Standard EN 50160

Voltage characteristics of electricity supplied by public electricity networks

Standard EN 50160 should be understood as representing a compromise between the three parties which exert an influence on the power quality, i.e. network operator, network user, and manufacturer of equipment. Each of these three parties has an interest in playing their part. It is essential that electricity suppliers provide, as a minimum, a nominally adequate quality of supply. If the customer has higher requirements, mitigation measures should be provided by the user, or a separate agreement for a higher supply quality must be negotiated with the supplier. However, the important advantages of this standard are:

  • Definition of the voltage parameters important for power quality
  • Quantitative determination of reference values that can be used in the evaluation of the power quality

It is the task of the electricity regulator to set a level of quality that requires best practice from the supplier, while not setting the level so high that the price of electricity increases for everybody.

Comments

Stefan Fassbinder's picture

Most standards are fairly reasonable, adequate and targeted at the point. Unfortunately there are a few exceptions where you really wonder what had originally been desired. EN 50160 is one of them. It was initially meant to become a guide describing what may expect you, and as such it would have made some sense. However, on search for discrete limit values one would normally not expect to find statements like these in a standard:

  • “Under normal operating conditions the number of voltage dips lies between some tens and several thousands per year. They usually last less than 1 s and have a retained voltage of over 40%.”
  • “Under normal operating conditions rapid voltage changes usually remain below 5% of the rated voltage, but deviations of up to 10% may under certain circumstances occur several times a day.”
  • “Short interruptions of up to 3 minutes occur some tens up to several hundred times a year. Up to 70% of these may last for less than 1 s.”
  • “Switching transients usually do not exceed 1.5 kV, surges commonly stay below 6 kV. In individual cases, however, they may be higher than that.”
  • “95% of all 10-minute mean values must have an inverse system of less than 2% the direct system. But where there are many single- and two-phase loads in operation, it may as well give rise up to 3%.”
  • “The frequency should be between 49.5 Hz and 50.5 Hz for at least 99.5% of a given year.”

This would resemble a traffic rule “regulating” the maximum permissible speed like: “The usual speeds on motorways lie between 100 km/h and 200 km/h. Some cars, however, travel even faster than this, while on the other hand the traffic may come to a complete stall in certain situations.”

Now how fast are you allowed to drive?

Let us compare the last “limit”, referring to the frequency, to what happens in the European grid when in Spain, on account of a failure, 900 MW vanish unforeseen from the grid. Instantaneously the frequency dropped from 50.005 Hz to 49.960 Hz, overshot to 50.015 Hz after another 2 s and back again to 49.965 Hz before stabilizing at 49.975 Hz. Or have a look at Turkey. Or see this one – uncertain where it happened but it does not actually make any difference, since the whole West European grid runs synchronous!

So when do the limits of 49.5 Hz and 50.5 Hz, respectively, ever assume any meaning at all? Touching this sleeve would in either case mean a Europe-wide blackout only seconds later.

Island networks? No, island networks not running synchronous with the UCTE grid are explicitly exempted. In these terms all of the British Isles, for instance, do not count as part of the former UCTE grid, since Britain is linked via a DC link and hence not synchronous.

A general remark at the end adds with reference to all of these statements: “These limits refer to normal operating conditions only, not to fault conditions.” So does the obligation for supply also drop out when power drops out?

By Stefan Fassbinder 03/04/2013
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