A new model to study ultra-saturation phenomenon during the energization of a loaded three-phase power transformer and its effects on differential protection

Noshad, Bahram; Tabatabaee, Sajad; Ghanavati, Behzad; Mohammadzadeh, Saeid

doi:10.1002/etep.2060

Cited by 7 publications

(3 citation statements)

References 49 publications

(154 reference statements)

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“…The method is essentially based on the measurement of the peak current and the magnetic flux in the iron core. In Noshad et al, a new method to investigate ultra‐saturation at the energization time of the loaded three‐phase transformer was presented, with consideration of its effect on differential protection. The ultra‐saturation phenomenon was modeled by taking into account the residual flux and the nonlinearity of the saturation curve.…”

Section: Introductionmentioning

confidence: 99%

Modified method for transformer magnetizing characteristic computation and point‐on‐wave control switching for inrush current mitigation

Yahiou

Bayadi

Babes

2019

Circuit Theory & Apps

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Summary This paper proposes a new model for the low‐frequency transient analysis of a transformer, with a modified equation for calculation of the flux‐current characteristic representing the saturation inductance of the transformer. The model is based on the V‐I (voltage‐current) no‐load curves and uses the no‐load reactive power losses. To validate the model, it was used to simulate the no‐load magnetizing current in steady‐state condition, as well as the transient inrush current at network frequency. Evaluation was done both by comparing the simulation results obtained with the proposed model and those available in the relevant literature, and by practical measurements. The experimental results presented in this paper were obtained via a laboratory setup and a data acquisition system based on the dSPACE board 1104. Moreover, a control switching to mitigate the transient inrush current in a transformer was developed and applied experimentally in the laboratory and also in the simulations. This control strategy was performed by taking into account the residual flux at the opening instant of the related circuit breaker. A comparative study was carried out showing the validity of the proposed model and the mitigation technique.

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Section: Introductionmentioning

confidence: 99%

Modified method for transformer magnetizing characteristic computation and point‐on‐wave control switching for inrush current mitigation

Yahiou

Bayadi

Babes

2019

Circuit Theory & Apps

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“…In Zheng et al, it is mentioned that in 1000 kV UHV AC experiment project in China, mal‐operation of differential protection in VRT occurred twice under magnetizing inrush current conditions when the power transformer was energized from the 500 kV side with no load. The traditional criterion based on the second harmonic ratio is unable to distinguish the inrush current from the fault current of the VRT, which challenges the proper operation of the VRT differential protection . However, for a VRT with OLTC, a key factor of protection reliability relies on the accurate detection of the tap position .…”

Section: Introductionmentioning

confidence: 99%

Adaptive algorithm for identifying OLTC position and its application on UHV voltage-regulating transformer differential protection

Zheng

Liu

et al. 2018

Int Trans Electr Energ Syst

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The voltage-regulating transformer (VRT) with on-load tap changer is specifically used to adjust the voltage on the medium-voltage side of the ultra-high voltage power transformer. In practice, during the process of on-load voltage regulation, it is difficult to acquire the tap changer's positon, which is necessary for the calculation of the VRT differential current. Therefore, a novel algorithm is proposed to identify the real-time turns ratio of the VRT, adaptively, according to the structure of the ultra-high voltage power transformer. On the basis of the real-time turns ratio, the adaptive differential current is calculated. Both theoretical analysis and simulation results indicate that the proposed algorithm can track and calculate the turns ratio accurately, thus preventing unbalanced currents during the tap-changing process. Moreover, the performance of the VRT differential protection is evaluated under inter-turn fault conditions. Simulation results verify that the proposed algorithm can overcome the disadvantages in the existing protection schemes.KEYWORDS differential protection, inter-turn fault, on-load tap changer (OLTC) position, ultra-high voltage (UHV), voltage-regulating transformer (VRT)

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“…Energization of power system components is accompanied by a switching transient, and the energization transients of components such as transformers, shunt capacitor banks, and conventional shunt reactors have been well documented. However, owing to their special body structures, MCSR energization transients are more complicated than those of conventional shunt reactors and transformers, and there has not been much research so far on the energization of MCSRs …”

Section: Introductionmentioning

confidence: 99%

Modeling and impacts analysis of energization transient of EHV/UHV magnetically controlled shunt reactor

Zheng

Huang

Zhang

et al. 2017

Int. Trans. Electr. Energ. Syst.

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To address the problems of overvoltage, harmonic distortion, and mal-operation that can occur in protection systems as a result of direct energization in magnetically controlled shunt reactors (MCSRs), this paper proposes a novel approach for MCSR energization-namely, pre-excited energization. Using the structure and operating principles of an MCSR, a detailed derivation of energization transient mathematical model for both direct and pre-excited energization are presented and the model-specific impacts of the 2 different energization modes are investigated. To validate the theoretical analysis, we performed physical model tests and simulations of different energization modes. The results indicate that pre-excited energization is capable of suppressing overvoltage on the DC link bus and alleviating harmonics caused by direct energization. KEYWORDS energization, impacts analysis, magnetically controlled shunt reactor (MCSR), mathematical model, transient characteristics 1 | INTRODUCTIONControllable shunt reactors placed on line terminals or substation bus bars play an important role in extra high-/ultra high-voltage (EHV/UHV) transmission networks of voltage control and reactive power compensation. 1-3 With the advantages of continuously adjustable capacity, 4 low harmonics, 5 and excellent steady-state control characteristics, 6 magnetically controlled shunt reactors (MCSRs) are preferable for reactive power compensation in EHV/UHV power systems. Energization of power system components is accompanied by a switching transient, 7,8 and the energization transients of components such as transformers, 9-11 shunt capacitor banks, 12-14 and conventional shunt reactors 15 have been well documented. However, owing to their special body structures, MCSR energization transients are more complicated than those of conventional shunt reactors and transformers, and there has not been much research so far on the energization of MCSRs. 16 The simplest energization strategy for MCSRs at present is direct energization, in which the DC excitation system is blocked. As with transformer energization, one of the main problems associated with the MCSR direct energization transient is the occurrence of inrush current with a large number Symbols: _ U m , System bus voltage where MCSR is equipped; α, Phase angle of the system bus voltage at the instant of energization; U k , DC excitation source voltage; i 1 , Current of the grid-side winding; i k , Current of the control winding in the single phase MCSR; R 1 , Resistance of the grid-side winding; R k , Resistance of the control winding; R w , Balance resistor; N 1 , Number of turns in the grid-side winding; N 2 , Number of turns in the control winding; N 3 , Number of turns in the compensation winding; A, Area of the iron limb; l, Magnetic path length of the iron limb; i kA , Current of phase A in the control windings; i kB , Current of phase B in the control windings; i kC , Current of phase C in the control windings; i t , Total current of control windings; I dc , DC excitation current;...

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A new model to study ultra-saturation phenomenon during the energization of a loaded three-phase power transformer and its effects on differential protection

Cited by 7 publications

References 49 publications

Modified method for transformer magnetizing characteristic computation and point‐on‐wave control switching for inrush current mitigation

Modified method for transformer magnetizing characteristic computation and point‐on‐wave control switching for inrush current mitigation

Adaptive algorithm for identifying OLTC position and its application on UHV voltage-regulating transformer differential protection

Modeling and impacts analysis of energization transient of EHV/UHV magnetically controlled shunt reactor

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