ECE 573 Power System Operations and Control Power System Security Monitoring, Analysis, and Control George Gross Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 1
POWER SYSTEM SECURITY Definition: power system security is the ability of the system to withstand disturbances without unduly impacting the service to the loads or its quality In security applications, we refer to the disturbances of interest as contingencies In power system operations, security assessment analyzes the vulnerability of the system to a set of postulated contingencies on a real or near real time basis ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 2
POWER SYSTEM DISTURBANCES Power systems are continuously subject to disturbances covering a wide range of conditions Typical examples are: sudden change in load demand generator failure equipment outage transmission line loss system configuration change customer load change ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 3
POWER SYSTEM SECURITY The concept of security is associated with the capability of the power system to serve the loads without violating any technical, physical, engineering or operational constraints in the operating state and in the state corresponding to a contingency from the set of postulated disturbances ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 4
POWER SYSTEM SECURITY Power system steady state security is an instantaneous condition: it is a function of time and of the robustness of the system with respect to imminent disturbances Security is the counterpart of reliability in power system operations; the attempt to refer to security as operational reliability is largely unsuccessful ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 5
POWER SYSTEM SECURITY In the post 9/11/2001 world, the word security has taken on the meaning of physical security NERC has replaced the term power system security by power system operational reliability security can include both physical vulnerability and cyber security the industry continues to use the term power system security in the sense defined here and we use the term in that way throughout the course ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 6
RELIABILITY ASSESSMENT system configuration load forecast reliability assessment planning to satisfy reliability requirements equipment characteristics planning involves a multi-year horizon during which the various activities are implemented ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 7
CLASSIFICATION OF STATES The system is in a normal state when all the loads in the system are supplied and no constraint is violated The system is in emergency state when all the loads in the system are supplied and one or more constraints are violated The system is in restorative state when there is loss of load (partial or total blackout) and no constraint is violated ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 8
CLASSIFICATION OF STATES state loads constraints normal all loads served no violations emergency all loads served one or more violations restorative loss of load no violations ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 9
STEADY STATE SECURITY CONTROL The aim of security control is to prevent the system state from transitioning from secure to emergency For an insecure normal state, i.e., an operating state that is insecure for a specified contingency (alert state), there are two possible responses: modification of the pre-contingency state to eliminate the potential emergency (overload), in case the contingency actually occurs formulation of a control strategy to manage the emergency once it occurs ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 10
STEADY STATE SECURITY CONTROL The various EMS security and economy functions are used to determine the security of the operating state; formulate appropriate control actions; study various what if situations; and, prepare information for pricing/financial applications in wholesale markets ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 11
STATIC SECURITY ASSESSMENT Security is determined with respect to the set of postulated, credible next contingencies An operating state is secure if the system operation is in a secure normal state; otherwise, the operating state is insecure Security assessment deals with the analysis of the system vulnerability to a set of postulated disturbances on a real or near real time basis ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 12
STATIC SECURITY ASSESSMENT The working definition of security was developed by Tom Dy Liacco Reference : Tomas Dy Liacco, The Adaptive Reliability Control System, IEEE Transactions on Power Apparatus & Systems, Vol. PAS-86, no.5, May 1967, pp. 517 523 ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 13
SECURITY MONITORING, ASSESSMENT AND CONTROL FRAMEWORK Security monitoring : identifies whether or not the system state is normal based on real time system measurements Security assessment : determines whether the normal state is secure or insecure with respect to the set of postulated contingencies Security control : emergency control is deployed in an emergency state and restorative control is activated under load loss ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 14
SECURITY MONITORING, ASSESSMENT AND CONTROL FRAMEWORK Preventive control : determines for an insecure state (there is at least one contingency that causes an emergency) the appropriate preventive action to make the system secure Emergency control : deploys corrective actions to make the system state normal Restorative control : develops appropriate actions to restore service to all system loads ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 15
SECURITY FRAMEWORK normal states secure preventive control restorative control insecure corrective control restorative states emergency states transition due to disturbance transition due to control action ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 16
FRAMEWORK FOR SECURITY, MONITORING, ASSESSMENT AND CONTROL security monitoring normal state security assessment secure state? yes secure state no no emergency state? restorative state? yes restorative control preventive control emergency control yes ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 17 no emergency control feasible? no yes
THE REAL-TIME MONITORING AND CONTROL SYSTEM data acquisition and processing measurements filtering observability analysis bad data processing state estimation network topology limit checking emergency state emergency control restorative control secure state contingency selection contingency evaluation exit normal state bus load forecast online power flow insecure state preventive control external network model security analysis ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 18
SECURITY SURVEY PAPERS B. Stott, O. Alsac and A. Monticelli, Security Analysis and Optimization, Proceedings of the IEEE, Vol. 75, No. 12, December 1987, pp. 1623 1644. F. F. Wu, Real-time Network Security Monitoring, Assessment and Optimization, Electrical Power & Energy Systems, Vol. 10, No. 2, April 1988, pp. 83 100. ECE 573 2001-2015 George Gross, University of Illinois at Urbana-Champaign; All Rights Reserved 19