Voltage Sag Propagation Research Articles

Homology detection method for voltage sags based on space vector and maximum mean discrepancy

A single voltage sag source may trigger multiple power quality monitors to record waveforms resulting in the redundancy of voltage sag monitoring data. To address this problem, a homology detection method for voltage sags based on a space vector and maximum mean discrepancy was proposed, which is conducive for locating accurate voltage sag sources and inverting sag event propagation paths. First, a waveform transformation method based on a space vector was proposed to eliminate the influence of the transformer on voltage sag propagation. Second, a two-sample test method for voltage sags based on the maximum mean discrepancy was proposed to detect whether any two voltage sag waveforms are caused by the same voltage sag source. The connected graph method was used to identify the number of sag sources; this avoids the difficulty in accurately selecting the number of clusters. The measured and simulation data of the IEEE 30-bus system were used for verification, and the results verified the correctness and effectiveness of the proposed method. The proposed method can be implemented in a power quality monitoring system as a pre-processing step to support related research activities.

A Comparative Study of the Voltage Sag Propagation under Un-Symmetrical Faults through Distribution Transformer on Low Voltage Power Network

In this paper, the characterization of the voltage sag propagation under unsymmetrical faults through distribution transformer for low voltage power network is tested with the help of a power analyzer, which is based on sequence components. The voltage sag is a big issue of the power quality (PQ) for the power system networks, which must be analyzed and characterized for the suitable protection schemes and the control strategy, separately. In this study, the voltage sag characterization is fully examined under the unsymmetrical faults through the delta-star with ground (D-Yg) connection, which is commonly imlemented in the distribution power transformers. The MATLAB/Simulink and power analyzer tools are used to characterize the voltage sag propagation. The power analyzer works on the symmetrical sequence component’s method of the voltage. Moreover, the phasor diagram of the voltage sag is also given in this paper for better understanding. The obtained results would help in the design of the protection schemes for low-voltage and controlling the impact of voltage sag through filters.

Classification of Voltage Sag Propagation under Double Line to Ground Fault on a Low Voltage Distribution Power Network

The key issue of the voltage-sag propagation on the different types of winding connections for the low voltage transformer in the distribution power network is considered in this study. The issues of voltage sag propagation depend upon the type of asymmetrical fault and the connection of the transformer windings. In this paper, the double line to ground fault is adopted for the voltage sag characterization. The depiction of the sage propagation is an outcome of the zero sequence components. Voltage sag propagation detection can be used to improve the power quality of the system. The obtained results reveal the characteristics of the voltage drop propagation from the primary to the secondary winding of the transformer throughout different connection. The implemented method will help analyze the Power Quality (PQ) problem in terms of voltage sag of the distributed transmission networks of the power system.

Analysis on propagation characteristics of voltage sag through different types of transformers

Transformer is a key factor that can not be ignored in the process of voltage sag propagation. In this paper, the transmission characteristics of voltage sag caused by different types of short circuit are analyzed through the different transfer matrix of transformer with different connection methods, including amplitude change, waveform distortion and phase jump. The distribution network model is established by PSCAD, and the propagation characteristics are verified. The conclusion has certain significance for judging the type of voltage sag from the load side, evaluating the degree of voltage sag, and selecting the treatment measures of voltage sag.

Propagation of Voltage Sag Considering Different Winding Connections: Impact on the Healthiness of Transformers

This article investigates the effect of voltage sag propagation through the transformer due to various symmetrical and asymmetrical faults in a chronological manner. A unique and precise explanation has been presented for the propagation of voltage sag through different transformer connections. The effect of voltage sag has been studied in determining the healthiness of the transformer by analyzing the parameters of insulating oil obtained through dissolved gas analysis. For this purpose, different transformer winding connections have been considered, and the analysis has been performed considering the occurrence of all major faults. In order to justify and strengthen the proposal, a real-time case study has been deliberated for depicting the correlation of propagation of fault and its effect on transformer remaining in-service period through dissolved gas analysis. The study presented in this article will help utilities to understand the voltage sag propagation along with realizing its effect on transformer healthiness, thereby ensuring total system reliability and better economical service.

Analysis of Unsymmetrical Voltage Sag Propagation Trough Distribution Transformer

In this study critical problem of voltage sag propagation through transformer winding in distribution network is taken into account. The sage propagation problem depends on the unsymmetrical fault type and winding connections of the distribution transformer. The characterization of the sage propagation is effected due to the zero sequence components. The detection of the voltage sage through sequence detection method is used to solve the problem. The obtained results reflect the characterization of voltage sag propagated from primary to the secondary winding of transformer during various connection schemes. The method adopted would be useful to analysis the power supply network for power quality in distribution transmission network.

Research of Voltage Sag Propagation through Transformers

Voltage sag is one of the most critical power quality problems. This paper calculates voltage sag propagation through YNd11 and Dyn11 winding connected transformers in series using symmetrical components, thus obtaining the voltage transfer matrix. Then the voltage sag propagation of single line-to-ground fault is computed using the transfer matrix. Simulation result proves the correctness of the analytical calculation, providing reference for the further study of voltage sag influence and estimation.

The influence of transformers, induction motors and fault resistance regarding propagation voltage sags

This article presents an analysis of voltage sag propagation. The ATPDraw tool was selected for simulating the IEEE 34 node test feeder. It takes into account both voltage sags caused by electrical fault network, as well as voltage sag propagation characteristics caused by induction motor starting and transformer energising. The analysis was aimed at assessing the influence of transformer winding connections, the impedance of these transformers, lines and cables, summarising the effects on disturbance magnitude and phase. The study shows that the influence of an induction motor on voltage sag propagation results in increased voltage sag severity. Voltage sags caused by induction motor starting and transformer energising have no zero-sequence component, so they are only affected by type 3 transformers. The influence of fault resistance on voltage sag magnitude and phase characteristics is examined and some aspects of interest in characterising these electromagnetic disturbances is identified.

The Influence of Induction Motors on Voltage Sag Propagation—Part II: Accounting for the Change in Sag Performance at LV Buses

This paper describes the influence of induction motors (IMs) on voltage sag characteristics at low-voltage (LV) buses. This influence is particularly pronounced in case of low magnitude and long duration voltage sags. Even though the conventional magnitude duration representation of voltage sags in the presence of IMs is not completely accurate, it is very convenient as it can be directly linked to a standard way of recording/reporting voltage sags. The equivalent rectangular sags developed in this study take into account the effect of IMs and establish voltage sag performance more accurately at LV buses in the distribution network. The methodology developed is not limited to simulation-based voltage sag studies. It can be equally well applied as a ldquopostprocessorrdquo to finely tune the results of monitoring distribution systems as its inputs are ldquoclassicalrdquo voltage sag magnitude duration tables. The automated procedure for counting and characterization of voltage sags at LV distribution buses is illustrated on a 295-bus generic distribution network.

The Influence of Induction Motors on Voltage Sag Propagation—Part I: Accounting for the Change in Sag Characteristics

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents an analytical approach to the analysis of the interaction between induction motors (IMs) and voltage sags. The presented methodology enables quick assessment of the influence of IM on sag characteristics and avoids time-consuming transient simulations. The accuracy of the derived analytical formulae is verified through classical transient simulations using the PSCAD/EMTDC package. This paper further proposes a simple, yet efficient transformation of resulting nonrectangular voltage sags, based on the loss of voltage index, into equivalent rectangular sags suitable for conventional voltage sag performance benchmarking. </para>

Influence of distributed wind generation and load composition on voltage sags

The envisaged increased penetration of distributed generation (DG) in electrical power networks poses challenging technical and contractual issues to both utilities and industry. Technical issues related to power quality, in particular to voltage-sag propagation and characteristics in networks with a large penetration of fixed speed wind DG are addressed. A comprehensive analysis of voltage-sag propagation in a realistic distribution network is performed. The influence of network topology, location and percentage of connected wind generation, network loading and load composition is investigated in detail. It is shown that the influence of DG on voltage-sag characteristics and propagation is strongly dependent on its location and on load composition.

Qualitative and quantitative analysis of voltage sags in networks with significant penetration of embedded generation

This paper summarizes the findings of the research carried out in the area of the voltage sag (dip) propagation in distribution networks. The emphasis is on the influence of embedded generation on voltage sag characteristics and propagation. Two different, realistic, network topologies are used in the analysis. Different types of faults and different levels of embedded generation penetration are considered. The influence of embedded generation on symmetrical and asymmetrical voltage sags is assessed. Variations in voltage sag magnitude, phase-angle jump and sag propagation through the network as a function of the level and type of embedded generation are illustrated. New indices for the assessment of voltage sag propagation are proposed. The results of the research have shown that the effects, either beneficial or detrimental, of the embedded generation on voltage sag propagation and characteristics are closely coupled with the level of their penetration into the network and the location of the generators. Copyright © 2005 John Wiley & Sons, Ltd.