Power oscillation protection

Electric power system, comprising:

• a number of nodes,
• power lines interconnecting said nodes,
• at least one power generator connected to one of said nodes,
• at least one power load connected to one of said nodes, and
• an SPS (System Protection Scheme) for protection of the integrity of said electric power system against poorly damped power oscillations,
• said SPS in turn comprising:
• a set of at least two system protection terminals, and
• a communication system interconnecting said at least two system protection terminals,
• said at least two system protection terminals in turn comprising:
• a processor unit, and
• a communication unit connected to said processor unit for communication on said communication system,
• wherein system protection terminals in a first subset of said set of system protection terminals comprise measurement signal obtaining means connected to said processor unit for collecting measurement signals of measured characteristics of said electric power system, said first subset comprising at least two system protection terminals, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,
• wherein said processor unit in system protection terminals in a second subset of said set of at least two system protection terminals in turn comprises evaluation means for detecting poorly damped power oscillations based on said measured characteristics from at least two of said system protection terminals in said first subset,
• wherein said evaluation means being arranged for obtaining node angle differences between different locations associated with said system protection terminals of said first subset and for determining at least one of amplitude, frequency and damping of said detected power oscillations from said node angle differences, and
• wherein said system protection terminals in said second subset further comprising control signal providing means connected to said processor unit for providing control signals to power system actuating units counteracting said poorly damped power oscillations in response to an output of said evaluation means.

System protection method for the protection of the integrity of an overall electric power system against poorly damped power oscillations, comprising the steps of:

• collecting measurement signals associated with measured characteristics of said electric power system in at least two locations of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,
• evaluating said measurement signals, for detecting poorly damped power oscillations based on said measured characteristics,
• said evaluating step in turn comprising the steps of obtaining node angle differences between said at least two locations and determining at least one of amplitude, frequency and damping of said poorly damped power oscillations from said node angle differences, and
• providing control signals to actuating units in said electric power system, if system protection measures are necessary according to said evaluating step.

System protection terminal for protection of the integrity of an overall electric power system against poorly damped power oscillations, comprising:

• a processor unit,
• a communication unit connected to said processor unit,
• measurement signal obtaining means connected to said processor unit for collecting measurement signals of measured characteristics of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,
• said processor unit in turn comprising evaluation means for detecting poorly damped power oscillations based on said measured characteristics and corresponding characteristics for different nodes in said electric power system received by said communication unit,
• said evaluation means being arranged for obtaining node angle differences between said different nodes and for determining at least one of amplitude, frequency and damping of said detected power oscillations from said node angle differences, and
• control signal providing means connected to said processor unit for providing control signals to power system actuating units.

A computer program product comprising at least one of computer code means and software code portions for making a processor perform the steps of:

• collecting measurement signals associated with measured characteristics of said electric power system in at least two locations of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,
• evaluating said measurement signals, for detecting poorly damped power oscillations based on said measured characteristics,
• said evaluating step in turn comprising the steps of obtaining node angle differences between said at least two locations and determining at least one of amplitude, frequency and damping of said poorly damped power oscillations from said node angle differences, and
• providing control signals to actuating units in said electric power system, if system protection measures are necessary according to said evaluating step.

A computer readable medium containing program product comprising at least one of computer code means and software code portions for making a processor perform the steps of:

• collecting measurement signals associated with measured characteristics of said electric power system in at least two locations of said electric power system, said measured characteristics comprising at least one of, time stamped voltage values, time stamped current values, and quantities derivable therefrom,
• evaluating said measurement signals, for detecting poorly damped power oscillations based on said measured characteristics,
• said evaluating step in turn comprising the steps of obtaining node angle differences between said at least two locations and determining at least one of amplitude, frequency and damping of said poorly damped power oscillations from said node angle differences, and
• providing control signals to actuating units in said electric power system, if system protection measures are necessary according to said evaluating step.