Power System Reliability Report - RTE

R-AUDIT-SG-DAR-MAS-11-2011/022010 Reliability ReportPage : 12/408 juillet 2011or of all the production and transmission facilities connected to this section). Safeguard measures areactivated when the expected consumption level exceeds the limit ensuring reliability only in case ofmore common incidents. These measures make it possible to reduce consumed power by several %points. In addition, the Automatic Load-Shedding Controller (ADO) installed in 2009 can act in a dozenseconds after an incident by load shedding consumption in Brittany.During the cold wave in late November early December, which was severe without being exceptional,with a variation of 9°C compared with normal temperatures, new situations of this type developed,giving rise to similar decisions in more extensive zones.In total, 31 ESS level A (20 in 2009) were logged for voltage reasons, including 23 during cold spells,each corresponding to at least one first level warning "low voltage critical situation" S order. Duringthese periods, 16 S "voltage profile downgrading" orders were issued in the West and Normandy–Paris regions, but also less systematically in the North-East, South-West and East regions, illustratingthe widespread nature of the voltage control problem, due to the meshing of the network and locationof the main generation facilities. These orders let producers and distributors know that they should dotheir utmost to activate available reactive power reserves.The "-5%" 4 safeguard orders were activated ten times in the North-West region (2 in 2009), fordurations of 2 to 4 hours each time, from January 4 th to 7 th , then on January 26 th , and from November30 th to December 2 nd in fairly large areas. For example, an order was issued on December 1 st fromPicardie to Brittany and La Vendée, encompassing Ile de France and Normandy, for an estimatedeffect of 1200 MW. The AutomaticLoad-Shedding Controller (ADO)was put on standby 19 times (82hours in total). Additional“transformer block 5 " safeguardorders were activated three timeson January 4 th , December 1 st and3 rd . It should be noted that onseveral days, these safeguardorders were issued to deal withsituations, that in the absence oforders, would have led to avoltage collapse not only inBrittany but also in the wholeWest region including Paris in thecase of the loss of a single generating unit. To illustrate this, the associated chart concerning theconsumption plan for the Normandy-Paris and West regions indicates the effect that safeguard ordershave in maintaining the system‟s operating point close to the pre-collapse safety limit on N-1 unit(limits shown by red lines, the operating point must remain below it to guarantee that a collapsedoesn‟t occur; without additional remedial actions).The results of voltage profile control in the PACA region are also worth noting. In January andFebruary, 4 "-5%" orders and 7 transformer block orders were issued for the eastern part of theregion but none at the end of the year. This is due to the commissioning of the 400 kV double line toNice (as well as the growing availability of generating means in the Fos area) that makes it possible tosubstantially raise the consumption limit before voltage collapse. The durability of this improvementwill depend on the regional control actions that are taken to limit the growth in consumption and onthe construction of the “225 kV safety net" decided in 2009.This information, and in particular the number of safeguard orders, confirms the criticality of thesesituations and their presence from one year to the next: the improvements made by RTE each year4 Order sent to distribution network control centres to lower the set-point voltage of the delivery point substationtransformers, resulting in a drop in consumption associated with passive loads5 Suspension of voltage regulation in HV2/HV1and HV1/MV transformers, which contributes to the stabilisationof voltage drop phenomena by using the natural behaviour of the loadsCopyright RTE. This document is the property of RTE. Any communication, reproduction, publication even partial is forbidden without the express written authorisationElectricity Transmission System operator (RTE)