Discrimination of Magnetizing Inrush and Internal Fault Currents Based on Stockwell Transform and ANN Approach for Transformer Protection

The discrimination of inrush currents and internal fault currents in transformers is an important feature of a transformer protection scheme. The harmonic current restrained feature is used in conventional differential relay protection of transformers. A literature survey shows that the discrimination between the inrush currents and internal fault currents is still an area that is open to research. In this paper, the classification of internal fault currents and magnetic inrush currents in the transformer is performed by using an extended Kalman filter (EKF) algorithm. When a transformer is energized under normal conditions, the EKF estimates the primary side winding current and, hence, the absolute residual signal (ARS) value is zero. The ARS value will not be equal to zero for internal fault and inrush phenomena conditions; hence, the EKF algorithm will be used for discriminating the internal faults and inrush faults by keeping the threshold level to the ARS value. The simulation results are compared with the theoretical analysis under various conditions. It is also observed that the detection time of internal faults decreases with the severity of the fault. The results of various test cases using the EKF algorithm are presented. This scheme provides fast protection of the transformer for severe faults.

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Simulation Design of Transformer Differential Protection Based on Mat Lab

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.722.282 ◽

2013 ◽

Vol 722 ◽

pp. 282-286

Author(s):

Hong Hua He

Keyword(s):

Simulation Model ◽

Relay Protection ◽

Fault Current ◽

Differential Protection ◽

Protection Device ◽

Simulation Design ◽

Transformer Protection ◽

Internal Fault ◽

Simulation Results ◽

Transformer Differential Protection

The microprocessor-relay protection device has gradually replaced regular simulation relay protection it is also difficult to visually determine protection device malfunction or tripping. Therefore, the use of the Mat lab toolbox to build transformer differential protection simulation model, the simulation results show that two-line ratio brake can correctly identify internal fault current, and rapidly remove fault, and the system also can provide convenient for microprocessor transformer protection.

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Calculation of the Three-Phase Internal Fault Currents in Medium-Voltage Electrical Installations

IEEE Transactions on Power Delivery ◽

10.1109/tpwrd.2008.923109 ◽

2008 ◽

Vol 23 (3) ◽

pp. 1685-1686 ◽

Cited By ~ 5

Author(s):

Xiang Zhang ◽

Jiaosuo Zhang ◽

G. Pietsch

Keyword(s):

Medium Voltage ◽

Fault Currents ◽

Internal Fault ◽

Three Phase

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A New Differential Relay Framework for Power Transformer

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.492.426 ◽

2014 ◽

Vol 492 ◽

pp. 426-430

Author(s):

Rachid Bouderbala ◽

Hamid Bentarzi

Keyword(s):

Power Transformer ◽

Circuit Breaker ◽

Differential Protection ◽

Test Results ◽

Transient Currents ◽

Fault Currents ◽

Internal Fault ◽

Time Signals ◽

Data Acquisition Card ◽

Frame Work

A differential relay that is very sensitive relay operating even at its limits may be used for protecting a power transformer. However, this characteristic may lead to unnecessary tripping due to transient currents. In order to avoid this unnecessary tripping, estimated harmonics of these currents may be required which need great computation efforts. In this paper, a new frame work is proposed using PC interfaced with a data acquisition card AD622, which acquires real-time signals of the currents, process them numerically in the computer and outputs tripping signal to the circuit breaker. All algorithms of differential protection function and blocking techniques have been implemented using the Simulink/Matlab. To validate the present work, the performance of developed relay is tested by signals generated by Simulink/MATLAB simulator under different conditions. The test results show that this proposed scheme provides good discrimination between the transient currents and the internal fault currents.

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