Derating of power distribution transformers serving nonlinear industrial loads

Cazacu, Emil; Petrescu, Lucian; Ioniţă, Valentin

doi:10.1109/optim.2017.7974953

Cited by 12 publications

(9 citation statements)

References 21 publications

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“…Derating distribution, industrial, or commercial transformers due to heating induced by harmonics distortion is a well-documented application [35][36][37][38][39]. As defined in Faiz, Ghazizadeh, and Oraee, the four methods applicable to derating transformers include IEEE recommendations, analytical methods, experimental approaches, and finite elements [14].…”

Section: Harmonic Distortion Evaluationmentioning

confidence: 99%

“…Historically, most system problems caused by harmonic distortion originate at a single source or customer, which prompts mitigation efforts to be directed exclusively at one location, bus, circuit, or subdistribution circuit. In fact, most research endeavors focus on derating transformers rated less than 2 MVA that serve mostly dedicated nonlinear loads [9,[35][36][37][38][39][40][41][42][43]. For substation transformers that serve a combination of residential, industrial, and commercial loads, accounting for harmonic is typically ignored due to the low levels of distortion and isolation of problems [1].…”

Section: Harmonic Distortion Evaluationmentioning

confidence: 99%

“…Therefore, it may be unlikely that the unit can deliver the same amount of peak demand without experiencing higher than expected internal temperatures and ergo increased loss of life. The best approach for preventing excessive aging of a unit is to derate the existing capacity limits [35][36][37][38][39][40][41][42][43]. Derating is established by reducing the peak energy demand of the unit to a level that maintains the hottest spot temperature (Θ H ) below acceptable levels according to IEEE Std.…”

Section: Existing Unit Derating-normal Operationsmentioning

confidence: 99%

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Demand Side Management Effects on Substation Transformer Capacity Limits

2019

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In high penetrations, demand side management (DMS) applications augment a substation power transformer’s load profile, which can ultimately affect the unit’s capacity limits. Energy storage (ES) applications reduce the evening peaking demand, while time-of-use rates incentivize end-users to charge electric vehicles overnight. The daily load profile is further augmented by high penetrations of photovoltaic (PV) systems, which reduce the midday demand. The resulting load profile exhibits a more flattened characteristic when compared to the historical cyclic profile. Although the initial impact of PV and ES applications may reduce a unit’s peak demand, long-term system planning and emergency conditions may require operation near or above the nameplate rating. Researchers have already determined that a flattened load profile excessively ages a unit’s dielectrics more rapidly. The focus of this research was to identify an approach for establishing new transformer capacity limits for units serving flattened load profiles with a high harmonic content. The analysis utilizes IEEE standards C57.91 and C57.110 to develop an aging model of a 50 MVA SPX Waukesha transformer. The results establish a guideline for determining transformer capacity limits for normal operation, long-term emergency operation, and short-term emergency operation when serving systems with high penetrations of DSM applications.

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Section: Harmonic Distortion Evaluationmentioning

confidence: 99%

Section: Harmonic Distortion Evaluationmentioning

confidence: 99%

Section: Existing Unit Derating-normal Operationsmentioning

confidence: 99%

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Demand Side Management Effects on Substation Transformer Capacity Limits

2019

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“…The main power quality parameters at the transformer are measured at the machine secondary part (low-voltage windings) with a C.A 8335 Qualistar Plus power quality analyzer [9]. The most import of them are: root mean square (RMS), Total Harmonic Distortion (THD), distorsion factor (DF), crest factor (CF) and Harmonic loss factor (KF) and voltage flicker (PLS) [17][18][19]. According to their values, presented in Figure 9, the transformer operates under normal condition…”

Section: Predictive Maintenance Of a Power Distribution Transformermentioning

confidence: 99%

The Major Predictive Maintenance Actions of the Electric Equipments in the Industrial Facilities

Cazacu

Petrescu

2018

The Scientific Bulletin of Electrical Engineering Faculty

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In modern low-voltage electrical installations, the predictive maintenance of the major electrical equipments involved in the power delivery process (transformers) or in the conversion of the electrical energy (especially electric motors) becomes mandatory. Thus, a high level of reliability and safety is assured for both the electric facility and operators. The proactive maintenance is to be non-invasively performed and mainly requires an infrared (IR) thermographic inspection and power quality analysis of the installation loads. A vibration investigation is also necessary for the motor drive systems. The paper critically studies the first two main maintenance procedures revealing their main characteristics, performances and limits. A case-study presents a 1000 kVA distribution transformer that supplies a bakery facility that comprised mainly heaters and inductions motors as loads.

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“…One of the most common power quality issue encountered in the modern electric power grids is the distortion of the current or voltage waveforms. That is mainly caused by the proliferation of the nonlinear loads, which are to be found in any industrial or domestic low-voltage installations [1][2][3]. One could rightly state, that due to the extensive electronic device usage, the linear loads are nowadays increasingly rare.…”

Section: Introductionmentioning

confidence: 99%

Nonsinusoidal load current effect on the electrical and thermal operating parameters of oil filled power distribution transformers

Cazacu

Petrescu

Ioniţă

et al. 2018

2018 18th International Conference on Harmonics and Quality of Power (ICHQP)

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Most of the in-service power distribution transformers from the industrial electric facilities were designed to operate under pure sinusoidal state conditions. Nevertheless, the majority of the loads from modern electric installations are intrinsically nonlinear and consequently, they generate nonsinusoidal currents. These high-order harmonics (present into the current waveform spectrum) have a negative impact on the transformers thermal and electrical operating parameters and, ultimately, limit the machine loading capability. The paper quantitatively investigates the transformer behavior under distorted current conditions by developing a procedure for evaluating different relevant operating quantities (maximum permissible current, the hottest spot temperature, aging acceleration factor and the machine remaining lifetime). The computation relays on the international standard recommendation and mainly uses the load current harmonic spectrum and the transformer rated data. To reveal the proposed procedure performance, a distribution transformer of 400 kVA from an industrial plasterboard facility is investigated.

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Derating of power distribution transformers serving nonlinear industrial loads

Cited by 12 publications

References 21 publications

Demand Side Management Effects on Substation Transformer Capacity Limits

Demand Side Management Effects on Substation Transformer Capacity Limits

The Major Predictive Maintenance Actions of the Electric Equipments in the Industrial Facilities

Nonsinusoidal load current effect on the electrical and thermal operating parameters of oil filled power distribution transformers

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