Cairns23 Symposium - Best Papers

These papers have been selected by the respective Study Committees from the 240 papers presented, as the best papers from each of the eleven Study Committees which presented at the Cairns23 Symposium (4-7 September 2023). The papers cover a range of important issues ranging from asset management to planning under increasing uncertainty, main grid and microgrid frequency control and the impact of faults on electric vehicle charging loads. The full papers will be made available in a special December edition of Electra CSE.

Identification of capacitor divider parameters used in CVTs for condition evaluation and future power quality measurement applications.
SC A3 Paper 1217 by Erik Spurling

CVTs are the more commonly used equipment for voltage measurements at power frequency in HV applications: however, they cannot be used when PQ measurements are needed, unless modifications are introduced.
In the paper, methods to measure the capacitances of the divider to obtain information to both assess the condition of the equipment and the features of additional capacitances for allowing PQ measurement are presented, as well as some simulation and test results.

Rebounding and learning from a HV Cable Termination Mid-life Crisis
SC B1 Paper 1165 by Glenn Stapleton, Kevin Andrew

Transmission utilities in Australia began to adopt XLPE insulated cables for voltages 220 kV and higher in the 1990's. In Queensland, 275 kV XLPE cables first came online in 1996. After 22 years of operation, some noted inspection irregularities triggered a detailed investigation using dissolved gas analysis for this oldest 275 kV cable system. This paper outlines some key learnings from a serious degradation issue noted in the cable terminations and how these learnings can be applied for utilities to manage their aging fleets of HV and EHV cables.

Estimation of degradation curves for substation equipment using text mining
SC B3 Paper 1180 by Tomohiro Kobayashi and Osamu Segawa

This paper proposed a method for estimating degradation curves for substation equipment based on the frequency of occurrence of each failure event, automatically classified into categories of failure mode. To evaluate the proposed method, we conducted the experimental evaluations to estimate the degradation curves using automatic classification data. The results demonstrated the effectiveness of the method for estimating degradation curves. We confirmed that the text classification technique is useful for augmentation of failure data and reducing data preparation costs.

Design Decisions of Process Bus Technology for a Distribution Utility
SC B5 Paper 1395 by Ben Armstrong, Kyle Malvern and Ray Robinson

Sydney is undergoing significant growth and redevelopment. To support the required upgrades to electrical infrastructure, the project team chose IEC 61850 digital substations and process bus technology to expedite construction, reduce costs, and enhance operational efficiency.
Extensive research and development resulted in modular prefabricated buildings for concurrent construction and compact control room layouts with reduced cabling. The project demonstrated the agility of digital substations and achieved substantial cost savings.

Flexible planning of low-carbon power systems under deep uncertainty
SC C1 Paper 1446 by Sebastián Püschel-Løvengreen, Sleiman Mhanna and Pierluigi Mancarella

The uptake of large-scale and distributed renewable energy sources and the electrification of different sectors around the world are engendering massive changes and creating unprecedented operational and planning challenges to power systems. In response, this paper addresses the development of planning methodologies and metrics to deal with system-wide, long-term uncertainty. This includes the consideration of adaptive and flexible investment strategies that can optimally respond to unfolding uncertainty and assess the option value of proactive or delayed investments. To achieve this, stochastic optimisation modelling is applied here aiming at defining new methodological approaches and computational tools for planning of different transmission assets under deep long-term uncertainty. In turn, the results from the stochastic planning approach are compared with those obtained from deterministic approaches adopted by industry worldwide. Various studies, conducted on the Australian power system, reveal new roles of different transmission investment options to deal with planning uncertainty. The results show that, relative to deterministic approaches, stochastic planning not only yields lower expected total costs, but also results in lower total costs (and thus in more efficient risk hedging) for the worst performing scenarios.

Impact of Grid-Forming Inverters on Frequency Control of a Grid with a High Share of Inverter-Based Resources
SC C2 Paper 1300 by Ahvand Jalali, Ehsan Farahani, Marina Delac and Nilesh Modi

Increasing penetration of inverter-based resources (IBRs) and decreasing number of online synchronous generators (SGs) increases the complexities of managing stable controls of voltage and frequency. In this paper, the contribution of a grid forming inverter (GFM) battery energy storage system (BESS) and a grid following inverter (GFL) BESS to the overall
frequency stability of the power system is investigated and compared for a large-scale power system. The impacts of the inertia constant, damping coefficient, and droop constant of the GFM inverter on the frequency stability of the grid are also investigated. It is shown that the system strength support provided by the GFM inverter can enhance the frequency stability of the grid.

Assessing the response of electric vehicles during network fault conditions
SC C4 Paper 1254 by Evan Franklin, Nathan McKillop, James Lord and Chris Wembridge

In this paper, we use a programmable regenerative grid emulator to investigate the response of four different electric vehicles (EVs) to a range of network fault conditions. EVs are exposed, during charging operations, to connection point voltages of between 0.1 per unit and 0.7 per unit, for fault durations of between 60 msec and 480 msec, and their active power response is measured and analysed. For 120 msec fault durations, consistent with transmission-level fault clearing times, we find that all EVs tested continue charging if the voltage drops to 0.5 per unit or above. However, EVs were observed to either cease charging temporarily for between about 2 and 10 seconds or otherwise were locked out and ceased charging completely when the connection point voltage dropped to 0.3 per unit or below. Based on the measured fault responses, we used a real-time simulator with the Tasmanian power system as a case-study, to investigate the potential impact at power system level of a large fleet of EVs responding in aggregate to a plausible 2-phase-to-ground fault in the 220 kV transmission system. We found that the coincident fault response of aggregated EVs can cause frequency excursions outside of normal operating bounds. This is caused by a significant loss of EV load immediately after the fault is cleared.

Regulating Service provision for intermittent inverter-based sources in tropical environments
SC C5 Paper 1346 by Jake Saunders, Daniel Marshman and Peregrine Tonking

Electricity market design and associated power system management tools should accommodate technologies with various technical and economic characteristics. For example, forecasting available capacity of variable renewable resources (wind and solar PV) is commonly recognised as being less accurate than thermal and storage technologies, and may require “firming” services when in generation mixes above moderate levels.
This work explores a market design and methodology to determine requirements for a firming service for solar resources in particular, where such resources are unable to meet certain minimum forecast accuracy standards.

Microgrid frequency Control
SC C6 Paper 1330 by David Stephens, David Edwards, Steve Lilliss, Johannes Rickerman, Stanislav Cherevatskiy, Michael Schalk and Craig Blizard

Integration challenges associated with a high penetration of renewable energy have prompted a rethink of the control philosophy for remote and embedded microgrids.
This paper outlines a new approach to frequency control that includes operating battery energy storage systems in a grid-forming droop mode, and configuration of a microgrid controller to provide the isochronous frequency function. The philosophy allows for broader participation in frequency response, including a suitable response from the Distributed Energy Resources.
The paper provides an overview of the in-field and in-factory tests conducted. Benefits of the change in frequency control are already being observed.

Accuracy testing of a high-voltage transformer under rated fundamental voltage and superimposed harmonics
SC D1 Paper 1170 by Yi Li, Imanka Ranmanna Dewayalage and Wei Yan

Measurement of harmonics in high-voltage networks has become increasingly important due to the increasing presence of harmonic voltages produced by power electronics in renewable energy generation plants. The ratio and the phase errors of a 33 kV inductive voltage transformer (IVT) were measured under harmonic voltages up to 2500 Hz. Tests were performed not only with the harmonic voltages, but also with harmonic voltages superimposed on the rated fundamental voltage. Accuracy results were obtained with different levels of harmonic voltages. The test results showed that the maximum ratio error and maximum phase displacement of this particular IVT were +4.5% and -1.2 crad respectively, and did not differ significantly from those measured with the individual harmonic voltages alone.

Implementing IP/MPLS network-based synchronization for line differential protection and control.
SC D2 Paper 1279 by Amadou Louh, Andrej Goerbing, Dominique Verhulst, René Loef, Keenan Royle, Jörg Blumschein and Philipp Stachel

Power utilities are faced with the end-of-lifetime for their Synchronous Digital Hierarchy/Time Division Multiplexing communication networks. This paper discusses how line differential protection relays were tested by Stedin in the Netherlands to operate across an Internet Protocol/Multi-Protocol Label Switching wide area network. It covers the issues encountered and how they were addressed when trying to attain end-to-end synchronization. Both IEEE C37.94 and Ethernet/IP based line differential protection communication were considered.
This paper presents the different failure scenarios that were tested to observe the performance and resilience of the line differential protection scheme.
Finally, an outlook is given how a Distribution Network Operator like Stedin operational telecom team is intending to deliver “synchronization as a service” to their operational teams to enable C-PACS across the network.