| 45291. |
- Sutaria, Jil, et al.
(författare)
-
Factors influencing the induced primary emission and induced secondary emission in the frequency range of 2 to 150 kHz
- 2023
-
Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- The induced primary emission leads to changes in the primary emission of a device and the induced secondary emission leads to changes in the propagation of supraharmonics in the adjacent phase due to the connection of single-phase loads spread over three phases in an installation. The induced primary emission and induced secondary emission are shown to give a significant contribution to the total emission measured at a given point in an installation. The induction of the emission is caused by the inductive and capacitive coupling among the conductors within the cables. This paper presents an analysis of four parameters that impact the magnitude of the induced emissions. Simulations carried out in COMSOL, show that the type of cable used impacts the induced emission and studies show that shielded cable with a stranded conductor with the shield grounded will lead to a reduction in the induced emissions. Among the other parameters, i.e., the load and transformer impedance and the length of the cable, the length of the cable is dominating in deciding the magnitude of the induced emissions. Analysis is carried out using Monte Carlo simulation and varying parameters stochastically. For all investigated parameters there is a strong frequency dependency. The stochastic variation of the load impedance in one phase causes a variation of 5% whereas the change in length of the cable leads to a maximum 40% variation in the considered frequency range for induced primary emission. Measurement results are presented to validate the results.
|
|
| 45292. |
- Sutaria, Jil, et al.
(författare)
-
High Frequency Interaction Of Power Electronics Converters In Ac And Dc Powered Data Centers
- 2021
-
Ingår i: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution. - : Institution of Engineering and Technology. ; , s. 718-722
-
Konferensbidrag (refereegranskat)abstract
- There has been an increase in the number of data centers due to the increase in the requirement of IT services in recent years. While data centers supplied by AC are an established industry, data centers supplied by DC are more research based. Many industries have set up small and experimental DC data centers. In both AC and DC data centers, power electronic converters are employed to supply continuous and reliable power to the servers. The paper aims to study the interaction of these converters in their switching frequency regions within data centers. The paper focuses on beat frequency oscillations caused by high frequency interaction and the impact of cable length on beat frequency.
|
|
| 45293. |
- Sutaria, Jil, et al.
(författare)
-
Measurements and modeling of the frequency behavior of residual current devices- from 4 Hz to 40 kHz
- 2022
-
Ingår i: Electric power systems research. - : Elsevier. - 0378-7796 .- 1873-2046. ; 209
-
Tidskriftsartikel (refereegranskat)abstract
- Residual current devices (RCDs) are a common means of protection against shock due to indirect contact in low voltage (LV) systems. Due to the increasing penetration of power electronics equipment in LV systems, higher amounts of waveform distortion at a broad range of frequencies, from dc, subharmonics up to hundreds of kHz (supraharmonics), are expected to be present both during normal operation and during faults. The standardization committees and manufacturers have responded to this challenge by proposing different types of RCDs that are expected to function under given conditions of fault current waveform. However, subharmonic and supraharmonic frequency components are not considered in the standards for most of the RCD types. This article studies the effect of these frequency components on RCDs type AC, A, B and F. An assessment is made in terms of two types of RCD failure: blinding and nuisance tripping, for which both magnitude of the current and breaking time is considered. A frequency mapping of the RCDs is performed, and an assessment of these results based on the frequency-dependent response of the human body to currents is performed. Finally, a frequency model for RCDs type A, F and B is developed.
|
|
| 45294. |
- Sutaria, Jil
(författare)
-
On the supraharmonics in single-phase and three-phase installations
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Society has increasingly started depending on the continuity of internet services, the interruption can be crucial for vital societal functions. It is therefore important to maintain continuous and reliable operations of e.g., installations housing sensitive IT (Information Technology) loads. The establishment of a data center attracts huge investments, thereby boosting the economy. The electrical load within the data center is more structured with a similar type of load, i.e., power supplies supplying the servers connected repetitively. They also use power-conditioning equipment such as an uninterruptible power supply (UPS), which ensures uninterrupted power to the servers. The power supplies use switching techniques to modulate and condition the power supplied to the IT load. The switching residues from the power supplies are often in the frequency range from 2 kHz to 150 kHz, known as supraharmonics. The switching frequency of power electronic converters and power line communication are identified as the main contributors to supraharmonics. The increase in the number of power electronic converters in the power system has sparked interest in supraharmonics. Limited standards are available on the magnitude of supraharmonics allowed in the system. For installations that house multiple power converters, prior knowledge about the propagation and consequences of the supraharmonics can be an advantage in increasing their reliability. This work is focused on supraharmonics within data centers, but the results of the study can be applied to other installations.The data centers are usually three-phase installations where single-phase devices, i.e., servers are distributed over three phases. To understand the holistic view of the system, it is important to understand the spread of supraharmonics in phase, neutral, and protective earth conductors. A perspective on the behaviour of supraharmonics in three-phase installation is presented in this work. The focal point of the work is the summation of supraharmonics in the neutral conductor and conductor crosstalk. The behaviour of the device connected in single-phase installation and when the same devices are spread over three phases may differ depending on the design of the installation. Since the focus is on a greater number of devices, analysis for the change in the magnitude of supraharmonics in a neutral conductor with the change in the number of devices is also undertaken. The IT workload in a data center changes continuously, thus a constant unbalance in the electrical load between the three phases can exist. The thesis aims to understand the factors influencing the change in supraharmonic magnitude and propagation in phase and neutral conductors according to a balanced and unbalanced voltage supply and loading conditions. The presence of a supraharmonic emitting load in one phase can cause interference on the adjacent phase due to conductor crosstalk. Crosstalk leads to the propagation of supraharmonics between the phases. The work focuses on the parameters influencing the crosstalk phenomena for supraharmonics. Among the parameters studied, the type of cable used in an installation and the cable length is dominating. The measurement of supraharmonic emission from the device connected as single-phase and connected as three-phase would differ because of crosstalk.A large number of servers in data centers connected close by may lead to an increased leakage current. The composite leakage current can comprise subharmonics, harmonics, and supraharmonics. This can cause unwanted tripping of the residual current device (RCD), which is installed for human protection. The work aims to understand the impact of the composite residual current on the operation of the residual current devices.The main contributions of this work are summarized as:• A sensitivity analysis is presented based on the parameters impacting the propagation of supraharmonics for different operating modes of a UPS.• A characterization of supraharmonics emission from different devices according to their time and frequency varying behaviour.• A mathematical model to predict the change in the supraharmonic emission in the neutral conductor.• An increased understanding of the behaviour of supraharmonics for constant powerloads under voltage reduction conditions in three-phase installations.• Introduction and definition of the terms induced primary emission and induced secondary emission to explain conductor crosstalk for supraharmonic emission.• A mathematical model to show the factors influencing the magnitude of induced primary emission and induced secondary emission.• The frequency response of RCDs of type AC, A, B, and F under residual currents comprising pure tones and composite currents is presented by measurements andmodeling.
|
|
| 45295. |
- Sutaria, Jil, et al.
(författare)
-
Propagation of supraharmonics in a data center with different operating modes of UPS
- 2023
-
Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 11, s. 36823-36833
-
Tidskriftsartikel (refereegranskat)abstract
- A data center is a major hub of different converters ensuring continuous power to the server loads. The pulse width modulation switching techniques with frequency emission from 2 to 150 kHz (i.e., supraharmonics) in these converters call for a study of the magnitude and propagation of this emission within data centers where UPS is one of the main contributors of supraharmonics. The paper shows, with measurements and model, the change in magnitude and propagation of supraharmonics with the change in the operating mode of the UPS. The magnitude of supraharmonics shows a non-linear dependency on the power consumed in the online mode. In bypass mode, the magnitude of supraharmonics shows a dependency on the type of load connected. The filter connected between PE-N at the input side of the UPS can cause resonance in the phase conductors. The results show that to study the emission, immunity, and electromagnetic compatibility of supraharmonics for UPS, the factors such as operating mode, the type of load connected, and the input and output impedance need to be considered.
|
|
| 45296. |
|
|
| 45297. |
- Sutaria, Jil, et al.
(författare)
-
Summation of Supraharmonics in Neutral for Three-Phase Four-Wire System
- 2020
-
Ingår i: IEEE Open Journal of Industry Applications. - : IEEE. - 2644-1241. ; 1, s. 148-156
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the increase in electronic loads such as LED lamps, power supply units for computing loads, voltage frequency drives in industries; high-frequency distortion is introduced into the power system. These high-frequency components appear due to the switching components of different power electronic converters present in the mentioned loads. The switching frequency components are most often in the range of 2 kHz to 150 kHz referred to as supraharmonics. The paper aims to show, with simulations and measurements, how supraharmonics sum in neutral and to quantify the neutral supraharmonic current as a ratio of single-phase current. This paper defines characteristics of supraharmonic emission that influence their summation in the neutral conductor through studies of devices connected in a balanced three-phase four-wire system. The paper further defines the relation of the supraharmonics emission with the number of devices connected at each phase. A mathematical model to predict the supraharmonics in a neutral conductor based on single-phase current and the number of devices further proposed.
|
|
| 45298. |
- Sutaria, Jil, et al.
(författare)
-
Supraharmonics within a Datacenter-Emission and Propagation
- 2022
-
Ingår i: 2022 20th International Conference on Harmonics & Quality of Power (ICHQP) Proceedings. - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- The reliability of the electrical and cooling systems is of utmost importance for the uninterrupted operation of the data center information technology (IT) load. The electrical distribution of the data center includes many subsystems starting with the utility and building transformers, uninterruptible power supply (UPS), power distribution units (PDUs), and power supplies ultimately powering the fans and the internal components of IT equipment. The various converters in data centers emit switching frequency residue due to PWM (pulse width modulation) techniques. The switching frequency range falls within the supraharmonic range, i.e., 2 to 150 kHz. This paper aims to show, with measurements, the different types of supraharmonic emissions measured in the data center, and the difference between their maximum and average magnitudes. The paper shows a method to identify the equipment emitting supraharmonic emission and possible disturbances caused by it. The paper traces the propagation of supraharmonic emission from the source through the transformer to the grid. Lastly, a comparison of measurements is made with the compatibility levels given by standard IEC 61000-2-2.
|
|
| 45299. |
- Suteerasak, Thongchai, et al.
(författare)
-
Deposition rates and C-14 apparent ages of Holocene sediments in the Bothnian Bay of the Gulf of Bothnia using paleomagnetic dating as a reference
- 2017
-
Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227 .- 1872-6151. ; 383, s. 1-13
-
Tidskriftsartikel (refereegranskat)abstract
- Three 6-m-long cores of sediments were collected in the northern, middle and southern part of the Bothnian Bay. The sediments were dated by paleomagnetic dating techniques, constrained by magnetic properties and geochemical data. The results indicate the ages of the sediments in the bottom part of the cores in the northern, middle and southern parts of the Bothnian Bay to be approximately 5300 years BP, 5350 years BP and 3500 years BP, respectively. The deposition rate calculated from the estimated ages at various depths show that the deposition rate was generally in the range 0.5-1.5 mm/year but it was higher in the southern part than in the middle and northern parts of the bay. There was a significant increase in the deposition rate at ca 2200 years BP, recorded in all three cores, a rate varying between 2.47 and 3.07 mm/year and lasting until ca 1840 years BP. A proposed constant uplift rate of the crust during the period ca 5500 years BP to present is thus not reflected by a constant deposition rate. The peaks in deposition rates at ca 2200-1840 years BP were followed by a decrease in salinity. This phenomenon is suggested to be caused by crustal uplift, with a threshold being formed in the southern part of the bay, thereby increasing the reactivation of bottom sediments and reducing the inflow of brackish water from the Bothnian Sea. The C-14 ages of the sediments reveal differences in age compared with the paleomagnetic ages. In the southern core, the C-14 ages are ca 1350 years older, and in the north, the age offset is mixed. The reactivation and re-deposition of sediments is argued to be the reason for the apparent C-14 age differences. This finding demonstrates that C-14 cannot be used for the dating of Bothnian Bay sediments unless the radiocarbon age offset has been determined.
|
|
| 45300. |
|
|
