Fault section identification and location on a distribution feeder using travelling waves

This paper describes how the fault generated travelling waves detected in the current signals at a single location on a distribution feeder can be used for fault section identification and location. The method identifies the fault section and the probable location of the fault by comparing the relative distance of each "peak" in the high frequency current signals to the known reflection points in the distribution feeder. The probable fault location is then used within a transient power system simulator that models the actual network. The resulting simulated current waveforms are then cross-correlated against the signal captured on the real network. If the estimated fault location is correct, the high frequency signatures in the simulated waveform will be similar to that of the measured waveforms and the cross-correlation value will be a high positive value. Simulation studies using PSCAD/EMTDC and analysis using cross-correlation technique suggest that the method described can accurately locate a fault on a distribution feeder using measurement at a single location

Loss of mains detection and amelioration on electrical distribution networks

Power system islanding is gaining increasing interest as a way to maintain power supply continuity. However, before this operation become viable, the technical challenges associated with its operation must first be addressed. A possible solution to one of these challenges, out-of synchronism reclosure, is by running the islanded system in synchronism with the mains whilst not being electrically connected. This concept, known as 'synchronous islanded operation' avoids the danger of out-of-synchronism reclosure of the islanded system onto the mains. The research in this thesis was based on the concepts presented in [1-3] and specifically applied to multiple-DG island scenarios. The additional control challenges associated with this scenario are identified and an appropriate control scheme, more suited for the operation of multiple-DG synchronous islands, is proposed. The results suggest that multiple-DG synchronous islanded operation is feasible, but a supervisory controller is necessary to facilitate the information exchange within the islanded system and enable stable operation.For maximum flexibility, the synchronous island must be capable of operating with a diversity of generation. The difficulties become further complicated when some or all of the generation consists of intermittent sources. The performance of the proposed control scheme in the presence of a significant contribution of renewable sources within the island is investigated. Two types of wind technologies were developed in PSCAD/EMTDC for this purpose, they are a fixed speed induction generator (FSIG) based wind farm and a doubly-fed induction generator (DFIG) based wind farm. The results show that although synchronous islanded operation is still achievable, the intermittent output has an adverse effect on the control performance, and in particular limits the magnitude of disturbances that can happen in the island without going beyond the relaxed synchronisation limits of ±60o.Energy storage is proposed as a way to reduce the wind farm power variation and improve phase controller response. A supplementary control is also proposed such that DFIG contributes to the inertial response. The potential of the proposed scheme (energy storage + supplementary control) is evaluated using case studies. The results show massive improvement to the load acceptance limits, even beyond the case where no wind farm is connected. The benefit of the proposed scheme is even more apparent as the share of wind generated energy in the island grows.EThOS - Electronic Theses Online ServiceThe Engineering and Physical Sciences Research CouncilSchool of Electrical and Electronic EngineeringGBUnited Kingdo

Regression with an imputed dependent variable

Published online: 29 September 2022Researchers are often interested in the relationship between two variables, with no single data set containing both. A common strategy is to use proxies for the dependent variable that are common to two surveys to impute the dependent variable into the data set containing the independent variable. We show that commonly employed regression or matching-based imputation procedures lead to inconsistent estimates. We offer a consistent and easily implemented two-step estimator, “rescaled regression prediction.” We derive the correct asymptotic standard errors for this estimator and demonstrate its relationship to alternative approaches. We illustrate with empirical examples using data from the US Consumer Expenditure Survey (CE) and the Panel Study of Income Dynamics (PSID)

Examiner training: A study of examiners making sense of norm-referenced feedback

PURPOSE: Examiner training has an inconsistent impact on subsequent performance. To understand this variation, we explored how examiners think about changing the way they assess. METHOD: We provided comparative data to 17 experienced examiners about their assessments, captured their sense-making processes using a modified think-aloud protocol, and identified patterns by inductive thematic analysis. RESULTS: We observed five sense-making processes: (1) testing personal relevance (2) interpretation (3) attribution (4) considering the need for change, and (5) considering the nature of change. Three observed meta-themes describe the manner of examiners' thinking: Guarded curiosity - where examiners expressed curiosity over how their judgments compared with others', but they also expressed guardedness about the relevance of the comparisons; Dysfunctional assimilation - where examiners' interpretation and attribution exhibited cognitive anchoring, personalization, and affective bias; Moderated conservatism - where examiners expressed openness to change, but also loyalty to their judgment-framing values and aphorisms. CONCLUSIONS: Our examiners engaged in complex processes as they considered changing their assessments. The 'stabilising' mechanisms some used resembled learners assimilating educational feedback. If these are typical examiner responses, they may well explain the variable impact of examiner training, and have significant implications for the pursuit of meaningful and defensible judgment-based assessment

MPCs in an economic crisis: Spending, saving and private transfers

MPCs were directly elicited from a representative sample of UK adults in July 2020 using receipt of a hypothetical unanticipated, one-time income payment. Reported MPCs are modest, around 11% on average. They are higher, but still modest, for individuals in households with high current needs. Significant fractions of respondents report they would use a windfall to pay down debt, or that they would change their transfer payments to or from family and friends. The latter means that the aggregate MPC out of a stimulus payment need not equal the population-average MPC

A year of COVID: the evolution of labour market and financial inequalities through the crisis

We use high-quality UK panel data to document the extent that pre-existing labour market and financial inequalities were exacerbated by the pandemic between April 2020 and September 2021. Some inequalities worsened, others did not, and in some cases, initial widening of labour market inequalities was subsequently reversed. We find no evidence of an overall divergence in labour market outcomes by gender. Initial changes for ethnic minorities and the young were largely reversed by March 2021. Those in the top third of the long-run income distribution experienced income falls, but also increased saving. Net wealth increased not for only the affluent, but also for middle deciles of the long-run income distribution. These deciles were most protected by the furlough scheme. Those at the bottom of the income distribution were more likely to report a decline in net wealth over the year