Alexander Apostolov

Superimposed components based sub-cycle protection of transmission lines

Requirements for improvements of system stability and reduction in the effects of shunt type faults in transmission and bulk systems on sensitive industrial loads result in the development of protection relays with sub-cycle operating times. At the same time the relays have to be stable under wide area disturbance conditions. The paper discusses in detail the concept of superimposed components and their application for directional detection, faulted phase selection and power swing detection. Complex distance characteristics can be used to provide sufficient resistive reach to cover the expected range of fault arc resistances, while at the same time are not affected by encroachment of the load impedance in the distance characteristic. Direct relay-to-relay communications allow the implementation of high-speed directional comparison protection.

Protection of Double Circuit Transmission Lines

This paper describes different cases of parallel transmission lines and analyzes some well known application problems associated with their protection. Distance protection performance problems are in the focus due to the fact that they are the most commonly used protection type for parallel transmission lines. The behavior of ground overcurrent protection on double circuit applications is also discussed in the paper. Finally, some advanced features of communications assisted schemes, non-communications protection schemes and fault location for double circuit lines are discussed

Impact of IEC 61850 on Power System Protection

IEC 61850 is a new international standard for communication networks and systems in substations that has a significant impact on the developments in power system protection. It allows the implementation of high-speed peer-to-peer communications based applications, as well as distributed protection solutions using sampled analog values. The paper describes the principles of different IEC 61850 communications based protection functions and analyses the factors that will affect their performance. It also discusses the advantages of distributed applications based on high-speed peer-to-peer communications compared with conventional hard wired schemes. Examples of comparison testing are presented at the end of the paper

Multi-agent systems and IEC 61850

IEC 61850 is an approved international standard for substation communications that is becoming the foundation of a new generation of substation automation systems. At the same time multi-agent systems are being considered for many different utility applications. The paper presents and overview of the new IEC 61850 standard and some of its applications. It attempts to demonstrate the relationship between the concepts in the standard and how they can be used in different multi-agent systems for protection, control, monitoring and recording in substations. The substation configuration language is also analyzed as a tool that identifies the relationships between the different components in a multi-agent based substation automation system

IEC 61850 GOOSE applications to distribution protection schemes

The industry is going through significant changes due to the increased requirements for improved quality of power supplied by the utility in order to avoid costly interruptions of manufacturing or other processes caused by voltage sags, swells or unbalanced conditions when a short circuit fault occurs in the distribution system.

Advanced distance protection applications fot dynamic loading and out-of step condition

Distance relays have been successfully used for many years as the most common type of protection of transmission lines. The development of electromechanical and solid state relays with mho characteristics can be considered as an important factor in the wide spread acceptance of this type of protection at different voltage levels all over the world. Zone 1 of distance relays is used to provide primary highspeed protection of a significant portion of the transmission line. Zone 2 is used to cover the rest of the protected line and provide some backup for the remote end bus. Zone 3 is the backup protection for all the lines connected to the remote end bus. The experience from the North American blackout in August 2003, as well as the recent European disturbance in November 2006 demonstrated the importance that the behavior of many distance relays had during the dynamic loading at different stages of the disturbance and the out-of-step conditions that followed in some areas The implementation of distance relays requires understanding of its operating principles, as well as the factors that affect the performance of the device under different abnormal conditions. The paper analyzes different methods for resolving the load encroachment of the apparent impedance into the distance characteristic as a result of dynamic loading and the detection of faults at that time. Another important issue is the operation of distance relays during stable or unstable out-of-step conditions. Depending on the location of the distance relays in the system and the type of event the relays may use blocking of the selected distance elements or tripping if separation is required.

IEC 61850 process bus based distributed waveform recording

IEC 61850 is the new standard for communications in substations that defines process bus and substation bus communications allowing the development of distributed waveform recording systems. The paper describes the different components of such systems and the distribution of functions between the devices included in it. Multiple merging units communicate over a 100 Mb Ethernet with a central computer that receives and records current and voltage waveforms with a sampling rate of 256 samples/cycle. The samples from the different merging units is saved as a combined single COMTRADE file. The architecture of the system, triggering criteria, system performance and analysis tools are described in the paper

Adaptive protection of distribution feeders

Adaptive protection of distribution feeders is a powerful tool for reducing the fault clearing time and improving the quality of service. The paper describes adaptive features in multifunctional Intelligent Electronic Devices (IEDs), as well as distribution protection schemes that adapt to changing substation and system conditions.

Simplifying the configuration of multifunctional protection relays

The paper analyzes the functionality of state-of-the-art protection relays and presents solutions that simplify their configuration. Visibility control and graphical user interface are some of the tools that can help reduce engineering time and probability for costly errors. Some features that automatically calculate relay settings are also described in the paper. IEC 61850 related configuration settings are also discussed.

Requirements for testing of power swing blocking functions in protection IEDs

The 2003 North American blackout demonstrated the importance of power swing detection, blocking and tripping for the development of a wide area disturbance into a system-wide blackout.