System Defence Plan
European Union Electricity Market Glossary





System Defence Plan is the technical and organisational measures to be undertaken to prevent the propagation or deterioration of a disturbance in the transmission system, in order to avoid a wide area state disturbance and blackout state (Network Code on System Operation, Article 3(2)(63)).


Pursuant to the ENTSO-E Supporting Document for the Network Code on Emergency and Restoration of 25 March 2015, p. 23, System Defence Plan measures may include, but are not limited to the following:


- start or stop/disconnection of Power Generating Modules;

- Demand disconnection or Energy Storage disconnection;

- instruction to Significant Grid Users to change their Active and Reactive power outputs;

- instruction to DSOs to change voltage regulator set-points on transformers on their grid;

- behaviour change of the Load Frequency Control Structure (e.g. freezing the automatic
activation of FRR);

- Low Frequency Sensitive Mode activation;

- HVDC Systems active and reactive power control;

- System Protection Schemes actions (including Automatic Low Frequency Demand
Disconnection and On-Load Tap Changer Blocking Schemes);

- Requesting maximum or minimum values of Reactive Power to Significant Grid Users in
coordination with DSOs;

- Assistance for Active Power; and

- Cross-Zonal Allocated Capacity curtailment.


In turn, the ENTSO-E Supporting Document for the Network Code on Operational Security of 24 September 2013 2nd Edition Final (p. 73, 74) gives the examples of applicable measures of the System Defence Plan in the breakdown for load, Frequency, power flows and Voltage constraints (it should be noted that all those measures are not always available, depending on the national legal and regulatory frameworks):


Load/Frequency constraints

• Start or stop Power Generation Modules;
• Start or stop pump storage units;
• Increase or decrease (automatically or on request) production level of Power Generating Modules or pumps;
• Adapt active LFC control mode;
• Use of manual or automatic load shedding;
• Changes of Voltage regulator set points on transformers at distribution level.


Power Flow Constraints

• Cancellation of maintenance (grid elements urgently backed to operational service);
• Changes in the pattern of reactive power flow within the own TSO grid or with the support of neighboring TSOs;
• Automatic unit trip triggered by line outage;
• Counter-trading with neighboring Responsibility Areas;
• Intervention in scheduling;
• Freezing of scheduled exchanges;
• Schedule of exchange reduction;
• Reduction of interconnection capacities;
• Pump trip;
• Manual load shedding of interruptible Demand Facilities;
• Automatic shedding of interruptible Demand facilities triggered by line outages;
• Manual load shedding of domestic Demand Facilities;
• Automatic shedding of Demand Facilities.


Voltage Constraints

• Requesting maximum or minimum values of generation for Active Power and Reactive Power;
• Reduction of Active Power in favor of additional Reactive Power output;
• Preventive start of units with provision of additional Reactive Power;
• Stop of Voltage and Reactive Power optimization;
• Stop of maintenance, switching-on of all elements previously in maintenance;
• Limitation of Intraday trade (influence on transits);
• Blocking of on load tap changers of transformer.




IMG 0744





Network Code on System Operation, Article 3(2)(63)


Network Code on Emergency and Restoration


ENTSO-E Supporting Document for the Network Code on Emergency and Restoration, 25 March 2015, p. 23

















Last Updated on Friday, 08 September 2017 20:27


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