POWER QUALITY STANDARDS - powermonitoring.com

1 POWER QUALITY STANDARDSMark McGranaghanElectrotek Concepts, Contractor MagazinePower QUALITY for the Electrical Contractor CourseIntroductionPower QUALITY has always been important. However, for many years the equation definingpower QUALITY was very simple: POWER QUALITY = RELIABILITYC ustomer loads were linear in nature. When a sinusoidal voltage was supplied to them,they drew a sinusoidal current. They typically fell into the categories of lighting, heating,and motors. In general, they were not very sensitive to momentary variations in the supplyvoltage, such as transients and voltage sags. The loads were not connected together innetworks so grounding issues other than safety were not very major changes in the characteristics of customer loads and systems have completelychanged the nature of the POWER QUALITY first is the sensitivity of the loads themselves. The devices and equipmentbeing applied in industrial and commercial facilities are more sensitive to powerquality variations than equipment applied in the past.

2 New equipment includesmicroprocessor-based controls and POWER electronics devices that are sensitive tomany types of disturbances besides actual interruptions. Controls can be affected bymomentary voltage sags or relatively minor transient voltages, resulting in nuisancetripping or misoperation of an important second is the fact that these sensitive loads are interconnected in extensivenetworks and automated processes. This makes the whole system as sensitive asthe most sensitive device and increases the problem by requiring a good zeropotential ground reference for the entire changes in the load characteristics have created a growing market for powerconditioning equipment that can protect the loads from the wide variety of POWER qualityvariations that can cause problems. In order to apply POWER conditioning equipmenteffectively, customers must become experts in the types of POWER QUALITY variations, theircauses, their possible impacts, and the solutions available to mitigate them.

3 Since some ofthe causes are on the utility system, the utility must also understand the full range of QUALITY FOR THE ELECTRICAL CONTRACTORPQ StandardsElectrotek Concepts, 2 The POWER QUALITY problems don t always come from the utility system either. Most of thetransient voltages in a facility are caused by switching operations within the facility. Wiringand grounding problems increase susceptibility to problems. POWER electronics equipment,such as adjustable speed drives, result in a continuous string of transients (notching) as wellas steady state harmonic distortion that can cause heating in other loads within the are We Doing to Understand the Problems?Understanding the problems associated with POWER QUALITY variations is the first steptowards developing STANDARDS and the optimum approach to solutions. Understandingmeans being able to relate the causes of POWER QUALITY variations to impacts on equipmentand processes within customer facilities.

4 This requires an understanding of the utility powersystem, the customer electrical system, and the equipment are a number of significant research efforts under way to help improve theunderstanding of POWER QUALITY problems. There are three important categories for Utilities and customers are both doing more and more monitoring ofpower QUALITY . This monitoring is being performed on the POWER system and withincustomer facilities. The Electric POWER Research Institute (EPRI) is sponsoring amulti-year project to monitor POWER QUALITY on distribution systems around thecountry with 24 host utilities (Figure 1). Some of these utilities are extending themonitoring to include customer facilities so that they can relate events and variationson the distribution system with problems in the customer 1. Participants in the EPRI-Sponsored Distribution POWER QUALITY MonitoringProjectPOWER QUALITY FOR THE ELECTRICAL CONTRACTORPQ StandardsElectrotek Concepts, Studies.

5 Case studies are a way of characterizing POWER QUALITY concerns forindividual customers and systems. There are numerous case studies beingperformed by utilities, their customers, and EPRI. When the results of all these casestudies are shared and combined, the results illustrate important generalcharacteristics of POWER QUALITY concerns for different kinds of customers andequipment. The solutions implemented in particular case studies can be patterns formore general solutions to POWER QUALITY Tools. The results of monitoring efforts and case studies are being usedto improve analytical models for simulating system disturbances. There are UsersGroups for harmonic analysis and transient analysis that can provide guidance inevaluating problems and the range of possible solutions. The advantage of thesimulation approach is that it allows evaluations of systems and conditions that maynot yet actually exist ( future expansion plans).The Role of StandardsPower QUALITY problems ultimately impact the end user.

6 However, there are many otherparties involved in creating, propagating, and solving POWER QUALITY problems (Figure 2). POWER QUALITY STANDARDS must provide guidelines, recommendations, and limits to helpassure compatibility between end use equipment and the system where it is applied. Thestandards affect all of the parties shown in Figure ConditioningEquipmentManufacturersConsul tantsMonitoring EquipmentManufacturersArchitects/Enginee rsFacility DesignersResearchOrganizations(EPRI)Stan dardsOrganizations(IEEE, ANSI)UtilityCustomerManufacturerFigure 2. Players That Influence End-Use POWER QualityPOWER QUALITY FOR THE ELECTRICAL CONTRACTORPQ StandardsElectrotek Concepts, 4 There is active interest in this country as well as the rest of the world to establish powerquality STANDARDS to deal with these problems. The international STANDARDS developmentorganization is the IEC. The IEC has defined a category of STANDARDS calledElectromagnetic Compatibility (EMC) STANDARDS that deal with POWER QUALITY issues.

7 Theyfall into the following six These provide definitions, terminology, etc. (IEC 1000-1-x) Characteristics of the environment where equipment will be applied(1000-2-x). Emission limits define the allowable levels of disturbances that can becaused by equipment connected to the POWER system. These STANDARDS wereformerly the IEC 555 series but now are numbered 1000-3-x. For instance, IEC555-2 has now become IEC and Measurement Techniques. These provide detailed guidelines formeasurement equipment and test procedures to assure compliance with the otherparts of the STANDARDS (1000-4-x). and Mitigation Guidelines. These are designed to provide guidancein application of equipment, such as filters, POWER conditioning equipment, surgesuppressors, etc., to solve POWER QUALITY problems (1000-5-x). and Product STANDARDS . These will define immunity levels required forequipment in general categories or for specific types of equipment (1000-6-x).

8 This is a very impressive breakdown and organization for POWER QUALITY standardsdevelopment. Unfortunately, very few of these STANDARDS have actually been written andthose that have been drafted are controversial. For instance, it took almost ten years to getIEC 1000-2-2 (IEC 555-2) approved and there are still questions about when it will QUALITY FOR THE ELECTRICAL CONTRACTORPQ StandardsElectrotek Concepts, 5 PowerLinesMobileRadioConducted NoiseAC POWER CircuitElectric MotorsIgnitionLightningFigure 3. Some factors affecting Electromagnetic CompatibilityThese IEC STANDARDS are generally adopted by the European Community (CENELEC) andbecome requirements for equipment sold in Europe. Their application in the rest of theworld varies and very few of them are adopted outright in the United QUALITY STANDARDS in the USIn the United States, STANDARDS are developed by the IEEE, ANSI, and equipmentmanufacturer organizations, such as NEMA. We also have safety-related STANDARDS , like theNational Electrical Code.

9 We have very few STANDARDS that define requirements for specificequipment. Our STANDARDS tend to be more application oriented, like IEEE 519-1992, whichprovides recommendations to limit harmonic distortion levels on the overall POWER has formed a STANDARDS Coordinating Committee (SCC-22) that has the job ofcoordinating STANDARDS activities regarding POWER QUALITY from all the different organizationsdoing development. Table 1 provides a listing of existing STANDARDS and STANDARDS underdevelopment related to POWER QUALITY FOR THE ELECTRICAL CONTRACTORPQ StandardsElectrotek Concepts, 6 Table 1. Listing of Important POWER QUALITY Electric POWER Systems142 Industrial & Commercial POWER System Grounding241 Commercial Electric POWER Systems242 Industrial & Commercial POWER System Protection399 Industrial & Commercial POWER System Analysis446 Industrial & Commercial POWER System Emergency Power493 Industrial & Commercial POWER System Reliability518 Control of Noise in Electronic Controls519 Harmonics in POWER Systems602 Industrial & Commercial POWER Systems in Health Facilities739 Energy Conservation in Industrial POWER Systems929 Interconnection Practices for Photovoltaic Systems1001 Interfacing Dispersed Storage and Generation1035 Test Procedures for Interconnecting Static POWER Converters1050 Grounding of POWER Station Instrumentation & ControlANSIC62 Guides & STANDARDS on Surge Ratings for POWER Systems & EquipmentC37 Guides and STANDARDS for Relaying & Overcurrent Derating for Supplying Nonlinear LoadsIEEEP487 Wire Line

10 Communication Protection in POWER Stations1100 Powering and Grounding Sensitive EquipmentP1159 Monitoring and Definition of Electric POWER QualityP1250 Guide on Equipment Sensitive to Momentary VoltageDisturbancesP1346 Guide on Compatibility for ASDs and Process ControllersNEMAUPSU ninterruptible POWER Supply SpecificationNFPA70 National Electric Code75 Protection of Electronic Computer Data Processing Equipment78 Lightning Protection Code for BuildingsNIST94 Electric POWER for ADP InstallationsSP678 Overview of POWER QUALITY and Sensitive Electrical EquipmentUL1449 STANDARDS for Safety of Transient Voltage Surge SuppressorsThere has been a general fear on the part of the utility industry to create any STANDARDS thatdefine the level of POWER QUALITY required of the supply system. This fear is slowly beingbroken down as utilities realize the need to define the base level of POWER QUALITY in order tobe able to offer any kind of differentiated service for those customers that require a higherperformance is worthwhile to look at the current state of STANDARDS development related to eachimportant type of POWER QUALITY QUALITY FOR THE ELECTRICAL CONTRACTORPQ StandardsElectrotek Concepts, 7 STANDARDS for Steady State Voltage Regulation and UnbalanceThere is no such thing as steady state on the POWER system.