Impact Assessment of Hypothesized Cyberattacks on Interconnected Bulk Power Systems

The first-ever Ukraine cyberattack on power grid has proven its devastation by hacking into their critical cyber assets. With administrative privileges accessing substation networks/local control centers, one intelligent way of coordinated cyberattacks is to execute a series of disruptive switching executions on multiple substations using compromised supervisory control and data acquisition (SCADA) systems. These actions can cause significant impacts to an interconnected power grid. Unlike the previous power blackouts, such high-impact initiating events can aggravate operating conditions, initiating instability that may lead to system-wide cascading failure. A systemic evaluation of "nightmare" scenarios is highly desirable for asset owners to manage and prioritize the maintenance and investment in protecting their cyberinfrastructure. This survey paper is a conceptual expansion of real-time monitoring, anomaly detection, impact analyses, and mitigation (RAIM) framework that emphasizes on the resulting impacts, both on steady-state and dynamic aspects of power system stability. Hypothetically, we associate the combinatorial analyses of steady state on substations/components outages and dynamics of the sequential switching orders as part of the permutation. The expanded framework includes (1) critical/noncritical combination verification, (2) cascade confirmation, and (3) combination re-evaluation. This paper ends with a discussion of the open issues for metrics and future design pertaining the impact quantification of cyber-related contingencies

Concepts for design of an energy management system incorporating dispersed storage and generation

New forms of generation based on renewable resources must be managed as part of existing power systems in order to be utilized with maximum effectiveness. Many of these generators are by their very nature dispersed or small, so that they will be connected to the distribution part of the power system. This situation poses new questions of control and protection, and the intermittent nature of some of the energy sources poses problems of scheduling and dispatch. Under the assumption that the general objectives of energy management will remain unchanged, the impact of dispersed storage and generation on some of the specific functions of power system control and its hardware are discussed

Medium Voltage Network Residual Earth Fault Current Estimation Methods

Extensive cabling during 2010s has drastically changed the earth fault behaviour of the rural area distribution network. Against the assumptions of traditional earth fault analysis, cable net-work zero sequence series impedance is nonnegligible, thus zero sequence voltage applied over the zero sequence impedance during an earth fault generates a resistive component to the earth fault current in addition to the capacitive component. In the resonant earthed neutral sys-tem, capacitive earth fault current can be compensated with inductive Petersen coils, but the resistive current component cannot be compensated with Petersen coils. Increase of resistive earth fault current will increase the absolute value of the residual earth fault current flowing to ground during the earth fault and consequently cause dangerous touch voltages. The reactive component of the residual earth fault current is mostly known but the resistive component is associated with multiple uncertainties. The harmonic component is out of the scope of this thesis and thus omitted. Due to the uncertainties, calculation of the resistive earth fault current has proven to be complicated, but if residual earth fault current is to be calculated accurately, the resistive component must be calculated or estimated first. The SFS 6001: 2018 standard states that if the residual earth fault current in resonant earthed neutral system is unknown the value can be assumed 10% of the network capacitive earth fault current. However, as extensive cabling increases resistive earth fault current production of the network, the validity of this assumption has caused concern. Therefore, the aim of this thesis was to develop a practically oriented model for estimating residual earth fault current that can easily be applied to multiple locations in the network. Secondly, the validity of the 10% assumption specified by the standard was studied in Elenia’s network. The network information system used in Elenia is currently unable to take into account the cable network zero sequence impedance, thus a statistical examination was performed based on network data from 45 primary transformer areas. The measurements from centralized Petersen coil regulators were utilized in the examination, since the regulators provide real-time measurement of the network resistive earth fault current production. In the statistical examination the dependency of resistive earth fault current from other network parameters was studied. The objective was to identify variables that correlate with resistive earth fault current, so that they could be used to estimate the resistive earth fault current. After the correlation analysis, correction factors were assigned to the variables and the results were compared to the measurements from the regulators. The conclusion was that the resistive earth fault current can be estimated to be 5% of the total capacitive earth fault current. This result was applied to residual earth fault current calculation and the obtained values were again compared to the values calculated from the measurements. There was only a minor difference, which implies that the developed model yields accurate results. More importantly, the developed model proved to provide more accurate results than the estimation method specified in SFS 6001, that acted as a reference. In addition, there are two alternative interpretations of the method specified in the standard, so depending on the interpretation, the results were either too high or too low when applied to Elenia’s network. However, the results of this thesis are heavily dependent on the properties of the network, thus results should only be applied to networks with similar configuration

Medium Voltage Network Residual Earth Fault Current Estimation Methods

Extensive cabling during 2010s has drastically changed the earth fault behaviour of the rural area distribution network. Against the assumptions of traditional earth fault analysis, cable net-work zero sequence series impedance is nonnegligible, thus zero sequence voltage applied over the zero sequence impedance during an earth fault generates a resistive component to the earth fault current in addition to the capacitive component. In the resonant earthed neutral sys-tem, capacitive earth fault current can be compensated with inductive Petersen coils, but the resistive current component cannot be compensated with Petersen coils. Increase of resistive earth fault current will increase the absolute value of the residual earth fault current flowing to ground during the earth fault and consequently cause dangerous touch voltages. The reactive component of the residual earth fault current is mostly known but the resistive component is associated with multiple uncertainties. The harmonic component is out of the scope of this thesis and thus omitted. Due to the uncertainties, calculation of the resistive earth fault current has proven to be complicated, but if residual earth fault current is to be calculated accurately, the resistive component must be calculated or estimated first. The SFS 6001: 2018 standard states that if the residual earth fault current in resonant earthed neutral system is unknown the value can be assumed 10% of the network capacitive earth fault current. However, as extensive cabling increases resistive earth fault current production of the network, the validity of this assumption has caused concern. Therefore, the aim of this thesis was to develop a practically oriented model for estimating residual earth fault current that can easily be applied to multiple locations in the network. Secondly, the validity of the 10% assumption specified by the standard was studied in Elenia’s network. The network information system used in Elenia is currently unable to take into account the cable network zero sequence impedance, thus a statistical examination was performed based on network data from 45 primary transformer areas. The measurements from centralized Petersen coil regulators were utilized in the examination, since the regulators provide real-time measurement of the network resistive earth fault current production. In the statistical examination the dependency of resistive earth fault current from other network parameters was studied. The objective was to identify variables that correlate with resistive earth fault current, so that they could be used to estimate the resistive earth fault current. After the correlation analysis, correction factors were assigned to the variables and the results were compared to the measurements from the regulators. The conclusion was that the resistive earth fault current can be estimated to be 5% of the total capacitive earth fault current. This result was applied to residual earth fault current calculation and the obtained values were again compared to the values calculated from the measurements. There was only a minor difference, which implies that the developed model yields accurate results. More importantly, the developed model proved to provide more accurate results than the estimation method specified in SFS 6001, that acted as a reference. In addition, there are two alternative interpretations of the method specified in the standard, so depending on the interpretation, the results were either too high or too low when applied to Elenia’s network. However, the results of this thesis are heavily dependent on the properties of the network, thus results should only be applied to networks with similar configuration

Application of Reactive Energy to UK Low Voltage Networks and Embedded Generation Effects on Networks Performance

The objective of this thesis is to study thoroughly a specific low-voltage network by determining its performance in different scenarios, in order to define voltages and currents in the various nodes with different operating conditions of the network, for a given maximum load provided by historical measures. The operating conditions cited include the reactive compensation using different methods and distributed generation with reactive compensatio

Improving Electricity Distribution System State Estimation with AMR-Based Load Profiles

The ongoing battle against global warming is rapidly increasing the amount of renewable power generation, and smart solutions are needed to integrate these new generation units into the existing distribution systems. Smart grids answer this call by introducing intelligent ways of controlling the network and active resources connected to it. However, before the network can be controlled, the automation system must know what the node voltages and line currents defining the network state are.Distribution system state estimation (DSSE) is needed to find the most likely state of the network when the number and accuracy of measurements are limited. Typically, two types of measurements are used in DSSE: real-time measurements and pseudomeasurements. In recent years, finding cost-efficient ways to improve the DSSE accuracy has been a popular subject in the literature. While others have focused on optimizing the type, amount and location of real-time measurements, the main hypothesis of this thesis is that it is possible to enhance the DSSE accuracy by using interval measurements collected with automatic meter reading (AMR) to improve the load profiles used as pseudo-measurements.The work done in this thesis can be divided into three stages. In the first stage, methods for creating new AMR-based load profiles are studied. AMR measurements from thousands of customers are used to test and compare the different options for improving the load profiling accuracy. Different clustering algorithms are tested and a novel twostage clustering method for load profiling is developed. In the second stage, a DSSE algorithm suited for smart grid environment is developed. Simulations and real-life demonstrations are conducted to verify the accuracy and applicability of the developed state estimator. In the third and final stage, the AMR-based load profiling and DSSE are combined. Matlab simulations with real AMR data and a real distribution network model are made and the developed load profiles are compared with other commonly used pseudo-measurements.The results indicate that clustering is an efficient way to improve the load profiling accuracy. With the help of clustering, both the customer classification and customer class load profiles can be updated simultaneously. Several of the tested clustering algorithms were suited for clustering electricity customers, but the best results were achieved with a modified k-means algorithm. Results from the third stage simulations supported the main hypothesis that the new AMR-based load profiles improve the DSSE accuracy.The results presented in this thesis should motivate distribution system operators and other actors in the field of electricity distribution to utilize AMR data and clustering algorithms in load profiling. It improves not only the DSSE accuracy but also many other functions that rely on load flow calculation and need accurate load estimates or forecasts

A Review and Synthesis of the Outcomes from Low Carbon Networks Fund Projects

The Low Carbon Networks Fund (LCNF) was established by Ofgem in 2009 with an objective to “help Distribution Network Operators (DNOs) understand how they provide security of supply at value for money and facilitate transition to the low carbon economy”. The £500m fund operated in a tiered format, funding small scale projects as Tier 1 and running a Tier 2 annual competitive process to fund a smaller number of large projects. By 31st March 2015, forty Tier 1 projects and twenty-three Tier 2 projects had been approved with project budgets totalling £29.5m and £220.3m respectively. The LCNF governance arrangements state that projects should focus on the trialling of: new equipment (more specifically, that unproven in GB), novel arrangements or applications of existing equipment, novel operational practices, or novel commercial arrangements. The requirement that learning gained from projects could be disseminated was a key feature of the LCNF. The motivation for the review reported here was a recognition that significant learning and data had been generated from a large volume of project activity but, with so many individual reports published, that it was difficult for outside observers to identify clear messages with respect to the innovations investigated under the programme. This review is therefore intended to identify, categorise and synthesise the learning outcomes published by LCNF projects up to December 2015