The Research and Application of the Anti-Interference Techniques of Electronic Device in Power System

This paper presents the study and application of the electronic device anti-interference techniques underhigh voltage and/or heavy current electro-magnetic circumstance in power system.[

Anti-interference beam pattern design based on second-order cone programming optimization

When signal-to-interference ratio is low, the energy of strong interference leaked from the side lobe of beam pattern will infect the detection of weak target. Therefore, the beam pattern needs to be optimized. The existing Dolph-Chebyshev weighting method can get the lowest side lobe level under given main lobe width, but for the other non-uniform circular array and nonlinear array, the low side lobe pattern needs to be designed specially. The second order cone programming optimization （SOCP） algorithm proposed in the paper transforms the optimization of the beam pattern into a standard convex optimization problem. Thus there is a paradigm to follow for any array formation, which not only achieves the purpose of Dolph-Chebyshev weighting, but also solves the problem of the increased side lobe when the signal is at end fire direction The simulation proves that the SOCP algorithm can detect the weak target better than the conventional beam forming.

Reconfigurable anti-interference RF transceiver for cognitive radio application

An RF transceiver composed of a zero-IF receiver and a direct up-conversion transmitter for cognitive radio applications is presented. The adjustable channel filter array in the receiver is used to suppress adjacent channel interference in televisions signal coexistence environments. The low noise amplifier （LNA） with wide dynamic range and high linearity is employed to enhance the anti-interference competence of the zero-IF receiver. Meanwhile, the high linearity power amplifier （PA） .is used to promote the adjacent channel power ratio （ACPR） characteristic of the direct up-conversion transmitter. The measured error vector magnitude （EVM） results show that the anti-interference competence of the zero-IF receiver is dramatically enhanced by employing a channel filter array. The measured ACPR of the direct up-conversion transmitter is -47. 98 dBc on the channel centered at 714 MHz when the output power is 27 dBm.

Single-phase-to-ground fault protection based on zero-sequence current ratio coefficient for low-resistance grounding distribution network

Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance(low-resistance grounding systems).These systems frequently malfunction owing to their high settings of the action value when a high-impedance grounding fault occurs.In this study,the relationship between the zero-sequence currents of each feeder and the neutral branch was analyzed.Then,a grounding protection method was proposed on the basis of the zero-sequence current ratio coefficient.It is defined as the ratio of the zero-sequence current of the feeder to that of the neutral branch.Nonetheless,both zero-sequence voltage and zero-sequence current are affected by the transition resistance,The influence of transition resistance can be eliminated by calculating this coefficient.Therefore,a method based on the zero-sequence current ratio coefficient was proposed considering the significant difference between the faulty feeder and healthy feeder.Furthermore,unbalanced current can be prevented by setting the starting current.PSCAD simulation results reveal that the proposed method shows high reliability and sensitivity when a high-resistance grounding fault occurs.

An Improved Algorithm of Grounding Grids Corrosion Diagnosis Based on Total Least Square Method

A new model considering corrosion property for grounding grids diagnosis is proposed,which provides reference solutions of ambiguous branches.The constraint total least square method based on singular value decomposition is adopted to improve the effectiveness of grounding grids' diagnosis algorithm.The improvement can weaken the influence of the model's error,which results from the differences between design paper and actual grid.Its influence on touch and step voltages caused by the interior resistance of conductors is taken into account.Simulation results show the validity of this approach.

Determination of grounding line on the Amery Ice Shelf using Sentinel-1 radar interferometry data

Delineation of the grounding line(GL) is necessary for calculating the mass balance of Antarctica, but GL measurements for most of the continent remain at a relatively coarse level. We used Sentinel-1 constellation data to map the GL of the Amery Ice Shelf(AIS) using double-differential synthetic aperture radar interferometry. The ice thickness anomaly deduced from hydrostatic equilibrium and existing Antarctic GL products is compared with our result. With this new and very accurate GL, we detected new ice rises in the north of the AIS. Our new measurement shows no major change of the AIS GL, particularly in the southernmost part.

An Investigation into Substation Grounding and Its Implementation on Gaza Substation

An investigation into the optimal design of a substation grounding system for the transmission substation in Gaza City, Palestine has been carried out. A research into the most influential parameters on the effectiveness of the substation grid system has been performed and its results have been incorporated into the Gaza case study. Through modelling and simulating the power station in Gaza while considering some field data, an optimal substation grounding grid has been designed and has shown complete conformance to safety. It is thus considered that such a design will protect personnel in any area of the substation in addition to the installed machinery if the largest possible fault current was to traverse the earth.

The Research on Grounding Protection for 110kV Resistance Grounding Distribution System

Using the neutral grounding method by the resistance in 110?kV system, it can limit the voltage sag and short circuit current when one-phase grounding fault occurred, but it will change the sequence of the network structure and parameters. This paper analyzes the size and distribution of zero sequence voltage and current when one-phase grounding fault occurred in the 110 kV resistance grounding system, and puts forward the grounding protection configuration setting principle of this system combining the power supplying characteristics of 110?kV distribution network. In a reforming substation as an example, the grounding protection of 110 kV lines and transformer have been set and calculated.

Static-shift suppression and anti-interference signal processing for CSAMT based on Guided Image Filtering

Shallow conductive heterogeneity can lead to static shifts ain the apparent resistivity sounding curve of controlled-source audio-frequency magnetotellurics(CSAMT).The static effect will shift the apparent resistivity curves along with axial log-log coordinates.Such an effect,if not properly processed,can distort the resistivity of rock formation and the depth of interfaces,and even make the geological structures unrecognizable.In this paper,we discuss the reasons and characteristics of the static shift and summarize the previous studies regarding static shift correction.Then,we propose the Guided Image Filtering algorithm to suppress static shifts in CSAMT.In detail,we use the multi-window superposition method to superimpose 1D signals into a 2D matrix image,which is subsequently processed with Guided Image Filtering.In the synthetic model study and field examples,the Guided Image Filtering algorithm has effectively corrected and suppressed static shifts,and finally improved the precision of data interpretation.

Anti-interference ultra-wideband system based on spreading and interleaving

To suppress the interference in the ultra-wideband （AI-UWB） system is a challenging problem. An anti-interference multiband orthogonal frequency-division multiplexing ultra-wideband （AI-UWB） system, based on spreading and interleaving is addressed. It will exploit the frequency diversity across the subcarriers and provide the robustness to narrow-band interference, by spreading the coded bit streams within each sub-band and interleaving across all sub-bands. Simulating results show that the spreading and interleaving provide about 5 dB to 10 dB advantages over the conventional multiband orthogonal frequency-division multiplexing ultra-wideband system in signal-to-interference ratio. Spreading and interleaving is an effective cure for enhancing the robustness to narrowband interference.

Study on Decision Method of Neutral Point Grounding Mode for Medium-Voltage Distribution Network

The neutral grounding mode of medium-voltage distribution network decides the reliability, overvoltage, relay protection and electrical safety. Therefore, a comprehensive consideration of the reliability, safety and economy is particularly important for the decision of neutral grounding mode. This paper proposes a new decision method of neutral point grounding mode for mediumvoltage distribution network. The objective function is constructed for the decision according the life cycle cost. The reliability of the neutral point grounding mode is taken into account through treating the outage cost as an operating cost. The safety condition of the neutral point grounding mode is preserved as the constraint condition of decision models, so the decision method can generate the most economical and reliable scheme of neutral point grounding mode within a safe limit. The example is used to verify the feasibility and effectiveness of the decision method.

Fault Line Selection Method Considering Grounding Fault Angle for Distribution Network

In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line selection always existed in existing methods. According to the characteristics that transient current was different between the fault feeder and other faultless feeders, wavelet transformation was performed on data of the transient current within a power frequency cycle after the fault occurred. Based on different fault angles, wavelet energy in corresponding frequency band was chosen to compare. The result was that wavelet energy in fault feeder was the largest of all, and it was larger than sum of those in other faultless feeders, when the bus broke down, the disparity between each wavelet energy was not significant. Fault line could be selected out by the criterion above. The results of MATLAB/simulink simulation experiment indicated that this method had anti-interference capacity and was feasible.

Application of Atomic Sparse Decomposition to Feature Extraction of the Fault Signal in Small Current Grounding System

Applying the atomic sparse decomposition in the distribution network with harmonics and small current grounding to decompose the transient zero sequence current that appears after the single phase to ground fault occurred. Based on dictionary of Gabor atoms and matching pursuit algorithm, the method extracts the atomic components iteratively from the feature signals and translated them to damped sinusoidal components. Then we can obtain the parametrical and analytical representation of atomic components. The termination condition of decomposing iteration is determined by the threshold of the initial residual energy with the purpose of extract the features more effectively. Accordingly, the proposed method can extract the starting and ending moment of disturbances precisely as well as their magnitudes, frequencies and other features. The numerical examples demonstrate its effectiveness.

Study on Earth Surface Potential and DC Current Distribution around DC Grounding Electrode

DC magnetic biasing problem,caused by the DC grounding electrode, threatened the safe operation of AC power grid. In this paper, the characteristics of the soil stratification near DC grounding electrode was researched. The AC-DC interconnected large-scale system model under the monopole operation mode was established. The earth surface potential and DC current distribution in various stations under the different surface thickness was calculated. Some useful conclusions are drawn from the analyzed results.

The Research on Neutral Grounding Scheme of Fengxian 35kV and 10 kV Power Grid

Combined with actual situation of Fengxian power Supply Company, the neutral grounding modes of Fengxian 35 kV and 10 kV power grid are studied in the paper. The different frequencies injected method is used to measure the capacitive current of Fengxian 28 substations, and the neutral grounding modes of the 28 substations are determined based on the measured values of capacitive current.

Residual current compensation for single-phase grounding fault in coal mine power network

The way of neutral point to earth via full compensation arc suppression coil can solve the problem of residual current compensation in coal mine power network effectively. Based on the analysis on the grounding current detection results of Xieqiao coal mine, the conclusion that harmonic component of grounding current is dominated by higher harmonics with complex harmonic sources in coal mine power network system was obtained. The influences of harmonic source type and fault point position on harmonic voltage and harmonic current were analyzed theoretically. The influences of earthed fault feeder detection result and the estimation errors of parameters to earth on residual current compensation were analyzed. A new thought of residual current prediction and the selections of model method and control method were proposed on this basis. The simulation results prove that harmonic amplitudes of zero sequence voltage and zero sequence current are determined by harmonic source type as well as fault point position in coal mine power network, and also prove that zero sequence voltage detection can avoid the unstable problem of coal mine power network system caused by undercompensation of capacitive current. Finally, the experimental device of full compensation arc suppression coil is introduced.

Small-current grounding fault location method based on transient main resonance frequency analysis

The small-current grounding fault in distribution network is hard to be located because of its weak fault features.To accurately locate the faults,the transient process is analyzed in this paper.Through the study we take that the main resonant frequency and its corresponding component is related to the fault distance.Based on this,a fault location method based on double-end wavelet energy ratio at the scale corresponding to the main resonant frequency is proposed.And back propagation neural network(BPNN)is selected to fit the non-linear relationship between the wavelet energy ratio and fault distance.The performance of this proposed method has been verified in different scenarios of a simulation model in PSCAD/EMTDC.

Analysis of a Large Grounding System and Subsequent Field Test Validation Using the Fall of Potential Method

This paper examines various aspects of the design process and subsequent field test measurements of a large and complex substation grounding system. The study and measurements show that soil layering and lead interference can have a significant impact on the appropriate test location that yields the exact substation ground impedance. Applying a specific percentage rule such as the 61.8% rule for uniform soils to obtain the true ground impedance may lead to unacceptable errors for large grounding systems. This poses significant problems when attempting to validate a design based on raw test data that are interpreted using approximate methods to evaluate substation ground impedance, and determine ground potential rise (GPR), touch and step voltages. Advanced measurement methodologies and modern software packages were used to obtain and effectively analyze fall of potential test data, compute fault current distribution, and evaluate touch and step voltages for this large substation. Fault current distribution between the grounding system and other metallic paths were computed to determine the portion of fault current discharged in the grounding system. The performance of the grounding system, including its GPR and touch and step voltages, has been accurately computed and measured, taking into account the impedance of the steel material used of the ground conductors and circulating currents within the substation grounding system.

The Research of Voltage Sag and Power Frequency Overvoltage on 110kV Resistance Grounding System

This paper researches the voltage transfer characteristics when one-phase ground fault occurred in the resistance grounding system, by using the theory of the asymmetric variable characteristics and the sequence network analysis of the -11 transformer, and concludes the scope of voltage sag and swell and the degree of power frequency overvoltage and their influencing factors in the 110 kV resistance grounding system. Accordingly this paper puts forward the resistance choosing principle: the resistance grounding coefficient must be equal to or greater than 10. So it can not only wipe out the voltage sag and voltage swell but also make sure the overvoltage is limited to electrical equipment allowing range. The method mentioned above is verified by simulation results of a 110 kV power system in ATP.

Effects of Transformer DC Bias and the Relationship Between UHVDC Grounding Current and Grounding Resistances

Recently years,UHVDC transmission system is paid more attention to in the field of China's power system.It takes key part in the China electrical power development stratagem.But,many problems are caused by UHVDC system,such as DC bias,corrosion of metal underground and so on.DC bias is harm to the transformers nearby UHVDC grounding polar.In this paper,the influences of DC grounding current on transformer are introduced and some suggestions of DC bias solution were provided.And,the relationship between UHVDC Grounding Current and grounding Resistance of Substation was analyzed.Firstly,two-part network circuit was used to equivalent the grounding circuit.Then,an analysis of rules was done between DC bias current and grounding resistance.Finally,the conclusion is given that DC bias current rises fast as DC grounding resistance or AC grounding resistance rises.It drops when resistance of AC transmission line or interaction resistance between DC grounding system and AC grounding system rises.Decreasing AC grounding resistance and DC grounding resistance is important to restrain DC bias current.Increasing resistance of AC transmission line such as adding resistance into transformer neutral-point grounding is a useful way to limit DC bias current.