2011The International Conference on Advanced Power System Automation and ProtectionPreventive Methods against Blackouts Based on Protection SecurityAssessment in Future Grids!!2Jochen Fuchs , Johann Jager , Rainer KrebsI FAU University Erlangen, Germany;2 Siemens Erlangen, Germany;Abstract: The paper presents a new automated method for assessing the security of protection systems concerning selectivityand speed to reduce the risk of unnecessary disturbances and blackouts. The invented algorithms are capable to handle complex structures. Hence, the system behavior of a protection system and network is analyzed and assessed as a whole and it has not to be reduced to its single components or devices. The simulation tool is used as an engine to provide the possibility of a holistic si mulation of networks together with the protection.The system-method can be divided into two main approaches: Fault pattern analysis (FPA) and economic impact assessment (EIA). The FPA calculates running faults through the whole grid for diverse scenarios of load flows. Economic aspects of non selective protection systems are also be introduced and presented by the EIA method. It benefits from the fact that protection devices violating dependability or security will lead to additional outage. This outage is calculated and evaluated by the differ ences of simulated outage and unavoidable outage. The large amount of resulting data is stored in a central database. Intelligent filtering and data preparation allow a holistic assessment and visualization of complete networks of different architecture. Routinely checks of contingency sequences with the presented methods will reveal bottlenecks of the protection behavior itselfand of the coordination of network and protection.Keywords: Protection security assessment, selectivity, speed, blackout prevention, protection coordination, holistic simulation, routinely contingency check, fingerprint analysis1 IntroductionThere is a change of global energy supply going on with increasing demand of energy transportation, reversal of load flows in distribution grids and a huge amount of dispersed generation,i.e. caused by wind energy plants. Especially in those grids of rural regions the load flow is more often turning from a top-down into a down-top principle, which means that the load flow is not always nmning from higher to lower voltage levels. The varying states of grids, the behavior of secondary equipment and the consequences out of switching operations are getting more and more difficult to predict. The analysis of past blackouts studiedby the North American Electric Reliability Council (NERC)shows that protection relays are involved in about 75% of all major disturbances. One reason for that is the non adequate adap tion of the protection systems to the changing network conditions.In particular the relay hidden milures caused relay malfunctionsand blackouts, following cascading trippings.In this context Protection security assessment (PSA) of power grids becomes an important task in the course of a competitiveenergy business and a decarbonized power generation. PSA will provide the opportunity and capability for improvement by ana lyzing the holistic behavior of the grid with automatic identifica tion of weak-points by technical or economic impact.2 Method of investigationThe presented method is analyzing networks as a whole. Bysimulation of routinely sequences of mult and contingency scena rios bottlenecks due to the selectivity of the protection system can be revealed. Based on the identification of bottlenecks, adapted settings can be derived, improving the protection behavior under the changing network conditions. The principle structure of theautomatic system is shown in figure 1. The system includes astorage system to store all information and also the grid model data, a system for management of simulation, an evaluation toolto control routinely methods to analyze the tripping behavior and effect of those reactions on the grid and a qualification and as sessment center for the interpretation of these effects.A. Data storageThe holistic approach of the presented method demands an ex traordinary effort of calculations and storage of all results follow ing from these calculations. Therefore, a well-designed data handling structure and storage system is essential. The data storage system is implemented on a mysql-database nmning on a data base server. At the beginning of the procedure the underlyingAPAP2011 www.apap2011.orgCorresponding author (email: fuchs@eev.eeLuni-eriangen.de)978-1-4244-9621-11111$26.00 2011 IEEE1857FAULT PATrERN ANALYSIS (FPA)ECONOMIC IMPACT ASSESSMENT (EIA)2011The International Conference on Advanced Power System Automation and Protectionresistance and to the related scenario of the power gridC. Evaluation ToolA general evaluation method of protection system behavior is given by the terms of Fig. 2. Following definitions are stated [1]:Reliability - The probability that a protection system willoperate with the required performance. This parameter includes the aspects dependability and security.Dependability - The probability that a protection system willtrip circuit breakers when it is required.Security - The probability that a protection system will not tripcircuit breaker when it is not required to do so.EVALUATION TOOL:;::DependabilitySecurityFigure 1Principle structure of method of investigationFigure 2 General structure of protection behavior evaluationpower grid model will be copied to the database. All other systems read required information from and write their calculated results to the database. By the use of an entity-relationship-model, the data storage system enables associations and filtering by keys between all scenarios, simulated :faults, results and the selection of data under consideration of various conditions.The use of the database with entity-relationship-model as storage system enables automatic evaluation of all calculated results in many different ways. This paper will be focusing on two main approaches to evaluate the protection system: Fault Pattern Anal ysis and Economic hnpact Assessment.B. Simulation toolThe simulation tool starts with the initialization of the power grid model to be assessed. ill the first step, all installed protection devices are analyzed, categorized and linked to their associated electric equipment. From these results protection zones and selec tivity-requirements may be defined. After initialization and sto rage of the results, the scenario builder generates a broad diversi fication of grid states with different load flows. For each defined scenario and for each protection zone the SC :fault simulation program calculates different kind of short circuits and different amounts of :fault resistances. As the simulation engine PSSSINCAL is used. [8] The location of the SC-faults is mov ing from calculation to calculation through the whole network in steps of i.e. 1 - 5% of the line length. The setngs for step size, resistances, scenarios, etc. either may be on standard values or may be limited or specialized by user's selection over graphical user interfuces. The use of an automatic control of the applied simulation tool allows various simulations of different networks and fault scenarios without making any time-consuming manual changes in the simulation model. The simulation tool calculates the reaction of all considered protection devices during all simu lated SC-faults. After simulation, those reactions are saved into the database and are linked according to their :fault type, to theI.Fault Pattern Analysis (FPA)The :fault pattern analysis calculates and displays the effect ofan occurring fault by relating the protection response according to the :fault. hnportant parameters are :fault clearance time, selectivi ty in combination with over- and underfunction and electrical equipment that is still in operation or has been disconnected. These values and elements are evaluated for every single simu lated :fault. For the selection of the clearing time, it is important to ensure that protection devices, which just tripped because of sympathetic tripping, but without shutting down an active cur rent-path to the :fault, are not taken into account. Those malfunc tions are recognized by the selectivity analysis, which is also part of the :fault pattern analysis.II.Economic hnpact Assessment (EIA)While for protection systems of transmission networks the reliability must be maximized, for distribution networks economic aspects must also be taken into account. To determine the eco nomical effect of a protection system's response to faults and to assess the need for improvement there is a second automated evaluation mode- the economic impact assessment. The general idea of those outage cost assessment methods can be divided into three approaches: macroscopic, microscopic and analytic [5].1858DATA STORAGECl:;::zClmZ-lC/>->= 2.33 In. For phase-to-phase faults a voltage dropE. Visualization tool18592011The International Conference on Advanced Power System Automation and Protectiondown to 70010 of Un leads to a sensitive pick-up between0.67...2.33 m. Thenon-directional pick-up delay time for tripping is 400 ms. Only the wderreaching tripping zone 1 with a time delay of 50ms is activated. It covers between 10% and100% of the feeder length depending on the consmner stations along the feeder. The rest of the feeder is protected by the non-directional starter mcility. Both overcurent relays have onlyactivated one definite time stage as I> =2.33 . m and t>=100 msnon-directional.The considered protection fimctions of the DG tmits at the PCCare: Undervoltage (27) - U =0.45 .Un, t(U)=300 msU =51.5 Hz, t(t>) =100msf