Resilience (energy industry)

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The most important requirement for a critical infrastructure is its reliability . In the previous energy world, this was achieved by making the power supply system robust. A technical system is said to be robust if it can handle most of the foreseeable disruptive events without significantly impairing its functionality. The electricity supply system does this, among other things, through the so-called N-1 principle : Every essential element in the system may fail; the maximum load in normal operation is then taken up by redundant reserve capacities.

In the future complex electricity supply system, resilience , i.e. the ability of technical systems not to fail completely in the event of a partial failure and to return to the initial state after a fault, is of great importance . The previous robustness cannot be continued one-to-one due to the changed structure of the energy supply.

Definition

Resilience is defined as the ability of a system to maintain its functionality under stress or to restore it in the short term. Resilience goes beyond the property of robustness . A system is referred to as resilient if its functionality is only slightly impaired in the event of malfunctions, there is no major damage and full performance is available again as quickly as possible after the malfunction.

Reasons for a new approach

A failure or a mere impairment of the energy supply leads to long-term supply bottlenecks and considerable disruptions to public order and security. Cascading disruptions spread quickly and across regions, particularly in the electrical power supply. Furthermore, electricity is difficult to substitute, especially in other infrastructures, for example the telecommunications network cannot function without a supply of electrical energy.

For three reasons, the previous redundancy principle can no longer be adhered to consistently in the future:

  1. The energy transition : sun and wind are increasingly becoming the backbone of electricity generation. This is accompanied by the multiplication of decentralized generating plants, which will mean that not all generating plants can be connected redundantly.
  2. The sector coupling means a large number of new consumers in the heating and transport sector .
  3. The digitization of the network, sales and end users is necessary to cope with the two previous challenges. For example, it will only be possible through digitization to forecast and control the large number of future generation plants in real time. Decentralized intelligence is an answer to increasing complexity. The restructuring of the energy industry and the digitization of the grids are mutually dependent.

Considerable efforts are required in order to be able to guarantee the stability and quality of the electricity supply in the face of these challenges of the energy transition and sector coupling. Cyber ​​resilience (“safe-to-fail”) plays a key role here, since the concepts that have proven themselves in the past and rely on robustness (“fail-safe”) are increasingly reaching their limits. In the future, the energy system must react to unforeseen disturbances in such a way that it still maintains its basic functionality or can regain it independently. For this self-organization, it is essential to understand information and communication technology as an integral part of the electricity system and to fully exploit the potential of digitization to increase its resilience.

Digitization of distribution networks as a prerequisite for resilience

In the power supply system, there is growing pressure to make demand more flexible and to establish communication options between the actors in the supply and demand of electricity. As the digitization of energy networks advances, not only do the possibilities for more efficient network operation increase, but also worries about cyber attacks and disruptions increase considerably. This also applies to critical infrastructures in general.

The digitization of power grids, especially distribution grids , is currently showing a very wide range of fluctuations. In particular, the lower network levels ( low voltage and parts of medium voltage ) have not yet been digitized to a large extent and are therefore largely unobservable. In contrast to this, high and extra high voltage networks are equipped with extensive IT-supported sensors and actuators to enable efficient network management.

The system services include, for example, the black start capability, i.e. the ability of the energy system to restore the supply after a complete power failure. This case exemplifies the mutual dependency, because restarting after a complete failure must be coordinated via the telecommunications infrastructure. The wireless infrastructure is already in parts via battery storage at the base stations black fall fest . However, if the telecommunications infrastructure becomes an indispensable prerequisite for a black start in the future, it must be possible to maintain its functionality for even longer periods of time by using larger memories. In addition, with the imminent rollout of 5G technology, the number of radio locations will increase significantly (by a factor of three to five), so that additional efforts will be required if the new technology is to be suitably secured. A financing framework for this new task for society as a whole and a market organization are still lacking.

With the help of information and communication technology, the energy supply system can be designed to be resilient. For this, on the one hand, the information and communication technology itself must be made more robust against attacks through organizational, personnel and technical measures. On the other hand, it can above all contribute to resilience in the true sense of the word by recognizing faults at an early stage, automatically initiating countermeasures and taking over system services. In the acatech study Future Energy Grid , an overarching scenario was developed in 2012 that provides for, among other things, end-to-end digitization, demand management , sector coupling, Europe-wide networking (digital, physical and regulatory), system services through renewable generation plants and markets for small transactions.

Technologies and technological solutions

Sensors / actuators

Sensors help to analyze the behavior of the networks. Deductions from measured values ​​help generate forecasts and thus improve planning. Actuators, in turn, enable flexibility, for example by switching off excess generation systems (generator dropping) or shedding loads in the event of excessive consumption (load shedding). The use of sensors and actuators enables the flexible optimization of supply and distribution networks. Remotely controllable circuit breakers, circuit breakers and tie switches are increasingly replacing classic fuses. Using these switches in the course of network automation not only reduces recommissioning times, but regular remote monitoring is also possible. Network topologies can be automatically adapted to current generation and consumption situations using telecontrol technology.

Prosumer

Prosumers play a major role in intelligent energy networks. You can absorb generation peaks from supply-dependent, renewable energies through the use of storage systems or the targeted activation of disposable loads. But even if there is a lack of generation capacity, they can reduce their reference capacity by shifting the load or increasing generation by discharging the storage tank. In a swarm, not only individual prosumers but entire groups of prosumers can increase resilience.

Microgrids

Microgrids reduce the dependency on the large power plants in the event of a fault. In the event of failures in the upstream network, some of these can continue to operate their own small island network in a stable manner in order to supply critical loads. The best example of this is the safety power supply in hospitals or data centers. This enables self-sufficiency for a defined period of time. In the future, such island structures could be used on a larger scale and contribute to resilience.

However, there are currently major problems with such island structures

  1. the question of protection technology if the earthing system changes in stand-alone operation, and
  2. the resynchronization of the respective islands to a network with the same frequency, in order to enable further areas to be supplied again after a blackout .

Furthermore, technical standards and grid codes for microgrids have to be further developed and detailed (see IEC TS 62898 series).

Integrated energy system

Classic municipal utilities have long looked not only at electrical energy, but also at other sectors such as water, gas and heating. Power-to-heat , power-to-gas or power-to-cool are areas that come to the fore here. A network of different sectors is particularly helpful in decentralization in order to reduce dependencies, increase flexibility and also provide storage capacities. The intelligent control of the coupling systems enables the development of techno-economic potential.

Adjustable local network transformers (rONT)

By using voltage regulators at local network stations, the voltage level can be adapted to the current grid situation and the capacity for renewable energies can be expanded through flexible countermeasures when the permissible voltage limit is reached. In view of the prospective expansion of PV in low-voltage networks, the network expansion cannot be avoided, but at least it can be delayed.

Predictive maintenance

By means of predictive maintenance, taking into account the possible sensor values, a timely maintenance and thus cost planning and determination for the operation can be derived (ex-ante instead of ex-post), as already explained above. For example, through the integration of sensors, distributed across all network levels, a fault history can be evaluated using modern big data technologies and analytics methods. The basis for this can be relevant network data as well as external influences (e.g. weather, season ...). Structural weaknesses and their causes can be identified, geographical aspects can be considered and the associated optimization potential, such as shortening the recommissioning times by changing the allocation of necessary operating resources, can be derived and presented transparently.

Transformation path

In 2018, companies in the energy and digital industries outlined a transformation path in the discussion paper "Failure safety of the energy supply system - from robustness to resilience".

  1. Protection against cyber attacks can no longer be guaranteed with technical means such as data encryption, firewalls and virus scanners alone. Rather, organizational measures such as access control, employee awareness of dangers and authorization levels play an increasingly important role. Together with the Federal Office for Information Security (BSI), the Federal Network Agency has created a catalog of requirements for IT security measures for electricity and gas networks.
  2. Thanks to the ongoing decentralized and automated analysis of all available data of the energy system, it is possible in the event of a fault to get a comprehensive and detailed picture of the current situation and, with this knowledge, to initiate the right decisions for stabilization or recovery. The effects of the planned measures can not only be predicted using data-based simulation methods, but their effects can also be maximized through the information technology integration of all relevant actors. In this way, clear priorities can be set, counterproductive individual measures can be avoided and, through the exchange of information in real time across all levels of the energy system, the necessary agreements can be significantly accelerated - if necessary even (partially) automated - so that a faster reaction can be taken and the inevitable damage caused by faults keep it to a minimum. In the long term, it is conceivable that the energy system will stabilize itself autonomously in the event of minor local or regional disruptions without human intervention, in that the necessary steps are initiated independently by algorithms (self-organization).
  3. Due to the permanent analysis of the data streams in real time, disturbances in the energy system - caused for example by cyber attacks - can be recognized by identifying telltale or norm-deviating patterns in the energy system data while they are still emerging. This makes it possible to react proactively, that is, to anticipate the disturbances and to prevent them through suitable countermeasures or at least to keep them as small as possible. In the future, there is the possibility that the proactive countermeasures will be carried out automatically by algorithms, at least in the case of minor disruptions.
  4. The data analysis of fault histories offers the possibility of identifying structural weaknesses in the networks, deriving corresponding optimization potentials from them and increasing the resilience of the energy system through structural and / or organizational adjustments. The use of artificial intelligence makes it possible to deepen the understanding of the complex relationships and interactions between the various levels of the energy system and thus to gain new insights.

Individual evidence

  1. ↑ Future Energy Grid - Migration Paths to the Internet of Energy - acatech . In: acatech . ( acatech.de [accessed on October 11, 2018]).
  2. ↑ Failure safety of the energy supply system - from robustness to resilience. Retrieved October 11, 2018 .
  3. ↑ Federal Network Agency - IT Security. Retrieved October 11, 2018 .