Mirrasoul J. Mousavi

Voltage Sag Data Utilization for Distribution Fault Location

Fault location in distribution systems is an important function for outage management and service restoration directly impacting feeder reliability. In this paper, a fault location method based on matching calculated voltage sag data and data gathered at some nodes in the network is proposed. A method for characterization of voltage sags is utilized to reduce amount of transferred data. The proposed method can pinpoint fault location precisely, and is applicable to any complex distribution systems with load taps, laterals, and sub-laterals, single-phase loads, as well as networks with heterogeneous lines. The performance of the proposed method is demonstrated on the IEEE 123-node distribution test system via computer simulations in Alternate Transients Program software.

A Systematic Approach for Ranking Distribution Systems Fault Location Algorithms and Eliminating False Estimates

The need for distribution reliability enhancement in the age of smart grids requires reliable methods for locating faults on distribution systems leading to a faster service restoration and maintenance cost optimization. Given the numerous fault location methods, one faces the challenge of objectively evaluating and selecting the most proper method. In this paper, a two-step approach is proposed and discussed for ranking available fault location methods that takes into account application requirements and modeling limitations and uncertainties. The ranking method formulated as uncertainty analysis utilizes 2 n + 1 point estimation to calculate the statistical moments of the fault location estimation error. These moments plugged into the Chebyshevs inequality provide a basis for ranking the fault location method. The selected method may still suffer from multiple fault location estimations. To address this caveat, voltage sag characteristics reported by few intelligent electronic devices (IEDs) along the feeder are utilized. The number and location of these IEDs are determined through an optimal approach specifically formulated for this problem. The proposed two-step ranking methodology and the IED placement optimization approach were implemented on a simulated distribution system and their effectiveness was demonstrated through a few select scenarios and case studies.

Field investigation and analysis of incipient faults leading to a catastrophic failure in an underground distribution feeder

This paper deals with the subject of incipient faults in underground distribution systems and their progression over time leading to an eventual permanent failure. Field data recorded from an underground distribution feeder were analyzed in both time and frequency domain to identify the symptom parameters and characterize the observed incipient behavior. This exploratory data analysis sheds additional light on the progressive characteristics and nature of these self-clearing faults and advances the fundamental knowledge in an effort to detect such pre-mature failures before developing into a full-blown fault.

Reliability Modeling and Evaluation of Power Systems With Smart Monitoring

Smart grid technologies leveraging advancements in sensors, communications, and computing offer new avenues for reliability enhancements of complex power grids by increasing the up-times and reducing the down times. This paper discusses various aspects of smart grid monitoring and proposes a mathematical model to assess its impact on power grid reliability. Based on a multiple-state Markov chain model, the failure and repair rates of power components with and without monitoring provisions are determined and compared. The proposed formulation incorporates the failure rates of the monitoring systems themselves and the impact on system/component reliability.

Modeling distribution automation system components using IEC 61850

IEC 61850 was proposed as a standard protocol for communications within the substation. In its current edition, the standard does not cover communications outside the substation, either with the control center or with other substations, for instance for remote protection. However, during the recent years, there has been a general belief that some features of the standard can be efficiently utilized for applications outside the substation as well. With the advent of new monitoring and control technologies the idea of power system automation at the distribution system and feeder level is crossing new boundaries. In such applications, accessing the accurate data is a necessity. With its future-proof object oriented structure, IEC 61850 can provide comprehensive and accurate information models for various components of distribution automation systems. This paper provides some examples on how the standard can be employed for this purpose, and what measures need to be taken to enable it to efficiently respond to some of the emerging technologies in distribution automation systems.

Detecting Incipient Faults via Numerical Modeling and Statistical Change Detection

This paper deals with the detection of incipient faults in underground distribution systems using online voltage and current measurements. The approach presented in this paper is based on the numerical modeling of incipient fault patterns established from the oscillographic data. Specific energy features in the wavelet domain were extracted and used in the modeling task using the self-organizing map technology. The modified modeling errors are used as a chronologically ordered sequence in the change detection problem specifically formulated for this application. Three modified change detection algorithms, namely, cumulative sum, exponentially weighted moving averages, and generalized likelihood ratio were investigated and assessed as to the performance using field-recorded data from an underground cable lateral. The detection results demonstrate the detectability of these faults and application of the approach for real fault scenarios.

A Novel Condition Assessment System for Underground Distribution Applications

This paper discusses an automated measurement based condition assessment system for underground distribution.

Latency considerations in IEC 61850-enabled Substation Automation Systems

Substation Automation Systems (SAS) offer powerful, fast, and viable ways to design, automate, and implement substation protection, control, and monitoring functions in modern transmission and distribution grids. Todays SAS — ore than ever — rely on the adoption of IEC61850 as a worldwide standard for interoperability and dependable peer-to-peer and substation communications. Being based on the Ethernet computer networking technology, the reliability issues associated with latency in 61850-enabled SAS is of a design consideration. Unpredictability is the most important challenge for latency assessment. This paper discusses the background framework for latency evaluations in SAS by considering the delay elements in nodes and links. The methodology adopted for Local Area Networks has been applied to a real SAS case study and verified from engineering point of view.

Experimental investigation of internal short circuit faults leading to advanced incipient behavior and failure of a distribution transformer

Transformer fault detection and diagnosis is becoming more important due to the restructuring of the electric power industry. In this era of deregulation, loading transformers to their optimum capacity is becoming normal practice, which in turn applies high stresses on the insulation of the transformers and increases the probability of occurrence of internal short circuit winding faults. Such faults can lead to catastrophic failure and hence cause outages. Utilities and other entities in the electric power business are therefore exploring ways of detecting these faults in transformers in the incipient stage. Terminal values, primary and secondary currents and voltages of the transformer convey information that can be used to detect internal transformer failures before developing a detection method. The behavior of these terminal values should be understood. In an effort to characterize the behavior of the terminal values of a transformer during internal short circuit and incipient faults, short circuit faults were staged on a 25 kVA, 7200 V/240 V/120 V two winding custom-built transformer. This paper discusses the results of the field experiments performed over a 19-month period. It presents time domain results of selected short circuit experiments. It also presents recordings of advance incipient-like behavior during the last set of experiments.

Trend analysis techniques for incipient fault prediction

This paper extends the application of the Laplace Test Statistic for trend analysis and prediction of incipient faults for power systems. The extensions proposed in this paper consider the situation where two parameters believed to contribute explicitly to the eventual failure are monitored. The developed extensions applied to actual incipient failure events provide promising results for prediction of the impending failure. It is demonstrated that by incorporating two parameters in the trend analysis, the robustness to outliers is increased and the flexibility is augmented by increasing the degrees of freedom in the generation of the alarm signal.