A suggested differential protection scheme for power transformer

2014 ◽  
Vol 5 (2) ◽  
pp. 91-103 ◽  
Author(s):  
E. Ahmed ◽  
R. El-Sehiemy
Keyword(s):  
High Speed ◽  
Power Transformer ◽  
Normal Operation ◽  
Power Differential ◽  
Transformer Protection ◽  
Protection Scheme ◽  
Wide Range ◽  
Inrush Currents ◽  
Differential Scheme ◽  
External Faults

This paper integrates a Real Power Differential Scheme (RPDS) for power transformer protection. The suggested RPDS for power transformer computes the active power loci during normal operation, switching, normal, and internal, involves turn to turn, and external faults at varied load angles. The proposed RPDS concept is based on monitoring and comparing the transformers primary and secondary active and reactive powers. The dynamic response of the proposed RPDS is tested 300 MVA, 220/66 kV, Y/Δ transformer. Furthermore, the suggested scheme is simulated with the use of Matlab/Simulink then tested for various fault and switching conditions. Moreover, the RPDS is checked for inter turn fault conditions at primary and secondary sides. The evaluation of the suggested scheme confirms the superiority of the proposed scheme to distinguish internal and external faults as well as magnetizing inrush currents with good selectivity, high speed, sensitivity, stability limits and high accuracy response of the power differential scheme. Finally, the suggested scheme is able to detect correctly the turn to turn faults for wide range of fault resistances but fails at very low values.

A Novel Approach for Classifying Transient Phenomena in Power Transformers

2004 ◽  
Vol 1 (2) ◽  
Author(s):  
El Sayed M. Tag Eldin
Keyword(s):  
Fuzzy Logic ◽  
Wavelet Transforms ◽  
Power Transformer ◽  
Current Transformer ◽  
Transient Phenomena ◽  
Protective Relay ◽  
Novel Approach ◽  
Inrush Currents ◽  
Internal Faults ◽  
External Faults

The role of a power transformer protective relay is to rapidly operate the tripping during internal faults and block the tripping during magnetizing inrush. This paper presents a new approach for classifying transient phenomena in power transformer, which may be implemented in digital relaying for transformer differential protection. Discrimination between internal faults, external faults with current transformer saturation and magnetizing inrush currents is achieved by combining wavelet transforms and fuzzy logic. The wavelet transform is applied for the analysis of the power transformer transient phenomena because of its ability to extract information from the transient signals in both time and frequency domain. Fuzzy logic is used because of the uncertainty in the differential current signals and relay settings. MATLAB power system toolbox is used to generate current signals at both sides of a power transformer in a typical system with various conditions. The simulation results obtained show that the new algorithm provides a high operating sensitivity for internal faults and remains stable for external faults and inrush currents.

An Innovative Package EMC Solution Using a Highly Cost-Effective Sputtered Conformal Shield

2016 ◽  
Vol 2016 (DPC) ◽  
pp. 002152-002181 ◽  
Author(s):  
Nozad Karim ◽  
Rong Zhou ◽  
Jun Fan
Keyword(s):  
High Speed ◽  
Metal Layer ◽  
Near Field ◽  
Cost Effective ◽  
Circuit Board ◽  
System Level ◽  
Normal Operation ◽  
Far Field ◽  
Wide Range ◽  
The Cost

High-speed digital and wireless devices radiate undesired electromagnetic noises that affect the normal operation of other devices causing electromagnetic interference (EMI) problems. Printed circuit board (PCB) and system-level shielding may alleviate inter-system EMI between the PCB board and the outside environment, but does not prevent intra-system EMI within the shielding enclosure. Package and System in Package (SiP) level shielding is often used to minimize intra-system EMI issues. An external metal lid is traditionally employed to prevent noise emission from a device, but the cost and size of this technique makes it unattractive for modern electronics. Conformal shielding is gaining momentum due to its size and height advantages. However, high cost and complexity of the sprayed coating shield prevents it from being used for a wide range of low cost commercial applications. In this paper, an innovative shielding technology with sputtered metal conformal shield is investigated using a specially designed test vehicle. By sputtering a conductive material onto a package, a very thin (typically a few μm) metal layer is constructed on the top and around four sides of the package. This thin sputtered metal layer adds virtually zero penalty to the package size. The cost and complexity of the sputtering process is significantly lower compared to a spraying process. Several types of shielded and unshielded modules were built and extensively tested for both far-field and near-field shielding effectiveness (SE) in a semi-anechoic chamber. The performance of the sputtered conformal shield is compared to that of an unshielded module and the sprayed shield. The measured results show that the sputtered shield performs equally well to a sprayed shield, in far field test, with most measurements better than 40 dB of SE. In near field testing, sputtered shields mostly outperform the sprayed shield, especially when compared in the entire scanned region. A well-designed sputtered conformal shield can, therefore, be a very cost-effective EMI solution for a wide range of packages, such as SiP. Also in the paper, a full wave 3D HFSS model is presented and simulated results for both far and near field are compared with measured data.

scholarly journals Adaptive ANN based differential protective relay for reliable power transformer protection operation during energisation

2019 ◽  
Vol 8 (4) ◽  
pp. 307
Author(s):  
Azniza Ahmad ◽  
Mohammad Lufti Othman ◽  
Kurreemun Khudsiya Bibi Zainab ◽  
Hashim Hizam
Keyword(s):  
Power Transformer ◽  
Electrical Power ◽  
Circuit Breaker ◽  
Inrush Current ◽  
Electrical Power System ◽  
Transformer Protection ◽  
Protection Scheme ◽  
Internal Fault ◽  
Magnetizing Inrush Current ◽  
Harmonic Restraint

Power transformer is the most expensive equipment in electrical power system that needs continuous monitoring and fast protection response. Differential relay is usually used in power transformer protection scheme. This protection compares the difference of currents between transformer primary and secondary sides, with which a tripping signal to the circuit breaker is asserted. However, when power transformers are energized, the magnetizing inrush current is present and due to its high magnitude, the relay mal-operates. To prevent mal-operation, methods revolving around the fact that the relay should be able to discriminate between the magnetizing inrush current and the fault current must be studied. This paper presents an Artificial Neural Network(ANN) based differential relay that is designed to enable the differential relay to correct its mal-operation during energization by training the ANN and testing it with harmonic current as the restraining element. The MATLAB software is used to implement and evaluate the proposed differential relay. It is shown that the ANN based differential relay is indeed an adaptive relay when it is appropriately trained using the Network Fitting Tool. The improved differential relay models also include a reset part which enables automatic reset of the relays. Using the techniques of 2nd harmonic restraint and ANN to design a differential relay thus illustrates that the latter can successfully differentiate between magnetizing inrush and internal fault currents. With the new adaptive ANN-based differential relay, there is no mal-operation of the relay during energization. The ANN based differential relay shows better performance in terms of its ability to differentiate fault against energization current. Amazingly, the response time, when there is an internal fault, is 1 ms compared to 4.5 ms of the conventional 2nd harmonic restraint based relay.

Power transformer protection scheme based on MRA-SSVM

2014 ◽  
Vol 27 (4) ◽  
pp. 1659-1669
Author(s):  
Mehdi Hajian ◽  
Asghar Akbari Foroud ◽  
Ali Akbar Abdoos
Keyword(s):  
Power Transformer ◽  
Transformer Protection ◽  
Protection Scheme

Rotating Cavitation in a Centrifugal Pump Impeller of Low Specific Speed

2002 ◽  
Vol 124 (2) ◽  
pp. 356-362 ◽  
Author(s):  
Jens Friedrichs ◽  
Gu¨nter Kosyna
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Incidence Angle ◽  
Normal Operation ◽  
Pump Impeller ◽  
Wide Range ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Cavity Closure ◽  
Operating Points

The paper describes an experimental investigation of two similar centrifugal pump impellers of low specific speed. Both impellers show rotating cavitation over a wide range of part load operating points. The occurrence of this phenomenon produces a characteristic shape of creeping head-drop compared to the more usual sudden head-drop at “normal” operation points. The onset of rotating cavitation can be assigned to a certain value of the parameter σ/2α meaning the cavity volume in relation to the incidence angle. Optical analysis by video and high-speed camera techniques illustrates the development of this instability mechanism which is mainly driven by an interaction of the cavity closure region and the following blade. Combining these observations and the results of a fourier-transformation the characteristic propagation frequencies of rotating cavitation can be presented for one impeller.

scholarly journals Discrimination of Transformer Inrush Currents and Internal Fault Currents Using Extended Kalman Filter Algorithm (EKF)

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6020
Author(s):  
Sunil Kumar Gunda ◽  
Venkata Samba Sesha Siva Sarma Dhanikonda
Keyword(s):  
Kalman Filter ◽  
Extended Kalman Filter ◽  
Threshold Level ◽  
Transformer Protection ◽  
Protection Scheme ◽  
Fault Currents ◽  
Internal Fault ◽  
Absolute Residual ◽  
Inrush Currents ◽  
Internal Faults

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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