Innovative procedure for measurement of losses of transformers supplying nonsinusoidal loads

Fuchs, E.F.; Yıldırım, Deniz; Batan, T.

doi:10.1049/ip-gtd:19990684

Cited by 28 publications

(21 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…2 Pseries-l~Tpseries(t)dt. (2)(3)(4)(5)(6)(7)(8)(9) The power dissipated in Zshun t is Pshunt=r~rpshunt(t)dt. ( …”

Section: Direct Loss Measurementmentioning

confidence: 99%

“…2-12) are proportional to the square of the current and frequency: PEC = gee/2h2, (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) where KEc is a proportionality constant. Under rated (sinusoidal) conditions, the load loss resulting in the hot spot temperature can be expressed as PLL-R =/2R2 + PEC-R, (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) where PEC-R is the eddy-current loss resulting in the hot spot temperature under rated (sinusoidal) operating conditions. In per unit of the rated FR loss, Eq.…”

Section: Derating Of Transformers Determined From the K-factormentioning

confidence: 99%

“…Measuring transformer losses from the input power minus the output power in real time is inaccurate because the losses are the difference of two large values; this indirect approach results in maximum errors in the losses of more than 60% for high-efficiency (r/> 98%) transformers [7]. The usually employed indirect method consisting of no-load (iron-core loss) and short-circuit (copper loss) tests [67] cannot be performed online while the transformer is partially or fully loaded.…”

Section: Measurement Of Derating Of Three-phase Transformersmentioning

confidence: 99%

“…The measuring circuit is based on PTs, CTs, shunts, voltage dividers or Hall sensors [72], A/D converter, and computer (microprocessor). Using a computer-aided testing (CAT) program [7,73], losses, efficiency, harmonics, derating, and wave shapes of all voltages and currents can be monitored within a fraction of a second. The maximum errors in the losses are acceptably small and depend mainly on the accuracy of the sensors used.…”

Section: Measurement Of Derating Of Three-phase Transformersmentioning

confidence: 99%

See 3 more Smart Citations

Harmonic Models of Transformers

2008

Power Quality in Power Systems and Electrical Machines

View full text Add to dashboard Cite

Extensive application of power electronics and other nonlinear components and loads creates single-time (e.g., spikes) and periodic (e.g., harmonics) events that could lead to serious problems within power system networks and its components (e.g., transformers). Some possible impacts of poor power quality on power transformers are 9 saturating transformer core by changing its operating point on the nonlinear ~-i curve, 9 increasing core (hysteresis and eddy current) losses and possible transformer failure due to unexpected high losses associated with hot spots, 9 increasing (fundamental and harmonic) copper losses, 9 creating half-cycle saturation in the event of even harmonics and DC current, 9 malfunctioning of transformer protective relays, 9 aging and reduction of lifetime, 9 reduction of efficiency, 9 derating of transformers, 9 decrease of the power factor, 9 generation of parallel (harmonic) resonances and ferroresonance conditions, and 9 deterioration of transformers' insulation near the terminals due to high voltage stress caused by lightning and pulse-width-modulated (PWM) converters.Pfe = Phys + Peddy = ghys (Bmax)Sf + geddy(Bmax)2f 2, (2-1) where Phys, Peddy, Bmax, and f are hysteresis losses, eddy-current losses, maximum value of flux density, and fundamental frequency, respectively. Khys is a constant for the grade of iron employed and Keddy is the eddy-current constant for the conductive material. S is the Steinmetz exponent ranging from 1.5 to 2.5 depending on the operating point of transformer core.9 Elsevier Inc. All rights reserved. I ~,H I i r 9 FIGURE 2.4 Magnetic field strength inside and outside of a conductor. / / I i \ % o 9 "% ~Ho3 / %% u / / %

show abstract

“…2 Pseries-l~Tpseries(t)dt. (2)(3)(4)(5)(6)(7)(8)(9) The power dissipated in Zshun t is Pshunt=r~rpshunt(t)dt. ( …”

Section: Direct Loss Measurementmentioning

confidence: 99%

Section: Derating Of Transformers Determined From the K-factormentioning

confidence: 99%

Section: Measurement Of Derating Of Three-phase Transformersmentioning

confidence: 99%

Section: Measurement Of Derating Of Three-phase Transformersmentioning

confidence: 99%

See 2 more Smart Citations

Harmonic Models of Transformers

2008

Power Quality in Power Systems and Electrical Machines

View full text Add to dashboard Cite

show abstract

“…In Reference [16], a number of thermometers have been placed in different parts of the transformer and the factor K has been evaluated by the temperature measurements. In Reference [17], a data acquisition method has been proposed for independent real-time calculation of the core and copper losses under different linear and non-linear loads. The advantages of this method are the high speed of the digital circuit, high reliability, low cost and absence of thermocouple.…”

Section: Introduction and Literature Reviewmentioning

confidence: 99%

Derating of a distribution transformer for non-linear loads

Sharifian

Faiz

2006

Euro. Trans. Electr. Power

View full text Add to dashboard Cite

SUMMARYThis paper deals with an important problem related to power quality that has been tackled in the literature quite often. The three-phase distribution transformer in electrical power systems is generally installed for supplying loads with rated frequency. Non-linear loads introduce harmonics to the supply and result in a different performance compared with that of the designed transformer. In this paper a three-phase 50 kVA distribution transformer is modeled using the finite element (FE) method in order to evaluate its losses under non-linear loads.Comparison of the FE computation results with the analytical standard method results shows that the latter method leads to a more conservative estimate of the transformer derating.

show abstract

Liquid‐Filled Transformers: Design, Optimization, and Monitoring

Fuchs

2017

Wiley Encyclopedia of Electrical and Electronics Engineering

View full text Add to dashboard Cite

Liquid‐filled transformers have as cooling medium biodegradable, noncarcinogenic synthetic or natural esters. Three‐phase transformers of various configurations with and without grounding have several functions: increase/decrease of voltages and currents, filtering of harmonics, assist in protection of power systems, and permit a change of grounding reference. Oriented and amorphous electrical steels permit an efficient and economic design even for operating conditions above the knee of the nonlinear (B‐H) characteristic. Finite‐difference and finite‐element numerical methods can be successfully applied to model the influence of harmonics through phase‐factors to minimize skin effects. Real‐time monitoring of transformer losses is based on the calibration of voltage and current differences which limit the measuring errors to a few percent, for example, 6% at a measured power efficiency of larger than 98%, and permit the use of off‐the shelf transformers without any sensors installed within windings, iron cores, or coolant. Online measuring of total losses provides a mechanism for limiting the temperature increase. The performance of transformers underDCbias is important for renewable energy systems employing converters (e.g., rectifiers, inverters) and exposure to geomagnetically induced currents (GICs). Transformers are suitable for 6‐, 12‐ or 18‐pulse rectifiers used in high‐voltageDC(HVDC) transmission lines. Superconducting MW‐range transformers are available but costly, while superconducting magnets are widely used in the health (magnetic resonance imaging) and research fields: Large Hadron Collider in Switzerland/France and fusion reactor such as Wendelstein 7‐Xin Germany.

show abstract

Innovative procedure for measurement of losses of transformers supplying nonsinusoidal loads

Cited by 28 publications

References 3 publications

Harmonic Models of Transformers

Harmonic Models of Transformers

Derating of a distribution transformer for non-linear loads

Liquid‐Filled Transformers: Design, Optimization, and Monitoring

Contact Info

Product

Resources

About