Saturation Detection Algorithm Research Articles

One Method for Preprocessing Pulse Signal Based on Deep Learning

The collection of pulse signals is accompanied by considerable noise interference, and it is necessary to denoise the collected signals to eliminate the error brought about by the outside world and the instrument itself to the actual data to the greatest extent. Considering this, this article proposes a preprocessing scheme for noise reduction. Firstly, the saturation detection algorithm in signals is based on the gradient, and extreme is utilized to remove the saturation interference. On this basis, the artifact detection module based on complex network connectivity is proposed. Finally, the self-adjusting parameter integer coefficient filtering is utilized to include the baseline drift. The noise inside is filtered out. The experimental results demonstrate that the proposed method, in the case of a similar signal-to-noise ratio, has a mean square error of 15.7 and a shorter convergence time of 0.02s.

A New Differential Protection Scheme for Busbar Using d–q–0 Transformation

This paper presents a new differential protection scheme for busbar using d–q–0 transformation. The proposed method is based on derivation of operating and restraining currents by utilizing direct axis (d) component of current transformer (CT) secondary current signals of all bays. The dual slope relay characteristic (derived from the operating and restraining current) of the proposed scheme operates in conjunction with a CT saturation detection algorithm and hence, provides better stability during external faults with CT saturation. The performance of the proposed scheme has been evaluated by modeling a 400 kV sub-station with two different busbar configurations, namely Breaker-and-Half configuration (BHC) and single breaker double-bus configuration (SBDBC) in PSCAD/EMTDC software package. The proposed algorithm has been tested for various fault cases with diversified system and fault parameters. The proposed scheme is highly sensitive against in-zone faults even with a considerable value of fault resistance as the average fault detection time remains within one-and-half cycle. At the end, a comparative evaluation of the proposed scheme with the conventional bus differential protection scheme (87B) clearly indicates its superiority in terms of stability against close-in out-of-zone faults with CT saturation and sensitivity for high impedance internal faults.

Study on the Unusual Misoperation of Differential Protection During Transformer Energization and its Countermeasure

The differential protection of the transformer, generator, or transmission line under normal operating conditions may misoperate when the adjacent transformer is switched-on. To research the cause of the misoperations, impacting factors, such as magnetizing inrush, sympathetic inrush, and current-transformer saturation are analyzed based on the field-recorded fault data and the simulation results in this paper. It is disclosed that the CT transient or CT local transient saturation, which are caused by the long-lasting dc component from the magnetizing inrush current, will lead to misoperation. To solve this problem, a new CT saturation detection algorithm based on the dc component in secondary current is proposed to prevent this sort of misoperation, and the effectiveness of the proposed algorithm is proved by the field-recorded fault data and simulation results obtained under different conditions.

New Algorithm for current transformer saturation detection and compensation based on derivatives of secondary currents and Newton's backward difference formulae

This study presents a new current transformer (CT) saturation detection and compensation algorithm. The proposed algorithm depends on a saturation detection index ( D n ) which is derived by using the derivatives of the current signals and Newton's backward difference formulae. The calculated index is continuously compared with an adaptive threshold ( T h ) to estimate the start and the end point of CT saturation. A low-pass first-order Butterworth filter is used to suppress noise and harmonics which may be present in CT secondary current. The proposed saturation detection algorithm has been tested by considering different values of remanent flux, fault type, fault inception angle, burden resistance, decaying DC component of fault current and noise. At the same time, modified discrete Fourier transforms-based compensating algorithm has also been proposed to reconstruct the saturated samples. Validation of the proposed scheme is also performed on a developed laboratory prototype. A comparative evaluation of the proposed algorithm is also performed with the existing schemes. A series of test results from the simulation software and the laboratory prototype show the effectiveness of the proposed scheme.

CT Saturation Detection Based on Waveshape Properties of Current Difference Functions

Derivative-based approaches have been widely used for current-transformer (CT) saturation detection. Previous approaches dealt with the magnitude of current derivatives. This paper, however, proposes a novel CT saturation detection algorithm that is subject to the waveshape properties of current derivatives. Two indices are introduced to extract certain key features of a current waveshape using its first two difference functions. Combining these two indices, CT saturation is rapidly and reliably detected. This method operates correctly irrespective of CT parameters, fault current characteristics, and power system conditions. Derivative-based techniques are suspected to be noise sensitive. Meanwhile, appropriate measures are taken, and the robustness of this method against noise is guaranteed. Extensive analysis of various real and simulated currents confirms that this algorithm can meet the rigorous speed and accuracy standards of industrial relays.

A CT Saturation Detection Algorithm Using Symmetrical Components for Current Differential Protection

A method of symmetrical component analysis for the detection of current-transformer (CT) saturation in a numerical current differential feeder protection relay is presented in this paper. The performance of the differential relay is investigated for various faults on a typical Electro-Magnetic Transients Program/Alternative Transients Program (EMTP/ATP) simulated transmission feeder. The simulator includes the effects of CT saturation. A comparison between simulation and tests conducted on an analog model testbench are also evaluated. The results show a high degree of similarity and illustrate the effect that CT saturation imposes on the sensitivity and stability of the protection scheme. An algorithm is presented that shows significant improvement in sensitivity on internal faults while still maintaining a high level of stability on external faults and nonfault events.

A Busbar Differential Protection Relay Suitable for Use With Measurement Type Current Transformers

The design, evaluation and implementation of a busbar current differential protection relay suitable for use with measurement type current transformers (CTs) is described in the paper. The relay operates in conjunction with a saturation detection algorithm, which effectively detects the start and end of each saturation period using a technique based on the third-difference function applied to the current signal. A blocking signal is activated immediately after the onset of saturation and is maintained active until the saturation period plus an additional delay of one cycle has expired. For internal faults that result in CT saturation, the relay issues a trip command before the blocking signal is activated. For external faults, that result in CT saturation, the blocking signal arrives first and the trip command remains inactive. Test results indicate that the relay successfully discriminates between internal and external faults, even when the remanent flux in a CT is high and the fault capabilities of the measurement CTs are severely limited. The paper concludes by describing how the relay was implemented on a prototype relay based on a digital signal processor. Compared to a conventional busbar differential protection scheme, the new relay achieves greater stability on external faults and enhanced sensitivity for internal faults.

Design, evaluation and implementation of a busbar differential protection relay immune to the effects of current transformer saturation

The design, evaluation and implementation of a busbar current differential protection relay that operates in conjunction with a current transformer (CT) saturation detection algorithm is described. The detection algorithm detects the start and end of each saturation period based on the third-difference function of the current. A blocking signal is activated during saturation and for one cycle after it ends. For internal faults that cause CT saturation, the relay operates before activation of the blocking signal and consequently, a trip signal is issued. For external faults that cause saturation, the blocking signal arrives first and the trip signal remains inactive. The technique does not delay the operating time of the delay. Test results indicate that the relay can discriminate between internal and external faults even when a CT is severely saturated due to the effect of remanent flux. The relay is implemented in a protection scheme based on a digital signal processor. The new relay achieves a high level of stability on external faults and a major improvement in sensitivity for internal faults.

An impedance-based CT saturation detection algorithm for busbar differential protection

An impedance-based CT saturation detection algorithm for busbar differential protection