 172 GW in 2050. The only way to shut down the solar power supply is :
(b) By raising the Voltage to 253V in certain areas with weak infrastucture. Thus the inverters will shut down as a safety precaution, because actually they will have to produce above the max of 253V to let their power stream to the grid.
Inverters that feed back power are measuring the grid voltage. When the mains voltage that the inverter measures exceeds 253V, the inverter immediately stops its input and goes into fault mode. Technically, the inverter could work fine at a higher mains voltage, but the setting in the device causes it to stop working. The value of 253 Volt is determined, among other things, in the Netcode Electricity (law).
However , excess power from e.g. solar panels in NL is shared with UK ( and vice versa), why our grids as well as those of eDnmark, France, Belgium and Norway are connected. So send it to us
Very true. It has been quite a topic in the news here lately and , indeed, National Grid are looking at significant investment. This is also causing a lot of environmental concern with plans for considerable numbers of additional power pylons and other infrastructure installations.
I see that I’ve been tagged in this discussion a couple of times for input but I’m not sure I can really add anything of use to the discussion - when designing power supplies you design to the supply specs of territories that you’re going to be supplying kit into.
Remember it’s incredibly rare nowadays that you take the output from a transformer to drive a circuit directly - you take the transformer output and run it through further regulation and voltage conversion so the real world tolerance is much greater … if voltages get significantly higher than they should be then generally the voltage regulation stages will just be working harder (and hotter) than normal - remember that they’ll have been designed to be running in their own ‘comfortable’ region at the expected inputs - to accommodate the higher input rather than - say - everything working fine at 253v but going pop at 254v but IF for some reason the UK suddenly decided to push 480kv or more (instead of 400kv) continually across the grid AND the various substations all for some reason didn’t self protect (and there is one hell of a lot of layers of automated monitoring and protection that goes on at every substation that would all need to fail) and somehow 300v got thrown out onto the local distribution then I suspect the results would be rather messy (and expensive for some entity).
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