Calculating loadability limits of distance relays

Maintaining selectivity among protective devices in interconnected power systems is of crucial importance. Therefore, it is necessary to install distance relays on both ends of the transmission lines to ensure efficient main and backup protection of the system. In this study, the zones and tripping time settings of distance relay for phase and ground protection of interconnected power systems are set and implemented in the professional DIgSILENT PowerFactory software. The interconnected test system IEEE 9-bus test system is used to validate the proposed methodology. The obtained results have approved that the setting and coordination of distance relays ensure adequate system protection against various fault types and locations.

Enhanced real time coordination of distance and user defined over current relays

For power system protection, the distance relay settings are important. Apparent factor is a necessary parameter in distance relay settings. Apparent factors have to be calculated when setting the distance relays and doing the resetting in case of configuration change in power system. The problem is that the current method to calculate apparent factor requires tools and plenty of time to do fault analysis and this method is complex especially in case of configuration change. Therefore this paper proposes a fast algorithm to calculate apparent factor without the fault analysis. Test results prove that this algorithm is simple and accurate by simulation.

This paper proposes an adaptive characteristic for eliminating the adverse effects of fault resistance and static synchronous compensator (STATCOM) on the performance of distance relays in transmission line and collector lines of doubly-fed induction generator (DFIG)-based wind farms in the case of single-phase-to-ground resistive faults. The proposed method improves the performance in distance relaying and maintains the coordination between relay pairs in the transmission line and wind farm collector lines. In this method, an adaptive coefficient that can modify the zone settings of conventional distance relays is added to their characteristic to improve the accuracy and coordination under the mentioned conditions. Using analytical relationships and numerical results from simulations in Matlab/Simulink environment, the efficiency of the proposed method is confirmed.

Knowledge of accurate zero-sequence line impedance parameters of transmission lines is critical for power system engineers since they play a key role in the settings of distance and directional protection relays, and fault location applications. Double-circuit transmission lines involve zero-sequence mutual impedance due to mutual coupling between the conductors, in addition to the self-impedance. The paper presents an offline estimation technique for zero-sequence self and mutual impedance parameters for double-circuit transmission lines using data from disturbance recorders from both terminals. The most accurate distributed parameter line model is used, and simulation tests prove the accuracy of the algorithm. The application of zero-sequence mutual coupling compensation in distance protection of double-circuit lines using the estimated parameters is also presented.

Public management scholars are looking to longitudinal research designs and data to help overcome the many limitations associated with cross-sectional research. However, far less attention has been given to time itself as a research lens for scholars to consider. This article seeks to integrate time as a construct of theoretical importance into a discussion of longitudinal design, data, and public management research. First, I discuss the relative advantages of longitudinal design and data, but also the challenges, limitations, and issues researchers need to consider. Second, I consider the importance of time as a theoretical construct of interest in the pursuit of longitudinal public management research. Third, I offer a brief look at the use of longitudinal design and panel data analyses in the current public management literature. The overview demonstrates a notable absence of public management research considering the attitudes, motives, perceptions, and experiences of individual public employees and managers. Finally, I consider why there are so few longitudinal studies of public employees and point out the issues public management researchers interested in individual employee-level phenomena need to consider when advancing their own longitudinal research designs.

PurposeThe last ten years have shown a significant upward trend of engagement in public management reflecting a significant increase in interest in the topic. The purpose of this paper is to investigate the benefits and factors affecting the construct of civic engagement that thus far are missing in the current literature through the analysis of studies published in the main journals of management.Design/methodology/approachThrough a systematic literature review, the current research tries to advance the progress in the understanding of the civic engagement construct analyzing a sample of 96 papers published in the main journals on the subject areas of “communication,” “marketing” and “public sector management.”FindingsThe literature was codified and characterized as follows: level of analysis, variables that affect civic engagement; benefits of civic engagement; and theoretic and methodological approach. This research explores the construct through an analysis of the literature found in the main scientific journals to intercept its various profiles and facets alongside the mechanisms that precede and follow its manifestation.Practical implicationsPublic organizations can no longer do without engaging citizens in decision-making processes. Public managers can use these findings to establish a connection with their citizens and influence their publics through commitment and managerial actions that guarantee direct democracy.Originality/valueThis is the first research that aims to study the phenomenon in the public sphere from a multidisciplinary perspective that is as yet incomplete. An integrated vision can highlight current and future developments and eventual opportunities for further research.

Mal-operation of distance relay imposes serious threats to system stability and a big reason for large scale blackouts. These relays operate in its third zone due to the inability of detecting fault during stressed system conditions. These stressed conditions are load encroachment, power swing, voltage instability conditions, extreme contingencies, etc. Conventional distance relay operates on the basis of local measurements. It calculates the impedance from the relay to the fault point for its operation. Load encroachment and power swing are very similar to the symmetrical fault condition and it is difficult for these conventional relays to distinguish these stressed conditions from symmetrical faults. It is therefore important to make the distance relay intelligent enough so that it will be able to discriminate between a fault and stressed system condition. With the advancement in synchro-phasor technology, the drawbacks of conventional relays have been overcome. The wide-area monitoring system (WAMS) is capable of development of online intelligent techniques that can segregate the stressed system condition from any fault. With these advanced techniques, the mal-operation of distance relays can be avoided and thus wide-area blackouts can be stopped. In this chapter, a new scheme for detecting the zone-III operation of distance relay is proposed to discriminate the stressed system conditions such as voltage instability, power swing, or load encroachment from fault. The proposed scheme is based on the monitoring of active and reactive power of the load buses using WAMS. Various cases are created on WSCC-9, IEEE-14 and IEEE-30 bus system to test the performance of the proposed algorithm. The simulations have been done on the MATLAB Simulink platform. Results shows that the proposed method is helpful to avoid the unwanted distance relay operation under stressed system conditions.KeywordsWide-area monitoring systemPhasor measurement unitsDistance relaysPower system protection

The opportunity for distributed generators to be connected to the power system has been increasing since the introduction of electricity deregulation. Moreover, a power system which has a new concept such as a micro-grid or a smart-grid is going to appear. The increase in the uncertainty of power flow and the power system operation under an irregular system configuration is supposed in such new power systems. And the sensitivity of a protection relay may decrease or a protection relay may miscoordinate with other protection relays. Under the above conditions, to prevent the fault expansion is required of the electric power utilities. From the background, the development of a program that can check the relay setting and the coordination between protection relay systems is desired.The development of “Support System for Setting and Coordination between protection relays” called SSSC was initiated in 2006, and it will be completed in 2011. SSSC has the following features;·It enables us to check whether the protection relay is set as operate correctly against all of assumed system faults.·It enables us to check automatically whether the coordination between the protection relays is proper as prevent the fault extension even if an unexpected condition occurs.·It enables us to analyze the response of the protection relays in the power system where some apparatus with nonlinear characteristic is installed.This paper describes the prototype of the SSSC based on the dynamic analysis like Y-method. Furthermore, in this paper, the checking method of coordination between protection relays for short circuit fault, and the verification results of the prototype in the 6.6kV model distribution system are described.

The development of Pesanggaran Conventional Substation into the Pesanggaran GasInsulated Switchgear (GIS) as a form of increasing the reliability of the electric power system inBali which led to changes in the protection system configuration on the transmission lineconnecting the GIS Pesanggaran and Nusa Dua Substation. The distance relay that waspreviously functioning as a primary protection was changed to backup protection due to the lackof selectivity of the distance relay in isolate the disruption and as the backup protection if themain protection experiencing a failure. Simulation testing using power system analysis softwareafter determining the value of the distance relay setting and tested with short circuit at 110%and 180% of the transmission line length shows the distance relay has worked according to theP3B JB regulation No. 211/151/P3B/2010 and distance relay can detect disruption in zone 2with a delay time of 0,815 seconds and detect disruption in zone 3 with a delay time of 1,615seconds.

This paper presents a scheme of distance protection for a renewable energy plant in electric power distribution systems. In many developing countries where renewable energy power plants are typically located in rural remote areas, they must be connected to weak power distribution systems inevitably. Although over-current relays are used to protect feeders at substations, fuses are only available elsewhere along feeder lines. To secure the system operation, distance protection is assigned to protect feeders. In this paper, distance relays are placed in the feeder along with over-current relays and fuses. Design of the distance protection of multi-source systems is described. This study considered the system consisting of a renewable energy plant. The power plant was a 6-MW unit of firmed power generation. The test feeder was simplified to be an equivalent four-bus test feeder for relaying purpose. Fault analysis in this paper was performed by using PowerWorld™ software. Obtained fault currents were used to establish protective zones of distance relays. In addition, this paper also compared the result of using distance protection with those of using directional over-current protection. As a result, protection of the power feeder with renewable power plants by using distance relaying can reduce complication in relay setting due to the impedance-based setting of the distance relay.

Generalized distance-based protection design for DG integrated MV radial distribution networks — Part II: Application to an actual distribution line

Transmission lines are an important part of a power system. Transmission lines have high power transmission capacity and they are prone to faults of larger magnitudes. Various faults occur in transmission lines. Therefore, protection relays are necessary to protect transmission lines. The purpose of protection system is to interrupt the faulty section from the healthy section because the fault currents may damage the electrical equipments. One of the protection relays is distance relay and it is mainly used in transmission line. Sometimes these relay are used for backup protection. Distance relays for determining the impedance need the voltage and current. Transmission lines are typically protected by distance protection relay. Distance relays are considered of high speed class and can provide transmission lines. Nowadays, numerical distance relays have been used instead of using electromechanical and static distance relays. The proposed model was verified under different tests such as single line to ground (L-G) fault, double line to ground (L-L-G) fault, line to line (L-L) fault and three phase (L-L-L) fault. SimPower System was used for modelling and simulation of distance relay, transmission lines and faults. The simulation results were obtained from MATLAB software shows the feasibility of analysis of transmission line protection with mho type distance relay for single line to ground fault, double line to ground fault, line to line fault and three phase fault at different location of transmission lines. The difficulties understanding on operation of distance relay can be cleared by using MATLAB/SIMULINK software.

Public managers play a central role in the adoption and smooth implementation of social media tools in the workplace, with local governments increasingly expecting managers to utilize these tools. Nevertheless, we know little about how public managers perceive social media use for work activities and what factors shape such perceptions. Preliminary research has shown that social media use in government may enhance task efficiency, but it may also increase management complexity and workload. In this study, we draw from current literature on e-government adoption and use to investigate the role of personal and organizational use of social media, organizational culture, digital threats, and technological capacity in shaping public managers’ perceptions of social media use. Combining data from a national survey of 2,500 public managers in 500 U.S. local governments, Census data, and data collected from city websites, we find that perceptions of social media tools in the workplace are influenced by the interplay of personal and organization use of social media, an organizational culture of innovation, and formal guidance on social media use. Technological capacity and perceptions of digital threats are not significantly related to perceptions of social media. We conclude with a discussion of what these findings mean for research and practice.

The distance relays misinterpret power swings as fault like situation and produce undesirable tripping signals. So, the action of these relays is bypassed for power swing conditions. Distance relays are equipped with features like power swing blocking and out-of-step operation functions to deal with such situations. Although, the fault in the presence of the power swing can be identified, but to detect the faults when power swing is present in a series compensated line is quite problematic because of the issues related to effects generated by the series capacitor and its protection aspects. This paper introduces a technique that uses the sum of negative sequence and zero-sequence voltages to identify the faults in the presence of the power swings in a series compensated line. Various types of faults like fault involving single phase or two phases or all the phases incorporating high fault resistance are simulated using this technique in MATLAB from the data generated by simulating the system in EMTDC/PSCAD to test the proposed technique.KeywordsPower swingsCompensationSequence components