Wang et al 2024a - Revision history

WangLing: qw

2024-10-24T04:21:40Z

WangLing: o fdf

2024-10-24T04:13:42Z

o fdf

Rimni at 12:32, 26 April 2024

2024-04-26T12:32:40Z

Rimni at 12:30, 26 April 2024

2024-04-26T12:30:36Z

Rimni: /* 3.2 Disturbance detection threshold based on sudden change of zero sequence current waveform */

2024-04-26T12:23:57Z

‎3.2 Disturbance detection threshold based on sudden change of zero sequence current waveform

Rimni: /* 3.2 Disturbance detection threshold based on sudden change of zero sequence current waveform */

2024-04-26T12:19:03Z

‎3.2 Disturbance detection threshold based on sudden change of zero sequence current waveform

Rimni: /* 4. Simulation verification */

2024-04-26T12:14:26Z

‎4. Simulation verification

Rimni at 12:11, 26 April 2024

2024-04-26T12:11:38Z

Rimni at 12:08, 26 April 2024

2024-04-26T12:08:37Z

Rimni: /* 5. Field data validation of disturbance detection thresholds */

2024-04-26T12:07:59Z

‎5. Field data validation of disturbance detection thresholds

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 ==Abstract==
-This research is aimed at Laser processing of micro holes there are recast layer and microcracks, analyzed the laser processing of recast layer formation mechanism and surface geometry features not, and for the laser processing of the formation of the recast layer in the process of analog simulation, for electrochemical finishing processing to remove the recast layer to provide a theoretical basis. The laser-electrolysis asynchronous composite processing experimental system was developed, and the electrolytic removal of recast layer on the wall of laser perforated holes and the process research of aperture trimming were carried out, which mainly analyzed the effects of electrolysis voltage, electrolyte and pulse electrolysis parameters on the rate of electrolysis and the effect of the removal of the recast layer. The cathode lifting method is also proposed to lift the tool cathode for orifice shaping after effective removal of the recast layer. The experimental results show that: when the current density is greater than 10.09 A/cm2, the electrolysis rate is proportional to the voltage; when the constant voltage electrolysis, the mixed solution of NaNO3 and NaCl enhances the effect of the recast layer removal significantly, and relative to the single solution with the same electrical conductivity, the value of the change in the surface roughness of the workpiece before and after the finishing process is enhanced more significantly, and there is no significant difference in the processing efficiency; the low-frequency wide pulse and high-frequency narrow pulse in the pulse electrolysis processing is favorable for the removal of recast layer. Pulse, high-frequency narrow pulse is conducive to the improvement of electrolysis rate, and the frequency of 1 kHz, the duty cycle of 40% to 60% of the electrolysis rate is the largest; at the same time, the use of cathodic enhancement method of aperture trimming processing, the use of the truncation effect, through the appropriate electrolytic processing parameters, to achieve the complete removal of the laser hole hole wall recast layer at the same time to complete the aperture trimming processing, to meet the demand for the use of performance of the small holes to further enhance the processing efficiency and small holes, and to improve the processing efficiency of the laser hole. Enhance the processing efficiency and functionality of small holes.
+The integration of a large amount of renewable energy sources into the new distribution system has significantly altered its fault characteristics, resulting in variable operation modes and limited short-circuit currents. Hence, early arc faults can serve as indicators of impending system short-circuits, and prevent the difficulty of tripping the new distribution system by effectively detecting them in advance. A quantitative analytical model for the early fault current and temperature is developed, and a theoretical analysis reveals the challenges of achieving reliable detection based solely on either current or temperature. A novel early fault detection method that combines current and temperature is proposed, which further utilizes arc power as a complex feature to identify early faults. The proposed feature integrates the promptness of the electrical signal (zero-sequence current) and the high sensitivity and reliability of the thermal signal (temperature), and exhibits higher reliability than the existing method. The validity of the proposed method is verified by PSCAD simulation, field data and laboratory simulated fault tests.
 '''Keywords''': Early arc faults, fault detection method, new distribution system, arc model, compound eigenquantity criterion

@@ Line 14: / Line 14: @@
 ==Abstract==
-The assimilation of copious renewable energy sources into contemporary distribution systems has markedly transmuted fault dynamics, engendering fluctuating operational states and curtailed short-circuit currents. Consequently, incipient arc faults may herald imminent system short-circuits, obviating the complexities associated with the new distribution system's disconnection by facilitating their precocious detection. A quantitative analytical paradigm has been contrived for the nascent fault current and temperature, while theoretical scrutiny elucidates the impediments to dependable detection predicated solely on current or temperature metrics. An innovative detection methodology, amalgamating current and temperature readings and leveraging arc power as a composite indicator, has been advanced. This proposed mechanism synergizes the alacrity of the electrical signal—specifically, the zero-sequence current—with the heightened sensitivity and dependability of the thermal signal—temperature—thereby surpassing the reliability of extant approaches. The efficacy of this method has been corroborated through PSCAD simulations, empirical field data, and controlled laboratory fault experimentation.
+This research is aimed at Laser processing of micro holes there are recast layer and microcracks, analyzed the laser processing of recast layer formation mechanism and surface geometry features not, and for the laser processing of the formation of the recast layer in the process of analog simulation, for electrochemical finishing processing to remove the recast layer to provide a theoretical basis. The laser-electrolysis asynchronous composite processing experimental system was developed, and the electrolytic removal of recast layer on the wall of laser perforated holes and the process research of aperture trimming were carried out, which mainly analyzed the effects of electrolysis voltage, electrolyte and pulse electrolysis parameters on the rate of electrolysis and the effect of the removal of the recast layer. The cathode lifting method is also proposed to lift the tool cathode for orifice shaping after effective removal of the recast layer. The experimental results show that: when the current density is greater than 10.09 A/cm2, the electrolysis rate is proportional to the voltage; when the constant voltage electrolysis, the mixed solution of NaNO3 and NaCl enhances the effect of the recast layer removal significantly, and relative to the single solution with the same electrical conductivity, the value of the change in the surface roughness of the workpiece before and after the finishing process is enhanced more significantly, and there is no significant difference in the processing efficiency; the low-frequency wide pulse and high-frequency narrow pulse in the pulse electrolysis processing is favorable for the removal of recast layer. Pulse, high-frequency narrow pulse is conducive to the improvement of electrolysis rate, and the frequency of 1 kHz, the duty cycle of 40% to 60% of the electrolysis rate is the largest; at the same time, the use of cathodic enhancement method of aperture trimming processing, the use of the truncation effect, through the appropriate electrolytic processing parameters, to achieve the complete removal of the laser hole hole wall recast layer at the same time to complete the aperture trimming processing, to meet the demand for the use of performance of the small holes to further enhance the processing efficiency and small holes, and to improve the processing efficiency of the laser hole. Enhance the processing efficiency and functionality of small holes.
 '''Keywords''': Early arc faults, fault detection method, new distribution system, arc model, compound eigenquantity criterion

← Older revision		Revision as of 12:32, 26 April 2024
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−	As shown in Eq. (8), the arc power is inversely proportional to the transition resistance. The fault arc power value remains at 1.35 kW under the level of ~~3kΩ~~ transition resistance, and the temperature rise time scale of the fault point is in the second level. The cable load loss power during normal operation is typically less than 1 W/m, and the line temperature fluctuations induced by this are usually in the hourly range [12], which are negligible compared to the fault arc power. Hence, early failures exhibit significant temperature rise characteristics compared to normal operation.	+	As shown in Eq. (8), the arc power is inversely proportional to the transition resistance. The fault arc power value remains at 1.35 kW under the level of 3 kΩ transition resistance, and the temperature rise time scale of the fault point is in the second level. The cable load loss power during normal operation is typically less than 1 W/m, and the line temperature fluctuations induced by this are usually in the hourly range [12], which are negligible compared to the fault arc power. Hence, early failures exhibit significant temperature rise characteristics compared to normal operation.

	===2.2 Analysis of temperature characteristics of early fault arc===		===2.2 Analysis of temperature characteristics of early fault arc===

← Older revision		Revision as of 12:30, 26 April 2024
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−	As shown in Eq. (8), the arc power is inversely proportional to the transition resistance. The fault arc power value remains at 1.~~35kW~~ under the level of 3kΩ transition resistance, and the temperature rise time scale of the fault point is in the second level. The cable load loss power during normal operation is typically less than 1W/m, and the line temperature fluctuations induced by this are usually in the hourly range [12], which are negligible compared to the fault arc power. Hence, early failures exhibit significant temperature rise characteristics compared to normal operation.	+	As shown in Eq. (8), the arc power is inversely proportional to the transition resistance. The fault arc power value remains at 1.35 kW under the level of 3kΩ transition resistance, and the temperature rise time scale of the fault point is in the second level. The cable load loss power during normal operation is typically less than 1 W/m, and the line temperature fluctuations induced by this are usually in the hourly range [12], which are negligible compared to the fault arc power. Hence, early failures exhibit significant temperature rise characteristics compared to normal operation.

	===2.2 Analysis of temperature characteristics of early fault arc===		===2.2 Analysis of temperature characteristics of early fault arc===

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 The calculation symbols shown in Eqs. (16) and (17) are the basic operation rules defined by MMG, please refer to reference [14] for details. In Eq. (17),  <math display="inline">k</math> is the number of MMG operations, usually taken as 3.  <math display="inline">M_{g+}^k</math> and  <math display="inline">M_{g-}^k</math> are the values of the structural sub elements  <math display="inline">g^+</math> and  <math display="inline">g^{-}</math> after the k-th operation, respectively.  <math display="inline">M_g^k(f)</math> is the final calculation result.
-The key to applying MMG to the waveform mutation characteristics of fault zero sequence current is that the structural factor should match the geometric shape of the target signal in order to reliably identify the mutation characteristics in the signal. For sinusoidal periodic signals, the length l of the one-dimensional structural factor used in this article should correspond to the system's power frequency period. When the zero sequence current flowing through the measuring point is a sine wave, the MMG calculation result  <math display="inline">M_g^3(i_{0n})=0</math>. When the waveform undergoes a sudden change at a certain moment, the MMG calculation result <math display="inline">M_g^3(i_{0n}){>}0</math>. Set the setting value  <math display="inline">M_g^3_{set}</math> to obtain the criteria for sudden changes in the waveform of the fault zero sequence current as follows:
+The key to applying MMG to the waveform mutation characteristics of fault zero sequence current is that the structural factor should match the geometric shape of the target signal in order to reliably identify the mutation characteristics in the signal. For sinusoidal periodic signals, the length l of the one-dimensional structural factor used in this article should correspond to the system's power frequency period. When the zero sequence current flowing through the measuring point is a sine wave, the MMG calculation result  <math display="inline">M_g^3(i_{0n})=0</math>. When the waveform undergoes a sudden change at a certain moment, the MMG calculation result <math display="inline">M_g^3(i_{0n}){>}0</math>. Set the setting value  <math display="inline">M_{g_{set}}^3</math> to obtain the criteria for sudden changes in the waveform of the fault zero sequence current as follows:
 {| class="formulaSCP" style="width: 100%; text-align: left;"

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 {| class="wikitable" style="margin: 1em auto 0.1em auto;border-collapse: collapse;font-size:85%;width:auto;"
 |-style="text-align:center"
-! style="text-align:left;"| Stucture/Material !! Thickness/radius (mm) !! Relative permeability !! Conductivity (S/m) !! Relative dielectric constant !! Thermal conductivity (W/(m×K)) !! Density (kg/m<sup>3</sup>) !! Constant pressure heat capacity (J/(kg×K))
+! style="text-align:left;vertical-align:top;"| Stucture/Material !! style="vertical-align:top;"| Thickness/radius (mm) !! style="vertical-align:top;"| Relative permeability !! style="vertical-align:top;"| Conductivity (S/m) !!style="vertical-align:top;"|  Relative dielectric constant !! style="vertical-align:top;"| Thermal conductivity (W/(m×K)) !! style="vertical-align:top;"| Density (kg/m<sup>3</sup>) !! style="vertical-align:top;"| Constant pressure heat capacity (J/(kg×K))
 |-style="text-align:center"
 |  style="text-align:left;"|Cable core/Copper

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 As shown in [[#img-8|Figures 8]] (a) and (b), the voltage and current waveforms of the arc display significant nonlinearity after the fault occurs. The zero sequence current waveform in the system experiences significant waveform changes at time <math display="inline">t=0</math>, which agrees with the piecewise function equation (14). Additionally, due to the presence of the nonlinear resistor  <math display="inline">R_{arc}</math>, the zero sequence current after the fault has significant high-frequency harmonics. Therefore, the presence of fault arcs increases the waveform change characteristics of the zero sequence current, which is consistent with theoretical analysis.
-As can be seen from [[#img-8|Figures 8]] (c), the calculation results of the early fault arc power analytic formula derived from Eq. (8) are in good agreement with the simulation, and the waveforms of the two differ by a phase Angle <math display="inline">\Delta \phi</math> in phase, which accords with the conclusion obtained during the simplification of Eq. (5). Combined with theoretical calculation and simulation, it can be seen that the early fault arc power of 8kΩ is still as high as 1.46kW, which has obvious temperature characteristics, and the fault detection idea based on this feature is feasible.
+As can be seen from [[#img-8|Figures 8]] (c), the calculation results of the early fault arc power analytic formula derived from Eq. (8) are in good agreement with the simulation, and the waveforms of the two differ by a phase angle <math display="inline">\Delta \phi</math> in phase, which accords with the conclusion obtained during the simplification of Eq. (5). Combined with theoretical calculation and simulation, it can be seen that the early fault arc power of 8kΩ is still as high as 1.46kW, which has obvious temperature characteristics, and the fault detection idea based on this feature is feasible.
 ===4.2 Analytical verification of temperature distribution characteristics of early faults===

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 |style="text-align: center;padding:10px;"| [[File:图13.jpg|366x366px]]
 |-
-| style="background:#efefef;text-align:left;padding:10px;font-size: 85%;"| '''Figure 13'''. On site data recording and detection results. (a) Zero sequence current waveform. (b) Disturbance detection results
+| style="background:#efefef;text-align:left;padding:10px;font-size: 85%;"| '''Figure 13'''. On site data recording and detection results. (a) Zero sequence current waveform. <br> (b) Disturbance detection results
 |}

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-As [[#img-13|Figure 13]](a) illustrates, the zero sequence current exhibits a large waveform mutation at t=0 before and after the fault. The MMG calculated value of the disturbance detection threshold surpasses the threshold in the output lines F1 and F2, which can initiate the subsequent fault detection algorithm reliably. Different decibels of noise were superimposed on the field data to verify the disturbance detection threshold’s anti-interference ability. The second test in [[#tab-4|Table 4]] displays the verification results. The disturbance detection threshold maintains a good detection effect when 10dB noise is superimposed.
+As [[#img-13|Figure 13]](a) illustrates, the zero sequence current exhibits a large waveform mutation at <math display="inline"> t=0 </math> before and after the fault. The MMG calculated value of the disturbance detection threshold surpasses the threshold in the output lines F1 and F2, which can initiate the subsequent fault detection algorithm reliably. Different decibels of noise were superimposed on the field data to verify the disturbance detection threshold’s anti-interference ability. The second test in [[#tab-4|Table 4]] displays the verification results. The disturbance detection threshold maintains a good detection effect when 10dB noise is superimposed.
 <div class="center" style="font-size: 85%;">'''Table 4'''. Noise impact results</div>
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 ! No. !! MMG calculation value (1) !! Result !! MMG calculation value (1) !! Result
 |-
-|  style="text-align: center;"|1(30dB)
+|  style="text-align: center;"|1 (30dB)
 |  style="text-align: center;"|67.5
 |  style="text-align: center;"|√
@@ Line 743: / Line 743: @@
 |  style="text-align: center;"|√
 |-
-|  style="text-align: center;"|2(20dB)
+|  style="text-align: center;"|2 (20dB)
 |  style="text-align: center;"|50
 |  style="text-align: center;"|√
@@ Line 749: / Line 749: @@
 |  style="text-align: center;"|√
 |-
-|  style="text-align: center;"|3(10dB)
+|  style="text-align: center;"|3 (10dB)
 |  style="text-align: center;"|40
 |  style="text-align: center;"|√
@@ Line 755: / Line 755: @@
 |  style="text-align: center;"|√
 |}
 ==6. Laboratory simulation of early failure test verification==