Introduction to Practical Power System Protection. 7. Reliability. Above all else, relays must be reliable, both dependable and secure. This definition of reliability. Description. Plant operators, electricians, field technicians and engineers will gain a practical understanding of the role and workings of power system protection. emphasis throughout the book is on giving the reader an understanding of power system protection principles. The numerous practical details of relay system.
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Practical Power Distribution for Industry (Jan de Kock and Cobus Strauss) better appreciation of the role played by power system protection systems. Fundamentals of Power System Protection Y.G. Paithankar Formerly High- Frequency Trading: A Practical Guide to Algorithmic Strategies and Trading. Presents. Practical Power Systems Protection for. Engineers and Technicians. Revision Website: ronaldweinland.info E-mail: [email protected]
Practical power system protection practical professional books Pdf , Text File. Already registered? It provides coverage that includes both the fundamentals and the basic fault and design calculations needed to specify, use and maintain power protection systems. Although I have only scan read the book yet the practical approach followed in this book is meeting my expectations. Download it once and read it on your Kindle device, PC, phones or tablets.
Wide area relay protection has quickly become a hot research topic with many research results published particularly in recent years. Integrated protection With the development of digital technology, more and more protection functions for any given apparatus line, transformer, generator, etc.
For example, a numeric line protection relay may have distance or current differential function as the main protection, and directional and overcurrent functions as the backup protection.
The recent developments in microprocessor and communication techniques provided new means to derive new protection principles and schemes based on the information obtained from multiple power plants and components, which could have significant advantages over the existing protection techniques based on the individual plant or component [ 5 ].
There was also research in the field of integrated wide area protection [ 9 ]. Wide area control The increased deployment of wide-area measurements will significantly enhance the power system wide-area power system operation and control.
They provide voltage and current phasor information, synchronized with high precision to a common time reference provided by GPS. Therefore, a wide range of power system monitoring and control applications can be implemented in the system for improving system awareness and reliability, which includes enhanced state estimation based on mixed Remote Terminal Unit RTU and Phasor Measurement Unit PMU measurements [ 10 ], dynamic model online estimation and validation [ 11 ], real-time congestion management, real-time stability estimation [ 12 ], detection and damping of inter-area oscillations [ 13 ].
However, the most important and challengeable applications are the implementations of wide area stability real-time detection and control to prevent blackouts [ 14 ].
There was also research in the integrated protection and control [ 15 ]. New concept and development Based on the developments mentioned above, a new concept of the integrated wide area protection and control IWAPC has been proposed recently. The main focus of the concept [ 16 , 17 ] is the integration between the protection and control, particularly at the wide-area or regional level, aimed to provide a number of benefits to the future protection and control system, e.
The information platform also supports the application of a cloud computing system, which is specially designed to implement a number of secondary functions for substations and power networks.
In addition to the basic functions of relay protection, the platform should have a large capacity of fault information and data storage, fast data processing functions, powerful communication functions, and other protection, control devices and scheduling network to share the whole system data, information and network resources, and can also carry out remote monitoring with the computer monitoring system of substation communication. With the proposed platform, the architecture of future substation equipment may be reshaped to provide a flexible framework for building an interactive grid and subsequently improve the reliability and security of power grids.
There have been fast developments in both power transmission and distribution networks, e. These new developments result in far more complicated characteristics than that of conventional systems. Consequently, the existing protection and control system will no longer be effective to cope with the new systems, and this has led to the proposed IWAPC system.
As is shown, the IWAPC system consists of different equipment at different layers: from bottom to top, there is the integrated multiple-function intelligent equipment at the local level; the substation communication network and the integrated substation protection and control at the substation level; the wide area communication network, the integrated wide area information platform and the integrated wide area regional protection and control at wide area level.
The key parts of the system are the high-speed wide area communication network and the real-time synchronisation information platform. Multiple functions intelligent equipment at the local level As shown in Fig. It has a redundant configuration to ensure reliability, together with other integrated functions such as fault recorder, data storage and network analysis, etc.
It utilizes information from the entire substation to achieve substation backup protection and safety automatic control, etc. The CBs are used as units to configure the adaptive backup protection, and current differential protection is used to replace the stage overcurrent protection, breaker failure protection and dead zone protection in the conventional protection system.
In addition, they both integrate functions of automatic UFLS and UVLS, voltage and frequency control, oscillation detection and out-of-step separation, etc. Unlike conventional protection and control, which are separated in both design and operation, the IWAPC integrates protection and control into one optimal combined system, which effectively coordinates the wide area regional protection and control, in order to achieve significant improvements in the protection and control of power systems.
Synchronised high speed communication network One of the most important elements of the IWAPC system is the fast communication network. In this respect, the latest development in communication network, the Packet Transport Network PTN may be a better choice to implement such a task.
The present power communication network is mainly used in multi-service transport platform based on the Synchronous Digital Hierarchy SDH. Its advantages lie in its high efficiency for carrying TDM services, low latency, high reliability, with end management capabilities. However, with the new trends in smart grid development, SDH technology gradually revealed its limitations, such as low bearing efficiency and poor flexibility for data services.
In contrast, PTN can realise statistical multiplexing and efficient transfer of packet service by using packet-switched core, which can overcome the weaknesses of SDH rigid bandwidth.
In addition, it can provide good quality of service, operation, administration and maintenance. Self-healing fibre optical network is employed to connect a number of substations in the region, to ensure full sharing of dynamic and transient information for all electrical measurements, breaker status and protection operations; using high reliability IEEE technology to ensure the synchronization timing of the sharing data, to prove the data for the integrated wide area protection and control.
However, SDH is still an option for the task since it has been widely applied in power network. Synchronized information platform Substation is installed with a wide range of electrical equipment with complex designs and is difficult to maintain. With the continuing improvement in power system automation and the intelligence level, the system network has been expanding, along with the huge amount of information in protection and control.
As each piece of information is collected and stored by different devices in each separate system, the interoperability of the internal power system data between systems is poor, whereas complex communication protocols tend to create information islands.
Consequently, the measurement data and protection control mechanism cannot be shared, which restricts the information integration.
The protection and control of smart grid requires dealing with the new situation demands of the application, in order to improve further the information platform capabilities for the future development of key technologies, and to make the information platform system more open.
The real-time synchronized information platform accurately collects wide area information and conducts data mining to investigate the logic relation between the real-time information to increase the sensitivity, reliability and fault tolerance capability. The data received from the platform includes static, dynamic, transient measurements and states of circuit breakers, etc.
Valuable information is extracted from the data and allocated to various specially-designed computation algorithms in the platform to perform advanced functions of protection and control for the power network. In the platform, sets of data need to be transferred and their transferring speed depends on the application, e. The information can also include other types of data, such as the oil and ambient temperature of the transformer, wind speed and direction, sun intensity, etc.
On the other hand, the information is stored in a hierarchical manner instead of a centralized one, which comprises the hierarchical protection and control system. Equipped with the latest high-speed synchronised communication technology, integrated with the advanced protection techniques and the latest developments in control system, the system offers not only fast protection, but also complete control of entire power network.
The advanced computing technology is introduced to establish a synchronized information platform for wide area protection and control, to build a panoramic operation and maintenance data collection network, providing a standardized interface to the terminal device, to form a resource sharing, flexible and interactive, open and ordered information platform. In summary, advanced computing technologies are used to build a distributed collaborative intelligent information platform, simplifying terminal data collection equipment, and breaking the barriers between protection and control systems at different substations through the specially designed synchronized information platform.
Wide area power cloud Based on the information platform mentioned above, a distributed cloud system is designed to implement functions at substation and regional levels, such as wide area fault location, fault line selection, power quality monitoring, protection settings, etc.
The extended functions also include the equipment monitoring, life cycle and operation management, as shown in Fig. The cloud at substation level receives the data from process level, and the regional cloud receives the data from the information platform, which includes static, dynamic, transient measurements and states of circuit breakers, extracting valuable information and allocating them to various specially-designed computation algorithms in the platform to perform advanced functions in order to identify the faulted line, the accurate fault location and the contents of harmonics, etc.
Based on big data technique, the computing clouds enjoy strong processing power based on demand. There is no need for endless upgrades to improve the processing capacity of the equipment, and there is also no need to update the software to achieve a variety of task processing.
There are many more advantages which can be derived from the cloud system, such as the wide area information sharing, standardization of software and algorithm, reduction of equipment investment, substation area occupation and work load for operation and maintenance. Conclusions This paper presents an integrated wide area protection and control system based on a hierarchical structure, which integrates protection and control at local, substation and regional levels.
Covering both transmission and distribution networks, the system is supported by the proposed high-speed synchronised communication network and the real-time protection and control information platform. The system, which integrates the advanced protection techniques and the latest developments in control system, offers not only fast protection, but also complete control of the entire power network. It offers a potential for the merger of the three lines of defence into a unified system to ensure more effectively the reliable and safe operation of power grid.
Based on the system information platform, a distributed power cloud system is also designed to support many advanced applications for the integrated wide area protection and control. With the continuous advances in measurement, communication and information technologies, the system presents a bright future for practical application. Overall improved performance of protection and control can be expected from the proposed system. However, for the system to become useful in power system application, it is equally important that its practical implementation be readily manageable, user-friendly and cost-effective.
There are three parts of protective devices: Instrument transformer : current or potential CT or VT Circuit breaker Advantages of protected devices with these three basic components include safety, economy, and accuracy.
Economy: Relays are able to be simpler, smaller, and cheaper given lower-level relay inputs. Accuracy: Power system voltages and currents are accurately reproduced by instrument transformers over large operating ranges. Types of protection High-voltage transmission network Protection on the transmission and distribution serves two functions: Protection of plant and protection of the public including employees. At a basic level, protection looks to disconnect equipment which experience an overload or a short to earth.
Some items in substations such as transformers might require additional protection based on temperature or gas pressure, among others. Generator sets In a power plant, the protective relays are intended to prevent damage to alternators or to the transformers in case of abnormal conditions of operation, due to internal failures, as well as insulating failures or regulation malfunctions. Such failures are unusual, so the protective relays have to operate very rarely.
If a protective relay fails to detect a fault, the resulting damage to the alternator or to the transformer might require costly equipment repairs or replacement, as well as income loss from the inability to produce and sell energy.
Overload and back-up for distance overcurrent Overload protection requires a current transformer which simply measures the current in a circuit. There are two types of overload protection: instantaneous overcurrent and time overcurrent TOC. Instantaneous overcurrent requires that the current exceeds a predetermined level for the circuit breaker to operate. TOC protection operates based on a current vs time curve. Based on this curve if the measured current exceeds a given level for the preset amount of time, the circuit breaker or fuse will operate.
Earth fault "ground fault" in the United States Earth fault protection again requires current transformers and senses an imbalance in a three-phase circuit.
Normally the three phase currents are in balance, i. If one or two phases become connected to earth via a low impedance path, their magnitudes will increase dramatically, as will current imbalance.
If this imbalance exceeds a pre-determined value, a circuit breaker should operate. Restricted earth fault protection is a type of earth fault protection which looks for earth fault between two sets current transformers  hence restricted to that zone.
Distance impedance relay Distance protection detects both voltage and current. A fault on a circuit will generally create a sag in the voltage level. If the ratio of voltage to current measured at the relay terminals, which equates to an impedance, lands within a predetermined level the circuit breaker will operate.
This is useful for reasonable length lines, lines longer than 10 miles, because its operating characteristics are based on the line characteristics. This means that when a fault appears on the line the impedance setting in the relay is compared to the apparent impedance of the line from the relay terminals to the fault. If the relay setting is determined to be below the apparent impedance it is determined that the fault is within the zone of protection.
When the transmission line length is too short, less than 10 miles, distance protection becomes more difficult to coordinate. In these instances the best choice of protection is current differential protection. Back-up The objective of protection is to remove only the affected portion of plant and nothing else. A circuit breaker or protection relay may fail to operate. In important systems, a failure of primary protection will usually result in the operation of back-up protection. Remote back-up protection will generally remove both the affected and unaffected items of plant to clear the fault.
Local back-up protection will remove the affected items of the plant to clear the fault. Low-voltage networks The low-voltage network generally relies upon fuses or low-voltage circuit breakers to remove both overload and earth faults.
Coordination Protective device coordination is the process of determining the "best fit" timing of current interruption when abnormal electrical conditions occur.