French TSO operational voltage risk management in a volatile electrical environment

摘要

Due to the specific behaviour of the load integrating a large part of electrical heaters, the French powersystem has to face historically high peaks of load in particular in winter during low temperatureperiods. Moreover, the evolution of the European electrical energy context with the development ofrenewable energy, increase exchanges of electrical energy through market coupling, cross bordersbalancing offers and emergence of demand response mechanisms lead to globally optimized thesystem operation closer to real time, closer to its security limits and in a more and more volatileenvironment. This involves adapting operational methodologies and tools in order to take the rightdecision at the right time with regard to the available action levers.These considerations concern particularly the voltage control issues of the French transmissionsystem. Indeed, RTE, the French TSO has to face:1. Low voltage phenomena and voltage collapse risks in winter depending obviously on theglobal load level, but also on the electrical flow over-passing on the transmission system andon a growing amount of wind and photovoltaic energy sources which can relieve the system orincrease the constraints with regard to their localisation and completely change the constraintstypology with regard to the historic one’s.2. More constraining high voltage phenomena in low load periods due to the increase ofrenewable energy generation which decreases the global injection of the concerned areas, butalso and more and more in intermediate or breaking periods during which system operatorshave to examine how to control the system in anticipation at both low and high voltage limitsin order to activate, when necessary, the adapted available action levers.Based on feedback experience of earlier voltage collapses, and in order to ensure voltage control inaccordance to the evolution of electrical energy environment, RTE developed dedicated3. voltage study methodologies and tools to lead precise and robust analysis mostly based ondynamic simulations and risk analysis at each study time scale to characterize the phenomena,to calculate the limits of the system and propose operational criteria available to systemsoperators to take the right decisions from usual control means up to emergency orders ifnecessary. Equivalent methodologies and tools are also used for planning studies to justify andimplement optimized long-term reactive power capacities to maintain the voltage within thelimits;4. operational procedures and processes to ensure in anticipation a right representation of thesystem situations using the best predictive and actualized hypothesis and a closed coordination between regional and national RTE control centres as well as with the neighbouring TSO oradjustment actors in particular concerning the short term analysis;5. dedicated automatisms to regulate the voltage in normal situation or to ensure the voltagesecurity as a defence plan in case of non predicable event or over sizing situations to avoidvoltage collapse which could lead to unacceptable consequences for the European system.This article will provide an overview of the French TSO operational voltage control frameworkillustrated thanks to experienced situations and descriptions of the methodologies and analysis tools,operational processes and automatisms presented above and main benefits resulting of this globalscheme.