Paul Myrda

Grid Modernization: Seamless Integration of Protection, Optimization and Control

The objectives of smart grid and grid modernization are to increase automation and seamlessly integrate data, models, protection, optimization and control of the power grid. This effort is affected by technological advances. One such technology is the numerical relay which has increased its domination to the point that today has almost completely displaced electromechanical and solid state relays and the most recent technology of merging units that has separated the data acquisition function from protective relays and SCADA systems. The capabilities of the numerical relays are not fully utilized today, specifically, by and large, they simply mimic the logics that were developed for the electromechanical relays but with much more flexibility. Recent developments towards substation automation are utilizing the numerical relays for SCADA, communications and in general an integrated system for protection and control. These approaches indicate the recognition that numerical relays offer much more than simply mimicking protection functions of the past. They also offer the ability to form the basic infrastructure towards a fully automated power system, the subject of this paper. In previous work, we presented a new protection scheme that is a generalization of differential protection. The approach is based on dynamic state estimation. Specifically, the protection scheme is based on continuously monitoring terminal voltages and currents of the component and other possible quantities such as tap setting, temperature, etc. as appropriate for the component under protection. The monitored data are utilized in a dynamic state estimation that continuously provides the dynamic state of the component. The dynamic state is then used to determine the health of the component. Tripping or no tripping is decided on the basis of the health of the component. The present paper takes the above concept one step further. Using the dynamic state estimation of a protection zone as the basic technology, it builds an integrated automation system that performs the protection functions, validates models, transmits the models to the control center, integrates monitoring and control, enables optimization and provides automated disturbance playback capabilities. The system provides the infrastructure and real time models for any application along the spatial extend of the power system.

Integration & automation: From protection to advanced energy management systems

This paper proposes an integrated and seamless infrastructure for protection, control and operation of an electric power system. At the lower level we propose a on dynamic state estimation of a protection zone for the purpose of providing protection for the zone. This scheme simplifies the protection approach for the zone by not requiring coordination with other protection zones (setting-less protection). The scheme provides the real time dynamic model of the zone as well as the real time operating conditions. The scheme can be also implemented in present day numerical relays with GPS synchronization. Using this basic protection infrastructure, we propose that the real time model of substation be autonomously created, send to the control center where the real time model of the system is also autonomously created. The system wide real time model is used to perform system optimization functions, and then send commands back through the same communication structure to specific power system components. Since protection is present in any power apparatus the proposed approach is realizable with very small investment. The availability of the real time dynamic state of the system enables the seamless integration of applications in the proposed system. Three applications are discussed in the paper: (a) setting-less protection, (b) stability monitoring, and (c) voltage/var control.

Dynamic State Estimation-Based Protection: Status and Promise

The introduction of the microprocessor-based numerical relay in the 1980s resulted in multifunctional, multidimensional, communications-enabled complex protection systems for zone and system protection. The increasing capabilities of this technology created new unintended challenges: 1) complexity has increased and selecting coordinated settings is a challenge leading to occasional miscoordination; 2) protection functions still rely on a small number of measurements (typically three voltages and three currents) limiting the ability of protection functions to dependably identify the type of fault conditions; and 3) present approaches are incapable of dealing with hidden failures in the protection system. Statistically, 10% of protection operations are misoperations. This paper presents a new approach to protection that promises to eliminate the majority of the problems that lead to misoperations. The approach is described, demonstrated in the laboratory, compared to traditional protection functions and its application to a substation coordinated protection system capable of detecting and dealing with hidden failures is described. This paper also discusses the planned field testing of the approach.

Protection and Control of Systems with Converter Interfaced Generation (CIG)

The protection of converter interfaced generation and associated circuits and components is challenging due to (a) insufficient separation between fault and load currents caused by converter interfaced sources, (b) large fault contributions from utility side -- small fault contributions from inverter based sources and (c) requirement to operate in utility connected mode as well as islanded mode. These issues are common for wind systems, PV systems and μGrids. They are addressed with the proposed dynamic state Estimation Based Protection (EBP) method applied to each component of a converter interfaced system and associated components. The paper discusses the issues, presents the EBP method and the integration of the method with the inverter controls for the purpose of increasing the reliability of these systems. Several examples are provided which compare the proposed method with traditional protection functions.

Cyber Security and Operational Reliability

This paper presents a new proposed infrastructure that enables simultaneous cyber security and operational security. The basis of the method is command interception and fast authentication from the cyber security point of view (reliable detection of cyber intrusions) and from the operational reliability point of view. To simplify the process, the command authentication is done at the relay level and relay controls. As such it does not depend on the communication architecture. The method is based on new developments on dynamic state estimation based protection and substation level distributed state estimation. This infrastructure provides the capability to monitor, intercept, and authenticate/block commands as they reach the relay and the control circuits of the relay. Since all controls are exercise through a relay, this approach provides 100% coverage. The authentication/blockage of commands is done quickly because of the distributed approach which enables quick assembly of a local real time model and fast analytics with this local model. Specifically, for each command the proper local real time model is constructed and quickly analyzed to determine the effects on the power system. The analytics determine the effect of the command, if executed, on the system and in particular on the operational reliability of the system. In case of a command that may have adverse effects on the operational reliability of the system, the command will be blocked and the operator will be alerted. In addition to the command authentication at the relay level, an open-source real-time network monitoring system for capturing and parsing network traffic is presented. Because the method is based on the substation level dynamic state estimator which uses only local substation level measurements and data, a byzantine type attack is not considered possible for the proposed approach. Finally, a discussion on the architecture required to integrate the network monitoring and state estimation systems is presented. The methodology is presently being tested in a laboratory setup that includes a digital simulator of the electric power system and hardware in the loop.

System-Wide Replacement Strategy for Substation Protection and Automation Systems

The protection and control systems in the US utility industry are still primarily composed of electromechanical relays and systems. Over 80 percent of the relays are still electromechanical at Michigan Electric Transmission Company (METC), with only incremental upgrading to microprocessor technology carried out in recent years. Maintenance costs of older equipment are high, and limited non-operational fault data is accessed via modem from the microprocessor relays. METC embarked on a program to develop a business and technical strategy to replace the aging protection and control equipment. This paper describes how an aggressive replacement strategy can be the most cost-effective solution for system-wide upgrading. This strategy and its benefits (from both reliability and financial perspectives) are described using the program to completely replace the protection and control equipment in all 82 of its substations. METC is developing enterprise-level processing of the masses of data to improve operational and business efficiency.

Breaker to Control Center Integration & Automation: Protection, Control, Operation & Optimization

Recent technological advances in protection, control and optimization are enabling a more automated power system. This paper proposes the use of these technologies towards an integrated and seamless infrastructure for protection, control and operation. This infrastructure is the basis for accommodating and providing robust solutions to new problems arising from the integration of renewables, namely more uncertainty and steeper ramp rates. At the lower level we propose a dynamic state estimation of a protection zone (EBP) for the purpose of providing protection for the zone. The estimation based protection (EBP) provides the real time dynamic model of the zone as well as the real time operating conditions. Since protection is ubiquitous, it can cover the full system. We assume that GPS synchronization of the EBP is available providing accurate time tags for the real time model and operating conditions. The real time model and operating conditions can extent from the “turbine to the toaster”. We propose a methodology for automatically constructing the power system state locally and centrally at the control center with distributed controls as well as centralized controls depending on the application. For example, the centralized system wide real time model is used to perform system optimization functions, and then send commands back through the same communication structure to specific power system components. Since protection is ubiquitous and the modern power system has several layers of communication infrastructure, the proposed approach is realizable with very small investment. The availability of the real time dynamic model and state locally and centrally enables the seamless integration of applications. Three applications are discussed in the paper: (a) settingless protection, (b) voltage/var control and (c) feeder load flexibility scheduling. The proposed approach and infrastructure can form the basis for the next generation of Energy Management Systems.