Load-Flow Studies in the Presence of Geomagnetically-Induced Currents

Albertson, V. D.; Kappenman, John G.; Mohan, Ned; Skarbakka, G. A.

doi:10.1109/tpas.1981.316916

Cited by 120 publications

(57 citation statements)

References 7 publications

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“…When a transformer has different values of GIC in its windings, an "effective GIC" can be calculated that gives the same degree of transformer saturation as GIC in a single winding (Albertson et al, 1981;Zheng et al, 2014). For both two-winding transformers and autotransformers, the effective GIC is given by…”

Section: Discussionmentioning

confidence: 99%

Comparison of methods for modelling geomagnetically induced currents

Boteler

Pirjola

2014

Ann. Geophys.

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Abstract. Assessing the geomagnetic hazard to power systems requires reliable modelling of the geomagnetically induced currents (GIC) produced in the power network. This paper compares the Nodal Admittance Matrix method with the Lehtinen-Pirjola method and shows them to be mathematically equivalent. GIC calculation using the Nodal Admittance Matrix method involves three steps: (1) using the voltage sources in the lines representing the induced geoelectric field to calculate equivalent current sources and summing these to obtain the nodal current sources, (2) performing the inversion of the admittance matrix and multiplying by the nodal current sources to obtain the nodal voltages, (3) using the nodal voltages to determine the currents in the lines and in the ground connections. In the Lehtinen-Pirjola method, steps 2 and 3 of the Nodal Admittance Matrix calculation are combined into one matrix expression. This involves inversion of a more complicated matrix but yields the currents to ground directly from the nodal current sources. To calculate GIC in multiple voltage levels of a power system, it is necessary to model the connections between voltage levels, not just the transmission lines and ground connections considered in traditional GIC modelling. Where GIC flow to ground through both the high-voltage and low-voltage windings of a transformer, they share a common path through the substation grounding resistance. This has been modelled previously by including non-zero, off-diagonal elements in the earthing impedance matrix of the Lehtinen-Pirjola method. However, this situation is more easily handled in both the Nodal Admittance Matrix method and the Lehtinen-Pirjola method by introducing a node at the neutral point.

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Section: Discussionmentioning

confidence: 99%

Comparison of methods for modelling geomagnetically induced currents

Boteler

Pirjola

2014

Ann. Geophys.

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“…The inclusion of the impact of GICs in the power flow was first described in [4]. The gist is that the GICs can be determined by first solving a dc network of the form I = G V (1) in which G a square matrix similar in form to the power system bus admittance matrix, except 1) it is a real matrix with just conductance values, 2) the conductance values are determined by the parallel combination of the three individual phases, 3) G is augmented to include the substation neutral buses and substation grounding resistance values, and 4) the transformers are modeled with their winding resistance to the substation neutral and in the case of autotransformers both the series and common windings are represented.…”

Section: Overview Of Gic Power Flow Modelingmentioning

confidence: 99%

“…The voltage vector V contains entries for the substation neutral dc voltages and the bus dc voltages. Two main methods have been proposed for modeling the impact of the GMD-induced electric field variation in the power grid: either as dc voltage sources in the ground or as dc voltage sources in series with the transmission lines [4], [5]. In both approaches the dc voltages are represented as Norton Equivalent currents in the I vector of (1).…”

Section: Overview Of Gic Power Flow Modelingmentioning

confidence: 99%

“…In the simplest case of a grounded wye-delta, such as is common for generator step-up transformers (GSUs), I GIC is straightforward -just the current in the grounded coil. For transformers with multiple grounded windings and autotransformers the value of I GIC depends upon the current in both coils [4]. Here we use the approach of [8], which shows that the equations for I GIC for an autotransformer can be generalized as t H L GIC t a I I I a + = (7) where I H is the per phase dc current going into either the high side winding or the series winding of an autotransformer, I L is the per phase dc current going into either the low side winding or the common winding of the autotransformer, and a t is the transformer turns ratio defined as…”

Section: Overview Of Gic Power Flow Modelingmentioning

confidence: 99%

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Integration of geomagnetic disturbance modeling into the power flow: A methodology for large-scale system studies

Overbye

Hutchins

Shetye

et al. 2012

2012 North American Power Symposium (NAPS)

108

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Abstract-This paper presents a methodology for integrated power flow modeling of the impact of geomagnetic disturbances (GMDs) on the power system voltage stability. GMDs cause quasi-dc, geomagnetically induced currents (GICs) in the transformers and transmission lines, which in turn cause saturation of the high voltage transformers, greatly increasing their reactive power consumption. GICs can be calculated using standard power flow modeling parameters such as line resistance, augmented with several GIC specific fields including substation geographic coordinates and grounding resistance, transformer configuration, and transformer coil winding resistances. When exact values are not available estimated quantities can be used. By then integrating GIC into power flow analysis, the changes in reactive power losses and bus voltages can be quantified to assess the risk of voltage instability and large-scale voltage collapse. An example calculation is provided for a North American Eastern Interconnect model.

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“…The method is based on power system analysis and Boteler presents how the methods normally used for AC modelling can be adapted to model the quasi-DC GICs. Albertson et al (1981) carried out load-flow studies in the presence of GIC in the northern United States and Canada. Their results clearly show serious voltage drops and real and reactive power flow changes during a GMD.…”

Section: Introductionmentioning

confidence: 99%

North Europe power transmission system vulnerability during extreme space weather

Piccinelli

Elisabeth

2018

J. Space Weather Space Clim.

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-Space weather driven by solar activity can induce geomagnetic disturbances at the Earth's surface that can affect power transmission systems. Variations in the geomagnetic field result in geomagnetically induced currents that can enter the system through its grounding connections, saturate transformers and lead to system instability and possibly collapse. This study analyzes the impact of extreme space weather on the northern part of the European power transmission grid for different transformer designs to understand its vulnerability in case of an extreme event. The behavior of the system was analyzed in its operational mode during a severe geomagnetic storm, and mitigation measures, like line compensation, were also considered. These measures change the topology of the system, thus varying the path of geomagnetically induced currents and inducing a local imbalance in the voltage stability superimposed on the grid operational flow. Our analysis shows that the North European power transmission system is fairly robust against extreme space weather events. When considering transformers more vulnerable to geomagnetic storms, only few episodes of instability were found in correspondence with an existing voltage instability due to the underlying system load. The presence of mitigation measures limited the areas of the network in which bus voltage instabilities arise with respect to the system in which mitigation measures are absent.

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Load-Flow Studies in the Presence of Geomagnetically-Induced Currents

Cited by 120 publications

References 7 publications

Comparison of methods for modelling geomagnetically induced currents

Comparison of methods for modelling geomagnetically induced currents

Integration of geomagnetic disturbance modeling into the power flow: A methodology for large-scale system studies

North Europe power transmission system vulnerability during extreme space weather

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