Interconnection Protection Research Articles

Probabilistic method for risk analysis of unintentional islanding of distributed generators

Unintentional islanding can be a harmful event, requiring the fast actuation of the anti-islanding protection to disconnect the distributed generators. Although passive techniques are mostly used, they have non-detection zones and fail to detect islanding under specific conditions. Therefore, knowing in advance such operative conditions and the risks associated with the islanding occurrence can be a strategic information to support grid operators in the decision-making process regarding the effectiveness of distributed generators interconnection protection. In this context, this paper proposes a probabilistic method to assess the risk of energized island formation by combining the probability of breaker (or recloser) opening with the probability of anti-islanding protection failure. The method employs probabilistic short circuit associated with overcurrent protection actuation by using Monte Carlo simulation and time-domain analysis to obtain the cases of unintentional islanding and to calculate the risk of distributed generator islanded operation. The results drove more realistic and less conservative conclusions than previous literature. Additionally, it is shown that faults as the cause of breaker opening do play a relevant role in the performance of the anti-islanding protection.

Soka education and the land ethic: educational leadership toward the ‘creative co-existence of nature and humanity’[1

As research has shown, the kind and degree of environmental ethics and eco-philosophy (or the lack thereof) may determine the effectiveness of pre-service teacher training in education for sustainable development. This is especially the case where in the ethical substratum of the conservationist Aldo Leopold and his Japanese precursor, the human geographer, Tsunesburo Makiguchi, sustainability is understood as the joint growth and development, the interconnected safety and protection of humans and non-humans alike, members of the biosphere. In reducing human beings to their own existence, anthropocentrism limits the parameters of that existence to the lesser self, when in Leopoldian and Makiguchian terms a greater self permeates and encompasses natural laws and principles over all time and space. Two global initiatives of the United Nations, the Universal Declaration of Human Rights (1948) and more recently the UN Agenda for Sustainable Development (2005) and its 17 Sustainable Development Goals (SDGs), counterintuitively run against this non-anthropocentric environmental ethics. The search for a ‘creative co-existence of nature and humanity’ lies, on the other hand, at the heart of Soka education, a philosophy of education founded by Makiguchi and implemented worldwide at K-12 and tertiary schools by his successor, Daisaku Ikeda, a philosophy calling instead for the ‘sympathetic interaction’ of self and the environment. This is the epistemological revolution that environmentalists need to undergo for the sake not simply of sustainability but to decolonize and extend the Land Ethic from place-based to truly land-based in both theory and practice, the planet earth and the surrounding universe laying the foundation.

Highly Conductive Mn-Co Spinel Powder Prepared by Cu-Doping Used for Interconnect Protection of SOFC

Mn-Co Spinel is considered as one of the most promising materials for the interconnect protection of solid oxide fuel cells; however, its conductivity is too low to maintain a high cell performance as compared with cathode materials. Element doping is an effective method to improve the spinel conductivity. In this work, we proposed doping Mn-Co spinel powder with Cu via a solid phase reaction. CuδMn1.5−xCo1.5−yO4 with δ = 0.1, 0.2, 0.3, and x + y = δ was obtained. X-ray diffraction (XRD) and thermogravimetry-differential scanning calorimetry (TG-DSC) were used to evaluate the Cu-doping effect. After sintering at 1000 °C for 12 h, the yield exhibited the best crystallinity, density, and element distribution, with a phase composition of MnCo2O4/CuxMn3−xO4 (x = 1, 1.2, 1.4 or 1.5). X-ray photoelectron spectroscopy (XPS) was used to semi-quantitatively characterize the content changes in element valence states. The areal fraction of Mn2+ and Co3+ was found to decrease when the sintering duration increased, which was attributed to the decomposition of the MnCo2O4 phase. Finally, coatings were prepared by atmospheric plasma spraying with doped spinel powders and the raw powder Mn1.5Co1.5O4. It was found that Cu doping can effectively increase the conductivity of Mn-Co spinel coatings from 23 S/cm to 51 S/cm. Although the dopant Cu was found to be enriched on the surface of the coatings after the conductivity measurement, which restrained the doping effect, Cu doping remains a convenient method to significantly promote the conductivity of spinel coatings for SOFC applications.

SoC interconnection protection through formal verification

The wide adoption of third-party hardware Intellectual Property (IP) cores including those from untrusted vendors have raised security concerns for system designers and end-users. Existing approaches to ensure the trustworthiness of individual IPs rarely consider the entire SoC design, especially the IP interactions through SoC bus. These methods can hardly identify malicious logic (or design flaws) distributed in multiple IPs whereas individual IPs fulfill security properties and can pass the security testing/verification. One possible solution is to treat the SoC as one IP core and try to verify security properties of the entire design. This method, however, suffers from scalability issues due to the large size of SoC designs with multiple IP cores integrated. In this paper, we present a scalable SoC bus verification framework trying to verify the security properties of SoC bus implementation where the bus protocol plays the role of the golden reference. More specifically, finite state machine (FSM) models will be constructed from the bus implementation and the trustworthiness will be verified based on the property set derived from the bus protocol and potential security threats. Along with IP level formal verification solutions, the proposed framework can help ensure the security of large-scale SoCs. Experimental results on ARM AMBA Bus demonstrate that our approach is applicable and scalable to prevent information leakage and denial-of-service (DoS) attack by verifying security properties.

Performance of Interconnection Protection Based on Distance Relaying for Wind Power Distributed Generation

This paper proposes a method to analyze and improve the performance of interconnection protection based on distance relaying for wind power distributed generation (DG) in distribution systems. Of particular importance is distance protection that uses the concept of prefault voltages as reference quantities found to have issues with intermittent behavior of wind power DG. This concept is normally used in different distance protective relaying applications in order to increase the fault resistance coverage capability of the distance relays as well as to ensure selectivity, dependability, and security under extreme undervoltages. The main contributions of this paper are to analyze this issue and propose a method to enhance the performance of distance protection to mitigate this issue. In this methodology, several case studies are investigated with different penetration levels, weather patterns, and configuration topology of DGs under both normal operating conditions as well as fault conditions. Results for a case study are given.

Performance of Multiframe Digital Interconnection Protection for Distributed Cogeneration Systems

This paper presents the application of the multiframe digital interconnection protection for cogeneration systems. The multiframe digital interconnection protection is constructed from two frequency main frames; one frame to detect islanding events and the other frame to detect faults on either side of the point-of-common-coupling (PCC). Islanding events are detected based on the wavelet packet transform high-frequency subband, which is extracted from the $d\!-\!q$ -axis components of the instantaneous $3\phi$ apparent powers determined at PCC. The detection of faults, on either side of PCC, is achieved by extracting the magnitudes and phases of the high-frequency contents present in PCC currents. The high-frequency contents present in PCC currents are extracted by a phaselet filter bank that is composed of six digital high-pass filters, which are designed to implement six phaselet subframes. The multiframe digital interconnection protection is experimentally tested on a 3.6 kVA cogeneration system for islanding events, different faults on both sides of PCC, and nontransient conditions. Test results demonstrate the ability of the proposed interconnection protection to initiate accurate, fast, and reliable responses to various types of transient disturbances.

The Performance of a Digital Interconnection Protection for Grid-Connected WECSs

This paper develops and experimentally tests the performance of a digital interconnection protection for grid-connected wind energy conversion systems (WECSs). The developed protection is constructed by two frequency frames to process voltages and currents measured at the point-of-common-coupling (PCC). The first frequency frame is set to process the $d-q$ -axis components of the instantaneous $3\phi$ apparent powers ( $s_{d}$ and $s_{q}$ ) determined at PCC. This processing of $s_{d}$ and $s_{q}$ aims to extract their high-frequency subband contents in order to detect the islanding condition. The second frequency frame is set to extract the high-frequency contents (magnitudes and phases) present in the $3\phi$ currents flowing through PCC. These high-frequency contents provide signature information for detecting faults occurring on either side of PCC. The multiframe digital interconnection protection is implemented for performance evaluation on two different WECSs operated in grid connection. Performance results show accurate and reliable detection and identification of the islanding condition and faults occurring on either side of PCC. In addition, performance results show that the multiframe digital interconnection protection has minor sensitivity to the type, structure, ratings, and levels of power delivery to the host grid.

Protection of Utility–Refinery Interconnection

This paper discusses the protection requirements to interconnect a typical refinery to the utility system. However, the information provided is applicable to other industrial facilities that have generation. It covers applications involving service to a refinery that normally requires a transformation between the utility's supply voltage and the refinery's utilization voltage. This paper specifically addresses refineries with generation that are connected to utility transmission circuits. The protection discussed must protect the refinery from the effects of utility system faults, but must also protect the utility from the effects of refinery faults. Coordination between these two systems is essential to minimize the effects of fault-induced outages. This paper specifically addresses typical refinery-utility interconnections system one-line designs, determining utility supply performance expectations, impact of generation on interconnection protection, relay functional requirements for typical interconnections protection, relay communication requirements, and grounding of the interconnection transformer(s) and its impact on protection. In addition, this paper will discuss the North American Electric Reliability Corporation requirements and their effect on refinery interconnection protection.

An interconnection protection design for the interface of alternating current microgrids

The interface of AC microgrids plays an important part in implementing the flexible operation modes. It always manages the disconnection and reconnection between microgrids and the host distribution networks. This study proposes a new protection design interconnection protection (IP), for the interface of microgrids especially the multiple and large-scale ones. IP is intended to decouple interconnected subsystems to prevent disturbances or faults from damaging the both subsystems. IP can be classified into facility IP, circuit IP, and utility IP corresponding to the microgrid served. The deployments, features, and protection schemes of different IPs are analyzed according to the operation characteristics and requirements of the typical microgrid in IEEE Std 1547.4. Facility IP detects faults and disturbances by monitoring the power quality at the point of common coupling. Circuit IP and utility IP have alternative schemes, for example, current differential protection, distance protection, and overcurrent protection. A fault-direction-judgment overcurrent method is proposed for their overlap protection zone. Besides, a time-grading method is used to ensure the coordination of the IPs in the large-scale microgrid. The effectiveness of the proposed designs and protection schemes are demonstrated by the simplified microgrid in IEEE Std 1547.4.

The Interconnection Protection of the MV Multiple Microgrid

The MV multiple Microgrid includes not only a lot of DGs, and may also contain some small microgrids. To the large scale MV multiple microgrid, the interconnection protection problems of different levels microgrid will decide the safe and stable operation of the maximum range. In this paper, list the challenges which are crucial to the microgrid protection, put forward a protection scheme based on the digital integrated protection terminal (DIPT) to solve these problems according to the structure characteristics, analyze the basic principle with comparing composite modulus of fault currents in a DIPT control zone to identify the fault branch and the necessary communication scheme between DIPTs is discussed. At last, build the system model in PSCAD/EMTDC and verify the theory feasibility in different operation modes and different fault types.

Synchronous Distributed Generation Islanding Protection Using Intelligent Relays

Islanding protection is an essential and one of the more challenging aspect of distributed generation interconnection protection. This article demonstrates how intelligent relays, employing multivariate analysis and data mining techniques, can be used for the islanding protection of synchronous distributed generation in the presence of high-speed reclosing. The developed methodology is outlined and its application is illustrated for a number of diverse system operating states. The performance of the intelligent relays is assessed and compared against currently used islanding protection devices.

Studies on characteristics of lightning generated currents in an interconnected lightning protection system

An in-depth knowledge about the characteristics of lightning generated currents will facilitate evaluation of the interception efficacy of lightning protection systems. In addition, it would aid in extraction of valuable statistics (from measured current data) on local lightning parameters. Incidentally, present day knowledge on characteristics of lightning induced current in typical lightning protection systems is rather limited. This is particularly true with closely interconnected protection systems, like the one employed in Indian Satellite Launch Pad-II. This system is taken as a specific example in the present study. Various aspects suggest that theoretical modelling would be the best possible approach for the intended work. From the survey of pertinent literature, it is concluded that electromagnetic modelling of lightning return-stroke with current source at the channel base is best suited for this study. Numerical electromagnetic code was used for the required electromagnetic field solution and Fourier transform techniques were employed for computing time-domain results. A validation for the numerical modelling is provided by laboratory experiments on a reduced scale model of the system. Apart from ascertaining the influence of various parameters, salient characteristics of tower base currents for different kinds of events are deduced. This knowledge can be used in identifying the type of event, as well as its approximate location. A method for estimation of injected stroke current has also been proposed.

A technical evaluation framework for the connection of DG to the distribution network

Technical advances and institutional changes in the electric power industry have resulted in a constantly increasing penetration of distributed generation (DG) resources in the grids. For the connection of new DG installations to the network a variety of factors are taken into account, including technical requirements imposed by utilities to ensure that the DG station does not adversely affect the operation and safety of the network. In this paper, fundamental issues related to the interconnection of DG installations to the grid are discussed and evaluation rules are presented, which address power quality considerations and are suitable for application by electric utility and DG engineers. The attention is focused on the steady-state and fast voltage variations, flicker and harmonic emissions. The simplified evaluation procedures of the paper are largely based on the relevant IEC publications and reflect the current practice of several European utilities. A discussion of the interconnection protection requirements is also included in the paper.

Development of a CuFe2O4 Interconnect Coating

Use of commercial grade ferritic steel interconnects in solid oxide fuel cells leads to problems of high resistance and chromium poisoning of the cathode during operation between 750-800°C. To avoid this problem, a novel method of applying coatings for interconnect protection has been tried. Copper and iron films have been deposited sequentially on the surface of a ferritic steel (UNS-430), which upon heat treatment in air at 750-775°C form an adherent coating of CuFe 2 O 4 spinel phase. Electrical and microstructural characterization of spinel-coated steel samples have been carried out. The area specific resistivity (ASR) value of a 15 pm CuFe 2 O 4 -coated sample was found to be as low as 0.025 Ω.cm 2 .

A207 INTERCONNECTION PROTECTION OF DISTRIBUTED GENERATION

Much of the new generation capacity installed during the next 10 years will be accomplished through the construction of IPP (Independent Power Producer) generating facilities. These facilities can take the form of small distributed generating (DG) units, or large capacity plants owned and even operated by non-utility personnel. It is forecasted that many of the distributed generating units will be at smaller industrial and commercial facilities and operating in parallel with the utility system to reduce energy cost through load sharing or "peak shaving." This paper discusses the protection requirements to interconnect these generators to utility systems, as well as methods to reconnect these generators after interconnect protection tripping.

Interconnection protection of IPP generators at commercial/industrial facilities

Much of the new generation capacity installed during the next millennium will be accomplished through the construction of independent power producer (IPP) generating facilities. These facilities can take the form of small dispersed generating units, or large-capacity plants owned and even operated by nonutility personnel. It is forecasted that many of these dispersed generating units will be at smaller industrial and commercial facilities and operating in parallel with the utility system to reduce energy cost through load sharing or "peak shaving." This paper discusses the protection requirements to interconnect these generators to utility systems, as well as methods to reconnect these generators after interconnect protection tripping.

Residential photovoltaic power generating system connected to utility line

Abstract We successfully developed a utility grid interconnected photovoltaic (PV) power generating system with reverse power flow capability and installed it in an occupied private residence for the first time in Japan. The system, which consists of a 1.8-kW PV array, a 3-kVA inverter, and an interconnection protection device, has been operating satisfactorily since July 31, 1992. On a clear day, about 77% of the PV generated power was reversed to the utility between 10:00 AM and 2:00 PM. For a one-month period in May, 1993, the system generated 180 kWh of power, and fed 61% of this generated power back to the utility line. A 3-kW PV array could be installed on the roof of an ordinary Japanese house, which would supply almost all of the power required for household consumption and alleviate peak power demand.