Voltage unbalance (VU) emission assessment is an integral part in the VU-management process where loads are allocated a portion of the unbalance absorption capacity of the power system. The International Electrotechnical Commission Report IEC/TR 61000-3-13:2008 prescribes a VU emission allocation methodology establishing the fact that the VU can arise at the point of common connection (PCC) due to upstream network unbalance and load unbalance. Although this is the case for emission allocation, approaches for post connection emission assessment do not exist except for cases where the load is the only contributor to the VU at the PCC. Such assessment methods require separation of the post connection VU emission level into its constituent parts. In developing suitable methodologies for this purpose, the pre and postconnection data requirements need to be given due consideration to ensure that such data can be easily established. This paper presents systematic, theoretical bases which can be used to assess the individual VU emission contributions made by the upstream source, asymmetrical line, and the load for a radial power system. The methodology covers different load configurations including induction motors. Assessments obtained by employing the theoretical bases on the study system were verified by using unbalanced load-flow analysis in MATLAB and using DIgSILENT PowerFactory software.Index Terms-Current unbalance, load asymmetry, power quality (PQ), system inherent asymmetry, voltage unbalance (VU), VU emission allocation, VU emission assessment.

The International Electrotechnical Commission (IEC) Technical Report IEC/TR 61000-3-13:2008 considers voltage unbalance (VU) emission assessment as a key aspect of the VU management of power systems. Compliance assessment of unbalanced installations at the post connection stage is essential to ensure that the limits set by the IEC VU emission allocation methodology in the pre-connection stage are met. Although VU is known to be caused by load asymmetries and inherent network asymmetries, locating all VU emission sources is not a straightforward process, especially in a network with interconnections. Such assessment methodologies should ensure that the contributions from various sources of unbalance to the total VU emission are determined using data which is not overly demanding. This paper presents deterministic methodologies which can be used to assess constituent components of post-connection VU level at the point of evaluation in an interconnected network utilising post connection voltage/current measurements and known system parameters. The theoretical bases are developed to cover different load types including induction motors. Emission assessment outcomes of different study systems obtained by employing the proposed methodologies are verified using unbalanced load flow analysis. Abstract-Voltage unbalance (VU) emission assessment is an integral part in the VU management process where loads are allocated a portion of the unbalance absorption capacity of the power system. The International Electrotechnical Commission Report IEC/TR 61000-3-13:2008 prescribes a VU emission allocation methodology establishing the fact that the VU can arise at the point of common connection (PCC) due to both upstream network unbalance and load unbalance. Although this is the case for emission allocation, approaches for post connection emission assessment do not exist except for cases where the load is the only contributor to the VU at the PCC. Such assessment methods require separation of the post connection VU emission level into its constituent parts. In developing suitable methodologies for this purpose, the pre-and post-connection data requirements need to be given due consideration to ensure that such data can be easily established. This paper presents systematic, theoretical bases which can be used to assess the individual VU emission contributions made by the upstream source, asymmetrical line and the load for a radial power system. The methodology covers different load configurations including induction motors. Assessments obtained employing the theoretical bases on the study system were verified by using unbalanced load flow analysis in MATLAB and using DIgSILENT PowerFactory software.

Recent government policy initiatives have significantly increased the number of grid connected solar PV systems in distribution networks. Thus, it is of vital importance to understand the technical impacts of high penetration levels of solar PV systems on the operating performance of these networks. This paper presents an analysis of power quality aspects of an urban low voltage (LV) distribution network with high solar PV penetration levels in Sri Lanka. The study includes three-phase load flow analysis carried out by modeling the selected network in DIgSILENT PowerFactory simulation platform using 15 -minute load data. Effects on net power flows and voltages of the LV network, which have been verified using field measurements, are discussed. Factors influencing the hosting capacity of solar PV are investigated by analysing technical impacts at varying solar PV penetration levels.

Voltage unbalance propagation is an important aspect in relation to the voltage unbalance management process which aims to maintain acceptable voltage unbalance levels in the power system. The IEC Technical Report IEC/TR 61000-3-13:2008 incorporates the effects of voltage unbalance propagation in the voltage unbalance emission allocation methodology by introducing the voltage unbalance transfer coefficient, in order to evaluate the influence made by background voltage unbalance at the point of evaluation. However, no comprehensive approaches exist in the literature to evaluate these coefficients and the IEC work follows some approximations, which are deduced based on simulations and practical measurements. Recent work completed on voltage unbalance emission assessment at the post-connection stage of unbalanced installations allows separation of the voltage unbalance emission contribution made by upstream/surrounding unbalance sources as a constituent component of the resultant voltage unbalance emission level at the point of evaluation. These new methodologies implicitly deal with the important aspects of voltage unbalance propagation and allow the quantification of coefficients associated with voltage unbalance propagation, which is the main thrust of this study. The theoretical work completed by considering different types of loads in radial and interconnected networks is supplemented by the simulation results.

The International Electrotechnical Commission (IEC) Technical Report IEC/TR 61000-3-13:2008 considers voltage unbalance (VU) emission assessment as a key aspect of the VU management of power systems. Compliance assessment of unbalanced installations at the post connection stage is essential to ensure that the limits set by the IEC VU emission allocation methodology in the pre-connection stage are met. Although VU is known to be caused by load asymmetries and inherent network asymmetries, locating all VU emission sources is not a straightforward process, especially in a network with interconnections. Such assessment methodologies should ensure that the contributions from various sources of unbalance to the total VU emission are determined using data which is not overly demanding. This paper presents deterministic methodologies which can be used to assess constituent components of post-connection VU level at the point of evaluation in an interconnected network utilising post connection voltage/current measurements and known system parameters. The theoretical bases are developed to cover different load types including induction motors. Emission assessment outcomes of different study systems obtained by employing the proposed methodologies are verified using unbalanced load flow analysis. Abstract-Voltage unbalance (VU) emission assessment is an integral part in the VU management process where loads are allocated a portion of the unbalance absorption capacity of the power system. The International Electrotechnical Commission Report IEC/TR 61000-3-13:2008 prescribes a VU emission allocation methodology establishing the fact that the VU can arise at the point of common connection (PCC) due to both upstream network unbalance and load unbalance. Although this is the case for emission allocation, approaches for post connection emission assessment do not exist except for cases where the load is the only contributor to the VU at the PCC. Such assessment methods require separation of the post connection VU emission level into its constituent parts. In developing suitable methodologies for this purpose, the pre-and post-connection data requirements need to be given due consideration to ensure that such data can be easily established. This paper presents systematic, theoretical bases which can be used to assess the individual VU emission contributions made by the upstream source, asymmetrical line and the load for a radial power system. The methodology covers different load configurations including induction motors. Assessments obtained employing the theoretical bases on the study system were verified by using unbalanced load flow analysis in MATLAB and using DIgSILENT PowerFactory software.