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Sensitivity of DC Network Representation for GIC Analysis

Aniruddh Mishra, Arthur K. Barnes, Jose E. Tabarez, Adam Mate

TL;DR

This work tackles how the dc-network representation used for GIC analysis affects blocker-placement decisions in power systems. It leverages PowerModelsGMD to generate dc networks from ac models and compares blocker representations (neutral, substation, and series capacitors) under uniform and nonuniform electric-field assumptions, assessing consequent power losses via the transformer K-factor model. The study finds that uniform-field modeling suppresses losses regardless of blocker type, while nonuniform-fields reveal substantial sensitivity to blocker representations, with substation blocking potentially overestimating losses and series-capacitor blocking sometimes required to drive losses to zero. The results emphasize careful, field-consistent modeling for accurate GIC mitigation planning and point to coupling dc analyses with AC dynamics for realistic risk assessment.

Abstract

Geomagnetic disturbances are a threat to the reliability and security of our national critical energy infrastructures. These events specifically result in geomagnetically induced currents, which can cause damage to transformers due to magnetic saturation. In order to mitigate these effects, blocker devices must be placed in optimal locations. Finding this placement requires a dc representation of the ac transmission lines, which this paper discusses. Different decisions in this process, including the method of representing the blocking devices, result in significant variations to the power loss calculations. To analyze these effects, we conclude the paper by comparing the losses on a sample network with different modeling implementations.

Sensitivity of DC Network Representation for GIC Analysis

TL;DR

This work tackles how the dc-network representation used for GIC analysis affects blocker-placement decisions in power systems. It leverages PowerModelsGMD to generate dc networks from ac models and compares blocker representations (neutral, substation, and series capacitors) under uniform and nonuniform electric-field assumptions, assessing consequent power losses via the transformer K-factor model. The study finds that uniform-field modeling suppresses losses regardless of blocker type, while nonuniform-fields reveal substantial sensitivity to blocker representations, with substation blocking potentially overestimating losses and series-capacitor blocking sometimes required to drive losses to zero. The results emphasize careful, field-consistent modeling for accurate GIC mitigation planning and point to coupling dc analyses with AC dynamics for realistic risk assessment.

Abstract

Geomagnetic disturbances are a threat to the reliability and security of our national critical energy infrastructures. These events specifically result in geomagnetically induced currents, which can cause damage to transformers due to magnetic saturation. In order to mitigate these effects, blocker devices must be placed in optimal locations. Finding this placement requires a dc representation of the ac transmission lines, which this paper discusses. Different decisions in this process, including the method of representing the blocking devices, result in significant variations to the power loss calculations. To analyze these effects, we conclude the paper by comparing the losses on a sample network with different modeling implementations.

Paper Structure

This paper contains 23 sections, 7 equations, 7 figures, 2 tables.

Table of Contents

  1. Introduction
  2. DC Network Generation
  3. Constructing GMD Buses
  4. Constructing GMD Branches
  5. Lines
  6. Transformers
  7. Power Loss Calculations
  8. Coupled Electric Field Calculations
  9. CSV Line Information
  10. Static Electric Field Vector
  11. Implicit Components
  12. Implicit Generator Step-up Transformers
  13. Implicit GMD Branches
  14. Assumed Series Capacitors
  15. Blocker Modeling
  16. ...and 8 more sections

Figures (7)

  • Figure 1: DC equivalent circuit of a $Y_g$-$Y_g$ transformer mate21-pmsgmd
  • Figure 2: DC equivalent circuit of a $Y_g$-$Y_g$ autotransformer mate21-pmsgmd
  • Figure 3: DC equivalent circuit of a three-winding transformer
  • Figure 4: DC equivalent circuit of a $Y_g$-$a$-$\Delta$ transformer
  • Figure 5: GIC blocker modeling test case
  • ...and 2 more figures