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Candelaria J.,University of Colorado at Denver | Candelaria J.,NEI Electrical Power Engineering Inc. | Park J.-D.,University of Colorado at Denver
2011 IEEE/PES Power Systems Conference and Exposition, PSCE 2011 | Year: 2011

Currently classical thyristor-based high voltage direct current (HVDC) systems hold the market in bulk power transmission. However, recent advances in semiconductor technology have led to voltage source converter based HVDC (VSC-HVDC) systems becoming a viable competitor. Not only is VSC-HVDC a competitor for transmission but it can also be used in multi-terminal systems, which have become an attractive option for renewable energy applications or for distribution in large cities. As more and more VSC-HVDC systems are installed, the protection of these systems must be taken into account. This paper explores different options and ideas for VSC system protection. © 2011 IEEE.

Smith S.C.,Lockheed Martin | Sen P.K.,Colorado School of Mines | Kroposki B.,National Renewable Energy Laboratory | Malmedal K.,NEI Electrical Power Engineering Inc.
Papers Presented at the Annual Conference - Rural Electric Power Conference | Year: 2010

There is an increasing demand both by legislation and the public for a more secured, reliable and efficient power system using dispatchable and non-dispatchable renewable resources. However, the existing design and operational practice of the electrical power grid does not lend itself easily to the incorporation of non-dispatchable renewable energy resources. Distributive Electrical Energy Storage (DESS) is a key to the development and future of all non-dispatchable renewable energy resources in the electrical power grid. This paper provides an overview, discusses the state-of-the-art status and will introduce how DESS can be used to incorporate non-dispatchable renewable resources into the power grid and also provide additional benefits to the power system. © 2010 IEEE.

Bates C.,Colorado School of Mines | Cain D.,NEI Electrical Power Engineering Inc. | Malmedal K.,NEI Electrical Power Engineering Inc.
Conference Record - Industrial and Commercial Power Systems Technical Conference | Year: 2016

Previous papers proposed a method to find the maximum possible dried area of soil expected due to heating by underground cables. A method was also proposed to include this dried soil area in cable ampacity calculations. This assumed cables would be loaded 100% of the time. To dry soil to the maximum possible extent may take very long time periods, and in many installations the cables actually carry current for a limited time. In these cases the soil may never dry to its maximum extent. This paper proposes a method to approximately determine the radius of dried soil that will occur due to cable heating for limited periods of time. It similarly proposes a method to approximate the time it will take for the dried soil to be replenished to its original moisture content after heating by the cables has ceased. © 2016 IEEE.

Malmedal K.,NEI Electrical Power Engineering Inc. | Bates C.,NEI Electrical Power Engineering Inc. | Cain D.,NEI Electrical Power Engineering Inc. | Cain D.,Metropolitan State University of Denver
IEEE Transactions on Industry Applications | Year: 2016

Cables are often installed in underground conduits surrounded by concrete. To calculate the cable ampacity in these duct banks, the concrete thermal resistivity must be known. A set of experiments was performed to determine the effects that a concrete mixture has on the resulting thermal resistivity. Concrete flow-fill mixtures containing water-cement-sand and water-cement-fly-ash-sand were studied. Experiments showed that the water content of a mixture is not a factor in the final concrete thermal resistivity unless fly ash was included in the mixture; however, the water-to-cement ratio is significant for all mixtures. Empirical equations were derived to find the resistivity of concrete as a function of the constituents of the concrete mixture. These equations may be used to design a concrete mixture to produce the desired thermal resistivity or to calculate the thermal resistivity of a known concrete mixture. © 1972-2012 IEEE.

Malmedal K.,NEI Electrical Power Engineering Inc. | Bates C.,NEI Electrical Power Engineering Inc. | Cain D.,NEI Electrical Power Engineering Inc.
IEEE Power and Energy Society General Meeting | Year: 2015

The heat generated by underground cables has been known to cause the soil around the cables to dry, increasing its thermal resistivity and potentially causing the cables to overheat. The ability of soil to maintain a constant resistivity while being subjected to a heat source is known as its 'thermal stability'. A method using the Law of Times has often been recommended to find soil stability. To test whether this method can accurately predict soil thermal stability an experiment was performed that tested the hypothesis inherent in the Law of Times that the diameter of the heat source affects the drying time of the soil surrounding it. This paper reports the results of that experiment and includes the statistical analysis of the data. The experimental evidence resulted in rejecting the Law of Times as an accurate predictor of the drying time of soil around a buried cable. © 2015 IEEE.

Nelson J.P.,NEI Electrical Power Engineering Inc.
IEEE Transactions on Industry Applications | Year: 2015

High resistance grounding (HRG) is a well-proven technology for improving electric reliability for many industrial and utility facilities such as used in petrochemical, automotive, and generating plants. Many such facilities require the increased reliability for production and operational reasons. This paper will discuss the improved personnel safety aspects of using HRG on low-voltage systems. In particular, this paper will discuss the following: 1) the probability of the three common faults occurring within an industrial plant, namely, three-phase, phase-to-phase, and ground faults; 2) how the probability of a ground fault can be used to improve electrical safety with HRG; 3) the impact of a ground fault on a system and the speed at which the ground fault on a solidly grounded system may propagate into a multiphase fault; 4) the risk reduction of a ground fault on an HRG system propagating into a multiphase fault; 5) the potential reduction in serious and fatal arc blast injuries through the use of an HRG system; and 6) potential single-pole breaker clearing issues when a second ground fault occurs on a second phase. This paper will include comments from recent testing, which was conducted at the KEMA Laboratories and presented in a recent IEEE Industry Applications Society Petroleum and Chemical Industry Committee paper in September 2014. © 2015 IEEE.

Nelson J.P.,NEI Electrical Power Engineering Inc. | Billman J.D.,NEI Electrical Power Engineering Inc. | Bowen J.E.,Aramco Services Company
IEEE Transactions on Industry Applications | Year: 2014

This paper provides a discussion on the theory behind reducing the risk and severity of an arc flash incident. In particular, the variables associated with the calculations of energy from an arcing fault are presented in an effort to show the futility of present methods for determining incident energy levels in the electrical industry. A number of commonly ignored design concepts that significantly reduce the risk of electrical hazards will be discussed, two of which include: 1) system grounding; and 2) solid insulation. This paper will discuss risk and the management of risk as a means of reducing the probability of an incident. It will then show how risk reduction should be used in the design, construction, operation, and maintenance of electrical equipment as means for the safeguarding of employees in the workplace. © 2014 IEEE.

Ammerman R.F.,Colorado School of Mines | Gammon T.,John Matthews and Associates | Sen P.K.,Colorado School of Mines | Nelson J.P.,NEI Electrical Power Engineering Inc.
IEEE Transactions on Industry Applications | Year: 2010

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. © 2010 IEEE.

Bates C.,NEI Electrical Power Engineering Inc. | Malmedal K.,NEI Electrical Power Engineering Inc. | Cain D.,NEI Electrical Power Engineering Inc.
Papers Presented at the Annual Conference - Rural Electric Power Conference | Year: 2015

When designing electrical power systems, it is often necessary to determine underground cable ampacity. Various methods are in use today including computer simulation, ampacity tables, and a method that has recently been suggested that includes the effects of moisture migration through soil. Each of these methods can yield substantially different ampacity results for the same installation. Regardless of the method, using the correct value of soil thermal resistivity is critical and using the wrong value can result in cables that are incorrectly sized. This paper examines several commonly used methods and their underlying assumptions. Examples are provided to illustrate the differences in the results obtained from various methods and the consequences of using incorrect assumptions. It is hoped that these examples will provide guidance on the implementation of each method. © 2015 IEEE.

Nelson J.P.,NEI Electrical Power Engineering Inc. | David Lankutis J.,POWER Engineers
Papers Presented at the Annual Conference - Rural Electric Power Conference | Year: 2014

This paper provides a process to quantify the costs associated with interruptions of service to customers of electric utilities. A basic assumption is that in a majority of cases, the most cost effective solution to a given power quality issue involves investment of time and money on both sides of the electric meter. The information included in this paper is intended to guide the engineer from the utility and the engineer from the customer of the utility as they collaborate to justify funds for the solution they have designed. The paper shows that gross errors may be made by utilizing general costs for power outages. It does present reasonable methods to develop realistic costs of power outages to customers in an effort to justify capital investments for improving reliability for the utility customer in their specific situation. © 2014 IEEE.

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