Phase angle as an additional indicator of imminent voltage collapse in electric transmission and distribution systems

P. Adelson, N. Nigalye, Z. Zabar, D. Czarkowski, L. Birenbaum, T. Sulawa, J. Hajagos, F. Peritore

Research output: Contribution to journalArticlepeer-review


The work presented here explores the feasibility of using the phase angle between two system voltages, one at a strong bus and the other at a weak bus, as an indicator of imminent voltage collapse at the weak bus. The idea is that this would permit the system operator to complement the practice of using voltage magnitude data with a second indicator, thus giving him a clearer picture of the problem at hand, and hence would enable him to judge more accurately whether and how to take corrective action, if necessary. First, a mathematical analysis was performed; then, a computer simulation of a scaled-down (9-bus) version of the Long Island Power Authority (LIPA) network was made; next, a load-flow simulation of the entire LIPA system was made; and finally the simulation was compared with PMU (phase measurement unit) recordings for two locations on the system, during July and September of 2005. The results, similar to those obtained from the simulations, suggest that the idea of using phase angle indicators has merit. However, for this concept to be developed into a useable tool, even for the radial LIPA system, an adaptation study is needed. For example, using a load-flow program, different operating conditions and contingencies should be examined, so that a critical phase angle difference could be defined for the system.

Original languageEnglish (US)
Pages (from-to)282-291
Number of pages10
JournalInternational Journal of Power and Energy Systems
Issue number4
StatePublished - 2009


  • Electric transmission and distribution systems
  • Phase angle measurement
  • Power system stability
  • Voltage collapse

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering
  • Applied Mathematics


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