There is demand for a substation automation system (SAS) that is simple to integrate and provides high performance and flexibility The increasing application of intelligent electronic devices (IEDs) with International Electrotechnical Commission (IEC) Standard 61850 capacities provides interoperability and advanced communications capabilities in substation protection, coordination, control, monitoring, metering, and testing IEC 61850 is the result of the efforts of IEC Technical Committee 57 (TC57) to produce an open standard for substation modeling and communications The standard has gained popularity and continues to spread throughout the world In this article, we explore an IEC 61850 application in a typical SA and introduce a real-world SAS modernization case that highlights the benefit of the IEC 61850 in substation monitoring and operation

Modernizing Substation Automation Systems: Adopting IEC Standard 61850 for Modeling and Communication

This paper proposes a new method for diagnosis of fault type and faulty phase of a series compensated transmission line. The standard deviation (SD) principle together with the fast discrete orthonormal s-transform (FDOST) and the decision tree (DT) is applied for the purpose of fault classification. The FDOST, as an efficient signal processing tool, is used for extracting the features from a half cycle window of voltage and current signals sampled from one end of the power system network. Finally, the SD of a half cycle post-fault samples of the FDOST coefficients is calculated to form the input feature vector for the DT-based classifier. The features are processed by the DT to classify faults. The practicability of the proposed method is validated by modified Western System Coordinating Council 3-machine 9-bus system simulated in the PSCAD/EMTDC software and field fault data captured from a real transmission network of Chhattisgarh state, India. The results confirm that the proposed method reliably classifies all types of faults with high efficacy.

FDOST-Based Fault Classification Scheme for Fixed Series Compensated Transmission System

A new method to numerically estimate the primary voltage waveform of coupling capacitor voltage transformers is presented. The outcome is a simple digital filter suitable for the frequency range from 10 to 60 Hz, enabling us to recover the transformer primary voltage waveform from its secondary voltage waveform. Unlike the techniques reported in the literature, the method does not depend directly on the transformer topology nor on the operational characteristics of the protected system, once only the coupling capacitor voltage transformer frequency response is required as input. The evaluation of the technique is performed through digital simulations using the Alternative Transients Program and transmission-line data from the Brazilian National Power System Grid. Frequency- and time-domain analysis of two coupling capacitor voltage transformers with different topologies and voltage levels are presented. It is shown that the proposed method is effective for the dynamic correction of low-frequency disturbances that may improve the speed, reliability, and security of the numerical distance relay.

Tuning CCVT Frequency Response Data for Improvement of Numerical Distance Protection

In this work, a directional relaying algorithm is proposed for transmission line to prevent relay maloperation during coupling capacitor voltage transformer (CCVT) subsidence transient. The effect of CCVT subsidence transient during single-pole-tripping condition is highlighted in this paper. The proposed method which is based on phase angle difference of post fault and prefault positive sequence current can help the directional relay to take accurate decision during erroneous CCVT secondary response. The available CCVT model in PSCAD is not able to generate significant subsidence transient in the secondary side. So, a new CCVT model is developed in EMTDC/PSCAD domain for transient response analysis and to check the relay operation. Next, the performance of different voltage and current information based directional relaying techniques have been analyzed and compared with the proposed method. The results are evaluated for different system and fault conditions. Results demonstrate the accuracy of the proposed method.

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A positive-sequence current based directional relaying approach for CCVT subsidence transient condition

The measured fault voltage signal through coupling capacitor voltage transformer (CCVT) contains transient components which highly affect the estimated fundamental frequency phasor. This paper presents a new hybrid method which aims to calculate and remove the unwanted effect of CCVT transient on the fundamental phasor estimation. The main novelty of the proposed method is that proposed method is independent from the CCVT parameters involved in the transient response. In other words, unlike previously published papers, this method calculates the CCVT characteristics involved in the transient response. To such aim, by utilizing frequency modulation, fault voltage signal is shifted. Utilizing simple but comprehensive formulations based on integration and Prony-complex theory, the CCVT characteristics are calculated in the first cycle after fault inception. After that, by utilizing modified discrete Fourier transform (MDFT), the fundamental phasor component is calculated in one cycle. Several simulated test signals are applied to the proposed method. The simulation results illustrate that the proposed method removes the unwanted effects of CCVT. Also, it is fast and has a good precision in estimating the fundamental phasor component of fault voltage signal under different simulation scenarios.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-smt.2018.5390

Auxiliary Prony‐based algorithm for performance improvement of DFT phasor estimator against transient of CCVT

Performance assessment of distance protection fed by capacitor voltage transformer with electronic ferro-resonance suppression circuit

Distance relay protecting series-compensated parallel transmission lines may maloperate due to the presence of zero-sequence mutual coupling. In case of the line terminating at the same bus at both ends, one practically feasible option is to exchange zero-sequence information between relays. This information can be used in impedance estimation and to estimate fault location in relays. However, the presence of series capacitors in both lines may further aggravate the problem. The existing magnitude-based logic to classify healthy and faulty lines may fail in the presence of the series capacitor owing to the fault location and compensation level. Recently, angle-based logic was proposed, but the analysis was limited to steady-state fundamental frequency-sequence impedance information. This paper analyzes the performance of this angle information by time-domain simulation studies. The performance is analyzed by considering different compensation levels, fault location, and for varying in-feed conditions for the capacitor located at one end of the line. Analysis based on time-domain simulation studies along with the nonswitched positive-sequence polarized distance relay shows that the angle-based logic is able to classify healthy and faulty lines.

Limitations of Angle-Based Faulty Line Identification Logic in Series-Compensated Parallel Transmission Lines

Cross Country faults (simultaneous/evolving faults at different locations) in transmission and distribution systems create challenges to distance, directional and phase-selection functions. Relay can miss to operate for in-zone faults or incorrectly operate for out-of-zone faults. This is because zerosequence and negative-sequence components distribution through the protected line, used by above mentioned functions is not easy to predict. This affects both solidly-grounded and isolated/impedance grounded systems.Single-pole switching is used in transmission network as it improves power system stability, compared to three-pole switching and also ensures system availability. In-order to correctly isolate the faulted phase, phase selector is used to supervise distance element when single-pole switching is enabled. However, certain fault scenarios such as high resistance faults, cross country faults pose a challenge to phase selector.In this paper, we start with the basic principles of phase selection for single-location faults and then we provide insights into the limitations of detecting the faulted phase during cross country faults. Finally, we introduce the improved phase selection logic to handle cross country fault scenarios, which provides correct detection of faulted phase using local information.

Cross Country Faults - Protection Challenges and Improvements

Distance relay is typically assisted by earth-current balance scheme (ECBS) to classify healthy and faulty lines when used to protect parallel transmission lines. This paper highlights the problem of distance relay maloperation when conventional ECBS is used to classify healthy and faulty lines in series compensated parallel transmission lines (SCPTL). The existence of the problem is shown mathematically for different tower configurations, varying compensation levels and for different remote end in-feed levels. Analysis shows that conventional ECBS is not able to classify healthy and faulty lines which may result in tripping of both lines depending upon the fault location. This paper proposes a similar logic, which relies on angle information instead of magnitude information. Analysis shows that angle information is able to classify healthy and faulty lines, which can be used to assist distance relay protecting SCPTL.

Faulty line identification by distance relay in series-compensated parallel transmission lines

With the increasing adoption and implementation of IEC 61850 based substation automation systems (SAS), it has now become very important for power system engineers to know and understand technologies outside the realm of regular power system concepts which are not taught until graduate studies. Present day tools and systems are either costly and proprietary in nature or, are open source but not easy to understand and use them to implement and test protection and automation schemes based on International Electro technical Commission (IEC) 61850 in a lab based environment. Taking this as motivation, an IEC 61850 based laboratory prototype is developed using royalty free and free and open source software (FOSS) for modeling the power system and the distance relay. In order to show the flexibility of the proposed framework, a complex and vital protection scheme known as local breaker backup (LBB) which has been recently integrated into a centralized bus bar protection scheme is implemented and tested. Personal computers are used as merging unit (MU) and intelligent electronic devices (IEDs), and, Ethernet based local area network (LAN) and switches have been used for implementing process bus and station bus. This cost effective prototype can be used by the academia and engineers to study, understand, implement and test various IEC 61850 based protection and automation schemes.

C Venkatesh

Papers

Performance assessment of distance protection fed by capacitor voltage transformer with electronic ferro-resonance suppression circuit

Limitations of Angle-Based Faulty Line Identification Logic in Series-Compensated Parallel Transmission Lines

Cross Country Faults - Protection Challenges and Improvements

Faulty line identification by distance relay in series-compensated parallel transmission lines

An open source framework for IEC 61850 based protection and automation schemes