| 1. |
- Bollen, Math, et al.
(author)
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CIGRE/CIRED/UIE JWG C4.110 - Voltagedip immunity of equipment in installations : status April 2008
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- This paper presents the status of the work, by April 2008, in C4.110, a joint working group by CIGRE, CIRED and UIE. The scope of the working group is to gather technical knowledge on the immunity of equipment, installations and processes against voltage dips, and to use this knowledge in the further development of methods and standards. The activities of the working group are divided in seven "chapters". Chapters 1 and 7 are introduction and conclusions, respectively. Chapter 2 gives a general description of voltage dips as they appear at the terminals of sensitive equipment. Chapter 3 describes the performance of equipment and processes during voltage dips. This chapter also includes recommendations on the design of processes. In Chapter 4 the results from Chapter 2 and Chapter 3 are combined to set requirements for the dip characteristics that should be included in immunity testing. Chapter 5 is the data gathering chapter, covering data on voltage-dip statistics at different locations, but also data on the economics of equipment immunity and testing. Finally, in Chapter 6, recommendations for immunity objectives will be given. Important contributions of the working group are: a check-list of voltage dip characteristics to be used early in the design of equipment; a methodology to assess the performance of a complete installation and to include voltage-dip performance in the design of the installation; recommendations for characterization testing of equipment against voltage dips; recommendations for voltagedip immunity of equipment.
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| 2. |
- Bollen, Math, et al.
(author)
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Integration of distributed generation in the power system : a power quality approach
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- This paper gives an overview of the design and operation issues in distribution and transmission systems due to the integration of distributed generation. The hosting-capacity approach has been developed to obtain a quantitative measure on the amount of generation that can be connected without impairing the performance of the system. The hosting-capacity approach requires a set of well-defined performance indices together with acceptable limits.
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| 3. |
- Djokic, Sasa, et al.
(author)
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Dip segmentation method
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- An alternative approach for the analysis of various types of dip events, termed Dip Segmentation Method, is presented in this paper. The description of a voltage dip in the proposed method includes both pre-dip and postdip parts/segments of a dip-related event, while the during-dip part is divided into a number of "during-event segments" and "transition segments". In that way, the proposed method allows for an improved assessment of standard and commonly used dip characteristics, incorporating, at the same time, several usually neglected characteristics, aspects and features of dip events into the analysis. After identifying the corresponding dip segments, direct correlation between the individual segments and particular effects on equipment operation could be established, allowing a more detailed description of the dip events and more accurate assessment of their influence on equipment performance.
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| 4. |
- Larsson, Anders, et al.
(author)
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Waveform distortion at computer festivals : 2002 to 2008
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- This paper shows measurements of the harmonic emission by large groups of state-of-the-art computers measured at five different occasions from 2002 to 2008. The emission was measured during LAN-festivals where the participants use mainly the newest models of computer. This allows insight in the change in emission of computers during the last 6 years. The results from these measurements show that the distortion level generated by computers is decreasing while the power consumption does not show any significant change.
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| 5. |
- Lin, Yufeng, et al.
(author)
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Evaluation of dip and interruption costs for a distribution system with distributed generations
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- This paper propose a method to evaluate the dip and interruption costs in the distribution system with distributed generation units (DGs). The game theory is used to allocate the additional cost caused by operating DGs. To evaluate the impacts of DGs on dip and interruption costs, which could be positive impact or negative impact, the operating hours of DGs, the frequencies of the power quality events and the cost of a power quality event are estimated. In this paper, the operation hours of DGs are estimated according to the load duration curve and the operation cost of DGs; the frequencies of power quality events are calculated according to the reliability theory; the cost of a power quality event is evaluated using weighting factors. The additional dip and interruption costs caused by operating DGs are allocated among the DGs using the Shapley value axiom.
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| 6. |
- Rönnberg, Sarah, et al.
(author)
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Equipment currents in the frequency range 9-95 kHz, measured in a realistic environment
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- A number of measurements have been performed on a full-scale electric model of a house to examine how enduser equipment affect the impedance in the frequency range 9-95 kHz. It is shown that the impedance level for the grid itself is fairly high and that it decreases when end-user equipment is connected. End-user equipment can be divided in to different categories, loads for which impedance is constant over time (for one cycle) and frequency and loads for which impedance varies over time, frequency or both. The measurements indicate that currents in high frequencies travel between loads at a much higher degree than between the load and the transformer.
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| 7. |
- Tjäder, A., et al.
(author)
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Performance Evaluation for Frequency Estimation of Transients Using the ESPRIT: Measured Noise versus White Noise
- 2008
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In: ICHQP 2008: 13th International Conference on Harmonics and Quality of Power; Wollongong, NSW. - Piscataway, NJ : IEEE Communications Society. ; , s. 8-
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Conference paper (peer-reviewed)abstract
- A number of papers have proposed to use the ESPRIT method for estimating some power system transients. The mathematical model for using the ESPRIT requires that the additive noise be white. Fail to satisfy this could lead to degraded performance of frequency estimation. However, in practical situations the noise is often non-white. In this paper we study the performance of the ESPRIT frequency estimation method when the additive noise is measured from power systems. It is shown that tests using synthetic white noise are not sufficient for realistic power-system scenarios, as the noise is often non-white and not i.i.d. distributed. First, a set of measured voltage waveforms is superimposed to synthetic transients with known frequencies. This yields a set of semi-measured transients. The ESPRIT method is then applied to estimate the frequencies. The performance of the ESPRIT is then evaluated in term of the mean value and standard deviation. Our experiments show that, for a transient contains one sinusoid, the ESPRIT of sinusoidal model order K=2 results in an acceptable accuracy if the amplitude of the transient is well above the noise level and the transient frequency is not too close to the power-system frequency. This is sufficient for most practical applications. A better performance for higher noise levels is obtained by significantly increasing the sinusoidal model order in the ESPRIT.
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| 8. |
- Wämundsson, Mikael, et al.
(author)
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Predicting the number of voltage dips as a function of both voltage and duration
- 2008
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In: 2008 13th International Conference on Harmonics and Quality of Power. - Piscataway, NJ : IEEE Communications Society. - 9781424417704
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Conference paper (peer-reviewed)abstract
- This paper present a method for predicting voltage dips as experienced by customers due to faults in the power grid. Where earlier methods considered only the magnitude (residual voltage) of the dips, this paper considers both magnitude and duration. A triangular distribution is assumed for the dip duration for each of three zones, together with probabilities for each zone. The dips are generated randomly by means of a Monte-Carlo simulation, with fault location along the line and dip duration as random variables. The results can next be analyzed by any of the methods developed for analyzing voltage-dip measurements. The method is illustrated by means of the dips experienced by an industrial installation connected to the 130-kV subtransmission network.
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