Power distribution feeder voltage transformer on-line monitoring method and system based on phasor measurement

Abstract

The application discloses a power distribution feeder voltage transformer online monitoring method and system based on a phasor measurement, and the method comprises the following steps: collecting phasor data of each key node in real time through a phasor measurement unit arranged at a key node of a power distribution network; based on topological structure information and a switch state of the power distribution network, taking the key node which has an electrical correlation with a node to be monitored as a neighboring measurement node; based on the phasor data, identifying line parameters between the node to be monitored and each neighboring measurement node, and obtaining the line parameters; calculating a virtual reference voltage of the node to be monitored based on the line parameters; comparing a measured voltage of the node to be monitored with the virtual reference voltage, and obtaining a ratio error and a phase error; and based on error criteria corresponding to the ratio error and the phase error, monitoring an operation state of a voltage transformer.

Description

Technical Field

[0001] This invention relates to the field of power system condition monitoring technology, and more specifically, to a method and system for online monitoring of distribution feeder voltage transformers based on phasor measurement. Background Technology

[0002] Voltage transformers (VTs or PTs) are crucial primary measuring devices in power distribution networks. Their function is to reduce high voltage in the distribution network to a lower voltage suitable for measuring instruments and relay protection devices according to a specific transformation ratio. The accuracy of voltage transformer measurements directly affects various aspects, including electricity metering, electricity billing, the reliability of relay protection operations, power system condition monitoring, and control decisions. Therefore, they are a vital foundation for ensuring the safe and stable operation of the power system.

[0003] With the increasing automation of distribution networks and the continuous advancement of smart grid construction, the requirements for the measurement accuracy and operational reliability of voltage transformers in distribution networks are becoming increasingly stringent. However, during long-term operation, voltage transformers are affected by various factors such as ambient temperature, humidity, load changes, equipment aging, and insulation deterioration. Their measurement errors may gradually increase or even exceed the allowable range, leading to measurement inaccuracies. In severe cases, this can cause metering disputes, protection malfunctions or failures to operate, and deviations in state estimation results, posing potential threats to the safe and stable operation of the power system.

[0004] Traditional methods for detecting voltage transformer errors primarily rely on periodic offline calibration. This involves periodically shutting down the operating voltage transformers according to regulations and performing on-site comparison measurements using standard transformers or transformer calibrators. While this method is technically mature, it suffers from the following significant drawbacks:

[0005] 1. It requires power outages for work, which affects the reliability of power supply, and the detection cycle is long, making it difficult to detect equipment abnormalities in a timely manner;

[0006] 2. The transportation, installation, and calibration of standard instrument transformers are complex and costly.

[0007] 3. It cannot achieve real-time monitoring of equipment operating status, and cannot meet the requirements of smart distribution networks for equipment status perception;

[0008] 4. The operating conditions during offline testing differ from actual operating conditions, resulting in limited representativeness of the test results.

[0009] In recent years, with the gradual application of phasor measurement unit (PMU) technology in power distribution networks, a new technical approach has been provided for the online monitoring of voltage transformers. However, the core challenge in using PMU data for voltage transformer error monitoring is the lack of a reliable reference voltage standard.

[0010] In the existing technology, researchers have proposed some solutions, but they all have obvious shortcomings: the method based on the voltage conversion of the high voltage side of the main transformer requires the accurate transformation ratio parameters of the transformer and is affected by load loss; the anomaly detection method based on state estimation has high requirements for data redundancy and it is difficult to quantify the specific transformer error value.

[0011] Therefore, there is an urgent need for a method that can establish a virtual reference voltage using the distribution network's own measurement data under actual operating conditions, without relying on external standard equipment, and thus realize online monitoring of voltage transformer operating errors. Summary of the Invention

[0012] The present invention provides a method and system for online monitoring of distribution feeder voltage transformers based on phasor measurement, in order to solve the problem of how to monitor distribution feeder voltage transformers online based on phasor measurement data.

[0013] To address the aforementioned problems, this invention provides an online monitoring method for distribution feeder voltage transformers based on phasor measurement, the method comprising:

[0014] Phasor data of each key node is collected in real time by phasor measurement units deployed at key nodes of the distribution network.

[0015] Based on the distribution network topology information and switch status, the key nodes that are electrically related to the node to be monitored are designated as neighboring measurement nodes;

[0016] Based on the phasor data, the line parameters between the node to be monitored and each neighboring measurement node are identified, and the line parameters are obtained.

[0017] The virtual reference voltage of the node to be monitored is calculated based on the line parameters;

[0018] The measured voltage of the node to be monitored is compared with the virtual reference voltage to obtain the ratio error and phase error;

[0019] The operating status of the voltage transformer is monitored based on the error criteria corresponding to the ratio error and phase error.

[0020] Preferably, the sampling frequency of the phasor measurement unit is not less than 25 frames per second;

[0021] The phasor data includes: three-phase voltage phasors, three-phase current phasors, and timestamp information.

[0022] Preferably, the adjacent measurement node is a critical node whose electrical distance from the node to be monitored is within 3 nodes;

[0023] The adjacent measurement nodes include upstream and downstream nodes of the same feeder, nodes of different voltage levels connected by transformers, and adjacent feeder nodes connected by tie switches.

[0024] Preferably, the step of identifying the line parameters between the node to be monitored and each neighboring measurement node based on the phasor data, and obtaining the line parameters, includes:

[0025] For the line between the node to be monitored i and the neighboring measurement node j, establish the voltage phasor relationship:

[0026]

[0027] in, Let i be the voltage phasor of the node to be monitored. Let j be the voltage phasor of the neighboring measurement node j. For the line ij The current phasor, For the line ij The line impedance; The resistance of the circuit. The reactance of the line;

[0028] The least squares method is used to obtain the resistance and reactance of the line by using the estimated amount of measurement data within a preset period.

[0029] Preferably, calculating the virtual reference voltage of the node to be monitored based on the line parameters includes:

[0030] Based on Kirchhoff's voltage law for electrical networks, the virtual reference voltage of the node to be monitored is calculated by using the measured voltage of nearby measurement nodes and the identified line parameters.

[0031] For a node k to be monitored with n neighboring measurement nodes, the voltage estimate of node k is calculated from the line parameters and current values ​​of each neighboring measurement node j (j=1,2,...,n) and node k:

[0032]

[0033] in, Let be the current phasor of the line between the neighboring measurement node j and the node to be monitored k. The line impedance is the line impedance between the neighboring measurement node j and the node k to be monitored.

[0034] Using a weighted fusion method, the voltage estimate of the line between the monitored node k and multiple neighboring measurement nodes j is calculated, and the virtual reference voltage of the monitored node k is determined.

[0035]

[0036] in, The weighting coefficients satisfy the normalization condition. The weighting coefficients are determined by the inverse variance weighting method based on measurement uncertainty.

[0037] Preferably, the step of comparing the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error includes:

[0038] The measured voltage of the node to be monitored With virtual reference voltage Compare and calculate the ratio error of the voltage transformers. and phase error :

[0039]

[0040] .

[0041] Preferably, the monitoring of the operating status of the voltage transformer is based on the error criteria corresponding to the ratio error and the phase error, wherein the error criteria include a ratio error threshold and a phase error threshold;

[0042] Establish voltage transformer error criteria:

[0043] when or At that time, in order to meet the voltage transformer error criterion; among which The ratio error threshold, This is the phase error threshold;

[0044] When the voltage transformer error criterion is met for multiple consecutive measurement cycles, the voltage transformer is confirmed to be faulty.

[0045] Preferably, the ratio error threshold is 0.2% to 1.0%, and the phase error threshold is 10 minutes to 40 minutes.

[0046] Preferably, the method further includes: correcting the virtual reference voltage based on the injected current phasor of the distributed source:

[0047]

[0048] in, The injected current phasor for distributed power sources.

[0049] Preferably, the method further includes evaluating the reliability of the virtual reference voltage:

[0050]

[0051] when At that time, the virtual reference voltage was assessed as reliable;

[0052] in, The threshold for credibility assessment The reliability of the virtual reference voltage.

[0053] Based on another aspect of the present invention, the present invention provides an online monitoring system for distribution feeder voltage transformers based on phasor measurement, the system comprising:

[0054] The initial unit is used to collect phasor data of each key node in real time through phasor measurement units deployed at key nodes of the distribution network.

[0055] The determining unit is used to identify the key nodes that are electrically associated with the node to be monitored as neighboring measurement nodes based on the distribution network topology information and switch status.

[0056] The identification unit is used to identify the line parameters between the node to be monitored and each neighboring measurement node based on the phasor data, and to obtain the line parameters.

[0057] A calculation unit is used to calculate the virtual reference voltage of the node to be monitored based on the line parameters;

[0058] The comparison unit is used to compare the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error;

[0059] The result unit is used to monitor the operating status of the voltage transformer based on the error criteria corresponding to the ratio error and phase error.

[0060] This invention provides a method and system for online monitoring of voltage transformers in distribution feeders based on phasor measurement. The method includes: real-time acquisition of phasor data from key nodes via phasor measurement units deployed at these nodes; identification of nearby measurement nodes as electrically connected to the node to be monitored based on the distribution network topology and switch status; identification of line parameters between the node to be monitored and its nearby measurement nodes based on the phasor data; calculation of a virtual reference voltage for the node to be monitored based on the line parameters; comparison of the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error; and monitoring of the voltage transformer's operating status based on error criteria corresponding to the ratio error and phase error. This invention enables online monitoring of voltage transformer operating errors under actual distribution network operating conditions, without relying on external standard equipment, by establishing a virtual reference voltage using the distribution network's own measurement data. Attached Figure Description

[0061] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0062] Figure 1 This is a flowchart of an online monitoring method for distribution feeder voltage transformers based on phasor measurement according to a preferred embodiment of the present invention.

[0063] Figure 2 This is a complete process flowchart for data acquisition and anomaly diagnosis according to a preferred embodiment of the present invention;

[0064] Figure 3 This is a schematic diagram of the topology of distribution network measurement nodes according to a preferred embodiment of the present invention;

[0065] Figure 4 This is a schematic diagram of the virtual reference voltage calculation principle based on a neighboring node according to a preferred embodiment of the present invention;

[0066] Figure 5 A schematic diagram illustrating the establishment of a virtual reference voltage through multi-node data fusion according to a preferred embodiment of the present invention;

[0067] Figure 6 A schematic diagram of voltage transformer error monitoring results according to a preferred embodiment of the present invention; and

[0068] Figure 7 This is a structural diagram of an online monitoring system for distribution feeder voltage transformers based on phasor measurement according to a preferred embodiment of the present invention. Detailed Implementation

[0069] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0070] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0071] Figure 1 This is a flowchart of an online monitoring method for distribution feeder voltage transformers based on phasor measurement according to a preferred embodiment of the present invention.

[0072] This invention provides a method for establishing a virtual reference voltage based on distribution network phasor measurement. This invention makes full use of the synchronous phasor data collected by the phasor measurement units deployed in the distribution network from multiple measurement points. Based on the topology of the distribution network and Kirchhoff's voltage law of the electrical network, a high-precision virtual reference voltage standard is established through line parameter identification and multi-node data fusion technology. Online real-time monitoring of voltage transformer operating errors can be achieved without external standard equipment.

[0073] This invention discloses a method for establishing a virtual reference voltage based on distribution network phasor measurement, belonging to the field of power system condition monitoring technology. This invention deploys PMUs at key nodes of the distribution network to collect synchronous phasor data, identifies adjacent measurement nodes and line impedance parameters, and establishes a high-precision virtual reference voltage using Kirchhoff's voltage law for electrical networks and multi-node data weighted fusion technology. By comparing this virtual reference voltage with the measured voltage, the ratio error and phase error of the voltage transformer are calculated, enabling online monitoring of the voltage transformer's operating error. This invention requires no external standard equipment and can continuously monitor the operating status of voltage transformers without power interruption, promptly detecting equipment anomalies. It has advantages such as low cost, good real-time performance, high accuracy, and strong adaptability, making it particularly suitable for condition monitoring of metering equipment in smart distribution network environments. It also has good applicability to new distribution networks with distributed power source integration.

[0074] like Figure 1 As shown, this invention provides an online monitoring method for distribution feeder voltage transformers based on phasor measurement, the method comprising:

[0075] Step 101: Collect phasor data of each key node in real time by deploying phasor measurement units at key nodes of the distribution network;

[0076] Preferably, the sampling frequency of the phasor measurement unit is not less than 25 frames per second;

[0077] Phasor data includes: three-phase voltage phasors, three-phase current phasors, and timestamp information.

[0078] In step 101, this invention acquires distribution network phasor data. This invention deploys phasor measurement units (PMUs) at key nodes in the distribution network to acquire three-phase voltage phasors, three-phase current phasors, and timestamp information at each measurement point in real time. The phasor data of this invention includes amplitude and phase angle information, with a sampling frequency of no less than 25 frames per second, voltage amplitude accuracy of no less than ±0.1%, phase angle accuracy of no less than ±0.01°, and time synchronization accuracy reaching the microsecond level. Figure 2 As shown.

[0079] Step 102: Based on the distribution network topology information and switch status, key nodes that are electrically connected to the node to be monitored are identified as neighboring measurement nodes;

[0080] Preferably, the nearest measurement node is a critical node whose electrical distance from the node to be monitored is within 3 nodes;

[0081] Adjacent measurement nodes include upstream and downstream nodes of the same feeder, nodes of different voltage levels connected by transformers, and adjacent feeder nodes connected by tie switches.

[0082] In step 102, this invention performs topology identification and neighbor node determination. Based on the distribution network topology information and switch states, this invention identifies neighboring measurement nodes of the node containing the voltage transformer to be monitored. These neighboring nodes include: measurement nodes upstream of the same feeder, measurement nodes downstream of the same feeder, measurement nodes of different voltage levels connected via distribution transformers, and measurement nodes of adjacent feeders connected via tie switches. This invention selects measurement points with an electrical distance of no more than three nodes from the node to be monitored as neighboring nodes. For example... Figure 3 As shown.

[0083] Step 103: Based on phasor data, identify the line parameters between the node to be monitored and each neighboring measurement node, and obtain the line parameters;

[0084] Preferably, based on phasor data, the line parameters between the node to be monitored and each neighboring measurement node are identified to obtain the line parameters, including:

[0085] For the line between the node to be monitored i and the neighboring measurement node j, establish the voltage phasor relationship:

[0086]

[0087] in, Let i be the voltage phasor of the node to be monitored. Let j be the voltage phasor of the neighboring measurement node j. For the line ij The current phasor, For the line ij The line impedance; The resistance of the circuit. The reactance of the line;

[0088] The least squares method is used to obtain the line resistance and reactance using a projected amount of measurement data within a preset period. The measurement data includes: three-phase voltage phasors, three-phase current phasors, and timestamp information acquired by the PMU.

[0089] In step 103, the present invention identifies line parameters. Utilizing historical measurement data and based on a multi-time measurement equation set, the present invention identifies the line impedance parameters between the node to be monitored and its neighboring nodes, including resistance R and reactance X.

[0090] For the line between node i and node j, establish the voltage phasor relationship:

[0091]

[0092] in Let be the voltage phasor of node i. Let be the voltage phasor at node j. Let be the current phasor of branch ij. Let be the line impedance of branch ij. The line impedance parameters are solved using the least squares method, utilizing measurement data from at least 100 times in the past 24 hours.

[0093] Step 104: Calculate the virtual reference voltage of the node to be monitored based on the line parameters;

[0094] Preferably, calculating the virtual reference voltage of the node to be monitored based on line parameters includes:

[0095] Based on Kirchhoff's voltage law for electrical networks, the virtual reference voltage of the node to be monitored is calculated by using the measured voltage of nearby measurement nodes and the identified line parameters.

[0096] For a node k to be monitored with n neighboring measurement nodes, the voltage estimate of node k can be calculated from the line parameters and current values ​​of each neighboring measurement node j (j=1,2,...,n) and node k:

[0097]

[0098] in, Let be the current phasor of the line between the neighboring measurement node j and the node to be monitored k. The line impedance is the line impedance between the neighboring measurement node j and the node to be monitored k.

[0099] Using a weighted fusion method, the voltage estimate of the line between the monitored node k and multiple neighboring measurement nodes j is calculated, and the virtual reference voltage of the monitored node k is determined.

[0100]

[0101] in, The weighting coefficients satisfy the normalization condition. The weighting coefficients are determined using an inverse variance weighting method based on measurement uncertainty. For example... Figure 4 As shown.

[0102] In step 104, the present invention performs virtual reference voltage calculation. Based on Kirchhoff's voltage law for electrical networks, the present invention uses the measured voltage of neighboring nodes and the identified line parameters to calculate the virtual reference voltage of the node to be monitored.

[0103] For a node k to be monitored with n neighboring measurement nodes, the voltage estimate of node k can be derived from each neighboring node j (j=1,2,...,n):

[0104]

[0105] A weighted fusion method is used to combine the calculation results of multiple neighboring nodes:

[0106]

[0107] in The weighting coefficients satisfy the normalization condition. The weighting coefficients are preferably determined using the inverse variance weighting method based on measurement uncertainty. For example... Figure 5 As shown.

[0108] Step 105: Compare the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error;

[0109] Preferably, the measured voltage of the node to be monitored is compared with the virtual reference voltage to obtain the ratio error and phase error, including:

[0110] The measured voltage of the node to be monitored With virtual reference voltage Compare and calculate the ratio error of the voltage transformers. and phase error :

[0111]

[0112]

[0113] In step 105, this invention compares the measured voltage with the virtual reference voltage. This invention uses the actual measured voltage of the node to be monitored. With virtual reference voltage Compare and calculate the ratio error and phase error of the voltage transformers:

[0114] Ratio error:

[0115] Phase error: (Unit: points)

[0116] Step 106: Monitor the operating status of the voltage transformer based on the error criteria corresponding to the ratio error and phase error.

[0117] Preferably, the operating status of the voltage transformer is monitored based on error criteria corresponding to the ratio error and the phase error, wherein the error criteria include a ratio error threshold and a phase error threshold;

[0118] Establish voltage transformer error criteria:

[0119] when or At that time, in order to meet the voltage transformer error criterion; among which The ratio error threshold, This is the phase error threshold;

[0120] When the voltage transformer error criterion is met for multiple consecutive measurement cycles, the voltage transformer is confirmed to be faulty.

[0121] In step 106, this invention performs error assessment and anomaly diagnosis. This invention establishes a voltage transformer error criterion: when... or If the error exceeds the threshold for N consecutive measurement cycles (N is typically 3-5), the voltage transformer is confirmed to be faulty and an alarm is issued. The ratio error threshold is determined based on the accuracy class of the current transformer, and is generally taken as 0.2%-1.0%. The phase error threshold is typically set between 10 and 40 points. For example... Figure 6 As shown.

[0122] Preferably, the ratio error threshold is 0.2% to 1.0%, and the phase error threshold is 10 minutes to 40 minutes.

[0123] Preferably, the method further includes: correcting the virtual reference voltage based on the injected current phasor of the distributed source:

[0124]

[0125] in, The injected current phasor for distributed power sources.

[0126] This invention corrects the virtual reference voltage by taking into account the influence of distributed power sources:

[0127] When the node to be monitored or a neighboring node has distributed generation (DG) access, the impact of the DG injection current must be considered when calculating the virtual reference voltage in step 104.

[0128]

[0129] in This refers to the injection current phasor for distributed generation. This modification allows the invention to adapt to new distribution network environments with a high proportion of distributed generation.

[0130] Preferably, the method further includes evaluating the reliability of the virtual reference voltage:

[0131]

[0132] when At that time, the virtual reference voltage was assessed as reliable;

[0133] in, The threshold for credibility assessment The reliability of the virtual reference voltage.

[0134] This invention performs dynamic accuracy evaluation on virtual reference voltage:

[0135] The reliability of the virtual reference voltage is evaluated by calculating the consistency between the voltages estimated from neighboring nodes.

[0136]

[0137] when If the virtual reference voltage is accurate, it is considered reliable; otherwise, the line parameters need to be rechecked or the measurement data quality of nearby nodes needs to be checked. Dynamic accuracy assessment can improve the self-diagnostic capability of the monitoring system and avoid misjudgments caused by inaccurate reference voltage.

[0138] This invention provides a method for establishing a virtual reference voltage based on distribution network phasor measurement, comprising the following steps: deploying phasor measurement units at key nodes of the distribution network to collect voltage and current phasors in real time; identifying neighboring measurement nodes of the node to be monitored; identifying line impedance parameters; calculating the virtual reference voltage based on Kirchhoff's voltage law; comparing the measured voltage with the reference voltage and calculating the error; and performing anomaly diagnosis based on error criteria.

[0139] The phasor data sampling frequency of this invention is no less than 25 frames per second, and the voltage amplitude measurement accuracy is no less than ±0.1%.

[0140] The adjacent measurement nodes of the present invention include upstream and downstream nodes on the same feeder, nodes of different voltage levels connected by transformers, and adjacent feeder nodes connected by interconnecting switches.

[0141] The line parameter identification of this invention adopts the least squares method and utilizes historical measurement data at no less than 100 times.

[0142] The virtual reference voltage of this invention is calculated using a weighted fusion method, with the weighting coefficients determined based on the measurement uncertainty.

[0143] The ratio error threshold of the present invention is determined to be 0.2%-1.0% based on the accuracy level of the mutual inductor, and the phase error threshold is 10-40 minutes.

[0144] In this invention, when the error exceeds the threshold for 3-5 consecutive measurement cycles, the voltage transformer is confirmed to be abnormal and an alarm is issued.

[0145] When a distributed power source is present, the calculation of the virtual reference voltage in this invention needs to take into account the influence of the current injected by the distributed power source.

[0146] This invention evaluates the reliability of a virtual reference voltage by calculating a consistency index between calculated voltages.

[0147] This invention considers the virtual reference voltage to be reliable when the consistency index is less than a preset threshold; otherwise, it re-verifies the parameters or checks the data quality.

[0148] Compared with the prior art, the present invention has the following significant advantages:

[0149] No external standard equipment is required, reducing monitoring costs. A virtual reference is established using the distribution network's own phasor measurement data, eliminating the need for external reference equipment such as standard instrument transformers.

[0150] It enables true online monitoring and timely detection of equipment anomalies. The monitoring frequency can reach 25-50 times per second, allowing continuous monitoring of the operating status of voltage transformers.

[0151] It does not affect power supply reliability and meets smart grid requirements. The entire monitoring process is conducted online without requiring power outages.

[0152] It reflects real-world operating conditions, resulting in more accurate monitoring results. Monitoring is conducted under actual equipment operating conditions, fully considering real-world environmental and load factors.

[0153] It is highly adaptable and suitable for various distribution network structures. It can adapt to various distribution network structures such as radial and ring networks, and can also be effectively applied to new distribution networks containing distributed power sources;

[0154] High accuracy and improved reliability through multi-node fusion. By weighted fusion of data from multiple neighboring nodes, the accuracy of the virtual reference voltage can reach within ±0.1%.

[0155] It possesses self-diagnostic capabilities, ensuring the reliability of monitoring results. Through a dynamic accuracy evaluation mechanism, the system can assess the reliability of the virtual reference voltage in real time.

[0156] It has good scalability and promising technological prospects. The technical framework of this invention can be extended to the online monitoring of other power equipment such as current transformers and electricity meters.

[0157] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0158] Example 1: Online monitoring of voltage transformers for 10kV distribution feeders

[0159] This embodiment describes an online monitoring application for voltage transformers on a 10kV distribution feeder in a certain city. The feeder is approximately 8 kilometers long, and its power supply load mainly consists of industrial and commercial users, with a maximum load of approximately 6MW.

[0160] Step 1: Distribution Network Phasor Data Acquisition

[0161] Five PMU (Phase Measure) devices, numbered PMU1 to PMU5, were deployed at key locations along the 10kV distribution feeder. Each PMU synchronously acquired three-phase voltage and current phasor data at a sampling rate of 50Hz.

[0162] The A-phase data collected by each PMU at a typical moment are shown in the table below:

[0163]

[0164] Steps 2-3: Topology identification and parameter recognition

[0165] Based on the distribution network topology, PMU3's nearest neighbors are PMU2 (upstream) and PMU4 (downstream). Using historical data from the past 24 hours, the line parameters were identified as follows:

[0166] PMU2-PMU3 segment:

[0167] PMU3-PMU4 segment:

[0168] Step 4: Calculation of Virtual Reference Voltage

[0169] Based on PMU2:

[0170]

[0171] Calculated backwards from PMU4:

[0172]

[0173] Weighted fusion (weight) =0.45, =0.55):

[0174]

[0175] Steps 5-6: Error Comparison and Diagnosis

[0176] PMU3 measured voltage: 9.85∠-1.20°kV

[0177] Ratio error:

[0178] Phase error:

[0179] Conclusion: The voltage transformer ratio of PMU3 has a slight negative deviation (approximately 0.5%), which maintenance personnel are advised to monitor. The phase error is normal.

[0180] Example 2: Monitoring including distributed photovoltaic power

[0181] Assuming a 500kW photovoltaic power station is connected near the PMU3 node, the injected current... .

[0182] Corrected calculation: The impact of photovoltaics is deducted when extrapolating from PMU2:

[0183]

[0184] Revised version: Reintegrated

[0185] Corrected ratio error: The monitoring accuracy has been improved.

[0186] Example 3: Dynamic Accuracy Assessment

[0187] Calculate the consistency index:

[0188]

[0189] Set threshold =50V. determination: = 2.8V < 50V, the virtual reference voltage has high reliability.

[0190] Abnormal situation simulation: If an abnormal measurement by PMU2 results in an estimated value of 9.750 kV, then... = 69V > 50V, the system automatically starts diagnostics, checks the PMU2 data quality, and temporarily suspends error judgment.

[0191] Figure 7 This is a structural diagram of an online monitoring system for distribution feeder voltage transformers based on phasor measurement according to a preferred embodiment of the present invention.

[0192] like Figure 7 As shown, this invention provides an online monitoring system for distribution feeder voltage transformers based on phasor measurement. The system includes:

[0193] The initial unit 701 is used to collect phasor data of each key node in real time through phasor measurement units deployed at key nodes of the distribution network.

[0194] Preferably, the sampling frequency of the phasor measurement unit is not less than 25 frames per second;

[0195] Phasor data includes: three-phase voltage phasors, three-phase current phasors, and timestamp information.

[0196] The determination unit 702 is used to identify key nodes that are electrically associated with the node to be monitored as neighboring measurement nodes based on the distribution network topology information and switch status.

[0197] Preferably, the determining unit 702 is used to identify the adjacent measurement node as a critical node whose electrical distance from the node to be monitored is within 3 nodes;

[0198] Adjacent measurement nodes include upstream and downstream nodes of the same feeder, nodes of different voltage levels connected by transformers, and adjacent feeder nodes connected by tie switches.

[0199] The identification unit 703 is used to identify the line parameters between the node to be monitored and each neighboring measurement node based on phasor data, and to obtain the line parameters.

[0200] Preferably, the identification unit 703 is used to identify the line parameters between the node to be monitored and each neighboring measurement node based on phasor data, and to obtain the line parameters, including:

[0201] For the line between the node to be monitored i and the neighboring measurement node j, establish the voltage phasor relationship:

[0202]

[0203] in, Let i be the voltage phasor of the node to be monitored. Let j be the voltage phasor of the neighboring measurement node j. For the line ij The current phasor, For the line ij The line impedance; The resistance of the circuit. The reactance of the line;

[0204] The least squares method is used to obtain the resistance and reactance of the line by using the estimated amount of measurement data within a preset period.

[0205] The calculation unit 704 is used to calculate the virtual reference voltage of the node to be monitored based on the line parameters;

[0206] Preferably, the calculation unit 704 is used to calculate the virtual reference voltage of the node to be monitored based on the line parameters, including:

[0207] Based on Kirchhoff's voltage law for electrical networks, the virtual reference voltage of the node to be monitored is calculated by using the measured voltage of nearby measurement nodes and the identified line parameters.

[0208] For a node k to be monitored with n neighboring measurement nodes, the voltage estimate of node k can be calculated from the line parameters and current values ​​of each neighboring measurement node j (j=1,2,...,n) and node k:

[0209]

[0210] in, Let be the current phasor of the line between the neighboring measurement node j and the node to be monitored k. The line impedance is the line impedance between the neighboring measurement node j and the node to be monitored k.

[0211] Using a weighted fusion method, the voltage estimate of the line between the monitored node k and multiple neighboring measurement nodes j is calculated, and the virtual reference voltage of the monitored node k is determined.

[0212]

[0213] in, The weighting coefficients satisfy the normalization condition. The weighting coefficients are determined by the inverse variance weighting method based on measurement uncertainty.

[0214] The comparison unit 705 is used to compare the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error.

[0215] Result unit 706 is used to monitor the operating status of the voltage transformer based on error criteria corresponding to ratio error and phase error.

[0216] Preferably, the measured voltage of the node to be monitored is compared with the virtual reference voltage to obtain the ratio error and phase error, including:

[0217] The measured voltage of the node to be monitored With virtual reference voltage Compare and calculate the ratio error of the voltage transformers. and phase error :

[0218]

[0219] .

[0220] Preferably, the operating status of the voltage transformer is monitored based on error criteria corresponding to the ratio error and the phase error, wherein the error criteria include a ratio error threshold and a phase error threshold;

[0221] Establish voltage transformer error criteria:

[0222] when or At that time, in order to meet the voltage transformer error criterion; among which The ratio error threshold, This is the phase error threshold;

[0223] When the voltage transformer error criterion is met for multiple consecutive measurement cycles, the voltage transformer is confirmed to be faulty.

[0224] Preferably, the ratio error threshold is 0.2% to 1.0%, and the phase error threshold is 10 minutes to 40 minutes.

[0225] Preferably, the method further includes: correcting the virtual reference voltage based on the injected current phasor of the distributed source:

[0226]

[0227] in, The injected current phasor for distributed power sources.

[0228] Preferably, the method further includes evaluating the reliability of the virtual reference voltage:

[0229]

[0230] when At that time, the virtual reference voltage was assessed as reliable;

[0231] in, The threshold for credibility assessment The reliability of the virtual reference voltage.

[0232] The preferred embodiment of the present invention provides an online monitoring system for distribution feeder voltage transformers based on phasor measurement, which corresponds to another preferred embodiment of the present invention, a method for online monitoring of distribution feeder voltage transformers based on phasor measurement. These will not be described in detail here.

[0233] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0234] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0235] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0236] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0237] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0238] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0239] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0240] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

Claims

1. A method for online monitoring of distribution feeder voltage transformers based on phasor measurement, the method comprising: Phasor data of each key node is collected in real time by phasor measurement units deployed at key nodes of the distribution network. Based on the distribution network topology information and switch status, the key nodes that are electrically related to the node to be monitored are designated as neighboring measurement nodes; Based on the phasor data, the line parameters between the node to be monitored and each neighboring measurement node are identified, and the line parameters are obtained, including: For the line between the node to be monitored i and the neighboring measurement node j, establish the voltage phasor relationship: in, Let i be the voltage phasor of the node to be monitored. Let j be the voltage phasor of the neighboring measurement node j. For the line ij The current phasor, For the line ij The line impedance; Rij The resistance of the circuit. Xij The reactance of the line; The least squares method is used to obtain the resistance and reactance of the line by using the estimated amount of measurement data within a preset period; Calculating the virtual reference voltage of the node to be monitored based on the line parameters includes: Based on Kirchhoff's voltage law for electrical networks, the virtual reference voltage of the node to be monitored is calculated by using the measured voltage of nearby measurement nodes and the identified line parameters. For a node k to be monitored with n neighboring measurement nodes, the voltage estimate of node k is calculated from the line parameters and current values ​​of each neighboring measurement node j (j=1,2,...,n) and node k: in, Let be the current phasor of the line between the neighboring measurement node j and the node to be monitored k. The line impedance is the line impedance between the neighboring measurement node j and the node k to be monitored. Using a weighted fusion method, the voltage estimate of the line between the monitored node k and multiple neighboring measurement nodes j is calculated, and the virtual reference voltage of the monitored node k is determined. in, The weighting coefficients satisfy the normalization condition. ; The measured voltage of the node to be monitored is compared with the virtual reference voltage to obtain the ratio error and phase error; The operating status of the voltage transformer is monitored based on the error criteria corresponding to the ratio error and phase error.

2. The method according to claim 1, wherein the sampling frequency of the phasor measurement unit is not less than 25 frames per second; The phasor data includes: Three-phase voltage phasors, three-phase current phasors, and timestamp information.

3. The method according to claim 1, wherein the adjacent measurement node is a critical node whose electrical distance from the node to be monitored is within 3 nodes; The adjacent measurement nodes include upstream and downstream nodes of the same feeder, nodes of different voltage levels connected by transformers, and adjacent feeder nodes connected by tie switches.

4. The method according to claim 1, wherein comparing the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error includes: The measured voltage of the node to be monitored With virtual reference voltage Compare and calculate the ratio error of the voltage transformers. and phase error : 。 5. The method according to claim 4, wherein the monitoring of the operating status of the voltage transformer based on the error criteria corresponding to the ratio error and phase error, wherein, The error criteria include the ratio error threshold and the phase error threshold; Establish voltage transformer error criteria: when or At that time, in order to meet the voltage transformer error criterion; among which The ratio error threshold, This is the phase error threshold; When the voltage transformer error criterion is met for multiple consecutive measurement cycles, the voltage transformer is confirmed to be faulty.

6. The method according to claim 5, wherein the ratio error threshold is 0.2% to 1.0%, and the phase error threshold is 10 minutes to 40 minutes.

7. The method according to claim 6, further comprising: The virtual reference voltage is corrected based on the injected current phasor of the distributed source: in, The injected current phasor for distributed power sources.

8. The method of claim 7, further comprising evaluating the confidence level of the virtual reference voltage: when At that time, the virtual reference voltage was assessed as reliable; in, The threshold for credibility assessment The reliability of the virtual reference voltage.

9. An online monitoring system for distribution feeder voltage transformers based on phasor measurement, the system comprising: The initial unit is used to collect phasor data of each key node in real time through phasor measurement units deployed at key nodes of the distribution network. The determining unit is used to identify the key nodes that are electrically associated with the node to be monitored as neighboring measurement nodes based on the distribution network topology information and switch status. The identification unit is used to identify the line parameters between the node to be monitored and each neighboring measurement node based on the phasor data, and to obtain the line parameters, including: For the line between the node to be monitored i and the neighboring measurement node j, establish the voltage phasor relationship: in, Let i be the voltage phasor of the node to be monitored. Let j be the voltage phasor of the neighboring measurement node j. For the line ij The current phasor, For the line ij The line impedance; Rij The resistance of the circuit. Xij The reactance of the line; The least squares method is used to obtain the resistance and reactance of the line by using the estimated amount of measurement data within a preset period; A calculation unit, used to calculate the virtual reference voltage of the node to be monitored based on the line parameters, includes: Based on Kirchhoff's voltage law for electrical networks, the virtual reference voltage of the node to be monitored is calculated by using the measured voltage of nearby measurement nodes and the identified line parameters. For a node k to be monitored with n neighboring measurement nodes, the voltage estimate of node k is calculated from the line parameters and current values ​​of each neighboring measurement node j (j=1,2,...,n) and node k: in, Let be the current phasor of the line between the neighboring measurement node j and the node to be monitored k. The line impedance is the line impedance between the neighboring measurement node j and the node k to be monitored. Using a weighted fusion method, the voltage estimate of the line between the monitored node k and multiple neighboring measurement nodes j is calculated, and the virtual reference voltage of the monitored node k is determined. in, The weighting coefficients satisfy the normalization condition. ; The comparison unit is used to compare the measured voltage of the node to be monitored with the virtual reference voltage to obtain the ratio error and phase error; The result unit is used to monitor the operating status of the voltage transformer based on the error criteria corresponding to the ratio error and phase error.

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