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comtac AG: Cluey – The configurable controller and monitor

Drastically shorten power outages in the electricity supply network

Project description:

In the local power supply networks, the transformer stations are lined up one after the other like a string of pearls along medium-voltage cables laid in the ground.

In the transformer stations, the voltage is reduced from the higher medium voltage in the range of 20,000 V, which is more suitable for distribution, to the voltage of 230 V, which is common in households, and distributed to the consumers.

A frequent cause of power failures are short circuits and earth faults in the medium-voltage cables between the transformer stations, which can occur due to ageing of the cables. If such a short circuit occurs, the power supply on the medium-voltage line is interrupted - as in the household by fuses. As a result, all consumers supplied by this medium-voltage line no longer have power.

In order to restore the power supply, it must be determined where the fault occurred.

In case of a short circuit, a very high current flows on the medium-voltage line section up to the short circuit, which is registered in the transformer stations on this section and indicated by so-called short-circuit/earth-circuit indicators in the station.

On the section after the short-circuit, no more current flows and consequently no short-circuit current is displayed in the transformer stations located on this section.

In order to determine where exactly, i.e. in which cable section between the transformer stations the short-circuit or earth fault has occurred, the short-circuit indicators must be read on site in the transformer stations. To do this, the stations must be approached and the indicators checked. This can take hours in cities due to traffic and hours in rural areas due to distance.

The fault is located between the last transformer station along the cable where a short circuit is indicated and the first where no short circuit is indicated.

Once the faulty section of the line is found, it can be disconnected and isolated by opening switches in the transformer station immediately before and in the one after it. The power supply to the line can then be switched on again, which means that all consumers in the section before the short circuit are supplied with power again. The section of the line after the fault can now be supplied from the other end, quasi backwards, by appropriate switching measures in the network, so that finally all consumers have power again. The power failure has been remedied and the defective section of line can be repaired.

So the duration of a power failure in such cases is mainly the time needed to locate the fault.

If the short-circuit messages from the transformer stations could be transmitted directly to a control centre instead of being read on site, the interruption time could be reduced to a few minutes.

Although this transmission technology is already available in newly built stations, there are still thousands of transformer stations, some of which are decades old. Here, a cost-effective and economical retrofit solution is required for digitisation.

With the Cluey product from comtac, this can be retrofitted easily and without great installation effort.

The Cluey records the short-circuit/short-circuit messages and, if necessary, other messages such as burglar alarm, fuse failure and switch positions on site and transmits them to a control centre. The modern and cost-effective LoRaWan® radio technology is used, which has a large range and building penetration. This is because transformer stations are often located in the basement of buildings or in urban canyons, thus offering poor conditions for classic radio technology.

In the event of a power failure, there is usually no more power available for the transmission technology to transmit the fault message! The Cluey, on the other hand, has a built-in battery so that transmission is possible even in the event of a power failure.

If necessary, the Cluey can also be used to remotely switch switches in the transformer stations, for example, via its control outputs.

With Cluey, a previously very time-consuming process - fault localisation in the power distribution network - can be simply and economically digitalised and the interruption times in the event of a fault can be considerably reduced.