This paper introduces a novel method of GNSS spoofing detection with applications in electrical substations. Time sensitive applications in electricity substations, including Phasor Measurement Units ...(PMU) and Merging Units (MU), rely on Global Navigation Satellite Signals (GNSS), often GPS, for time transfer. Recently, sophisticated 'spoofing' attacks have become feasible due to the availability of low cost Software Defined Radio (SDR) systems. The proposed method uses multiple GNSS receive antennas placed in close proximity at the electricity substation, such that it is not possible for an attacker to target a unique spoofing signal towards each antenna. In a system employing three or more receive antennas, during a spoofing attack two or more of the GNSS receive antennas will return an estimated position in impossible locations. This is sufficient to raise alarm that time sensitive applications should use an alternative time source or holdover clock. The contributions of this paper include a detailed description of the proposed method, an experimental assessment of GNSS receiver and substation clock position estimation variance to establish the minimum separation required between receive antennas, and a validation of the method by experimental demonstration. A further benefit of the authors' method is that it may be put into practice immediately using commercial-off-the-shelf (COTS) substation clock equipment.
The integration of an ever-growing proportion of large-scale distributed renewable generation has increased the probability of maloperation of the traditional RoCoF and vector shift relays. With ...reduced inertia due to nonsynchronous penetration in a power grid, system-wide disturbances have forced the utility industry to design advanced protection schemes to prevent system degradation and avoid cascading outages leading to widespread blackouts. This paper explores a novel adaptive nonlinear approach applied to islanding detection, based on wide-area phase-angle measurements. This is challenging since the voltage phase angles from different locations exhibit not only strong nonlinear but also time-varying characteristics. The adaptive nonlinear technique, called moving window kernel principal component analysis, is proposed to model the time-varying and nonlinear trends in the voltage-phase angle data. The effectiveness of the technique is exemplified using DigSilent simulated cases and real test cases recorded from the Great Britain and Ireland power systems by the OpenPMU project.
Loss-of-mains protection is an important component of the protection systems of embedded generation. The role of loss-of-mains is to disconnect the embedded generator from the utility grid in the ...event that connection to utility dispatched generation is lost. This is necessary for a number of reasons, including the safety of personnel during fault restoration and the protection of plant against out-of-synchronism reclosure to the mains supply. The incumbent methods of loss-of-mains protection were designed when the installed capacity of embedded generation was low, and known problems with nuisance tripping of the devices were considered acceptable because of the insignificant consequence to system operation. With the dramatic increase in the installed capacity of embedded generation over the last decade, the limitations of current islanding detection methods are no longer acceptable. This study describes a new method of loss-of-mains protection based on phasor measurement unit (PMU) technology, specifically using a low cost PMU device of the authors’ design which has been developed for distribution network applications. The proposed method addresses the limitations of the incumbent methods, providing a solution that is free of nuisance tripping and has a zero non-detection zone. This system has been tested experimentally and is shown to be practical, feasible and effective. Threshold settings for the new method are recommended based on data acquired from both the Great Britain and Ireland power systems.
This paper presents a data acquisition unit which synchronously samples multiple channels in a manner such that the time of day at which each sample is taken is known. This allows measurements taken ...at multiple locations to be compared with confidence. The intended application is wide area electrical power system measurements, in particular phasor measurement units (PMUs). The novelty of the authors' design is the application of an open hardware development platform to discipline a commodity analog-to-digital converter (ADC) to a broadcast time signal, usually but not exclusively GPS. The methodology used creates a driver layer for the ADC to achieve real-time sampling in a nonpreemptive Linux environment. The use of open hardware and software addresses the need for a transparent instrument for use in research and development of PMU technology. Through a choice of either a software or hardware phase-locked loop, the ADC is controlled to acquire exactly 256 samples per nominal power system cycle (i.e., 50/60 Hz), precisely time synchronized to GPS, at 16-b resolution and 94.2-dB SNR. The design of a printed circuit board expansion board featuring all necessary components is provided. The performance of the system is evaluated. Interoperability and data exchange with other systems is achieved by use of open schemas and communication protocols. This allows rapid integration with popular numerical simulation environments.
This paper presents a novel and cost‐effective solution for detecting the islanding condition at embedded generators using an innovative new type of phase angle detector, the "quasi‐PMU". The method ...works by checking the synchronism of the embedded generator with respect to a robust reference location. The method is low cost, effective, and easy to configure using a modern broker based "one‐to‐many" solution for the telecommunications needs. The new "quasi‐PMU" is validated against appropriate IEEE compliance standards and shown to be effective in detecting the islanding condition using data obtained by an experimental study and through simulations. The islanding detection method presented in this paper is particularly suited to grids with increasingly large dynamic events and frequency excursions arising from lowering system inertia. The authors’ design gives the system operator confidence for consistent operation of embedded generation protection. The method is affordable, reliable and is ready for immediate implementation.
To assess the association between low physical activity, cardiovascular disease (CVD) and risk factors, health service utilization, risk of catastrophic health expenditure, and work productivity in ...Indonesia.
In this population-based, panel data analysis, we used data from two waves of the Indonesian Family Life Survey (IFLS) for 2007/2008 and 2014/2015. Respondents aged 40-80 years who participated in both waves were included in this study (
= 5,936). Physical activity was assessed using the International Physical Activity Questionnaire (IPAQ-SF). Multinomial logistic regression model was used to examine factors associated with physical activity levels (low, moderate, and high). We applied a series of multilevel mixed-effect panel regression to examine the associations between physical activity and outcome variables.
The prevalence of low physical activity increased from 18.2% in 2007 to 39.6% in 2014. Compared with those with high physical activity, respondents with low physical activity were more likely to have a 10-year high CVD risk (AOR: 2.11, 95% CI: 1.51-2.95), use outpatient care (AOR: 1.26, 95% CI: 1.07-1.96) and inpatient care (AOR 1.45, 95% CI: 1.07-1.96), experience catastrophic health expenditure of 10% of total household expenditure (AOR: 1.66, 95% CI: 1.21-2.28), and have lower labor participation (AOR: 0.24, 95% 0.20-0.28).
Low physical activity is associated with adverse health outcomes and considerable costs to the health system and wider society. Accelerated implementation of public health policies to reduce physical inactivity is likely to result in substantial population health and economic benefits.
OpenPMU is an open platform for the development of phasor measurement unit (PMU) technology. A need has been identified for an open-source alternative to commercial PMU devices tailored to the needs ...of the university researcher and for enabling the development of new synchrophasor instruments from this foundation. OpenPMU achieves this through open-source hardware design specifications and software source code, allowing duplicates of the OpenPMU to be fabricated under open-source licenses. This paper presents the OpenPMU device based on the Labview development environment. The device is performance tested according to the IEEE C37.118.1 standard. Compatibility with the IEEE C37.118.2 messaging format is achieved through middleware which is readily adaptable to other PMU projects or applications. Improvements have been made to the original design to increase its flexibility. A new modularized architecture for the OpenPMU is presented using an open messaging format which the authors propose is adopted as a platform for PMU research.
In many countries distributed energy resources (DER) (e.g. photovoltaics, batteries, wind turbines, electric vehicles, electric heat pumps, air-conditioning units and smart domestic appliances) are ...part of the ‘Green Deal’ to deliver a climate neutral society. Policy roadmaps, despite providing a framework and penetration targets for DER, often lack the network planning strategies needed to transition from passive to active distribution networks. Currently, DER's dynamic performance parameters and location identification techniques are not fully standardised. In fact, it can be very ad hoc. Standardised distributed load modelling and non-intrusive load monitoring (NILM) for equipment manufacturers, installers and network operators is critical to low and medium voltage network management in order to facilitate better balancing, flexibility and electricity trading across and within the power system for mass DER deployment. The aim of this paper is to fill this load modelling and NILM knowledge gap for DERto inform the ‘Green Deal’ transition and support standardisation. In the paper, existing load modelling techniques and NILM methodologies are critically examined to inform and guide research activity, equipment development and regulator thinking, as well as network operators. Seven key findings that need urgent attention are identified to support a smooth power system reconfiguration.
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•A thorough review of existing monitoring and modelling methods for DER on distribution networks is provided.•Efficacies between 65% and 95% for conventional load identification exist.•Increasing DER penetrations are creating technological challenges in distribution networks.•Optimum DER integration in low voltage networks is vital for electric networks reliability.•Seven aspects to enable massification of DER on distribution networks are established.
International policies and targets to globally reduce carbon dioxide emissions have contributed to increasing penetration of distributed energy resources (DER) in low‐voltage distribution networks. ...The growth of technologies such as rooftop photovoltaic (PV) systems and electric vehicles (EV) has, to date, not been rigorously monitored and record keeping is deficient. Non‐intrusive load monitoring (NILM) methods contribute to the effective integration of clean technologies within existing distribution networks. In this study, a novel NILM method is developed for the identification of DER electrical signatures from smart meter net‐demand data. Electrical profiles of EV and PV systems are allocated within aggregated measurements including conventional electrical appliances. Data from several households in the United States are used to train and test classification and regression models. The usage of conventional machine learning techniques provides the proposed algorithm with fast processing times and low system complexity, key factors needed to differentiate highly variable DER power profiles from other loads. The results confirm the effectiveness of the proposed methodology to individually classify DER with performance metrics of 96% for EV and 99% for PV. This demonstrates the potential of the proposed method as an embedded function of smart meters to increase observability in distribution networks.
•Method to assess dynamic performance of PMUs using a standard relay test set.•Time synchronisation of the relay test set (e.g. using GPS) is not required.•This test represents a necessary ...requirement for IEEE C37.118.1 compliance.•Performance is evaluated using widely available software tools.
This paper introduces a technique for ‘pre-compliance’ testing of Phasor Measurement Units (PMUs) against the dynamic requirements of the IEEE C37.118.1-2014 standard, which include dynamic and steady-state test scenarios. The tests described are a necessary, but not complete, requirement for passing the IEEE standard and quickly highlight shortcomings in PMU operation during dynamic conditions. The pre-compliance test presented in this paper only requires typical relay test equipment, with little requirement for significant temporal accuracy when initiating waveform test files. The compliance test is intended to allow PMU owners to assess a device’s performance before considering its use in monitoring dynamic performance. Failure of these tests can indicate the need to recalibrate or replace the PMU or find another vendor. The described method is applied to the voltage inputs of a typical commercial PMU and the results presented. The process for the creation of test waveforms is described, along with the data analysis technique used. The test waveforms and analysis source code are made available under open source licenses.
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