Data from phasor measurement units (PMUs) inform powerful diagnostic tools that can help avert catastrophic failures in the power grid. Because of this, understanding PMU measurement errors is particularly valuable. This paper examines internal and external factors contributing to PMU phase angle and frequency measurement errors and gives a reasonable explanation for each. Based on these explanations, the impact of those measurement errors on several synchrophasor applications are analyzed: event location detection, oscillation detection, islanding detection, and dynamic line rating.

This paper analyzes the theoretical accuracy limitation of synchrophasors measurements on phase angle and frequency of the power grid. Factors that cause the measurement error are analyzed, including error sources in the instruments and in the power grid signal. Different scenarios of these factors are evaluated according to the normal operation status of power grid measurement. Based on the evaluation and simulation, the errors of phase angle and frequency caused by each factor are calculated and discussed.

This paper provides a summary of eight instrumentation and control (&C) technology areas, with applications in nuclear power plants (NPPs), that were the focus of a recent study performed by Oak Ridge National Laboratory (ORNL) for the Nuclear Regulatory Commission (NRC.) The state of the technology s application in NPPs, along with potential regulatory impact(s), are discussed. The technology focus areas are: (1) sensors and measurement systems, (2) communications media and networking, (3) microprocessors and other integrated circuits, (4) computational platforms, (5) surveillance, diagnostics, and prognostics, (6) human-system interactions, (7) high-integrity software, and (8) I&C architectures in new plants. The regulatory implications of these focus areas with regard to their application in NPPs are also discussed.

- Oak Ridge National Laboratory (ORNL) was engaged by the U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research (RES) to develop the technical basis for regulatory guidance to address design and implementation practices for lightning protection systems in nuclear power plants (NPPs). Lightning protection is becoming increasingly important with the advent of digital and low-voltage analog systems in NPPs. These systems have the potential to be more vulnerable than older analog systems to the resulting power surges and electromagnetic interference (EMI) when lightning strikes facilities or power lines. This paper discusses the technical basis for guidance to licensees and applicants covered in Regulatory Guide (RG) 1.204, Guidelines for Lightning Protection of Nuclear Power Plants, issued August 2005. RG 1.204 describes guidance for practices that are acceptable to the NRC staff for protecting nuclear power structures and systems from direct lightning strikes and the resulting secondary effects.

Currently, wireless technology is not used as an integral element of safety-related systems in nuclear facilities. The most prevalent introductory uses of wireless technology are for in-facility communications among personnel and for supplemental information transmission. However, further system upgrades and implementations at new facilities might introduce wireless communications into safety-significant applications. This paper documents the deployment issues and implementation considerations that can contribute to the technical basis for guidance on wireless systems. (authors)

This paper describes the underlying basis for guidance on the protection of nuclear power systems from direct lightning strikes to facilities and resulting transient effects. Oak Ridge National Laboratory has been engaged by the U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research to develop a technical basis for guidance to address design and implementation practices for lightning protection systems in nuclear power plants (NPPs). Lightning protection is becoming increasingly important given the use of digital and low-voltage-analog systems in NPPs. Although these modern systems have advantages and useful features, they have the potential to be more vulnerable than older, analog systems to the power surges and electromagnetic interference that result when lightning strikes facilities or power lines.

This document presents recommendations and the associated technical basis for addressing the effects of conducted electromagnetic interference (EMI) and radio-frequency interference (RFI) along interconnecting signal lines in safety-related instrumentation and control (I&C) systems. Oak Ridge National Laboratory has been engaged in assisting the U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research in developing the technical basis for regulatory guidance on EMIIRFI immunity and power surge withstand capability (SWC). Previous research efforts have provided recommendations on (1) electromagnetic compatibility design and installation practices, (2) the endorsement of EMI/RFI and SWC test criteria and test methods, (3) the determination of ambient electromagnetic conditions at nuclear power plants, and (4) the development of recommended electromagnetic operating envelopes applicable to locations where safety-related I&C systems will be installed. The current research focuses on the susceptibility of l&C systems to conducted EMIIRFI along interconnecting signal lines. Coverage of signal line susceptibility was identified as an open issue in previous research on establishing the technical basis for EMIIRFI and SWC in safety-related I&C systems. Research results provided in this report will be used to establish the technical basis for endorsing U.S. Department of Defense and European Committee for Electrotechnical Standardization test criteria and test methods that address signal-line susceptibility. In addition, recommendations on operating envelopes are presented based on available technical information.

The Oak Ridge National Laboratory (ORNL) has been engaged by the U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research to assist in developing the technical basis for regulatory guidance on electromagnetic interference (EMI) and radio-frequency interference (RFI) immunity and power surge withstand capability (SWC). Previous research has provided recommendations on electromagnetic compatibility (EMC) design and installation practices, endorsement of EMII/RFI immunity and SWC test criteria and test methods, and determination of ambient electromagnetic conditions at nuclear power plants. These recommendations have been incorporated into the technical basis for guidance in addressing EMI/RFI and power surges in safety-related instrumentation and control (I&C) systems in nuclear power plants. The recommendations by the ORNL staff on test criteria, test methods, and operating envelopes were significantly influenced by the military standards issued by the U.S. Department of Defense (DOD). That is the case because until recently there were no comprehensive commercial standards that covered EMI/RFI immunity. The present research involves reviewing and assessing the commercial standards issued by the International Electrotechnical Commission (IEC) and endorsed by the European Union in the last few years. This document reports the results of a study performed by the ORNL staff comparing Regulatory Guide 1.180, the U.S. military standards, and international EMC guidance.

This paper discusses the regulatory guidance implemented by U.S. NRC for minimizing malfunctions and upsets in safety-related instrumentation and control (I and C) systems in nuclear power plants caused by electromagnetic interference (EMI), radio-frequency interference (RFI), and power surges. The engineering design, installation, and testing practices deemed acceptable to U.S. NRC are described in Regulatory Guide (RG) 1.180, ''Guidelines for Evaluating Electromagnetic and Radio-Frequency in Safety-Related Instrumentation and Control Systems'' (January 2000) and in a Safety Evaluation Report (SER) endorsing EPRI TR-102323, ''Guidelines for Electromagnetic Interference Testing in Power Plants,'' (April 1996). These engineering practices provide a well-established, systematic approach for ensuring electromagnetic compatibility (EMC) and surge withstand capability (SWC).

Electromagnetic compatibility (EMC) has long been a key element of qualification for mission critical instrumentation and control (I&C) systems used by the U.S. military. The potential for disruption of safety-related I&C systems by electromagnetic interference (EMI), radio-frequency interference (RFI), or power surges is also an issue of concern for the nuclear industry. Experimental investigations of the potential vulnerability of advanced safety systems to EMI/RFI, coupled with studies of reported events at nuclear power plants (NPPs) that are attributed to EMI/RFI, confirm the safety significance of EMC for both analog and digital technology. As a result, Oak Ridge National Laboratory has been engaged in the development of the technical basis for guidance that addresses EMC for safety-related I&C systems in NPPs. This research has involved the identification of engineering practices to minimize the potential impact of EMI/RFI and power surges and an evaluation of the ambient electromagnetic environment at NPPs to tailor those practices for use by the nuclear industry. Recommendations for EMC guidance have been derived from these research findings and are summarized in this paper.

This paper presents progress to date of an NRC-sponsored confirmatory research program initiated to address hardware issues associated with the use of safety-related digital instrumentation and control (I&C) hardware in nuclear power plants. In particular, the potential vulnerability of digital technology to environmental stress effects and means for establishing environmental compatibility for digital I&C systems were studied. The research approach involved evaluating existing military and industrial guidance, identifying the most significant environmental stressors and, for advanced I&C systems in nuclear power plants, investigating the likely failure modes-both at the integrated circuit and system level-for digital technologies under varying levels of environmental stress. Environmental stressors used in the studies included smoke exposure, electromagnetic and radio-frequency interference (EMI/RFI), temperature, and humidity. The insights gained from these studies are being used to recommend appropriate methods for qualifying safety-related digital equipment in nuclear power plants. To characterize the EMI/RFI environment at current LWRs and to estimate the expected environment at ALWRs, ORNL conducted a long-term survey of ambient electromagnetic conditions at several nuclear power plants. A representative sampling of power plant conditions (reactor type, operating mode, site location) were monitored over extended observation periods (e.g., continuous measurements for up to 5 weeks at a single location) were selected to more completely determine the characteristic electromagnetic environment for nuclear power plants. The results of this study contributed to the technical basis for a Nuclear Regulatory Commission Draft Regulatory Guide (DG-1029) issued for comment in 1998. (C) 1999 Published by Elsevier Science S.A. All rights reserved.

This paper presents results to date of an NRC-sponsored confirmatory research program initiated at three national laboratories to address environmental compatibility/qualification concerns associated with the use of microprocessor-based safety-related instrumentation and control (I and C) systems in nuclear power plants. The research approach involved evaluating existing military and industrial guidance, identifying the most significant environmental stressors and, for advanced I and C systems in a nuclear power plant, investigating the likely failure modes--both at the integrated circuit and system level--for digital technologies under varying levels of environmental stress (such as smoke exposure and electromagnetic and radio-frequency interference). The insights gained from these studies are being used to recommend appropriate methods for qualifying safety-related digital equipment in nuclear power plants.

This document presents recommendations for electromagnetic operating envelopes to augment test criteria and test methods addressing electromagnetic interference (EMI), radio-frequency interference (RFI), and power surges that are applicable to safety-related instrumentation and control (I and C) systems in nuclear power plants. The Oak Ridge National Laboratory (ORNL) was engaged by the US Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research to assist in developing the technical basis for regulatory guidance on EMI/RFI immunity and power surge withstand capability (SWC). Previous research has provided recommendations on electromagnetic compatibility (EMC) design and installation practices, endorsement of EMI/RFI immunity and SWC test criteria and test methods, and determination of ambient electromagnetic conditions at nuclear power plants. The present research involves development of recommended electromagnetic envelopes that are applicable to nuclear power plant locations where safety-related I and C systems either are or may be installed. These recommended envelopes establish both emissions criteria and the levels of radiated and conducted interference that I and C systems should be able to withstand without upset or malfunction. The EMI/RFI operating envelopes are derived from conditions in comparable military environments and are confirmed by comparison with the nuclear power plant electromagnetic environment based on measured plant emissions profiles. Detailed information on specific power surge conditions in nuclear power plants is not available, so industrial guidance on representative surge characteristics for susceptibility testing is adopted. An engineering assessment of the power surge environment in nuclear power plants leads to the recommendation of operating envelopes based on location categories and exposure levels defined in IEEE Std C62.41-1991, IEEE Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits.

This document reports the results of a survey of ambient electromagnetic conditions in representative nuclear power plants. The U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research engaged the Oak Ridge National Laboratory (ORNL) to perform these measurements to characterize the electromagnetic interference (EMI) and radio-frequency interference (RFI) levels that can be expected in nuclear power plant environments. This survey is the first of its kind, being based on long-term unattended observations. The data presented in this report were measured at eight different nuclear units and required 14 months to collect. A representative sampling of power plant conditions (reactor type, operating mode, site location) monitored over extended observation periods (up to 5 weeks) were selected to more completely determine the characteristic electromagnetic environment for nuclear power plants. Radiated electric fields were measured over the frequency range of 5 MHz to 8 GHz. Radiated magnetic fields and conducted EMI events were measured over the frequency range of 305 Hz to 5 MHz. Highest strength observations of the electromagnetic ambient environment across all measurement conditions at each site provide frequency-dependent profiles for EMI/RFI levels in nuclear power plants.

This report discusses the development of the technical basis for the control of upsets and malfunctions in safety-related instrumentation and control (I&C) systems caused by electromagnetic and radio-frequency interference (EMI/RFI) and power surges. The research was performed at the Oak Ridge National Laboratory (ORNL) and was sponsored by the USNRC Office of Nuclear Regulatory Research (RES). The motivation for research stems from the safety-related issues that need to be addressed with the application of advanced I&C systems to nuclear power plants. Development of the technical basis centered around establishing good engineering practices to ensure that sufficient levels of electromagnetic compatibility (EMC) are maintained between the nuclear power plant`s electronic and electromechanical systems known to be the source(s) of EMI/RFI and power surges. First, good EMC design and installation practices need to be established to control the impact of interference sources on nearby circuits and systems. These EMC good practices include circuit layouts, terminations, filtering, grounding, bonding, shielding, and adequate physical separation. Second, an EMI/RFI test and evaluation program needs to be established to outline the tests to be performed, the associated test methods to be followed, and carefully formulated acceptance criteria based on the intended environment to ensure that the circuit or system under test meets the recommended guidelines. Third, a program needs to be developed to perform confirmatory tests and evaluate the surge withstand capability (SWC) and of I&C equipment connected to or installed in the vicinity of power circuits within the nuclear power plant. By following these three steps, the design and operability of safety-related I&C systems against EMI/RFI and power surges can be evaluated, acceptance criteria can be developed, and appropriate regulatory guidance can be provided.

This paper discusses the development of the technical basis for acceptance criteria applicable to the immunization of digital systems against electromagnetic interference (EMI). The work is sponsored by the US Nuclear Regulatory Commission and stems from the safety-related issues that need to be addressed as a result of the application of digital instrumentation and control systems in nuclear power plants. Designers of digital circuits are incorporating increasingly higher clock frequencies and lower logic level voltages, thereby leading to potentially greater susceptibility of spurious interference being misinterpreted as legitimate logic. Development of the technical basis for acceptance criteria to apply to these digital systems centers around establishing good engineering practices to ensure that sufficient levels of electromagnetic compatibility (EMC) are maintained between the nuclear power plant`s electronic and electromechanical systems. First, good EMC design and installation practices are needed to control the emissions from interference sources and thereby their impact on other nearby circuits and systems. Second, a verification and validation (V&V) program is needed to outline the EMI tests to be performed, the associated test methods to be followed, and adequate acceptance criteria to ensure that the circuit or system under test meets the recommended guidelines. V&V should be followed more » by periodic maintenance to assess whether the recommended EMI control practices continue to be adhered to as part of the routine operation of the nuclear power plant. By following these steps, the probability of encountering safety-related instrumentation susceptibility attributable to EMI will be greatly reduced. « less

This paper discusses the development of the technical basis for acceptance criteria applicable to the immunization of digital systems against electromagnetic interference (EMI). The work is sponsored by the US Nuclear Regulatory Commission and stems from the safety-related issues that need to be addressed as a result of the application of digital instrumentation and control systems in nuclear power plants. Designers of digital circuits are incorporating increasingly higher clock frequencies and lower logic level voltages, thereby leading to potentially greater susceptibility of spurious interference being misinterpreted as legitimate logic. Development of the technical basis for acceptance criteria to apply to these digital systems centers around establishing good engineering practices to ensure that sufficient levels of electromagnetic compatibility (EMC) are maintained between the nuclear power plant's electronic and electromechanical systems. First, good EMC design and installation practices are needed to control the emissions from interference sources and thereby their impact on other nearby circuits and systems. Secondly, a test and evaluation program is needed to outline the EMI tests to be performed, the associated test methods to be followed, and adequate test limits to ensure that the circuit or system under test meets the recommended guidelines. Test and evaluation should bemore » followed by periodic maintenance to assess whether the recommended EMI control practices continue to be adhered to as part of the routine operation of the nuclear power plant. By following these steps, the probability of encountering safety-related instrumentation problems associated with EMI will be greatly reduced.« less

Equations are derived for determining the time constants of the double exponential impulse from the commonly used parameters for several standard test impulses. A resistor-capacitor (RC) circuit is synthesized that will produce the desired impulse. The prototype network is realized through a computer-aided design (CAD) procedure using Cauer's RC ladder two-port synthesis method. Descriptions of prototype circuits and test data comparing the theoretical and experimental impulse shapes are also included. The results are a simplified method for determining the time constants of a double exponential function from given impulse parameters and a method for deriving the component values for prototype circuits

Standard techniques for testing devices and systems for their response to lightning, switching transients, and electromagnetic pulse (EMP) disturbances often call for impulse shapes characterized by double exponential functions. The double exponential impulse is defined by two time constants a and b in the function f(t) = K(e(-at) - e(-bt)). Unfortunately, the time constants and impulse parameters such as rise time, pulse duration, time to peak, and others are not directly related. The problem in generating test impulses is that the required standard impulses are sometimes defined by parameters and nomenclature lacking direct correlation to the desired time constants needed to derive component values for prototype impulse generator circuits. Historically, prototype circuits have been developed for the generation of double exponential voltage and current impulses. Component values for these prototype circuits can be calculated from approximations based on various definitions relating impulse parameters and the double exponential time constants. Various tables and approximations for the design of impulse generators have appeared in the literature as early as the 1930's. What is often lacking is the direct relationship between the time constants of the double exponential function and the given impulse parameters, as well as usable circuit design formulas. This paper derives equations for determining the time constants of the double exponential impulse from the commonly used parameters for several standard test impulses. It then proceeds to synthesize a resistor-capacitor (RC) prototype circuit that will produce the desired impulse. The prototype network is realized through a computer-aided design (CAD) procedure using Cauer's RC ladder two-port synthesis method. Descriptions of prototype circuits and test data comparing the theoretical and experimental impulse shapes are also included. The results are a simplified method for determining time constants of a double exponential function from given impulse parameters and a method for deriving the component values for prototype circuits.

This paper discusses the development of the technical basis for establishing acceptance criteria on the susceptibility of digital systems to electromagnetic interference (EMI). The effort is sponsored by the US Nuclear Regulatory Commission and stems from the safety-related issues that need to be addressed with the application of digital instrumentation and controls systems in nuclear power plants. Designers of digital circuits are incorporating increasingly higher clock frequencies and lower logic voltage levels, thereby leading to the risk of susceptibility when spurious interference is misinterpreted as legitimate logic. Development of the technical basis for acceptance criteria centers around establishing good engineering practices to ensure that sufficient levels of electromagnetic compatibility (EMC) are maintained between the nuclear power plant`s electronic and electromechanical systems. First, good EMC design and installation practices are needed to control the emissions from interference sources and their impact on other nearby circuits and systems. Then, a test and evaluation program is needed to outline the EMI tests to be performed, the associated test methods to be followed, and adequate test limits to ensure that the circuit or system under test meets the recommended guidelines. Test and evaluation should be followed by periodic maintenance to assess whether the recommendedmore » EMI control practices continue to be adhered to as part of the routine operation of the nuclear power plant. By following these steps, the probability of encountering safety-related problems associated with EMI will be greatly reduced.« less