John P. Nelson

Power quality and harmonic distortion on distribution systems

With the increase of nonlinear loads on utility distribution systems, the voltage and current waveforms are becoming more distorted and the power quality is deteriorating. Since this is becoming a widespread problem today, and new, more strict, distortion guidelines are under development, utility engineers are having to deal with analyzing and planning for the control of the distortion. The authors introduce some common harmonic analysis techniques and apply them to voltage waveforms recorded on a typical REA transmission and distribution system.<<ETX>>

High resistance grounding of low voltage systems: a standard for the petroleum and chemical industry

A debate has existed in the petroleum and chemical industry for years concerning low-voltage (480–600 V) power systems grounding. Since reliability and continuity of service are very important, some engineers in the past preferred using an ungrounded system. The practicality of such ungrounded system becomes questionable as the extent of coverage increases. Few ungrounded low-voltage systems are presently being designed due to the possible destructive nature of transient overvoltages resulting from an arcing ground fault. Most systems now utilize either a solidly grounded or high-resistance grounded source. This paper begins with a brief discussion on ungrounded, solidly grounded, and high-resistance grounded systems. Benefits and limitations of each system are also discussed. It is shown that the use of high-resistance grounded low-voltage systems makes good sense in the petrochemical industry. Design, construction, operation, and maintenance factors for such systems are discussed and analyzed together with systems when three-phase four-wire loads are present. Finally, operational problems and some appropriate solutions are discussed where significant variable-speed drive loads are utilized. It is suggested that this should become a standard of the industry and the solidly grounded system should be used only in applications where the high-resistance grounded system becomes impractical.

System grounding and ground-fault protection in the petrochemical industry: a need for a better understanding

This paper provides an in-depth discussion on system grounding and ground fault protection on systems from 480 volts and above. The paper also discusses modeling of ground faults, the proper design for ground fault protection and common problems associated with ground fault protection. The paper addresses many real life problems associated with system grounding and ground fault protection including safety issues and how to avoid those problems. The topics to be included in the paper include low voltage systems, under 600 volts, through high voltage transmission systems.

Basics and advances in battery systems

One of the most common components in both the utility and industrial/commercial power system is the stationary battery. In many cases, the original design is marginal or inadequate; the maintenance and testing is practically nonexistent; but the system is called upon during emergency conditions and is expected to perform flawlessly. This paper begins with basic battery theory starting with the electrochemical cell. A working knowledge of the battery cell is important to understand typical problems such as hydrogen production, sulfating, and battery charging. The paper then discusses some of the common batteries and battery chargers. While this paper concentrates primarily on the lead acid type of battery, the theory can be utilized on other types such as the nickel-cadmium. Reference is made to industry standards and codes which are used for the design, installation, and maintenance of battery systems. Along with these standards is a discussion of the design considerations, maintenance and testing, and, finally, some advanced battery system topics such as individual battery cell voltage equalizers and battery pulsing units. The goal of this paper is to provide the reader with a basic working understanding of a battery system. Only with that knowledge can a person be expected to design and/or properly maintain a battery system which may be called upon during an emergency to minimize the effects of a normal power outage, to minimize personnel hazards and to reduce property damage. >

Dc arc models and incident energy calculations

There are many industrial applications of large-scale dc power systems, but only a limited amount of scientific literature addresses the modeling of dc arcs. Since the early dc-arc research focused on the arc as an illuminant, most of the early data was obtained from low-current dc systems. More recent publications provide a better understanding of the high-current dc arc. The dc-arc models reviewed in this paper cover a wide range of arcing situations and test conditions. Even with the test variations, a comparison of dc-arc resistance equations shows a fair degree of consistency in the formulations. A method for estimating incident energy for a dc arcing fault is developed based on a nonlinear arc resistance. Additional dc-arc testing is needed so that more accurate incident-energy models can be developed for dc arcs.

A better understanding of harmonic distortion in the petrochemical industry

This paper provides an in depth discussion on harmonic distortion on power systems in the petrochemical industry. The paper begins with a discussion on harmonics caused by saturable magnetic devices such as generators, transformers and motors. Production and control of harmonic voltages and currents produced in these devices is covered. A discussion on the production and control of harmonic voltages and currents produced by power electronic devices is then discussed. An example of power system harmonics and harmonic suppression techniques is presented.This paper provides an in-depth discussion on harmonic distortion on power systems in the petrochemical industry. The paper begins with a discussion on harmonics caused by saturable magnetic devices such as generators, transformers, and motors. Production and control of harmonic voltages and currents produced in these devices will be covered. Then, a discussion on the production and control of harmonic voltages and currents produced by power electronic devices will be discussed. An example of power system harmonics and harmonic suppression techniques will be presented.

Application of out-of-step relaying for small generators in distributed generation

The recent popularity of distributed generation (DG) has caused an increasing number of small generators (rated between 100 kVA and 12.5 MVA) to be connected to the power system at the distribution level (480 V to 12.47 kV). Some utilities require that out-of-step relays be installed by the generation owner at the point of common coupling (PCC). This paper will examine out-of-step relaying practices as they apply to small generation protection. It will consider the value, purpose, and applicability and provide guidelines for setting of this type of relay when employed.

A harmonic distortion control technique applied to six-pulse bridge converters

A practical design aspect for controlling power system harmonics through the use of transformer connections applied to a distributed set of 6-pulse converter-type loads in industrial power distribution systems is presented. Some common system problems associated with harmonic distortion from 6-pulse-type converters are presented. A method for reducing harmonic distortion through the use of transformer bank connections to allow for harmonic cancellation is discussed.<<ETX>>

Power Systems in Close Proximity to Pipelines

In recent years, a trend has developed toward building energy corridors which better utilize land resources. Due to the adverse environmental impacts of building electrical power lines by utility companies and the installation of pipelines by the petrochemical industry, many governmental entities are requiring that electric power lines and underground pipelines use the same transmission (energy) corridor. The energy corridor, by design, is used to minimize the land requirements for transmitting energy¿whether by electrical transmission lines or through pipelines. The energy corridor does not necessarily minimize the lengths of transmission lines but, conversely, may require longer lines to utilize the land resources better by paralleling transmission systems. The electric power companies have utilized this practice in the past with electrical corridors and are being pressured to make every effort to parallel electric lines in the future on these same corridors. The effect of paralleling electric circuits has been long understood by the electrical engineer. Induced currents and voltages occur between the electrical circuits and may cause relaying, communications, and safety problems. Proper engineering has led to solutions to most of these problems. A problem has developed with the addition of pipelines to the electrical corridors or, conversely, electrical lines to the pipeline corridors. The problem is that the pipeline has become part of the electrical circuit due to electrostatic and electromagnetic coupling. This coupling may cause induced currents and voltages to exist on the pipeline. The pipeline is addressed as an electrical circuit.

A Cathodically Protected Electrical Substation Ground Grid

A discussion is presented on the design of a cathodically protected electrical substation grounding system in which a steel ground grid and steel ground rods were used in place of the commonly used copper ground grid and copperweld ground rods. Several electrical constraints are presented which discuss common electrical utility requirements, safety considerations, and economic factors. The grounding system materials chosen are discussed along with the means of cathodic protection. Finally, the design, construction, and testing considerations are presented as an aid to others who wish to design a similar system.