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After large-scale power outages: The defective cable is replaced

2021-08-10T14:57:21.094Z


2500 households were suddenly in the dark: A power failure had hit some people in Geretsried and Wolfratshausen. Bayernwerk AG is now exchanging a cable.


2500 households were suddenly in the dark: A power failure had hit some people in Geretsried and Wolfratshausen.

Bayernwerk AG is now exchanging a cable.

At Pentecost, parts of Geretsried and Wolfratshausen suddenly became duster - power failure.

After painstaking research, the power grid operator, Bayernwerk AG, has now found the error.

During these days, the company is replacing the defective cable - it is located in Geltinger Erde - over a length of around 600 meters.

On the evening of May 22nd, around 2500 Geretsried households were suddenly in the dark for an hour. Several malfunctions in a section of an underground cable with a voltage level of 20 kilovolts (KV) in Gelting had caused various power outages. The operator, Bayernwerk AG, then had to take the entire section off the grid and redirect the power supply to other areas. "This in turn has secondary errors, ie the failure of other vulnerable areas," says Michael Bartels, spokesman for the Regensburg company. This affected around 16,000 households, also in the Wolfratshausen district of Weidach, on four circuits. "According to the damage report, the cause here was actually the damage to the cable by a construction company, which caused the consequential failure," says Bartels."According to my information, it was on Münchner Strasse."

Cable is well protected - but it can still break

The layman may now ask himself why a cable encased in earth and thus apparently protected can break.

Bartels provides the explanation: In almost all cases it is external influences.

For example, cables would be damaged during the development of a building site.

An underground cable and the shovel of an excavator - the classic - just don't go well together.

Movements in the ground can also be a cause: "Even a sharp stone can damage the insulation of a cable over the years." Occasionally, water retention also makes the material brittle.

If a phase of the cable is damaged as a result - a 20 KV cable always has three phases - there is a short circuit to earth or colloquially, so the phase concerned is de-energized. "The 20 kilovolts are then automatically routed through the other two phases." Although this increases the load on the two intact phases, this usually does not lead to a power failure in this network area, the expert continues. “However, if the second phase is also damaged or prone to failure, possibly at a different point, then a“ double earth fault ”occurs. It becomes critical when the second phase is de-energized at the latest. The remaining third phase alone can no longer hold the voltage of 20 kilovolts. The result: lamps and televisions go out, monitors go dark,and the refrigerator defrosts. In short: the electricity is gone. This is exactly what happened on Whitsun in the aforementioned Geretsried / Wolfratshausen network area.

Bayernwerk AG found the culprit underground

On the following days, Bayernwerk AG went looking for errors.

First, the company had to pinpoint the faults - and then dig.

Experts from the energy supplier opened the cable trench and determined “damage from stones or as a result of short circuits”, the latter being evident from heavy sooting.

Elsewhere, according to Bartels, “a connection between two sections was damaged.

An exchange of cables in the affected supply area was urgently necessary here. ”Damage of this type would occur again and again, not only in Geretsried, but in all parts of Germany - especially on cable routes that have been in the ground for a long time.

The affected section in Gelting, for example, was relocated in 1973.

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Defect: This old cable caused the power failure

© Private

Despite the current problem, underground cables have advantages over overhead lines.

According to Bartels, they are less prone to failure and “cannot be damaged by storms, traffic or birds”.

Bayernwerk AG will now use a stronger medium-voltage cable on the new cable route.

"This enables us to keep pace with the increased network requirements, including through the expansion of renewable energies, e-mobility and heat pumps."

The construction project is expensive: Bayernwerk AG pays 123,000 euros

The work is being carried out by a subcontractor, the Benediktbeurer company Bloom Earth Moving.

"We are currently working with three excavation teams of two or three men," says owner Nick Bloom during a visit on site.

A cable section of 610 meters will be exchanged in Gelting, starting from the transformer station Auf der Blaicken via Loisachweg and Am Haken to the transformer station at Wolfratshauser Straße 12, says Bayernwerk spokesman Michael Bartels.

“We are spending around 123,000 euros on the construction project.” The construction time is around four weeks, and closures are only required in sections.

Also read: Was it a technical error?

In Icking, two S-Bahn trains ran towards each other.

A coincidence ensured that the catastrophe did not occur.

Source: merkur

All news articles on 2021-08-10

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