7504 System Frequency and Tie-Line Control

About This Course

The fourth course in the Transmission System Operation training program shows how frequency and tie-line flows between control areas are controlled. We begin by developing the concepts of an AC interconnection and synchronizing forces. Frequency deviations come about when unbalances develop between generation and load and these deviations are controlled by the combined action of speed governors and Automatic Generation Control (AGC) aided by the natural change in load as frequency changes. We describe how tie-line flows also change when generation to load imbalances occur. Finally, this course discusses Area Control Error (ACE), the fundamental input to AGC, and how it provides the intelligence required to restore generation to load unbalances. At the completion of this course, the student should be able to: Know what constitutes an AC interconnection, Identify the interconnection within which your facilities are located, Know at what frequency your interconnection operates, Explain why frequency is the same throughout an AC interconnection, Explain the role of transmission lines in maintaining synchronism, Know what causes frequency to deviate from nominal, Tell whether generation or load is changed to control frequency, Know what a speed governor is and what it does, Tell how the size of an interconnection affects frequency deviations, Know what limits are imposed on frequency excursions and why, Know why it is important to control tie-line flow, Know why the type of generating unit affects its speed of response to frequency changes, Explain the relationship between generation rotational speed and frequency, Understand that speed governors act as proportional controls, Describe what is meant by governor droop, Describe the units used for droop, Know that governors work to control both decreasing and increasing frequency, Understand why governor droop permits load sharing between generating units, Tell what are typical droop settings for various types of generating units, Understand why many classes of generating units do not participate in frequency control, Be able to describe the basic characteristics of the example system used, Total capacity, capacity under governor control and total load, Composite droop characteristic, Tell what happens to frequency under governor control only when an 800 MW unit trips off, Describe what is meant by the Load Effect, Describe what is meant by the Frequency Response Characteristic, Beta, Tell what happens to frequency under the influence of Beta when an 800 MW unit trips off, Be able to calculate how much generation is picked up and how much load is lost for a given drop in frequency, Understand why frequency does not drop instantly when a generation/load mismatch occurs, Be able to identify points A, B and C on a frequency chart taken while a generating unit tripped off line, Be able to compute the net tie-line flow following loss of generation within a control area, Understand how AGC assists system operators, Know how frequently AGC application software is run, typically, Be able to describe Area Control Error and how it is calculated, Know what is the Frequency Bias Coefficient, B, and how it relates to Beta, Be able to compute ACE given frequency deviation, net tie deviation and B, Know how to find the frequency stabilization point, Describe functions that AGC can perform other than responding to generation loss, Know why AGC is suspended when large frequency deviations occur.

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