T 0.8 Failure or Disruption of the Power Supply

In spite of high security of supply in the electricity sector, interruptions to the power supply on behalf of the distribution network operators or energy supply companies continue to occur. The majority of these disruptions are so short, with times of less than one second, that a human does not notice them. But interruptions of more than even 10 ms are capable of disrupting IT operation. However, besides disruptions in the supply networks, also shut-downs caused by unheralded works or cable damage due to civil engineering work, can lead to power failures.

It is not only those obvious, direct consumers of power (PC, lighting etc.) which are dependent on the power supply. Many infrastructure facilities depend on electric power today, e.g. lifts, air-conditioning devices, alarm systems, security gates, automatic door locking and sprinkler systems. Even the water supply in skyscrapers is power-dependent because of pumps in the upper floors required for producing pressure. Prolonged power outages resulting in failure of the infrastructure facilities can lead to a situation where no activity can be undertaken on these premises any more.

Besides failures, other disruptions of the power supply can impair the operation also. Voltage spikes can, for example, lead to malfunctions or even damage of the electrical equipment.

In addition it has to be taken into account that sometimes failures or disruptions of the power supply in the neighbourhood can affect one's own business processes, if access routes are blocked for instance.

Examples:

• Due to an error in the uninterrupted power supply unit of a computing centre, the unit was unable to return to normal operation after a short power failure. After discharging of its batteries (which took about 40 minutes) all computers in the respective server hall failed.
• At the beginning of 2001 in California there was a power supply crisis for more than 40 days. The power supply situation there was so tense that the Californian Independent System Operator ordered rotating power cuts. Not only households but also the high-tech industry was affected by these power cuts which lasted up to 90 minutes. Since during the power failure alarm systems and surveillance cameras were also turned off, the energy suppliers kept their shut-down schedule secret.
• In November 2005 many communities in Lower Saxony and North Rhine-Westphalia remained without a power supply for days after intense snowfall, because many pylons were knocked over by the load of snow and ice. The recovery of the power supply took several days.