Contemplation of Harmonic Currents Loading on Large-Scale Photovoltaic Transformers

Transformers are habitually designed and manufactured for operation at a fundamental frequency of 50Hz and sinusoidal load current. Transformers are susceptible to non-linear loads. The inception of switching action characterises Non-linear loads and consequently nonsinusoidal load current which brings about higher transformer service losses, hotspot temperature rise, and degradation of cellulosic and liquid insulation, and consequently untimely failure of transformers during service. This phenomenon yield current with different components that are multiples of the fundamental frequency of the distributed photovoltaic power (DPVP) generation system. In order to obviate these challenges, the continuous power rating of the transformer, which is intended to facilitate non-linear loads must be minimised using procedure ascribed by the standards as de-rating. This work, an extension of previous work, proposes a novel procedure by means of Finite Element Method (FEM) for the de-rating of DPVP transformers serving non-linear loads during their service life. The proposed procedure considers parameters such as skin effect, proximity effect, and the magnetic flux leakage on the windings that were not included in the IEEE recommended de-rating procedure. The theoretical examination is substantiated on a 500kVA, three-phase, oil-filled transformer.

Section: Astesj Issn: 2415-6698mentioning

confidence: 95%

“…In [10], transformer losses that occur when facilitating solar PV farm environment were investigated based on seasons. The study in particular draw attention to the injection of harmonics and distortion using the IEEE Std.…”

Section: Astesj Issn: 2415-6698mentioning

confidence: 99%

A Novel De-rating Practice for Distributed Photovoltaic Power (DPVP) Generation Transformers

Thango¹,

Jordaan²,

Nnachi³

2021

“…The winding Eddy loss in the closed-path dx is then expressed as shown in Eq. (10). Considering that the thickness of the closedpath is extremely small in relation to the height, then the distance x I negligible.…”

Section: = ×mentioning

confidence: 99%

“…Transformers are commonly designed under the presumption of sinusoidal loading conditions [6][7]. It is widely known that distorted harmonic load currents accentuates the service losses in transformer and ultimately the temperature rise and generation of hotspots in metallic structures, resulting in degradation of insulation materials and untimely failures as shown in Figure 1 (b) [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

A Novel Approach for Evaluating Eddy Current Loss in Wind Turbine Generator Step-Up Transformers

Thango¹,

Jordaan²,

Nnachi³

2021

South Africa is aiming to achieve a generation capacity of about 11.4GW through wind energy systems, which will contribute nearly 15.1% of the country's energy mix by 2030. Wind energy is one of the principal renewable energy determinations by the South African government, owing to affluent heavy winds in vast and remote coastal areas. In the design of newfangled Wind Turbine Generator Step-Up (WTGSU) transformers, all feasible measures are now being made to drive the optimal use of active components with the purpose to raise frugality and to lighten the weight of these transformers. This undertaking is allied with numerous challenges and one of them, which is particularly theoretical, is delineated by the Eddy currents. Many times the transformer manufacturer and also the buyer will be inclined to come to terms with some shortcomings triggered by Eddy currents. Still and all, it is critical to understand where Eddy currents emanate and the amount of losses and wherefore the temperature rise that may be produced in various active part components of WTGSU transformers. This is the most ideal choice to inhibit potential failure of WTGSU transformers arising from excessive heating especially under distorted harmonic load conditions. In the current work, an extension of the author's previous work, new analytical formulae for the Eddy loss computation in WTGSU transformer winding conductors have been explicitly derived, with appropriate contemplation of the fundamental and harmonic load current. These formulae allow the distribution of the skin effect and computation of the winding Eddy losses as a result of individual harmonics in the winding conductors. These results can be utilized to enhance the design of WTGSU transformers and consequently minimize the generation of hotspots in metallic structures.

“…It is widely accepted that the transformer losses in the renewable energy power systems is relatively high [17]- [18], and the manufactures design philosophies must be imbedded with data such as a complete harmonic spectrum to design the most optimised offers. The effect of such implementation will inescapably increase the transformer price.…”

Section: A) Optimization Of the Transformer Design Philosophymentioning

confidence: 99%

Application of Polynomial Regression Analysis in Evaluating the Techno-Economic Performance of DSPV Transformers

Thango¹,

Jordaan²,

Nnachi³

2021

To this extent, the delineation of techno-economic evaluations for transformers becomes more intricate through a lens of Distributed Solar Photovoltaic (DSPV) market in South Africa. Essentially, the transformer price and loss evaluation techniques should be tailored for calculating the Total Ownership Cost (TOC) of transformers facilitating decentralized energy systems. In South Africa, the traditional coal power generation and renewables operate concurrently under liberalized energy markets but have distinct operational requirements and therefore have distinct methods for evaluating their generating states, service loss costs and TOC. As a result, their techno-economic evaluations should be different. In this work, new formulae have been developed to contemplate on a comprehensive technique for calculating the transformer prices and losses necessitated to estimate the cost of service losses and TOC for DSPV transformers. These formulae are based on experimental studies undertaken on a fleet of DSPV transformers ranging from 1.25 to 250MVA. In order to substantiate these new formulae, 4 case studies have been presented. The calculated losses and associated cost results against the pragmatic values from the case studies yield an error of estimation of less than 1% and 2% respectively in all cases. Further, these results are used to calculate the cost of losses and TOC using a methodology that has been proposed in previous work exclusively for power producers who are proprietors of DSPV generation systems.