Multi-criterion sensitive trigger detection method and system based on adaptive threshold

Abstract

The invention discloses a multi-criterion sensitive trigger detection method and system based on an adaptive threshold, and the method employs three types of core parameters: current change rate, current break variable, and current instantaneous value / effective value out-of-limit as the composite criterion of trigger detection, and combines the cooperative criterion of multi-current parameters through the three-stage process of "preliminary judgment-exclusion-property determination". According to the method, the problems of misjudgment and missed judgment of single parameter detection are effectively avoided, fault hidden dangers can be accurately recognized in the early stage, meanwhile, the continuity of normal operation is not affected, and the algorithm is simple in recognition logic, low in hardware requirement and suitable for preliminary detection of local data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power systems, in particular to a multi-criteria sensitive triggering detection method and system based on adaptive threshold. BACKGROUND

[0002] In the power system, fast and accurate detection of early faults is the first line of defense for safe and stable operation of the system. Early faults usually refer to the initial stage of the fault, when the electrical quantity change characteristics are not obvious, but there is a potential risk of development. If the disturbance state can be identified and intervention measures can be taken in this stage, the expansion of the fault can be effectively prevented, and the damage of equipment and even large-scale power outage accidents can be avoided. At present, in the field of relay protection and fault recording, the main fault triggering criterion mainly depends on a single electrical quantity characteristic. The existing technology generally has the following technical defects: 1) Limitation of single criterion: relying on a single characteristic quantity (such as only effective value, only sudden change quantity or only change rate) for judgment, it is difficult to comprehensively and accurately describe the complex characteristics of early faults.

[0003] 2) Contradiction between sensitivity and reliability: in order to improve the detection sensitivity and reduce the setting value, it will introduce the risk of misjudgment; in order to ensure reliability and prevent misoperation, increasing the setting value will sacrifice the detection ability of early weak faults.

[0004] 3) Insufficient distinguishing ability: there is a lack of effective mechanism to accurately distinguish between "early fault disturbance" and "normal operation fluctuation" (such as load switching and motor starting), which leads to a decrease in the accuracy of triggering detection under complex operating conditions.

[0005] Therefore, there is an urgent need in the art for a new technical solution that can break through the bottleneck of existing technology and significantly improve the detection sensitivity of early faults while ensuring high reliability. SUMMARY

[0006] The present application provides a multi-criteria sensitive triggering detection method and system based on adaptive threshold to solve the above technical problems in the existing technology.

[0007] According to a first aspect, a multi-criteria sensitive triggering detection method based on adaptive threshold is provided in an embodiment, the method comprising: collecting three-phase line currents at a preset sampling frequency; determining whether there is a fault phase according to the current values of each phase, and determining the adaptive threshold of each detection criterion in the pre-established composite detection criterion according to the determination result, the composite detection criterion including current change rate, current sudden change quantity, and current instantaneous value / effective value; Fault determination is performed based on adaptive thresholds of various established detection criteria, including: first, initial disturbance judgment based on the rate of change of current; then, disturbance elimination based on sudden changes in current; and finally, disturbance distinction based on the nature of the instantaneous / effective value of current.

[0008] Furthermore, the three-phase current of the line is collected according to a preset sampling frequency, and the presence of a faulty phase is determined based on the current values ​​of each phase. Specifically, this includes: Based on measured three-phase line current , , The phase whose current value differs from the normal operating value by more than a preset threshold is designated as phase x. If the current values ​​of the other two phases, namely phases y and z, differ from the normal operating value by less than the preset threshold, then phase x is determined to be a faulty phase.

[0009] Furthermore, based on the judgment results, adaptive thresholds for each detection criterion in the pre-established composite detection criteria are determined, specifically including: If a faulty phase is identified, the current data of the non-faulty phase is used as the normal data reference segment, and the current change rate and current abrupt change are calculated, which are then used as adaptive thresholds for the current change rate and current abrupt change in this waveform recording event, respectively. and ; If the faulty phase is not identified, the first 10% of the current data sampling for any phase is used as the normal data reference segment, and the current change rate and current abrupt change are calculated, which are then used as the thresholds for the current change rate and current abrupt change in this waveform recording event, respectively. and ; Threshold of instantaneous current value The threshold value of the effective current is set to 1.2 times the rated peak value. Set to 1.1 times the rated effective value.

[0010] Furthermore, the initial disturbance judgment based on the rate of change of current specifically includes: If the rate of change of current at two consecutive sampling points is greater than the set threshold, it is preliminarily determined that there is a disturbance in the circuit, and the next stage of interference elimination based on the sudden change of current is initiated.

[0011] Furthermore, interference elimination based on sudden changes in current specifically includes: If the sudden change in current does not exceed the set threshold, it is determined to be an invalid disturbance, and the detection process is terminated. If the sudden change in current exceeds the set threshold, the next level of disturbance nature distinction based on the instantaneous / effective value of the current will be performed.

[0012] Furthermore, based on the nature of the disturbances caused by the instantaneous / effective value of the current, the distinction specifically includes: If the instantaneous / effective current value exceeds the set threshold, it is determined to be an early fault disturbance; If neither the instantaneous current value nor the effective current value exceeds the set threshold, it is determined to be a normal line disturbance.

[0013] Furthermore, the rate of change of current H is calculated as follows:

[0014] Where i is the instantaneous value of the phase current, and t is the corresponding sampling time.

[0015] Furthermore, the sudden change in current The calculation is as follows: In the instantaneous value sequence of phase current sampling, select a period m and calculate its effective value. Then calculate the effective value of the (m+1)th period. Mutation amount for and difference; The calculation formula is as follows:

[0016] Where N is the number of sampling points in one cycle, n is the sampling point currently being calculated, and i is the instantaneous value of the phase current.

[0017] Furthermore, the instantaneous current / RMS current ratio is calculated as follows: Instantaneous current value i: This is the instantaneous value of the phase current measured at the moment. RMS value of current Calculate the root mean square value of the current one cycle prior to the current sampling time. The calculation formula is as follows:

[0018] Where N is the number of sampling points in one cycle, and p is the number of sampling points at the current calculation time.

[0019] According to a second aspect, one embodiment provides a multi-criteria sensitive trigger detection system based on an adaptive threshold, the system comprising: The current sampling module is used to collect the three-phase current of the line according to a preset sampling frequency; An adaptive threshold determination module is used to determine whether there is a faulty phase based on the current value of each phase, and to determine the adaptive threshold of each detection criterion in the pre-established composite detection criterion based on the judgment result. The composite detection criterion includes current change rate, current sudden change, and current instantaneous value / effective value. The fault detection module is used to determine faults based on adaptive thresholds of various detection criteria, including: first, performing initial disturbance judgment based on the rate of change of current; then, performing disturbance elimination based on the sudden change of current; and finally, distinguishing the nature of disturbances based on the instantaneous / effective value of current.

[0020] Compared with existing technologies, this invention provides a multi-criteria sensitive trigger detection method and system based on adaptive thresholds, which has the following beneficial effects: This invention effectively avoids the problems of misjudgment and missed judgment in single parameter detection by combining a three-level process of "preliminary judgment-exclusion-determination" with the collaborative criteria of multiple current parameters. It can accurately identify potential faults in the early stage without affecting the continuity of normal operation. Moreover, the algorithm has simple recognition logic, low hardware requirements, and is suitable for the preliminary detection of local data. Attached Figure Description

[0021] Figure 1 A flowchart of a multi-criteria sensitive trigger detection method based on adaptive threshold provided in one embodiment of the present invention; Figure 2 This is a flowchart of a threshold setting process in a multi-criteria sensitive trigger detection method based on adaptive threshold provided in one embodiment of the present invention; Figure 3 This is a flowchart of a fault detection method based on an adaptive threshold and multi-criteria sensitive triggering detection method provided in one embodiment of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0023] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0024] The first embodiment of this invention provides a multi-criteria sensitive trigger detection method based on adaptive thresholds, which will be described below in conjunction with... Figure 1 Please provide a detailed explanation.

[0025] like Figure 1 As shown, in step S100, the three-phase current of the line is collected according to the preset sampling frequency.

[0026] Specifically, the measured three-phase current of the line , , .

[0027] like Figure 1 As shown, in step S200, it is determined whether there is a faulty phase based on the current value of each phase, and the adaptive threshold of each detection criterion in the pre-established composite detection criterion is determined based on the judgment result. The composite detection criterion includes current change rate, current sudden change, and current instantaneous value / effective value.

[0028] Threshold setting and adaptation: The recognition algorithm in this embodiment adopts an adaptive threshold setting mechanism based on the current waveform data, rather than a fixed threshold. This method can better adapt to different working conditions and data quality, improving detection accuracy. The threshold setting method is as follows: Figure 2 As shown. The main content is as follows: (1) Identification and extraction of normal data segments To avoid being affected by disturbances, the algorithm first identifies and extracts the "unperturbed" portion from the waveform data as a baseline. There are two selection methods: ① Identify suspected fault phases: Use features such as sudden current changes to determine possible fault phases, and prioritize using data from non-fault phases as normal data reference segments; ② Handling special cases: When all phases show signs of fault or it is difficult to determine the faulty phase, the first 10% of the recorded waveform data is used as the normal data reference segment. In this case, it is assumed that the fault occurs in the middle or late stage of the waveform recording, while the initial stage of the waveform recording remains normal.

[0029] (2) Calculate the threshold based on normal data Using the extracted normal data segments, the algorithm calculates the baseline values ​​of various feature parameters, which are then used as the threshold for this detection.

[0030] The core advantage of the adaptive threshold adjustment mechanism lies in its adaptability: for different data files, the system re-executes the threshold calculation process, and the threshold is automatically adjusted according to the current operating conditions. It can adapt to different load levels, equipment characteristics, operating environments, and recording conditions without manual intervention. This dynamic threshold setting method greatly improves the robustness and accuracy of the algorithm in various complex scenarios, avoiding the misjudgment or missed judgment problems that easily occur with fixed thresholds in changing environments.

[0031] In this embodiment, the specific implementation steps are as follows: S210, Determine the faulty phase: Identify the phase whose current has increased compared to normal operation, denoted as phase x. In high-current grounding systems, the increase is generally larger and more significant, while in low-current grounding systems, the increase is usually the system-to-ground capacitance current or residual compensation current. If the currents of the other two phases (denoted as phases y and z) remain essentially unchanged or only fluctuate slightly, then phase x can be determined as the faulty phase. If it is difficult to determine the faulty phase, skip this step and proceed to step S220.

[0032] S220, if the faulty phase is identified, calculate the current change rate and current surge of the non-faulty phases, and use them as the judgment threshold for this waveform recording event. , If the faulty phase cannot be identified, the first 10% of any phase is used as the normal data reference segment. The current change rate and current surge are calculated and used as the threshold for judging this recorded event. , Threshold for instantaneous current value The threshold value of the effective current is set to 1.2 times the rated peak value. Set to 1.1 times the rated effective value.

[0033] like Figure 1 As shown, in step S300, fault determination is performed based on the adaptive thresholds of the determined detection criteria, including: first, preliminary disturbance judgment based on the rate of change of current, then disturbance elimination based on the sudden change of current, and finally, disturbance nature distinction based on the instantaneous value / effective value of current.

[0034] To improve the sensitivity of trigger detection, this detection solution uses three core parameters as composite criteria for trigger detection: current change rate, current surge, and current instantaneous / RMS value exceeding limits. Through multi-dimensional verification, false positives are eliminated, accurately distinguishing between "early fault disturbances" and "normal operational fluctuations." The specific detection process is as follows: Figure 3 As shown, the decision logic and principles for each step are as follows: (1) First step: Initial judgment of disturbance based on the rate of change of current The rate of change of current (di / dt) reflects how fast the current changes over time and is the "first sensitive indicator" for identifying abnormal fluctuations in a circuit. During real-time detection, the system continuously collects current signals at a fixed sampling frequency (such as microseconds or milliseconds, depending on the application scenario's response speed requirements) and calculates and compares the rate of change of current at two consecutive adjacent sampling points.

[0035] If the calculation results show that the rate of change of current at two consecutive sampling points is significantly higher than the stable range during normal operation (the criterion for "significant" should be preset based on the specific circuit parameters, for example, set to 2-5 times the average normal rate of change to avoid false triggering due to minor fluctuations), then it is preliminarily determined that there is a "disturbance" in the circuit. The core function of this step is to quickly capture abnormal current trends, laying the foundation for subsequent accurate identification—but at this point, the "disturbance" still includes two possibilities: one is a real precursor to a fault, and the other is noise interference or a brief signal fluctuation, which requires further verification.

[0036] (2) Second step: Disturbance elimination based on sudden changes in current To eliminate potential "noise interference" in the first step, the solution introduces "current surge" as a secondary judgment criterion. By comparing it with historical periodic data, meaningful current anomalies are identified. The specific operational logic is as follows: ① Calculation of effective current value: The system first calculates the effective value of the half-wave point-by-point current in the current detection period based on the collected instantaneous current value sequence and the effective value calculation formula (for sinusoidal alternating current, the effective value is the root mean square of the instantaneous value; for non-sinusoidal current, the average power equivalent value within one period needs to be calculated by integration).

[0037] ② Current mutation calculation: The difference between the current effective value of the current in the current cycle and the current effective value of the previous complete cycle is calculated to obtain the "current mutation" (i.e., ΔI = current effective value - previous effective value).

[0038] ③ Limit Exceeding Judgment and Interference Elimination: The calculated current surge is compared with the preset "surge threshold". If the current surge does not exceed the limit, it indicates that the "disturbance" detected in the first step is most likely caused by interference factors with no actual impact, such as electromagnetic noise or sampling error, and can be judged as an "invalid disturbance", terminating the detection process; if the current surge exceeds the limit, it proves that the disturbance has "persistence" and "amplitude", and is not a random interference, requiring further judgment of the nature of the disturbance in the next step.

[0039] (3) Distinguishing based on the disturbance nature of current instantaneous value / effective value exceeding the limit After the first two steps of screening, it can be determined that there are "non-interference disturbances" in the circuit. However, such disturbances still need to be distinguished from "early fault disturbances" and "normal operation fluctuations" (such as current changes caused by routine operations such as load switching, motor starting and stopping). This step will complete the final judgment by checking whether the "instantaneous current value" or "effective value" exceeds the limit. ① Dual-parameter comparison logic: The system simultaneously retrieves the "instantaneous peak value of current" and "effective value of current" within the current detection cycle, and compares them with the preset "instantaneous value safety threshold" and "effective value safety threshold" respectively (the two thresholds need to be set in advance according to the rated parameters of the equipment and the safe operating range of the circuit. For example, the instantaneous value threshold can be set to 1.2 times the rated peak value, and the effective value threshold can be set to 1.1 times the rated effective value).

[0040] ② Determination of the nature of the disturbance: If either the instantaneous or effective value of the current exceeds the limit, it indicates that the disturbance has exceeded the safe range for normal circuit operation. It is highly likely that the abnormal current is caused by early faults such as insulation damage, poor contact, or component aging, and is judged as an "early fault disturbance". At this time, the system should immediately trigger a warning signal (such as audible and visual alarm, data upload) to prompt maintenance personnel to investigate in time.

[0041] If neither the instantaneous nor the effective current value exceeds the limit, it indicates that the disturbance is still within the normal tolerance range of the circuit. It is usually a temporary current fluctuation caused by routine operations such as load switching, equipment start-up and shutdown, and is judged as "normal operation fluctuation". The system does not need to trigger an alarm, but only needs to record the fluctuation data for subsequent operation analysis.

[0042] Key indicators and their calculation formulas: ① Rate of change of current H:

[0043] Where i is the instantaneous value of the fault phase current, and t is the corresponding sampling time.

[0044] If the rate of change of current at two consecutive sampling points exceeds a set threshold, it will trigger... If so, proceed to the next level of the process.

[0045] ② Sudden change in current : From the instantaneous value sequence of the fault phase current sampling, select a period m to calculate its effective value. Then calculate the effective value of the (m+1)th period. Mutation amount It is the difference between the two.

[0046] The calculation formula is as follows:

[0047] Where N is the number of sampling points in one cycle, and n is the sampling point currently being calculated.

[0048]

[0049] When the sudden change in current exceeds the threshold, it is triggered. At that time, proceed to the next level of the process.

[0050] ③ Instantaneous current value / RMS value (1) Instantaneous current value i: is the instantaneous value of the phase current measured at the moment.

[0051] (2) Effective value of current Calculate the root mean square (RMS) current value one cycle prior to the current sampling time. Where N is the number of sampling points in one cycle, and p is the sampling point at the current calculation time.

[0052]

[0053] When either the instantaneous current value or the effective current value exceeds the threshold setting, i.e.

[0054] Then proceed to the next level of the process, that is, determine that this waveform recording event is an early fault event.

[0055] like Figure 3 As shown, the specific operation of the fault determination process in this embodiment is as follows: (1) Calculate the rate of change of current. If the rate of change of current at two consecutive sampling points is greater than the set threshold, it is triggered. Then proceed to the next level of the process; (2) Calculate the current surge. When the current surge exceeds the threshold, it triggers the current surge. If the event occurs, proceed to the next level of the process; otherwise, the event is considered noise disturbance. (3) Calculate the effective value of the current. When either the instantaneous current value or the effective value of the current exceeds the threshold setting, i.e. If the recorded event is determined to be an early fault disturbance, it is otherwise a normal line disturbance event such as load fluctuation.

[0056] In summary, the detection scheme of this invention, through a three-level process of "preliminary judgment - elimination - nature determination" combined with the collaborative criteria of multiple current parameters, effectively avoids the problems of misjudgment and missed judgment in single-parameter detection. It can accurately identify potential faults at an early stage without affecting the continuity of normal operation. Furthermore, the algorithm has simple recognition logic, low hardware requirements, and is suitable for preliminary detection of local data.

[0057] Corresponding to the aforementioned multi-criteria sensitive trigger detection method based on adaptive threshold, this invention also discloses a multi-criteria sensitive trigger detection system based on adaptive threshold, which specifically includes: The current sampling module is used to collect the three-phase current of the line according to a preset sampling frequency; An adaptive threshold determination module is used to determine whether there is a faulty phase based on the current value of each phase, and to determine the adaptive threshold of each detection criterion in the pre-established composite detection criterion based on the judgment result. The composite detection criterion includes current change rate, current sudden change, and current instantaneous value / effective value. The fault detection module is used to determine faults based on adaptive thresholds of various detection criteria, including: first, performing initial disturbance judgment based on the rate of change of current; then, performing disturbance elimination based on the sudden change of current; and finally, distinguishing the nature of disturbances based on the instantaneous / effective value of current.

[0058] It should be noted that for a detailed description of the multi-criteria sensitive trigger detection system based on adaptive threshold provided in the embodiments of the present invention, please refer to the relevant description of the multi-criteria sensitive trigger detection method based on adaptive threshold provided in the embodiments of the present invention, which will not be repeated here.

[0059] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A multi-criteria sensitive trigger detection method based on adaptive threshold, characterized in that, The method includes: The three-phase current of the line is collected according to the preset sampling frequency; The presence of a faulty phase is determined based on the current values ​​of each phase. Based on the determination results, the adaptive thresholds of each detection criterion in the pre-established composite detection criteria are determined. The composite detection criteria include the rate of change of current, the sudden change of current, and the instantaneous / effective value of current. Fault determination is performed based on adaptive thresholds of various established detection criteria, including: first, initial disturbance judgment based on the rate of change of current; then, disturbance elimination based on sudden changes in current; and finally, disturbance distinction based on the nature of the instantaneous / effective value of current.

2. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 1, characterized in that, The three-phase current of the line is collected according to a preset sampling frequency, and the presence of a faulty phase is determined based on the current values ​​of each phase. Specifically, this includes: Based on measured three-phase line current , , The phase whose current value differs from the normal operating value by more than a preset threshold is designated as phase x. If the current values ​​of the other two phases, namely phases y and z, differ from the normal operating value by less than the preset threshold, then phase x is determined to be a faulty phase.

3. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 1, characterized in that, Based on the judgment results, the adaptive thresholds for each detection criterion in the pre-established composite detection criteria are determined, specifically including: If a faulty phase is identified, the current data of the non-faulty phase is used as the normal data reference segment, and the current change rate and current abrupt change are calculated, which are then used as adaptive thresholds for the current change rate and current abrupt change in this waveform recording event, respectively. and ; If the faulty phase is not identified, the first 10% of the current data sampling for any phase is used as the normal data reference segment, and the current change rate and current abrupt change are calculated, which are then used as the thresholds for the current change rate and current abrupt change in this waveform recording event, respectively. and ; Threshold of instantaneous current value The threshold value of the effective current is set to 1.2 times the rated peak value. Set to 1.1 times the rated effective value.

4. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 1, characterized in that, The initial disturbance assessment based on the rate of change of current specifically includes: If the rate of change of current at two consecutive sampling points is greater than the set threshold, it is preliminarily determined that there is a disturbance in the circuit, and the next stage of interference elimination based on the sudden change of current is initiated.

5. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 4, characterized in that, Interference elimination based on sudden changes in current specifically includes: If the sudden change in current does not exceed the set threshold, it is determined to be an invalid disturbance, and the detection process is terminated. If the sudden change in current exceeds the set threshold, the next level of disturbance nature distinction based on the instantaneous / effective value of the current will be performed.

6. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 5, characterized in that, Based on the nature of the disturbance, which is determined by the instantaneous / effective value of the current, the following specific characteristics are included: If the instantaneous / effective current value exceeds the set threshold, it is determined to be an early fault disturbance; If neither the instantaneous current value nor the effective current value exceeds the set threshold, it is determined to be a normal line disturbance.

7. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 1, characterized in that, The rate of change of current H is calculated as follows: Where i is the instantaneous value of the phase current, and t is the corresponding sampling time.

8. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 1, characterized in that, Current Sudden Change The calculation is as follows: In the instantaneous value sequence of phase current sampling, select a period m and calculate its effective value. Then calculate the effective value of the (m+1)th period. Mutation amount for and difference; The calculation formula is as follows: Where N is the number of sampling points in one cycle, n is the sampling point currently being calculated, and i is the instantaneous value of the phase current.

9. The multi-criteria sensitive trigger detection method based on adaptive threshold as described in claim 1, characterized in that, The instantaneous current / RMS current ratio is calculated as follows: Instantaneous current value i: This is the instantaneous value of the phase current measured at the moment. RMS value of current Calculate the root mean square value of the current one cycle prior to the current sampling time. The calculation formula is as follows: Where N is the number of sampling points in one cycle, and p is the number of sampling points at the current calculation time.

10. A multi-criteria sensitive trigger detection system based on adaptive threshold, characterized in that, The system includes: The current sampling module is used to collect the three-phase current of the line according to a preset sampling frequency; An adaptive threshold determination module is used to determine whether there is a faulty phase based on the current value of each phase, and to determine the adaptive threshold of each detection criterion in the pre-established composite detection criterion based on the judgment result. The composite detection criterion includes current change rate, current sudden change, and current instantaneous value / effective value. The fault detection module is used to determine faults based on adaptive thresholds of various detection criteria, including: first, performing initial disturbance judgment based on the rate of change of current; then, performing disturbance elimination based on the sudden change of current; and finally, distinguishing the nature of disturbances based on the instantaneous / effective value of current.

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