What is standard benefit? - Part 6

Electrical energy is the only product that always has to be generated literally at the same moment it is consumed. Nevertheless, it is practically always available in full - whether it is used or not. How does that work? And can electroplating systems perhaps help to keep it that way?

3 Wait a minute - are the clocks really running correctly?

Fig. 22: The UCTE network split into 2 parts [1]But then it happened: On January 8, 2021, the UCTE network experienced a prime example of an avoided large-scale outage when this synchronous zone split into a north-western and a south-eastern part at 14:05 h due to "an incident", as the report [1] stated (Fig. 22). Here too, the power fed into the grid was too high in one part and too low in the other at the first moment after the split. A coupling switch between two 400 kV busbars tripped due to overload, whereupon the current flowing from the south-eastern to the north-western section was split between several other coupling points, which then also opened due to overload - the well-known domino effect. In fact, the south-eastern section is said to have had a power surplus of 6.3 GW and the north-western section a corresponding deficit of 6.3 GW at this moment! No wonder, then, that there were overloads at the transition points.

As is so often the case, the report [1] cites the first overload as the cause - while the more exciting question is how such an overload could occur, as it has now occurred for the first time. The overview report announces a dedicated investigation and a detailed report by a special commission.

The frequencies diverged logically and almost abruptly (within 15 s) after the separation (Fig. 23). Naturally, the frequency in the smaller part (in terms of load or generation capacity) moved faster and further apart than in the larger part. In France and Italy - a good 500 km to 2000 km away from the location of the event and yet still effective - 1.7 GW of load was switched off immediately. These were exclusively loads intended for this purpose (i.e. paid for accordingly), as can be seen from the text. This did not result in a "load shedding" in the technical sense of the word as an emergency measure, but was a classic control power that was intended to prevent the shedding of other loads that had not been agreed. It should be noted that ENTSO-E's voluntary commitment provides for "only" 3 GW to be passed through an outage, but 6.3 GW are apparently still possible - supported by other ENTSO-E allies connected via HVDC lines: 420 MW could be "made afloat" immediately from the UKTSOA synchronous zone and 60 MW from the NORDEL synchronous zone (Fig. 2, GT 10/2020, p.1559). Only an interconnected grid can do this. The disconnected loads were reconnected at 14:48 and the two sub-grids could be operated in parallel again just 20 minutes later.

Fig. 23: Progression in the two sub-grids after disconnection [1]

However, this raises the question of whether it is not a case of déjà vu all over again: Was it a clever idea to reconnect the grids so quickly? According to the report [1], this was due to the desire to reconnect the disconnected loads as soon as possible. However, the north-west grid had been running too slowly the whole time and the south-east grid too quickly (Fig. 23). Now the number of periods was no longer correct in both sub-grids. In our case, however, the synchronous clocks seemed to be behind again. If this is corrected on this side, they are even more advanced on the other side than they already are. As this is the smaller part, the effect there is even stronger than here. It would have been better to let the two sub-networks run separately until both had the same number of periods behind them again. There is no other way to correct this error than to separate them again. It will be interesting to see what the final report has to say on this point.

4 Galvanic systems for quickly connected grid loads

Why was it then switched back on so quickly as soon as it was technically possible and not at the optimum time for grid operation? Why were the 1.7 MW that had been switched off as agreed supplied again 43 minutes later? Probably because the imbalance between the northwest and southeast was extreme at that time - and because the balancing energy required to compensate for this is very expensive (Fig. 13, 14, GT 12/2020 p.1887).

The electroplating industry could have pocketed this money - and perhaps it did to some extent; this is not known. In any case, however, participation in the balancing power market is worth considering for electroplating specialists. According to information from the Federal Network Agency, since November 2020, participants who have not taken part in the balancing power market can still participate in balancing energy (balancing work) [2].