System Protection Technology

The purpose of this videotape is to present protection schemes that are used to assist in maintaining system stability. The concept of steady-state operation and dynamic response is demonstrated with particular reference to the power angle curve. The physical consequences of instability are also discussed.

After study of this tape and associated workbook, participants should be able to understand the following overall concepts and be able to apply them to their day-to-day work activities. They will also be able to answer related test questions on these subjects:

• Power transmission
• Steady-state operation
• Function of turbine governor and voltage regulator
• Power transfer equation
• Effect of change in V, XL and power angle
• Critical power angle 90º
• Dynamic response – rotor inertia
• Power angle curve – equal area concept
• Loss of transmission line
• Effect of initial loading
• Phase-to-phase faults
• Automatic reclosing of transmission lines
• Automatic reclosing of distribution lines
• Limitations of automatic reclosing
• Synchrocheck relays
• Single pole tripping and reclosing
• Instability out-of-step operation
• Load swings
• Voltage profile – effect on distance relays
• Out-of-step relays, blocking and tripping
• Load shedding
• Frequency relays