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DISTRIBUTION SYSTEM TRAINING LEARNING OBJECTIVES
TABLE OF CONTENT
4502: Causes of Power QualityProblems
4503: Impact of Low Quality Power
4504: Solution Methods for Power Quality Problems
4505: Utility and Customer Roles in Power Quality
4507: Grounding of Premises & Equipment
4508: Powering and Grounding of Electronic Equipment
4509: A Primer for Power Quality Testing & Inspection
4510: Power Quality Case Studies
4511: Designing for Power Quality - Electronic Facilities
4512: Designing for Power Quality - Industrial / Commercial Facilities
4501: Power Quality Overview
The purpose of this first videotape in the Power Quality video series is to give the participant a broad overview of the topic, including: what types of issues are typically considered "power quality", which problems originate with the customer, which ones may be caused by utility events, and what role does grounding play in the overall power quality picture. At the completion of this videotape, and accompanying workbook, the participant should be able to:
- Identify measured waveforms representing power quality disturbances and state the probable causes
- List five effects of poor power quality on sensitive consumer equipment
- Name some common utility disturbances that may cause power-related problems at the customer's site
- State the differences between utility transmission, sub transmission and distribution systems, including typical operating voltages. Also describe common three-phase and single-phase arrangements for utility distribution primary and secondary systems, including typical operating voltages
- Describe five different distribution feeder configurations and compare their levels of service reliability
- State the three broad categories of customer load and their typical power requirements
- List several different types of consumer load that can introduce power quality problems onto the system
- List applications of static rectifiers in the home and in industry. Identify the dominant harmonics generated by both single-phase and three-phase static rectifiers
- Describe how magnetic core equipment, arc discharge devices, and voltage controllers can
- Understand the difference between a "normal" mode disturbance and a "common" mode disturbance
- Explain why the trend in utility distribution systems is to use 4-wire, multi-grounded arrangements as opposed to ungrounded systems
- State the reason why a common neutral connection is normally used between distribution primary and secondary systems
- Explain how stray voltage at the customer's location can develop as a result of a common neutral connection
- Describe the importance of single-point grounding and installation of a grounding conductor at the customer's facility.
4502: Causes of Power Quality Problems
This second tape in the Power Quality videotape series is intended to acquaint the participant with the different types of customer load and system events that can give rise to power quality disturbances. These disturbances include harmonic distortion caused by nonlinear loads, such as static power converters, magnetic core equipment, arcing loads, and thyristor-switched controllers. In addition, this tape looks at power quality problems that can result from utility system events, such as faults, lightning, and switching operations. System resonance is also discussed as a cause of harmonic magnification. At the completion of this videotape and accompanying workbook exercises, the participant should be able to understand and apply the following concepts:
- State the purpose and operating characteristics of a semiconductor diode. Show how these devices are the building block for any static device
- Describe the operation and application of half-wave, full-wave and 6-pulse static rectifiers on the power system
- Sketch the typical distorted ac current drawn by a 6-pulse static rectifier
- State the difference between a thyristor and a diode in a static rectifier circuit. Name 2 advantages of using a thyristor instead of a diode
- Explain the effect of varying thyristor firing angle on the output voltage of a static rectifier. State how a static rectifier can be controlled to operate as an inverter
- Describe the principle of multiphasing (high pulse order) and why it is employed in large converter installations
- Using a simplified Fourier analysis, derive the dominant harmonics generated by single-phase and three-phase static converters
- Discuss how "notching" in the ac line voltage occurs as a result of the normal operation of a static converter
- Beside static power converters, name 3 broad categories of harmonic producing loads, and describe where the harmonics come from
- State the consequences of high inrush current during motor starting or transformer energization
- Identify two types of load that can cause voltage flicker during normal operation
- List 3 common causes of system faults and explain how they can result in power outages, voltage sags, and voltage swells
- List 2 common causes of voltage surges and describe probable consequences to sensitive equipment
- Understand why capacitor switching can result in voltage surges up to 300% of nominal voltage
- Name 2 power quality problems that can result from a geomagnetic disturbance (GMD)
- Describe a typical scenario where a combination of utility and customer equipment may result in parallel or series resonance. Explain how a parallel resonance can magnify harmonics produced by non-linear loads, and how a series resonance can divert harmonic currents into undesirable paths.
- Understand how dynamic overvoltages and ferroresonance can develop on the utility system. State the possible consequences of these phenomena
4503: Impact of Low Quality Power
The purpose of the third tape in the Power Quality video series is to familiarize you with the effects of quality-related disturbances on equipment, systems, and human beings. Effects on equipment include sensitive electronic equipment, transformers, rotating machines, capacitors, and cables. System impacts include a variety of problems associated with poor power quality: instrumentation errors, false tripping, flicker annoyance, resonances, and economic penalties. In addition, we will consider the negative impact of power quality disturbances on communication systems, electric shock, and electromagnetic fields. At the completion of this videotape, the participant should be able to:
- Understand why microproessor-based equipment can be adversely affected by small variations in voltage
- State the difference in power-handling capability between microprocessor-based electronics and power electronics
- Given the CBEMA susceptibility curves for computer equipment, identify the range of computer tolerance for sustained over/under voltages
- Given the magnitude and duration of a voltage disturbance, state whether or not computer equipment can tolerate such a disturbance, based on the CBEMA curves
- List 3 operating problems associated with computers subjected to voltages outside the CBEMA tolerance envelope
- Describe the effects of lightning-induced voltages and static discharges on data Input/Output ports
- State the purpose of transient voltage surge suppressors, and how poor installation practices can render them ineffective
- Explain how a fast-front surge voltage can cause unexpected turn-on of power electronic components
- Discuss the effects of voltage sags and outages on common household electronic equipment
- Understand how high harmonic content in the load current can result in overheating and loss of life of distribution transformers
- Describe the practice of derating transformers to avoid loss of life due to harmonics
- Explain what a "K-factor" transformer is and how it is applied
- Discuss the mechanisms by which capacitors may suffer loss of life or insulation failure due to harmonic voltages
- Explain the problem of neutral overloading due to triplen harmonics
- Describe how watt-hour meters and other instruments may give false readings when harmonic frequencies are present
- State the reason why ground protection on a distribution feeder may falsely trip the feeder breaker when the load
- current contains a strong 3rd harmonic component
- Interpret industry standards for permissible voltage flicker -- given a magnitude and frequency of voltage fluctuation,
- state whether or not such a flicker is objectionable
- Describe the consequences of motor drop-out (due to deep sags) on industrial processes and on the overall stability of the utility system
- Explain how notch frequencies can excite natural system resonances, resulting in voltage magnification and component failure
- Discuss how current harmonics on power lines can cause noise and false signals on nearby telephone circuits
- State the meaning of Telephone Influence Factor, IT product, and kVT product. Give an example of an IT product that should result in minimum telephone interference.
- Describe how harmonic currents can lead to the development of stray voltages and shock hazard to humans and animals
- Explain how harmonic currents can elevate electromagnetic fields in the vicinity of power lines
4504: Solution Methods for Power Quality Problems
The intent of this fourth tape in the Power Quality video series is to acquaint you with the many types of solution techniques available for mitigating quality-related problems, as well as the application of these techniques. Solutions include equipment and methodologies for: harmonic filtering, power conditioning, isolation, cancellation, uninterruptible power, and advanced technologies, such as "custom" or "premium" power. At the completion of this videotape, the participant should be able to:
- Understand the difference between a series filter and a shunt filter and discuss typical applications for each type
- Name the two most common shunt filter designs applied in harmonic control, and explain their basic operating characteristics
- Describe a typical shunt filter arrangement for a 6-pulse converter installation
- Explain why harmonic filters normally include the function of power factor improvement
- List 4 different types of "power conditioning" equipment
- Sketch the voltage-current characteristic of a typical surge suppressor and describe its operation under both normal and surge conditions
- Discuss the importance of "clamping voltage", "let-through voltage", and "energy withstand" in applying surge suppressors in low voltage applications
- Understand why proper installation of surge suppressors is essential for good protection
- Explain why a simple transformer can offer some protection from power quality disturbances
- State the reason why a grounded shield may be installed in some transformers
- Describe the types and operation of constant voltage transformers
- Show how a motor-generator set can isolate the load from certain types of supply side disturbances
- Discuss the advantages of isolated grounding over conventional grounding in a customer's facility.
- Explain why isolating primary and secondary neutrals on the utility distribution system can help mitigate stray voltage
- Understand how multiphasing and the use of phase-shifted transformers help cancel harmonic injection onto the system
- List the basic components of an Uninterruptible Power Supply (UPS)
- Compare the features of "on-line", "off-line" and "line-interactive" UPSs
- State the reason why a standby generator is often necessary to supplement a UPS
- Describe some potential compatibility problems associated with standby generators and UPSs
- Discuss alternate UPS technologies, such as superconducting magnetic energy storage (SMES)
- Explain how static VAR compensators (SVCs) and adaptive VAR compensators (AVCs) work to track the changing VAR requirements of the load and greatly reduce voltage flicker
- State one advantage of retrofitting fluorescent lighting with "new breed" electronic ballasts.
- Discuss some emerging technologies and equipment associated with power quality improvement
4505: Utility and Customer Roles in Power Quality
The intent of this fourth tape in the Power Quality video series is to acquaint you with the many types of solution techniques available for mitigating quality-related problems, as well as the application of these techniques. Solutions include equipment and methodologies for: harmonic filtering, power conditioning, isolation, cancellation, uninterruptible power, and advanced technologies, such as "custom" or "premium" power. At the completion of this videotape, the participant should be able to:
- Cite 3 ANSI/IEEE Industry Recommended Practices relating to the subjects of harmonics, voltage surges, and voltage quality
- Distinguish between an industry "guide", "recommended practice", and "standard"
- Given a spectrum of harmonic magnitudes, calculate the Total Harmonic Distortion, "THD"
- Given a sample customer system and harmonic spectrum of load current, state whether the customer is in compliance with IEEE 519
- State the magnitude, frequency, and waveshape of voltage and current surges we would expect to find inside buildings
- Discuss the requirements for surge suppressors to protect against expected surges inside a customer facility
- Explain why expanded tolerance envelopes for voltage quality are being considered by the industry
- List and briefly describe the 5 broad categories of power quality monitoring equipment
- Explain why it is so important to test for wiring and grounding errors before proceeding with more sophisticated monitoring
- State the difference between "peak-actuated", "average-actuated", and "true rms" meters
- Describe the most versatile and sophisticated type of disturbance monitor and how it is typically used
- List several parties who may become involved in a site survey
- Discuss the general steps involved in conducting a site survey
- Explain the importance of the initial "walk-through" in a site survey
- Understand the difference between the main service ground and a separately-derived ground
- Name two installation errors commonly found on power conditioning equipment during site surveys
- Explain the purpose of a disturbance generator in a site survey
- Understand how problem areas can be pinpointed from data gathered in a site survey
- Describe the responsibilities of the electric utility and the customer in achieving and maintaining a high level of power quality
- Give examples of the need for service providers and users to work together to solve existing quality problems as well as plan future installations to minimize quality problems
4506: System Grounding
The sixth tape in the Power Quality video program serves as an overview of several different system grounding philosophies and methods. Since many power quality problems have their root cause in poor grounding practices, it is important to understand which techniques are recommended, and why. This material examines reasons for grounding, effective grounding, low/high impedance grounding, ungrounded systems, and utility and customer substation grounding. At the completion of this videotape, the participant should be able to:
- Give one example of a common grounding error, and explain how it can cause problems with power quality.
- Name 5 reasons why grounding is used on power systems.
- Explain why failure to ground the metallic enclosures of energized conductors can create a severe shock hazard.
- Discuss the effect of proper grounding on overcurrent protection.
- Describe 2 different methods of grounding computer installations to describe a method for grounding buildings to protect against direct lightning strokes.
- Explain the purpose of sky wires on overhead transmission lines.
- Show how multi-grounded distribution systems help limit 60 Hz voltage swells and high frequency voltage transients.
- State the IEEE standard definition of an effectively-grounded system. Explain the difference between effective grounding and solid grounding. State which types of systems use effective grounding.
- Discuss the reasoning behind using low-impedance grounding in industrial power systems.
- Compare typical values of ground fault current in effectively-grounded vs. low-impedance grounded vs. reactance-grounded systems.
- Give an example of an application for reactance grounding.
- Explain the philosophy behind high-impedance grounding and ungrounded systems.
- State a typical range for ground fault current in high-impedance grounded systems. Compare to low-impedance grounding.
- Describe how resonant grounding (Petersen coil, arc suppression coil, ground-fault neutralizer) works and state a typical application.
- Name 3 disadvantages of using an ungrounded system.
- Sketch a common arrangement for ground fault detection and alarm in an ungrounded system.
- Describe the purpose and application of a zig-zag grounding transformer. State how this device can be used as a
- zero-sequence trap for triplen harmonics.
- Discuss the need for using a ground mat supplemented with driven ground rods for grounding utility and customer substations.
- State why a low overall ground resistance is required in substation grounding.
- Explain the significance of "ground potential rise" (GPR) and why it needs to be limited in designing the substation grounding system.
- Give the expression for maximum allowable body current survivable by a human being, as described in IEEE Standard 80.
- Describe how touch and step voltages above a ground mat are determined, based on maximum GPR for the worst-case fault condition.
- Explain how proper substation grounding reduces communication circuit interference.
4507: Grounding of Premises & Equipment
The seventh module in the Power Quality video program is an extension of the previous material on System Grounding. The present module serves as an overview of different grounding philosophies and methods, with the focus on customer premises and equipment. Since many power quality problems have their root cause in poor grounding practices, it is important to understand which grounding techniques are recommended, and why. This module identifies applicable industry codes and standards, as well as the reasoning behind many of the commonly acceptable grounding arrangements for premises and equipment. This material examines multiple power sources, building electrode systems, multiple buildings, equipment grounds, grounding of generators and UPSs, grounding of unit substations and switching centers, and grounding for static and lightning protection. At the completion of this videotape and accompanying workbook exercises, the participant should be able to:
- State several reasons why some form of intentional grounding is preferred over ungrounded systems.
- Name two industry standards that apply to the grounding of large customer power systems
- Explain why industry codes prohibit premises grounding at any location except a power source (including separately-derived sources).
- Describe two acceptable methods for grounding multiple power sources, as well as any special precautions we must take when using these methods.
- List four code-approved metallic structures that must be used as part of the building's grounding electrode system, provided such structures are available on the premises.
- Describe the preferred grounding arrangement for serving more than one building from a single utility service.
- State the purpose of the equipment-grounding conductor, and distinguish between the grounding conductor and the grounded conductor.
- Explain why metal conduit can be used as an equipment-grounding conductor, and also why the conduit should be supplemented by a separate grounding conductor run inside the conduit.
- Discuss the difference between grounding and bonding, and why electrical codes require that all non-current-carrying metal parts of equipment be effectively bonded together.
- Compare the short circuit withstand capability of a generator with that of a transformer.
- Explain why it is necessary to ground most generators through an impedance, instead of through a solid connection to ground.
- State the advantage of using fractional-pitch machines in multi-generator installations.
- Discuss and compare three different methods of grounding for uninterruptible power supplies.
- State how compact unit substations are grounded and how the grounding system differs from conventional outdoor substations.
- List two common grounding mistakes that occur during field installations of indoor switching centers.
- Explain the phenomenon of static electricity and give an example from everyday life. vState how voltage can develop between an object with a static charge and ground.
- Give several examples of static charge accumulation in the workplace.
- List three negative effects of static discharge.
- Describe three methods for static control in industrial & commercial environments.
- Explain how lightning flashes are generated.
- Describe various methods of protecting buildings from direct lightning strokes.
4508: Powering and Grounding of Electronic Equipment
This eighth module in the Power Quality video program continues our discussion of system and facility grounding by focusing on the powering and grounding of electronic equipment. In this module, we identify various types of electronic equipment and discuss unique features that distinguish this equipment from other types of customer load. Because many power quality problems involving electronic equipment can be traced back to poor design/installation of the facility distribution system, this module covers recommended methods for powering sensitive equipment. This includes circuits, equipment, wiring, and the application of power conditioning equipment for lightning and surge protection. In addition, this module examines the various grounding considerations for sensitive equipment, including insulated equipment grounds and high frequency referencing systems. Throughout this material, applicable industry standards for powering and grounding of sensitive equipment are referenced. At the completion of this module, the participant should be able to:
- Describe what a "sensitive electronic load" means and give some examples.
- Explain why sensitive electronic loads are more susceptible to power quality disturbances than other types of load.
- Illustrate how noise coupling can develop between computers interconnected with data cables.
- Explain why conventional "green wire" grounding methods are often ineffective at high frequencies.
- Name 2 standards, recommended practices, or codes that apply to the powering and grounding of sensitive electronic equipment.
- Sketch a typical circuit configuration that avoids unwanted interaction between sensitive computer loads and other types of load.
- State the purpose of an isolation transformer in interfacing computer loads with the rest of the distribution system.
- Describe the proper way to ground an isolation transformer, and state some common grounding mistakes during installation.
- Discuss the importance of limiting voltage drops along distribution feeders and branch circuits, and cite examples of acceptable (recommended) voltage drops.
- Give an example of time-overcurrent relay coordination on the facility distribution system. Also, discuss the importance of adding time-delay devices in the protection of sensitive equipment.
- Explain why the neutral bus bar in a panelboard serving sensitive equipment is typically oversized (generally rated at 200% of the ampacity of the line bus).
- Explain why transformers must be de-rated when serving sensitive electronic loads. Discuss the application of K-factor transformers as an alternative to de-rating conventional transformers.
- State three hazards that can occur due to improper grounding of the facility distribution system.
- Name the components of the building electrode system, and describe the importance of connecting these components to the service entrance system neutral, as well as to the neutrals of all separately-derived sources within the building.
- Explain why all non current-carrying metallic frames, enclosures, etc. must be bonded together and grounded at the service entrance (or separately-derived source).
- State the reasons why solid grounding at service/derived neutrals is the recommended practice.
- Describe the configuration of a typical computer room dedicated to serving electronic process controls or data processing. Include the proper location of the isolation transformer, single-point-of-entry wiring strategy, installation/location of a signal reference grid, grounding of the reference grid, etc.
- Discuss why the "isolated ground (IG)" method is often installed to serve plug-in type electronic equipment. Also, state one common IG installation error that can lead to fire and safety hazards.
- Explain why the IG grounding technique can actually intensify ground loop currents between computers interconnected with data cables.
- State the reason why a zero voltage reference grid (in addition to conventional green wires) is usually required to assure high performance from a sensitive electronic installation.
- Describe how the addition of a reference grid helps eliminate high frequency resonances, thus providing a plane of
- constant potential over a broad band of frequencies.
- Name three types of reference grid in common use in electronic installations.
- Discuss the recommended application of transient voltage surge suppressors (TVSS) for lightning and surge protection of sensitive electronic installations.
- Compare the effects of direct lightning strokes and secondary (induced) surges on sensitive computer equipment.
- Compare the expected surge duty of TVSS devices at the service entrance, and at locations inside the building. Reference the applicable industry standards.
- Describe TVSS installation techniques that minimize the impedance in the ground path, for more effective surge mitigation.
- Explain why it is important to install a separate TVSS on each circuit (power, data, phone, etc.) entering an electronic component.
- Discuss the phenomenon of momentary ground-offset voltage during surge conditions, and how the problem can be remedied by adding a surge reference equalizer.
4509: A Primer for Power Quality Testing & Inspection
This ninth tape in the Power Quality videotape series is intended to introduce you to the hands-on part of Power Quality work. More and more, utility engineering departments are going into the customer’s facility to solve problems. Physically inspecting the wiring system is the first and most important step in helping your customers. To accomplish this you need to know what test equipment to use, how it works and where to use it. You need to know the how the Code applies to the requirements of sensitive electronic equipment, as well as the typical problem spots and how to identify them with measurements and observations. By doing your investigation in an orderly fashion, you can save time and frustration in making proper recommendations to improve your customer’s electrical system. In our effort to determine the soundness of the power distribution system, the IEEE Emerald Book will be the main guide in this tape, with references to the National Electrical Code and the Canadian Electrical Code. At the completion of the videotape and accompanying workbook exercises, the participant should be able to:
- Understand proper order of Power Quality investigations.
- State the difference between average reading, peak reading and true RMS reading meters.
- Explain how a true RMS meter works.
- Explain why and how to use a true RMS mulitmeter to measure voltage, RMS current, peak current, and Crest Factor.
- Understand how to use an Infrared Thermometer.
- Inspect a receptacle wiring connection.
- Measure voltage levels and voltage drop.
- Determine ground and neutral circuit impedance using an Impedance Meter.
- Become familiar with the use of a Circuit Tracer.
- Locate illegal neutral-to-ground bonds.
- Determine correct Isolated Ground wiring methods.
- Calculate neutral conductor size for harmonic loads.
- Inspect panels for proper wiring configurations.
- Understand causes of ground currents at main entrance.
- Inspect ground connections at the water main.
- Check for harmonic heating in busbar, cables and connections.
- Determine proper grounding schemes at Main Entrance.
- Check grounding of Cable, Data, Phone and Satellite feeds.
4510: Power Quality Case Studies
The purpose of the 10th tape in the Power Quality video series is to demonstrate the use of case studies to identify and resolve power quality problems. Case studies will be used to provide a practical background to some of the topics we have covered so far in the series. We will examine some common power quality problems, although we will only touch on some of the interactions that can take place between devices on the electrical network. Case study work is a fundamental part of developing power quality experience. At the completion of this videotape and accompanying workbook exercises, the operator should be able to:
- Identify the elements of a case study.
- Develop case studies to more confidently and rapidly solve problems for customers.
- Use case studies and other resources to identify grounding issues related to wiring techniques.
- Explain what environmental factors need to be considered when examining power quality problems.
- Gather all relevant information, including operator logs that identify symptoms of power quality problems.
- List the sources of information needed to determine possible causes of power quality problems.
- Understand the complexities associated with recommending solutions to power quality problems.
- Describe problems associated with improper wiring techniques leading to grounding problems.
- Identify problems created from neutral current harmonics.
- Understand the effects of load and capacitor switching on drives and other electronic loads.
- State the effects of radiated noise problems on the operation of computer equipment.
- Explain how thorough investigation of identified problems, such as wiring, can prevent future power quality problems.
- Understand the effects non-linear loads have on the building electrical distribution system.
- Explain how AC motor drive circuits are both susceptible to power quality problems and potential generators of power quality disturbances.
- Define line ringing and why it occurs.
- Describe the hazards caused by line ringing.
- Understand the usefulness of obtaining power quality waveforms to recognize signatures of typical power problems.
- List uses of isolation transformers and line reactors.
- Use IEEE 519 Harmonics Distortion Table specifications and some minor calculations to de-rate transformers.
- Describe how power frequency magnetic fields interfere with equipment.
- Name the two invisible fields surrounding every conductor.
- Describe briefly why power frequency magnetic fields do not produce any appreciable radiation.
- Define ELF magnetic fields and their effects.
- List 3 methods for mitigating ELF magnetic fields.
- Identify 3 sources of ELF magnetic fields.
4511: Designing for Power Quality - Electronic Facilities
The eleventh module in the Power Quality video program focuses on various design issues related to power quality in an electronic installation. By "electronic installation" we mean to convey a large area computer arrangement. Where the electronic installation is intended to comply with ANSI/NFPA 70 ("The National Electrical Code") and ANSI/NFPA 75 ("Standard for the Protection of Electronic Computer/Data Processing Equipment"), the installation is considered to be a "dedicated computer room". Electronic installations arranged in a distributed topology across walls and floors may also benefit from proper selection and application of the design guidelines given in this module. This module points out several factors that the power system designer must consider to assure a high level of power quality ¾ both the electronic equipment itself and the surrounding electrical environment must be factored into the equation. Such design factors include: the overall design objectives for the facility with respect to continuity of service and other disturbances, the requirements of the electronic load and the resources needed to meet them, power enhancement and conditioning equipment needed, interface of the electronics with other systems in the same environment (life-safety, communications), and compliance with electrical codes and other standards. General design examples for increasing the reliability of electronic installations are also addressed. Note that the purpose of this module is to present some general design considerations for the power engineer/technician. Many of these have been discussed in greater detail in other modules of this program on Power Quality (PQ). Where applicable, the reader will be referred to specific PQ modules and segments as an additional refresher. At the completion of this module and accompanying workbook exercises the participant should be able to:
- Give examples of some typical design objectives for an electronic installation.
- Explain the concept of redundancy in supplying critical loads.
- Explain why it is important to consider the complete electrical environment, in addition to the electronic equipment itself. Give some examples of components of the electrical environment.
- Describe 3 design techniques for improving the quality of power delivered to a critical load.
- State the advantages of transmitting power at a voltage higher than the equipment utilization voltage, as well as the benefits of using a shielded isolation transformer close to the load.
- Explain why it is important to balance single-phase, line-to-neutral connected loads among the 3 phases.
- State the NEC code rule for derating circuits supplying electronic loads. Give an example.
- Describe how an electrical designer would use a system power profile during the design process.
- Name some power quality disturbances that may be captured by PQ monitors. Discuss typical causes of such disturbances.
- List 3 common types of power enhancement devices recommended by IEEE Standard 1100, "Powering & Grounding Sensitive
- Electronic Equipment" (the Emerald Book). Briefly explain the purpose of each device.
- Discuss the importance of ride-through capability, and identify power conditioners that have such capability.
- State a typical design voltage range for a large computer system, in percent of nominal line voltage.
- Describe the advantages & disadvantages of using constant voltage (ferroresonant) transformers for control of voltage variations.
- Name 3 features of a typical life-safety system and state the purpose of each.
- Identify conditions under which the "panic" (Emergency Power Off) button would be activated, either manually or automatically.
- Explain how the life-safety system is powered & interfaced with the electrical system serving the computer facility.
- Discuss the various backup arrangements for powering the life-safety system.
- Give some examples of communication circuits that may be present in modern electronic facilities.
- Give the reason why the location of all conductors entering the computer room (both power and communication) must typically be controlled to a "single point-of-entry".
- Explain why it is important to ground all cable (CATV, phone, etc.) shields to the grounding electrode system of the building. State the hazards involved in driving an isolated ground rod, having no connection back to the building electrode system.
- State the purpose of the NEC - National Electrical Code (NFPA Std. 70).
- Identify one example whereby strict adherence to the NEC naturally results in an improvement of power quality.
- Name and describe the 6 special requirements for an "information technology equipment room", as stated in NEC Article 645.
- Explain the difference between "branch circuit conductors", "connecting cables", and "interconnecting cables" as described in Art. 645 of the NEC.
- Sketch a one-line diagram of a power supply system to a large, critical computer facility, where 100% up-time is required.
- Discuss why it is important to provide power backup not only for the computers, but also for their heating, ventilating and air conditioning (HVAC) systems.
- Explain the meaning of "N+1 Redundancy", "Parallel Redundancy", and "Isolated Redundancy".
4512: Designing for Power Quality – Industrial / Commercial Facilities
This twelfth module in the Power Quality video program extends the discussion of design issues to cover plant distribution arrangements, voltage drop and sag considerations, harmonic control and filter application, as well as the impact of adjustable speed drives on power quality. The main emphasis of this module switches from the electronic facility (addressed in PQ11), to industrial and commercial installations. By "industrial plant" we mean any building that is primarily machine and production oriented. Commercial sites are intended to mean office and apartment complexes, hotels, schools, stores, and other types of facilities that directly serve the public. Note that the purpose of this module, like the previous one, is to present some general design guidelines for the power engineer and technician. It is not meant to be a comprehensive "how to" manual on design. Many of the design issues summarized in PQ12 have been discussed in greater detail in other modules of this program on Power Quality. Where applicable, the reader will be referred to the specific PQ module and segment for additional refresher. At the completion of this module and accompanying workbook exercises, the participant should be able to:
- Name two IEEE Standards in the Color Book Series that address the overall design of industrial and commercial installations.
- Sketch a one-line diagram of an expanded radial circuit arrangement, and explain the advantage over a simple radial arrangement.
- Explain why the use of several small unit substations is superior to using one large unit substation.
- State two types of circuit arrangements that provide redundancy for loss of a primary feeder.
- State two types of circuit arrangements that provide redundancy for loss of a transformer.
- Describe the advantage of a secondary network system over a secondary selective system.
- Explain the operation and application of a ring-bus circuit in an industrial plant.
- State the NEMA recommended voltage tolerance range for induction motors.
- Describe the effect of low applied voltage on the performance of different loads, such as motors, incandescent lamps, resistance heaters, and capacitor banks.
- Discuss the ANSI C84.1 standard Range A and Range B voltage limits for service and utilization voltage.
- Name two common methods of controlling voltage drop on the utility system, and inside the customer’s facility.
- Discuss the application of power factor improvement capacitors in an industrial or commercial setting, including possible resonance or sustained overvoltage problems. vIdentify distorted current waveforms corresponding to different types of non-linear load.
- List the dominant current harmonics characteristic of single-phase, 6-pulse, and 12-pulse static converters.
- Describe the effect of dc-side inductance on the familiar square current wave drawn by a 6-pulse motor drive.
- Name 5 undesirable effects of harmonics on the power system.
- Identify the IEEE Standard devoted to harmonic control on electric power systems.
- Give an example of the maximum total harmonic distortion a consumer is permitted to inject onto the power system.
- Describe 5 methods commonly employed for mitigating the undesirable effects of harmonics.
- List 3 applications in which an adjustable speed drive (ASD) may be used to control the speed of an AC or DC motor.
- Discuss the AC motor speed control techniques used by a VSI (Voltage Source Inverter) drive, a CSI (Current Source Inverter) drive, and a PWM (Pulse Width Modulation) drive.
- Compare the AC current distortion on the input (source) side of the VSI and CSI drives.
- State the conditions under which ASDs are most likely to cause harmonic problems on the power system. Discuss typical solutions to such problems.
- Describe a situation in which utility capacitor switching transients can become magnified at the customer’s bus.
- Discuss common solutions.
- Identify methods for protecting ASDs from deep voltage sags and nuisance tripping.
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