Negative sequence (Symmetrical component)

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SUMMARY

The discussion focuses on calculating the negative sequence current (I2) using the known phase currents Ia, Ib, and Ic in a three-phase system. The user specifies a scenario with unbalanced loads, providing values of Ia = 85 A, Ib = 92 A, and Ic = 90 A. The key method to determine I2 involves using symmetrical components, particularly when the system is not in fault conditions. The user seeks to set the I2 pick-up for detecting low fault currents.

PREREQUISITES
  • Understanding of symmetrical components in electrical engineering
  • Knowledge of three-phase systems and their current relationships
  • Familiarity with current measurement techniques
  • Basic concepts of load balancing in electrical distribution
NEXT STEPS
  • Study the method of calculating symmetrical components in detail
  • Learn how to apply the symmetrical transformation to unbalanced loads
  • Research techniques for setting I2 pick-up values for fault detection
  • Explore the implications of negative sequence currents on system stability
USEFUL FOR

Electrical engineers, power system analysts, and technicians involved in monitoring and maintaining three-phase distribution systems.

sarayut
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I'd like to know how do i find I2 (Negative sequence current) if I know Ia, Ib and Ic but don't know angle (in normal system_not fault)? My system's 3 phases 3 wires.
 
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You need to specify what you mean by "normal system_not fault"?

Is the load balanced? If so, you know the angles relative to each other. You can then use the symmetrical transformation to find if there is a negative sequence current.

http://en.wikipedia.org/wiki/Symmetrical_components
 
Thank you very much for answer!, "Normal system_not fault" mean imbalance situation in distribution system. For example Ia= 85 A, Ib= 92 A and Ic= 90 A. I'd like to know I2 for set the I2 pick up to detect low fault current.
 

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