2.5 The relay types used in ungrounded systems
2.5.1 The 59N scheme
The 59N is the most popular over voltage protective relay for ungrounded power distribution networks. It uses the zero-sequence voltage component to detect single line to ground faults. The disadvantage of the 59N relay is that it can not detect the faulted feeder or faulted phase. This is because when a ground fault is present any one of the feeders faulted produces the same magnitude of zero-sequence voltage. The 59N systems are still in use in several industrial applications .
1.1 Significance of Overhead Distribution System Reliability
In relation to reliability issues, distribution system reliability is drawing more and more attention. Power distributionsystems receive electricity from transmission systems and deliver it to customers. The reliability of distributionsystems correlates directly with their ability to deliver power to the customers without outages. A very large part of the distributionsystems in the US consists of overhead feeders with radial configuration, which saves capital cost but is not always reliable. Locating in highly populated areas, unique configurations and relatively simple protection mechanisms in distributionsystems makes distributionsystems more responsible for most of the interruptions experienced by customers than generation and transmission systems . It has been reported that 80% of the interruptions experienced by customers are due to outages in distributionsystems  and on average, an outage of a segment on a feeder will interrupt service to about half of the customers it serves . Although historically utilities have maintained a very high level of reliability, pressure on them to continue to maintain this has gradually increased over the past several years. This is because some state utility commissions are imposing or proposing penalties on utilities for not providing certain expected levels of reliability. The situation is further compounded by the fact that customers of the digital age expect a higher level of reliability, while the utilities operate under a tighter budget. Thus, distribution system reliability is becoming a very significant part of the utility business.
Historically, electrical distribution networks have been the consumer interfaces with the power plants and transmission systems where electricity, which is normally produced far away from the center of load, is being transferred, delivered, and consumed. Although interruption in the distribution services or failure in the distribution equipment directly affects the end user, and the reliability and quality of the service, compared to the other sector of energy distribution system it has been less technologically advanced. However, in recent years with the rapid growth of alternative energy resources and the necessity for the integration of many new devices such as Distributed Generations (DG), microgrids, electric vehicles, etc., the distribution system is transforming to be at the forefront of the renovation of electrical grids. It is very important to note that because of the massive infrastructure of distributionsystems, it is very capital and labor intensive , and therefore, simplification and cost awareness have to be considered as chief characteristics that will be demanded from researchers and solution providers. In this chapter, the background of distribution system, with focus on the North American grid and some of the challenges it is facing relevant to the current work, is presented.
The growing awareness towards the environment, and the pressure for decarbonising energy systems have led to a significant change in the nature of traditional distributionsystems . This involves the connection of more small scale renewables, the deployment of demand side controls, and the electrification of more heat and transport demands. Such changes will lead to the requirement for the provision of significantly increased power capacity and the integration of more decentralised controls. The issue is that most of existing distributionsystems are very old, and already designed and operated close to their operating limits. Using traditional reinforcement solutions to increase the power capacity for addressing the aforementioned changes will be very expensive, slow, and power interruptive. Therefore, LVDC distributionsystems with help of advanced power electronics and information communication technologies (ICT) have the potential to be used as an alternative measure to improve the efficiency and cable capacities of existing distribution networks in more effective way -. The motivation is that
Proposed method is efficiently shows the broker less subscriber /publisher relationship without adding much hazards of trustworthiness. Here keys are been generating by permutation of the characters in run time based on the event owner data generation scenario and publisher access scenario with different keys. In the system owner is efficiently generate the key based on his profile data and event data. Whereas the publisher manages to re-encrypt the data by generating two tier key using owner key and time based key for the reverse circle cipher encryption cipher base. Again System successfully maintains the Event distribution scenario by using Gaussian distribution model for the publisher. And in the end the whole system is tightly coupled to handle many subscriber requests in run time with proper event publishing schemes. The proposed system can be enhancing to implement in heterogeneous network of internet of things using cluster based hierarchy. This makes the system to access completely in all possible types of network.Cluster based hierarchy in distributed paradigm is the scenario where many clustered node in the systems areassigned for the different work in the distributed network. So we can enhance our model by assigning clusters for handling publisher work and event owner work. This actually greatly reduces the task completion time.
the ac voltage instead of the ac RMS. Using dc voltages equiv- alent to the ac peaks will deliver the same power with lower current, resulting in reduced thermal losses in LV feeders. A typical 1 kV ac PVC insulated underground cable has been successfully used as a dc feeder with voltages up to ±750 Vdc for the Finnish LVDC test network, and the continuous 5000 h of operation have not caused any failure or damage to the cable . The only problem with using higher dc voltage is the requirement for converters with higher voltage ratings which may lead to higher cost. The research in  has considered the impact of different dc voltages on the life cycle costs of converters and dc cables in LVDC systems, and has found that the most optimal dc voltage lies between 0.6 and 1 kVdc. This analysis has based on the existing average cost of power elec- tronic devices. With technology advancement and increased application of dc, the cost of these devices will reduce. This may allow the optimal voltages to increase further, by which further capacity will be provided. To sum up, there is an urgent need for standards organizations to provide a nominal dc volt- age that will maximize the value of the application of dc technologies in public distributionsystems.
The ADMS is a decision support system that helps control room and field operating personnel to monitor and control the electric distribution system effectively while improving safety, reliability, asset protection and quality of service. ADMS delivers a single environment and user experience. This enables the streamlining of decision making and enhances emergency response performance. It resolves the critical barrier issues of real-time integration and enables the creation of high- performance network models. By providing a unified environment for control and dispatch, ADMS also allows for a more comprehensive view of the distribution system during an outage. The Advanced DMS is the utility depended technology that is why it should be interconnected with the existing Energy Management or Network Management System and OMS. Data sharing between these systems maximizes the efficiency of operation within your control room or control centers.
configuration based on the goals identified in the previous section. Although such methods are very fast, they are highly dependent on initial system configuration, hence there is no assurance that the sequence of switching operations is necessarily minimum. In  the restoration problem is addressed by using some heuristic rules together with an optimization technique (integer linear programming). In , the restoration problem is formulated as a mixed-integer non-linear problem, which is then solved using a generalized reduced gradient non-linear solver using a commercial solver package. In all these methods, optimal solution can be obtained if a large amount of data, obtained from complete system through SCADA is fed to the restoration algorithm residing centrally as a DMS (Distribution Management System) application.
The ETO has many desirable features. Theoretical analysis and experimental results suggest that the ETO has the combined advantages of both the GTO and the IGBT, namely, GTO’s high voltage and current rating, low forward voltage drop, and IGBT’s voltage control, high switching speed, wider RBSOA, high reliability . Its ability to turn off high currents while simultaneously sustaining the high voltage, gives it a robust Reverse Biased Safe Operating Area (RBSOA). The ETO thyristor also has another important feature of having a series MOSFET in the cathode terminal (emitter terminal) which is used for current sensing through the device. This current sensing can be very effectively used for turning off the device before the maximum controllable current limit is reached. This feature is used for the Switch Level Autonomous Protection, as will be described later. The operation of the semiconductor device (ETO or IGBT) in the active region has been discussed in literature [4, 24, 25, 27] as a useful technique for handling short circuits and for dv/dt control, as shown above in Figure 8.
This thesis introduces a new approach to enhance the reliability of conventional passive anti- islanding protection scheme in distributionsystems embedding distributed generation. This approach uses an Islanding-Dedicated System (IDS) per phase which will be logically combined with the conventional scheme, either in blocking or permissive modes. Each phase IDS is designed based on data mining techniques. The use of Artificial Neural Networks (ANNs) enables to reach higher accuracy and speed among other data mining techniques. The proposed scheme is trained and tested on a practical radial distribution system with six- 1.67 MW Doubly-Fed Induction Generators (DFIG-DGs) wind turbines. Various scenarios of DFIG-DG operating conditions with different types of disturbances for critical breakers are simulated. Conventional passive anti-islanding relays incorrectly detected 67.3% of non- islanding scenarios. In other words, the security is as low as 32.3%. The obtained results indicate that the proposed approach can be used to theoretically increase the security to 100%. Therefore, the overall reliability of the system is substantially increased.
Abstract—Future plans for integration of large non- synchronous generation and the expansion of the power system in the Nordic countries are a concern to transmission system operators (TSOs) due to the common interconnections and electricity exchanges among these operative areas. The expected reduction in the inertia anticipates an alteration of the frequency response, provoking high Rate of Change of Frequency (RoCoF) slopes that can jeopardize the security of the interconnected systems. Since power generation in the Nordic countries such as Sweden, Finland and Norway is hydro-dominated, in this paper, we propose a novel solution to tackle this problem including Wide Area Measurements (WAMS) to monitor and share the RoCoF in remote areas with lower inertia to enhance their primary frequency control. To demonstrate the effectiveness of the proposed solution, first a test benchmark control with optimized parameters is developed and later compared against the proposed method. Additionally, since the proposed solution is based on measurements from remote locations in order to guarantee stability of the system the impact of delays in the communication channels is also included in the problem formulation.
Overcurrents in a power distribution system can occur as a result of both normal (motor starting, transformer inrush, etc.) and abnormal (overloads, ground fault, line-to-line fault, etc.) conditions. In either case, the funda- mental purposes of current-sensing protective devices are to detect the abnormal overcurrent and with proper coordination, to operate selectively to protect equipment, property and personnel while minimizing the outage of the remainder of the system. With the increase in electric power consumption over the past few decades, dependence on the contin- ued supply of this power has also increased so that the direct costs of power outages have risen signifi- cantly. Power outages can create dangerous and unsafe conditions as a result of failure of lighting, elevators, ventilation, fire pumps, security systems, communications systems, and the like. In addition, economic loss from outages can be extremely high as a result of computer downtime, or, especially in industrial process plants, interruption of production. Protective equipment must be adjusted and maintained in order to function properly when an overcurrent occurs, but coordination begins during power system design with the knowledgeable analysis and selection and application of each overcurrent protective device in the series circuit from the power source(s) to each load apparatus. The objective of coordination is to localize the overcurrent disturbance so that the protective device closest to the fault on the power-source side has the first chance to operate; but each preceding protective device upstream toward the power source should be capable, within its designed settings of current and time, to provide backup and de-energize the circuit if the fault persists. Sensitivity of coordination is the degree to which the protective devices can minimize the damage to the faulted equipment. To study and accomplish coordination requires (a) a one-line diagram, the roadmap of the power distribution system, showing all protective devices and the major or important distribution and utilization apparatus, (b) identifi- cation of desired degrees of power continuity or criticality of loads throughout system, (c) definition of operating-current characteristics (normal, peak, starting) of each
SSTs are likely to stay online while there‟s a good balance between load and PV generation. The results from the first simulation show that, with a good PV/load balance, the SST can feed the fault and still stay online and make the reclosing unsuccessful. So the SSTs need to be equipped with a reliable anti-islanding protection to detect this kind of situation and to disconnect from the grid as soon as the recloser opens. However the reclosing open interval should be coordinated with the anti-islanding protection speed to make sure that it‟s long enough to let the anti-islanding work.
Many authors contributed to Advanced Water Distribution Modeling and Manage- ment. Led by Tom Walski and the staff of Haestad Methods, they include Stephen Beckwith, Scott Cattran, Donald Chase, Walter Grayman, Rick Hammond, Edmundo Koelle, Kevin Laptos, Steven Lowry, Robert Mankowski, Stanley Plante, John Przy- byla, Dragan Savic, and Barbara Schmitz. Information on the individual authors and the chapters to which they contributed is provided in the next section, “Authors and Contributing Authors.” It is the synthesis of everyone’s ideas that really makes this book such a practical and helpful resource. Extra special thanks to the project editors, Kristen Dietrich and Colleen Totz, for their countless hours of hard work and dedica- tion to weave the information from many authors and reviewers into a cohesive and accessible textbook.
The new method of phase step removal presented here is reasonably successful in removing the phase steps. In the case of a low underlying ROCOF (assumed to be close to 0 Hz/s), the phase step spike was reduced from a peak of 107 Hz/s to a peak of about 3 Hz/s. In the case of a changing underlying frequency and phase step, the improvement is not so good, reducing the ROCOF spike peak from about 25 to about 6 Hz/s. As already pointed out with this proposed operational- ist solution, changing the algorithm parameters, will change the output and both results presented here are sensitive to algo- rithm configuration. The reported results should be considered an indication of what can be achieved with this method. It is possible that the method can be improved by using superior estimators and particularly better alignment of the estimator to the real data at switch over; the ROCOF algorithm being extremely sensitive to any phase step introduced at the point of switching from real data to estimator data and vice versa.
909.15 Control diagrams. Identical control diagrams show- ing all devices in the system and identifying their location and function shall be maintained current and kept on file with the fire code official, the fire department and in the fire command center in a format and manner approved by the fire chief. 909.16 Fire-fighter’s smoke control panel. A fire-fighter’s smoke control panel for fire department emergency response purposes only shall be provided and shall include manual con- trol or override of automatic control for mechanical smoke control systems. The panel shall be located in a fire command center complying with Section 508 in high-rise buildings or buildings with smoke-protected assembly seating. In all other buildings, the fire-fighter’s smoke control panel shall be installed in an approved location adjacent to the fire alarm con- trol panel. The fire-fighter’s smoke control panel shall comply with Sections 909.16.1 through 909.16.3.
909.1 Scope and purpose. This section applies to mechanical or passive smoke control systems when they are required for new buildings or portions thereof by provisions of the Interna- tional Building Code or this code. The purpose of this section is to establish minimum requirements for the design, installation and acceptance testing of smoke control systems that are intended to provide a tenable environment for the evacuation or relocation of occupants. These provisions are not intended for the preservation of contents, the timely restoration of opera- tions, or for assistance in fire suppression or overhaul activities. Smoke control systems regulated by this section serve a differ- ent purpose than the smoke- and heat-venting provisions found in Section 910. Mechanical smoke control systems shall not be considered exhaust systems under Chapter 5 of the Interna- tional Mechanical Code.
904.3.2 Actuation. Automatic fire-extinguishing systems shall be automatically actuated and provided with a manual means of actuation in accordance with Section 904.11.1. 904.3.3 System interlocking. Automatic equipment inter- locks with fuel shutoffs, ventilation controls, door closers, window shutters, conveyor openings, smoke and heat vents, and other features necessary for proper operation of the fire-extinguishing system shall be provided as required by the design and installation standard utilized for the hazard. 904.3.4 Alarms and warning signs. Where alarms are required to indicate the operation of automatic fire-extin- guishing systems, distinctive audible, visible alarms and warning signs shall be provided to warn of pending agent discharge. Where exposure to automatic-extinguishing agents poses a hazard to persons and a delay is required to ensure the evacuation of occupants before agent discharge, a separate warning signal shall be provided to alert occu- pants once agent discharge has begun. Audible signals shall be in accordance with Section 907.6.2.