CN103941079B - Power distribution network PT on-line monitoring and fault diagnosis system - Google Patents

Abstract

A distribution network PT online monitoring and fault diagnosis system, the system can measure three phase currents, three phase voltages, three line voltages and zero-sequence voltage data of distribution network PTs. The measured data can accurately determine whether the system has a single-phase ground fault, a ferromagnetic resonance fault, or a PT disconnection fault. The system consists of three parts: current measurement terminal, collector and background server. The current measurement terminal is installed on the PT three-phase line of the distribution network, and uses the principle of electromagnetic induction to measure the three-phase current of the PT in the distribution network. The collector is installed on the panel of the PT cabinet, receives the data of the terminal, measures the phase voltage, line voltage and zero sequence voltage of the PT at the same time, and then uploads the data to the background server. The background server is installed in the substation, receives data from the collector, and performs online monitoring and fault diagnosis on the distribution network PT. The invention has mature technology and high reliability.

Description

Distribution Network PT Online Monitoring and Fault Diagnosis System

technical field

The invention belongs to the technical field of electric power monitoring, and in particular relates to electric power equipment, which is suitable for a 3-35kV distribution network. It can monitor PT three-phase voltage and current online, and can accurately judge whether the system has a single-phase ground fault, ferromagnetic resonance fault, or PT disconnection fault through the measured data based on rough set theory.

Background technique

my country's 3-35kV distribution network is prone to single-phase ground faults, ferromagnetic resonance faults, and PT disconnection faults. Because the phenomena of these types of faults are very similar, operators can only analyze based on experience, and it is often difficult to accurately diagnose the type of fault. If the operator makes a wrong judgment and takes the wrong operation, the fault may expand.

In order to more accurately analyze the type of system faults, practical technologies are urgently needed on-site for online monitoring and fault diagnosis of PTs. Since the PT will have a variety of frequencies in the case of ferromagnetic resonance faults, special consideration should be given to the compatibility of frequency measurement techniques during the measurement process.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and propose a PT online monitoring and fault diagnosis system for distribution network. The system can measure the data of three phase currents, three phase voltages, three line voltages and zero sequence voltage of PT in real time and accurately. The system can accurately judge whether the system has a single-phase ground fault, a ferromagnetic resonance fault, or a PT disconnection fault through the measured data. The system can provide correct guidance for operators.

Technical scheme of the present invention is as follows:

A distribution network PT online monitoring and fault diagnosis system, which consists of three parts: a terminal, a collector, and a background server, and is characterized by:

The terminal is installed on the PT three-phase line of the distribution network, and uses the principle of electromagnetic induction to measure the three-phase current of the PT of the distribution network. The terminal includes a low-power CPU module and a radio frequency communication module with a built-in AD function;

The collector is installed on the panel of the PT cabinet, receives the three-phase current data of the distribution network PT measured by the terminal, and simultaneously measures the phase voltage, line voltage and zero-sequence voltage of the PT, and then transfers the current data, phase The voltage, line voltage and zero sequence voltage data are uploaded to the background server;

The background server is installed in the substation, has an optical fiber communication module, receives data from the collector, and performs online monitoring and fault diagnosis on the distribution network PT.

The terminal adopts an amplifier circuit and a high-precision AD chip, and can measure a current of 10-1000mA.

The terminal can measure frequencies in the range of 25-250 Hz, and can accurately measure frequency division resonance, fundamental resonance and double frequency resonance.

The collector includes a voltage converter, a voltage measurement module, a radio frequency communication module and an optical fiber communication module. The radio frequency communication module is connected with the optical fiber communication module, and the radio frequency communication module receives the data of the terminal and sends it to the optical fiber communication module through serial port communication. The voltage converter and the voltage measurement module convert the PT phase voltage, line voltage and zero-sequence voltage into digital quantities respectively, and send them to the optical fiber communication module through serial communication. The optical fiber communication module sends voltage and current data to the background server located in the substation. Each collector only receives the terminal data of its own interval and measures the voltage of its own interval.

The present application also discloses a diagnosis method based on the aforementioned distribution network PT online monitoring and fault diagnosis system, characterized in that the method includes the following steps:

(1) Using rough set theory to establish a decision table for PT fault diagnosis in the distribution network, specifically including a single-phase ground fault decision table, a ferromagnetic resonance fault decision table, and a PT disconnection fault decision table;

(2) Discretize the three phase currents, three phase voltages, three line voltages and zero-sequence voltage data of the PT to form conditional attribute values;

(3) Query the PT voltage and current condition attribute values in the above four decision tables to obtain the corresponding decision attribute, that is, the diagnosis result;

(4) If it is judged that a fault occurs, an alarm is issued immediately.

This application can achieve the following functions:

(1) Accurately measure the three phase currents, three phase voltages, three line voltages and zero sequence voltage data of PT.

(2) Using rough set theory to establish decision tables for PT fault diagnosis in distribution network, including single-phase ground fault decision tables, ferromagnetic resonance fault decision tables, and PT disconnection fault decision tables. Fault diagnosis is realized by using decision table.

The advantages of the present invention are as follows:

1. Able to use the measured current and voltage data to diagnose the fault type.

2. Real-time monitoring of PT operation status, and timely alarm in case of abnormality.

3. High measurement accuracy.

4. Low power consumption, meeting the requirements of long-term operation.

5. With mature technology and high reliability, it is suitable for 3-35kV power distribution system.

Description of drawings

Fig. 1 is the structural representation of on-line monitoring and fault diagnosis system of the present invention;

FIG. 2 is a schematic diagram of the terminal 101;

Fig. 3 is the schematic diagram of collector 102;

Figure 4 is a flow chart of fault diagnosis based on rough sets;

Among them, 101 is the terminal, 101-A, 101-B, and 101-C represent the terminals installed on the PT three-phase line, 102 is the collector, 103 is the background server, 104 is the substation bus, 105 is the radio frequency communication, and 106 is the cable , 107 is an optical fiber communication, 201 is an induction coil, 202 is a temperature measurement module, 203 is a radio frequency communication module, 303 is an optical fiber communication module, 304 is a voltage converter, and 305 is a voltage measurement module.

detailed description

The technical solutions of the present invention will be further described in detail through specific embodiments below in conjunction with the accompanying drawings.

The application discloses a distribution network PT online monitoring and fault diagnosis system. The system can measure three phase currents, three phase voltages, three line voltages and zero-sequence voltage data of a distribution network PT. The measured data can accurately determine whether the system has a single-phase ground fault, a ferromagnetic resonance fault, or a PT disconnection fault. The system consists of three parts: current measurement terminal, collector and background server. The current measurement terminal is installed on the PT three-phase line of the distribution network, and uses the principle of electromagnetic induction to measure the three-phase current of the PT in the distribution network. The collector is installed on the panel of the PT cabinet, receives the data of the terminal, measures the phase voltage, line voltage and zero sequence voltage of the PT at the same time, and then uploads the data to the background server. The background server is installed in the substation, receives data from the collector, and performs online monitoring and fault diagnosis on the distribution network PT.

The structure of the present invention is shown in FIG. 1 , and the system consists of three parts: a terminal 101 , a collector 102 and a background server 103 . 101-A, 101-B, and 101-C represent the terminals installed on the PT three-phase line, and 102 represents the collector installed on the panel of the PT cabinet. Both the terminal 101 and the collector 102 are low-power embedded microcomputer devices, and the radio frequency communication 105 is used for data transmission between the terminal 101 and the collector 102 . In addition to receiving data from the terminal 101, the collector 102 can also measure PT phase voltage, line voltage and zero sequence voltage. 103 represents a background server, which is an industrial control computer installed in the substation, and is used to receive data from the collector 102 and perform analysis and calculation.

The principle of the terminal is shown in Figure 2. The terminal 101 is connected to the PT three-phase line of the distribution network, and 201 represents the induction coil. Through electromagnetic induction, a low-voltage simulation between -5V and +5V can be obtained on the secondary side of the induction coil 201. Quantity signal, the voltage signal is proportional to the current of distribution network PT. After the analog voltage signal enters the motherboard, it is first low-pass filtered, and then converted into a digital signal after AD conversion. The digital signal is transmitted to the CPU through the data bus for calculation. The CPU calculates the digital signal to obtain the voltage effective value and frequency, and then calculates the corresponding The effective value and frequency of PT current in the distribution network. 202 represents a temperature measurement module, which is used to convert the temperature into a level signal and transmit it to the CPU for calculation through the IO port. 203 represents a radio frequency communication module. The CPU sends current and temperature data to the radio frequency communication module 203 through the data bus, and uploads the current effective value of the distribution network PT to the collector 102 through the radio frequency communication 105 .

The principle of the collector is shown in FIG. 3 , and the radio frequency communication module 203 is used to receive data uploaded by the terminal 101 . 303 represents an optical fiber communication module, which is used to upload data to the background server 103 . Data transmission is performed between the radio frequency communication module 203 and the optical fiber communication module 303 through the 232 serial port. 304 represents a voltage converter, the input terminal of the voltage converter is connected to the secondary side of the PT through the cable 106, the output terminal of the voltage converter is connected to the input terminal of the voltage measurement module, and the secondary voltage of the PT can be converted into a low voltage within 5V . 305 is a voltage measurement module, the output end of the voltage measurement module 305 is connected to the optical fiber communication module 303, and the PT phase voltage, line voltage and zero sequence voltage are respectively converted into digital quantities, and sent to the optical fiber communication module 303 through serial communication. The optical fiber communication module 303 sends phase voltage, line voltage, zero-sequence voltage, and current data to the background server 103 located in the substation.

Figure 4 is a flow chart of the PT online diagnosis method for the distribution network. The diagnosis method includes the following steps:

(1) Using rough set theory to establish a decision table for PT fault diagnosis in distribution network, specifically including single-phase ground fault decision table, ferromagnetic resonance fault decision table, PT disconnection fault decision table, single-phase ground fault decision table as shown in Table 1 As shown, the specific attributes of the single-phase ground fault decision table are as follows, {Ua, Ub, Uc} are the three phase voltage condition attributes, {Uab, Uac, Ubc} are the three line voltage condition attributes, {Ia, Ib, Ic} It is three phase current conditional attributes, U0 indicates the zero-sequence voltage conditional attribute, "1" indicates that the conditional attribute value exceeds the limit and rises, "-1" indicates that the conditional attribute value decreases beyond the limit, and "0" indicates that the conditional attribute value is in the normal range Inside. {Fault} is a decision attribute, and "JD" means that a single-phase ground fault occurs in the system. The ferromagnetic resonance fault decision table is shown in Table 2. The specific attributes of the ferromagnetic resonance decision table are as follows, {Ua, Ub, Uc} are the three phase voltage condition attributes, {Uab, Uac, Ubc} are the three line voltage condition attributes , {Ia, Ib, Ic} are the three phase current conditional attributes, U0 is the zero-sequence voltage conditional attribute, {f} is the frequency conditional attribute, and the phase difference indicates the angle between the zero-sequence voltage and the voltage increase or decrease phase . Among its condition attribute values, for the three-phase voltage, line voltage, phase current and zero-sequence voltage condition attributes, "1" indicates that the measured value rises beyond the limit at the fundamental frequency, and "-1" indicates that the measured value at the fundamental frequency Reduce limit violation, "0" indicates that the measured value is within the normal rated range; for the frequency condition attribute "f", "1" indicates that the frequency of the measured value of the condition attribute is the fundamental frequency, and "2" indicates that the condition The frequency of the measured value of the attribute is a fractional multiple of the fundamental frequency, and "3" indicates that the frequency of the measured value of the conditional attribute is an octave. "*" indicates that the value of the conditional attribute has no effect on the classification. {Fault} is the decision attribute, "JP" indicates that the fundamental frequency resonance fault occurs in the system, "FP" indicates that the frequency division resonance fault occurs, and "BP" indicates that the multiplier frequency resonance fault occurs. The PT disconnection fault decision table is shown in Table 3. The specific attributes of the PT disconnection decision table are as follows, {Ua, Ub, Uc} are the three phase voltage condition attributes, {Uab, Uac, Ubc} are the three line voltage condition attributes , {Ia, Ib, Ic} are the three phase current conditional attributes, U0 indicates the zero-sequence voltage conditional attribute, "1" indicates that the value of the conditional attribute exceeds the limit and increases, "-1" indicates that the value of the conditional attribute decreases and exceeds the limit, "0 ” indicates that the condition attribute value is within the normal range. {Fault} is the decision attribute, "DX" indicates that the system has a PT primary circuit three-phase disconnection fault, "DX-I" indicates that the system has a PT primary circuit disconnection fault, "DX-II" indicates that the system has a PT secondary circuit disconnection fault line failure.

Table 1

Table 2

table 3

(2) The three phase currents, three phase voltages, three line voltages and zero sequence voltage data of PT are discretized to form conditional attribute values. If the voltage and current values increase beyond the limit, set the attribute value to "1"; if the voltage and current value decrease beyond the limit, set the attribute value to "-1"; if the voltage and current values are within the normal range, set The attribute value is "0". If the frequency is the fundamental frequency, set the value of the conditional attribute to "1"; if the frequency is the division frequency, then set the value of the conditional attribute to "2"; if the frequency is a multiplier, set the value of the conditional attribute to "0".

(3) Query the attribute values of the PT voltage and current conditions in the above three decision tables to obtain the corresponding decision attribute, that is, the diagnosis result.

From Table 1, the following decisions can be made:

Rule1: if(Ua=-1and Ub=Uc=1)and(Ia=1and Ib=Ic=-1)Then Fault=JD (phase A ground fault occurs in the system);

Rule2: if(Ub=-1and Ua=Uc=1)and(Ib=1and Ia=Ic=-1)Then Fault=JD (phase B ground fault occurs in the system);

Rule3: if(Uc=-1and Ua=Ub=1)and(Ic=1and Ia=Ib=-1)Then Fault=JD (phase C ground fault occurs in the system);

From Table 2, the following rules can be formed:

Rule1: if Ua=Ub=Uc=1and f=1Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule2: if Ua=1and Ub=Uc=-1and f=1and phase difference=0Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule3: if Ub=1and Ua=Uc=-1and f=1and phase difference=0Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule4: if Uc=1and Ua=Ub=-1and f=1and phase difference=0Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule5: if Ua=Ub=1and Uc=-1and f=1and phase difference=180Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule6: if Ua=Uc=1and Ub=-1and f=1and phase difference=180Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule7: if Ub=Uc=1and Ua=-1and f=1and phase difference=180Then Fault=JP (system fundamental frequency resonance fault occurs);

Rule8: if f=2Then Fault=FP (frequency division resonance fault occurs in the system);

Rule9: if f=3Then Fault=BP (multiple frequency resonance fault occurs in the system);

Table 3 can form the following rules:

Rule1: if Ua=Ub=Uc=U0=-1Then Fault=DX (the system has a PT primary circuit three-phase disconnection fault);

Rule2: if Ua=-1and Uab=Uac=-1and U0=-1Then Fault=DX-II (the system has a PT secondary circuit one-phase disconnection fault);

Rule3: if Ub=-1and Uab=Ubc=-1and U0=-1Then Fault=DX-II (the system has a PT secondary circuit one-phase disconnection fault);

Rule4: if Uc=-1and Ubc=Uac=-1and U0=-1Then Fault=DX-II (one-phase disconnection fault of PT secondary circuit occurs in the system);

Rule5: if Ua=Ub=-1and Uab=Ubc=Uac=-1and U0=-1Then Fault=DX-II (the system has a PT secondary circuit two-phase disconnection fault);

Rule6: if Ua=Uc=-1and Uab=Ubc=Uac=-1and U0=-1Then Fault=DX-II (the system has a PT secondary circuit two-phase disconnection fault);

Rule7: if Ub=Uc=-1and Uab=Ubc=Uac=-1and U0=-1Then Fault=DX-II (the system has a PT secondary circuit two-phase disconnection fault);

Rule8: if Ua=-1and Uab=Uac=-1and U0=0Then Fault=DX-I (the system has a PT primary circuit one-phase disconnection fault);

Rule9: if Ub=-1and Uab=Ubc=-1and U0=0Then Fault=DX-I (the system has a PT primary circuit one-phase disconnection fault);

Rule10: if Uc=-1and Ubc=Uac=-1and U0=0Then Fault=DX-I (the system has a PT primary circuit one-phase disconnection fault);

Rule11: if Ua=Ub=-1and Uab=Ubc=Uac=-1and U0=0Then Fault=DX-I (the system has a PT primary circuit two-phase disconnection fault);

Rule12: if Ua=Uc=-1and Uab=Ubc=Uac=-1and U0=0Then Fault=DX-I (the system has a PT primary circuit two-phase disconnection fault);

Rule13: if Ub=Uc=-1and Uab=Ubc=Uac=-1and U0=0Then Fault=DX-I (the system has a PT primary circuit two-phase disconnection fault);

(4) If it is judged that a fault occurs, an alarm will be issued immediately.

Claims (4)

1. power distribution network PT on-line monitoring and a fault diagnosis system, by terminal, harvester, three part groups of background server Become, it is characterized by:

Described terminal is arranged on power distribution network PT three-phase line, utilizes the electricity of the three-phase of electromagnetic induction principle measurement power distribution network PT Stream, terminal comprises low power consumption CPU module and the radio-frequency communication module of built-in AD function；

Described harvester is arranged on the panel of PT cabinet, the current data of the three-phase of reception power distribution network PT measured by terminal, with Time measure the phase voltage of PT, line voltage and residual voltage, then described current data, phase voltage, line voltage and residual voltage number According to uploading to background server；

Described background server is arranged in transformer station, has fiber optic telecommunications module, receives the data of harvester, to power distribution network PT Carry out on-line monitoring and fault diagnosis.

Power distribution network PT on-line monitoring the most according to claim 1 and fault diagnosis system, it is characterised in that:

Described terminal uses amplifying circuit and high-precision AD chip, it is possible to measure the electric current of 10-1000mA；

Described terminal can measure the frequency of 25-250Hz scope, can enter Subharmonic Resonance, fundamental resonance and frequency multiplication resonance Row is measured accurately.

Power distribution network PT on-line monitoring the most according to claim 1 and fault diagnosis system, it is characterised in that:

Described harvester includes voltage changer, voltage measurement module, radio-frequency communication module and fiber optic telecommunications module；Radio communication Module and fiber optic telecommunications module connect, and radio-frequency communication module receives the data of terminal, and is sent to light by serial communication mode Fiber communication module；

The input of voltage changer is connected to PT secondary side by cable, the outfan of voltage changer and voltage measurement module Input be connected, the outfan of voltage measurement module is connected to fiber optic telecommunications module；

PT phase voltage, line voltage and residual voltage are respectively converted into digital quantity by voltage changer and voltage measurement module, and lead to Cross serial communication mode and be sent to fiber optic telecommunications module；Fiber optic telecommunications module is by phase voltage, line voltage and residual voltage, electric current number According to being sent to be positioned at the background server of transformer station.

4. based on power distribution network PT on-line monitoring described in claim 1-3 any one claim and fault diagnosis system examine for one kind Disconnected method, it is characterised in that said method comprising the steps of:

(1) rough set theory is utilized to set up the decision table of power distribution network PT fault diagnosis, including singlephase earth fault decision table, ferromagnetic Resonance Decision Table for Fault, PT disconnection fault decision table；

(2) the three of PT phase currents, three phase voltages, three line voltages and residual voltage data are carried out sliding-model control, shape Become conditional attribute value；

(3) PT voltage, current condition property value are inquired about in above-mentioned three kinds of decision tables, obtain the decision attribute of correspondence, i.e. examine Disconnected result；

(4) if it is determined that break down, warning is sent immediately.