7506 Power System Stability

System Security is the focus of this 6th course in the Transmission System Operation training program. The concept of operating security is developed as the ability of a power system to withstand or limit the adverse effects of any credible contingency, including: overload beyond emergency rating excessive or inadequate voltage, loss of stability, or abnormal frequency deviation. This course begins with a discussion of the nature of large synchronous interconnections, and how AC power flows within such a network. It is demonstrated that, each time a large unit trips in an interconnected system, there is an inrush of power into the affected area that could seriously overload the transmission system. The operator's role of assuring that line loadings remain within pre-established limits is discussed, as well as the concept of transmission line loadability. Line loadability is analyzed from the standpoint of three major limits that can restrict the flow of MW across a given transmission corridor: the thermal limit, the voltage drop limit, and the stability limit. Loading limitations of other transmission equipment is described as well, including cable and transformer loading. This material then proceeds to give an overview of security monitoring in the control room, with the help of SCADA and EMS systems, on-line power flows and contingency analysis, and dynamic security monitoring. Finally, techniques for improving system security are presented, including the role of Security Coordinators, the exchange of security data, loading relief options, preservation of operating reserve, and emergency methods. At the completion of this course, the student should be able to: Explain what is meant by operating security, State and discuss two major reasons why individual companies or areas choose to interconnect their power systems, Name the four North American Interconnections, Describe what is meant by a 'control area', Explain what happens to tie-line flow in the first 10 to 20 seconds following a large unit trip in an interconnection, Understand the effect of a capacity emergency on the security of the interconnection, Discuss the problems that may be associated with loop flow and parallel flow during normal operating conditions, State the three main factors that determine a transmission line's loadability, Give examples of continuous, long-term emergency and short-term emergency thermal ratings for a transmission line, Describe the consequences of operating a transmission line above its emergency thermal rating, Explain how 'on-line', or 'dynamic' thermal ratings are used to increase line loadability, Understand the effect of increased MW loading on the reactive requirements of a transmission line and, consequently, on voltage drop, State applicable industry Standards for maximum permissible voltage drop following credible contingencies, Explain what is meant by the 'steady-state stability limit' across a given transmission path. Give the expression for steady state stability limit in terms of voltage and reactance, Describe the consequences of loss of synchronism on the transmission network, Sketch a typical power angle curve and compare it to the curve that would result if one or more parallel circuits trip, Sketch a typical line loadability curve for transmission lines of different lengths. Explain what the overriding limit is for short lines vs. long lines, Describe the effect of compensation on line loadability, Name other transmission equipment (besides overhead lines) that may be the limiting factor in determining how much power can be transmitted across a given path, Discuss the thermal and charging limitations of high voltage (transmission-level) underground cables, Explain the thermal capability of power transformers, as well as cooling methods that are employed to increase MVA rating, State a typical transformer overload magnitude, duration, and expected loss of life, based on established loading guides for power transformers, Describe how SCADA/EMS systems help operators to continuously monitor the security of the power network, Give examples of software tools (incorporated into an EMS) that alert operators to actual and predicted security problems on the network, Explain what is meant by dynamic security assessment (DSA), Discuss the North American Electric Reliability Council (NERC) and its mission in preserving security in the 4 North American Interconnections, Understand the role of Security Coordinators in the North American Interconnections, List several examples of operating security data that must be provided and updated by each control area every 10 minutes, Give 3 examples of loading relief methods that may be undertaken and supervised by Security Coordinators, Explain how FACTS devices can dynamically control the flow of power over specific transmission circuits, Describe the purpose and operation of a phase angle regulator (PAR), Explain what is meant by 'operating reserve', and state what portion of this reserve must be spinning. List examples of what can be included in 'non-spinning' reserve, Give examples of typical operating reserve practices, Describe 2 emergency measures for dealing with a capacity emergency.

If you are taking this course for NERC credit, the following credits will be reported.

NERC CE HOURS: CE HOURS = 4.00 OPS Topics=4.00 Standards=0.00 Simulation=0.00 EO=4.00