C.T. Gaunt

Why Space Weather Is Relevant to Electrical Power Systems

Twenty-five years of research has produced a wide range of models of the causal processes linking solar wind to geomagnetic disturbances to geomagnetically induced currents (GICs) and grid vulnerability. This review places the main concepts of each of the publications from the last 25 years in context with the others, categorizing them according to the following four themes: 1) flow of energy and momentum from the Sun to the Earth via the solar wind; 2) response of the terrestrial system to solar wind energy and momentum in the form of geomagnetic disturbances; 3) generation of quasi-DC electric currents (geomagnetically induced currents/GIC) in electric power grids as a consequence of geomagnetic disturbances (GMD); or 4) impact of GIC on operations of power grids. This review also reveals gaps in the knowledge of modeling, geophysical parameters, and the implications of GICs for power grids. More measurements from space, of geomagnetic disturbances, and on power systems are needed. There is scope to guide policy on the mitigation of societal risk and improve space weather forecasts for regular operational use by utilities.

Quantifying the daily economic impact of extreme space weather due to failure in electricity transmission infrastructure

Extreme space weather due to coronal mass ejections has the potential to cause considerable disruption to the global economy by damaging the transformers required to operate electricity transmission infrastructure. However, expert opinion is split between the potential outcome being one of a temporary regional blackout and of a more prolonged event. The temporary blackout scenario proposed by some is expected to last the length of the disturbance, with normal operations resuming after a couple of days. On the other hand, others have predicted widespread equipment damage with blackout scenarios lasting months. In this paper we explore the potential costs associated with failure in the electricity transmission infrastructure in the U.S. due to extreme space weather, focusing on daily economic loss. This provides insight into the direct and indirect economic consequences of how an extreme space weather event may affect domestic production, as well as other nations, via supply chain linkages. By exploring the sensitivity of the blackout zone, we show that on average the direct economic cost incurred from disruption to electricity represents only 49% of the total potential macroeconomic cost. Therefore, if indirect supply chain costs are not considered when undertaking cost-benefit analysis of space weather forecasting and mitigation investment, the total potential macroeconomic cost is not correctly represented. The paper contributes to our understanding of the economic impact of space weather, as well as making a number of key methodological contributions relevant for future work. Further economic impact assessment of this threat must consider multiday, multiregional events.

Investigating the usefulness of the Beta pdf to describe Parameters in Reliability Analyses

The work presented in this paper considers the possibility and the advantages of using the Beta pdf as a means to describe the behaviour of various parameters in the analysis of the reliability of power systems. These include input parameters such as hazard functions or failure rates. It also includes output parameters such as those for various reliability performance indices, commonly encountered in electrical power system reliability analyses. The Kolmogoroff-Smirnoff test is used to determine the goodness-of-fit measures from recorded data compared with other pdfs, quoted in classical reliability literature. The paper shows that there are several reasons why the Beta pdf can be a useful means for describing probability functions in reliability analyses. It shows that certain characteristics of the Beta pdf make its application attractive

Modeling hard uncertainty in rural electrification projects in South Africa using the Shackle model

A conceptualization of uncertainty in decision-making as soft or hard is introduced, along with a critique on how popular decision-making approaches deal with uncertainty. The Shackle model, as applied by Young, is introduced as a way of dealing with hard uncertainty in decision-making. Case studies of distributed generation rural electrification projects in South Africa are then used to identify hard uncertainties in these types of projects. Youngs single criteria application of the Shackle model is placed within a multiple criteria context, and finally applied in illustration to hard uncertainty in rural electrification projects

Flux measurements with AC and DC components of current present show transformer equivalent circuit models need core joint details

Banks of three single-phase transformers are easier to transport than large three-phase transformers, and single-phase four-limb (1P-4L) transformers have recently been installed in a power station in South Africa. Predicting the response of this core structure is important for network studies of the effects of geo-magnetically induced and dc leakage currents. A topological, equivalent circuit model of 1P-4L transformers was developed and tests carried out on model transformers to determine the equivalent parameters. The experiments used scaled down 8.3 kVA, 1P-4L transformers, which resemble a power transformer in respect of high quality core material and winding configuration. FEM studies assisted with placing some search coils used to examine the core response. The results show the core joints have a significant effect in the presence of dc components. Neglecting the effects of core joints in deep saturation might have implications for existing transformer models.

Measurements show need for transformer core joint details in finite element modelling of GIC and DC effects

Purpose To improve the finite element modelling of transformers subjected to dc excitation, by including core joint details. Design/methodology/approach Geomagnetically induced currents or leakage dc can cause part-cycle, half wave saturation of a power transformer’s core. Practical measurements and finite element matrix (FEM) simulation were made of three laboratory scale, untanked single-phase four limb transformers resembling real power transformers in terms of the core steel and parallel winding assemblies. ‘Equivalent air gaps’ at the joints, based on ac measurements, were applied to the FEM models for simultaneous ac and dc excitation. Findings Measurements confirm that introducing equivalent air gaps at the joints improves the FEM simulation of transformers carrying dc. Research limitations/implications The FEM simulations based on the laboratory transformers are exemplary, showing the difference between modelling core joints as solid or including equivalent air gaps. They show that, for more repre...

Proof of concept data logger for non-active power measurement

This paper discusses a metering concept design based on equipment cheaper and smaller than a laptop and able to meet the requirements of power measurements that need relatively high frequency, simultaneous sampling. Its size and cost make it useful when developing hardware for smart grid systems. Non-active power is a term used to describe both distortion and reactive power. In conventional power theory, the apparent power, S, and non-active power, Q, are based on RMS measurements of voltages and line currents. A novel general power theory was proposed recently to give a measure of the true efficiency of power delivery under conditions of distortion, unbalance and direct current components, and the approach requires the simultaneous sampling of all voltages and currents at relatively high frequency. A metering device was designed for the measurement of instantaneous, simultaneously sampled voltages and currents in a three-phase system. The system has an upper sampling frequency limit of 2 000 Hz. The prototype design was fast enough to perform the general power theory calculations and log the data accurately. The project provides direction for the further development of this type of device for measuring non-active power, power quality and power electronic control.

Penetration level of Capacitor Coupling Sub-station on a power transmission network

Generally, rural areas in Sub Saharan Africa (SSA) have low concentration of electrical energy users. As a result, most power utility will not be able to generate an adequate return on investment necessary to install a conventional distribution sub-station on the transmission line. Consequently, costs related to the deployment of a conventional distribution sub-station are prohibitive for most rural electrification projects. In order to address the drawback associated with costs of a conventional substation, a relatively small Capacitor Coupling Substation (CCS) which taps power from high voltage transmission lines and can be located close to or underneath extra high voltage transmission may be used. This paper investigates the penetration level of these Substations on a 220kV, 440km power transmission network of the Kenya Electricity Supply Industry (KESI). The objective or contribution is to establish the optimum penetration level of the technology with regard to cost, reliability, performance and local conditions.