A low-voltage distribution circuit cable head looseness fault diagnosis device and diagnosis method

Abstract

The application discloses a low-voltage distribution circuit cable head looseness fault diagnosis device and a diagnosis method, and belongs to the field of fault diagnosis devices. The device comprises a man-machine interface, a parameter management module, a fault diagnosis module and a data sampling module. The data sampling module realizes the monitoring data collection of bus side voltage, line side voltage, line side current and line side cable temperature through external sensors. The parameter management module is used for the storage of device fixed value parameters and the cyclic storage of monitoring data collection. A user sets the fixed value parameters of the device through the man-machine interface. The fault diagnosis module obtains real-time sampling parameters, combines the fixed value parameters set by the user, makes a fault diagnosis judgment when the switch is powered off, and returns the judgment result to the man-machine interface for display. The device can judge and identify whether the tripping power failure of the switch circuit is caused by cable head looseness and overtemperature, realizes the timely discovery of the "overtemperature capacity reduction" fault, and gives an early warning.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fault diagnosis device, and particularly relates to a cable head loosening fault diagnosis device and diagnosis method for low-voltage power distribution equipment. BACKGROUND

[0002] In the operation of power distribution network, the switch of 0.4kV side low-voltage power distribution often trips due to cable head loosening and temperature rise, which is referred to as "over-temperature capacity reduction" trip (referring to the switch in operation, due to temperature rise exceeding the predetermined value, the working current allowed by the switch is reduced, and finally the maximum working current / capacity or the allowed working current / capacity of the switch is reduced).

[0003] Under this working condition, the load of cable loop operation is equivalent to the normal load, and the switch trip reason cannot be judged from the load measurement. At the same time, the loosening inside the cable joint cannot be directly found from the outside, and the cable temperature rise changes slowly over time. Therefore, such fault is very difficult to judge, and the operation and inspection personnel often cannot determine whether the fault reason is the switch mechanism fault. In order to facilitate timely repair, a spare switch is often carried, which is a heavy workload and slow response speed.

[0004] The frequent occurrence of such events greatly increases the work pressure of power grid operation and maintenance personnel, and the failure to analyze and find the fault reason in time will also cause the satisfaction of users to decrease, thereby affecting the image of power supply enterprises.

[0005] The invention patent with the authorized announcement date of January 20, 2016 and the authorized announcement number of CN 104052156 B discloses a "low-voltage power distribution cabinet fault alarm and isolation method", which uses the built-in judgment program of the controller in the low-voltage power distribution cabinet to gradually screen and check the data of alarm information, improves the accuracy of alarm information, uses reasonable criteria, and cross uses single and double judgments to further quickly send the alarm information of the sudden event in the diagnosis process; adopts the way of gradually increasing data to solve the repeated sending of alarm by using preset value comparison, so as to achieve more correct fault diagnosis and higher efficiency, and in addition, the fault point can be automatically isolated after sending the alarm information to avoid accidents. However, the technical scheme is specific to the low-voltage power distribution cabinet with built-in controller, and cannot be widely applied to general low-voltage power distribution devices, and the use scene is limited.

[0006] The existing power quality monitor on the market has certain operation monitoring and recording wave analysis capability, but is limited to electric signal acquisition and cannot simultaneously acquire temperature signal quantity. Moreover, when the "over-temperature capacity reduction" trip fault occurs, the load operation level of the fault switch is normal, and the fault reason cannot be judged by measuring the load current change.

[0007] How can the phenomenon of "over-temperature reduction capacity" just occur, and can catch up with the switch tripping action before, timely detection of the existence of such a phenomenon of switch failure, is a technical problem in the actual low-voltage equipment operation, management work. SUMMARY

[0008] The technical problem to be solved by the present application is to provide a low-voltage distribution circuit cable head loose fault diagnosis device and diagnosis method. Through voltage, current, temperature and other signal inputs, it is judged whether the switch circuit tripping power failure is caused by cable head loose over-temperature, and provides on-site fault indication, which can be installed on the low-voltage distribution circuit of the distribution station and the box-type substation.

[0009] The technical solution of the present application is to provide a low-voltage distribution circuit cable head loose fault diagnosis device, characterized by:

[0010] On the bus side of the switch to be tested, four bus voltage sensors are arranged on the three-phase power supply incoming bus and the neutral line, and the output ends of each bus voltage sensor are respectively connected to the bus side voltage sampling input end of the fault diagnosis device;

[0011] The fault diagnosis device monitors the three-phase alternating current voltage signals and the neutral line voltage signals on the bus side of the switch circuit to be tested through the bus voltage sensor as the voltage sampling input of the fault diagnosis device;

[0012] On any one phase of the switch line side to be tested, a line side voltage sensor is arranged, and the output end of the line side voltage sensor is connected to the corresponding line side voltage sampling input end of the fault diagnosis device; the fault diagnosis device monitors the voltage signal of any one phase on the line side of the switch circuit to be tested through the line side voltage sensor as the fault judgment trigger signal of the fault diagnosis device when the switch circuit is powered off;

[0013] Four temperature sensors are respectively arranged on the A, B, C and N four-wire cables of the switch line side, and the output ends of the four temperature sensors are respectively connected to the temperature sampling input ends of the fault diagnosis device; the fault diagnosis device monitors the temperature signal of the switch line side cable through the temperature sensor;

[0014] The fault diagnosis device comprises at least a man-machine interface, a parameter management module, a fault diagnosis module and a data sampling module;

[0015] The data sampling module collects the monitoring data of the bus side voltage, the line side voltage, the line side current and the line side cable temperature through external sensors;

[0016] The parameter management module is used for storing the device setting parameters and cyclically storing the monitoring data collection;

[0017] The user sets the fixed value parameters of the device through the human-machine interface;

[0018] The fault diagnosis module acquires real-time sampling parameters, combines the fixed value parameters set by the user, judges the fault when the switch is powered off, and returns the judgment result to the human-machine interface for display.

[0019] Specifically, the fault diagnosis device collects bus side voltage, line side voltage, line side current, and line side cable temperature data, judges and identifies whether the switch loop tripping power failure is caused by cable head loosening and over-temperature when the switch power failure occurs, and realizes the timely discovery of the over-temperature capacity reduction fault.

[0020] Further, the fixed value parameters at least include the rated current of the switch loop, the over-current tripping action current, the cable temperature limit value, the tripping statistical time constant, the over-current statistical time constant, and the over-temperature statistical time constant.

[0021] Further, the fault diagnosis device connects the three-phase alternating current voltage signals and the neutral line voltage signals on the bus side of the switch loop to be tested through the bus voltage sensor, as the voltage sampling input of the device, and also provides the working power supply for the device.

[0022] The technical scheme of the present application also provides a diagnosis method of the above-mentioned low-voltage distribution circuit cable head loosening fault diagnosis device, characterized in that the diagnosis method comprises the following steps:

[0023] Step 1) starting the device;

[0024] Step 2) reading the rated current of the switch loop, the over-current tripping fixed value, the cable temperature limit value, and the statistical period and other parameters;

[0025] Step 3) real-time scanning of the sampling data of the switch and the cable to be tested, and cyclic storage of the sampling data;

[0026] Step 4) judging whether the switch trips by reading the sampling data; if not, returning to step 3); if yes, proceeding to the next step;

[0027] Step 5) judging whether the switch overflows by reading the sampling data; if yes, returning to step 3); if not, proceeding to the next step;

[0028] Step 6) judging whether the cable temperature is over-limit by reading the sampling data; if not, returning to step 3); if yes, proceeding to the next step;

[0029] Step 7) determining that the fault cause of the switch tripping is the cable joint loosening;

[0030] Step 8) recording the fault cause;

[0031] Step 9) pushing alarm information through the human-machine interface.

[0032] Specifically, the statistical period includes tripping statistical time, overcurrent statistical time and over-temperature statistical time.

[0033] Further, the criterion for judging whether the switch trips is that:

[0034] In the tripping statistical time Tn1, the average value of the effective value of the three-phase voltage on the bus side is greater than UN*0.85, and the average value of the effective value of the voltage on the line side is less than UN*0.1 in the tripping statistical time Tn1;

[0035] The tripping statistical time Tn1 can be set, and the default is 5 seconds; UN is the rated value of the working voltage, UN=220V.

[0036] Further, the criterion for judging whether the switch overflows is that:

[0037] In the overcurrent statistical time Tn2 before the switch trips, the average value of the effective value of the three-phase current of the switch is less than Icri;

[0038] Wherein Icri is the switch tripping current set by the user, and the overcurrent statistical time Tn2 can be set, and the default is 5 seconds.

[0039] Further, the criterion for judging whether the cable temperature exceeds the limit is that:

[0040] In the over-temperature statistical time Tn3 before the switch trips, the average value of the temperature of the three-phase cable is greater than Tcri;

[0041] Wherein Tcri is the cable temperature limit set by the user; the over-temperature statistical time Tn3 can be set, and the default is 5 minutes.

[0042] The diagnostic method of the technical scheme of the application judges and identifies whether the switch loop tripping power failure is caused by cable head loosening and over-temperature by collecting bus side voltage, line side voltage, line side current and line side cable temperature data, realizes the timely discovery of the "over-temperature capacity reduction" phenomenon, and provides early warning.

[0043] Compared with the prior art, the application has the following advantages:

[0044] 1. The technical scheme of the application only needs to collect bus side voltage, line side voltage, line side current and line side cable temperature data to conveniently and simply judge and identify whether the switch loop tripping power failure is caused by cable head loosening and over-temperature when the switch trips, and provide on-site fault indication.

[0045] 2. The technical scheme of the present application can realize timely discovery of the phenomenon of "over-temperature capacity reduction", early warning, and avoidance of larger accidents caused by "over-temperature capacity reduction" faults;

[0046] 3. The hardware involved in the technical scheme of the present application is mature and stable, easy to implement, low in implementation cost, and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a device principle schematic diagram of the present application;

[0048] Figure 2 is a device structure schematic diagram of the present application;

[0049] Figure 3 is a diagnostic method flowchart of the present application.

[0050] In the figure, 1 is a bus voltage sensor, 2 is a line voltage sensor, 3 is a current transformer, and 4 is a temperature sensor. DETAILED DESCRIPTION

[0051] The present application will be further described below in combination with the drawings.

[0052] The technical scheme of the present application provides a fault diagnosis device suitable for 0.4kV low-voltage distribution circuit cable head loosening.

[0053] 1. Device working principle:

[0054] The working principle diagram of the device in the technical scheme of the present application is shown in Figure 1 .

[0055] For unified description, the upper side of the three-phase switch in Figure 1 is called the bus side, and the lower side of the three-phase switch in Figure 1 is called the line side.

[0056] The fault diagnosis device accesses the three-phase alternating current voltage signals and neutral line voltage signals on the bus side of the switch circuit to be tested through the bus voltage sensor, as the voltage sampling input of the device, and also provides working power for the device.

[0057] The device accesses any one phase voltage signal on the line side of the switch circuit to be tested, as the fault judgment trigger signal when the switch circuit is powered off.

[0058] The device accesses the A, B, C, and N four-wire cables on the switch line side through the temperature sensor to collect the cable temperature signals.

[0059] The fault diagnosis device judges according to inputted various signal amounts and preset device parameters, judges whether the fault reason is the abnormal tripping of the switch caused by the loose cable head and temperature rise when the switch is tripped, and provides a man-machine interface indication.

[0060] Figure 1 The 0.4kV three-phase switch shown in the figure is a target measurement object, the bus side voltage sensor, the line side voltage sensor, the current transformer and the line side temperature sensor are all realized by conventional technologies, and will not be described in detail here.

[0061] 2. Device structure:

[0062] Figure 2 The figure shows a device structure diagram. The device is composed of a man-machine interface, a parameter management module, a fault diagnosis module and a data sampling module.

[0063] Among them, the data sampling module realizes the data acquisition of the bus side voltage, the line side voltage, the line side current and the line side cable temperature through external sensors.

[0064] The user sets the device parameters through the man-machine interface, and the parameter content includes the rated current of the switch loop, the overcurrent tripping action current, the cable temperature limit value, the tripping / overcurrent / overtemperature statistical time constant, etc.

[0065] The fault diagnosis module obtains real-time sampling parameters, combines the set value parameters of the user, judges the fault when the switch is powered off, and returns the judgment result to the man-machine interface for display.

[0066] Since there are various man-machine interface, parameter management module, fault diagnosis module and data sampling module products in the existing market products, the specific composition and working process of the man-machine interface, parameter management module, fault diagnosis module and data sampling module will not be described in detail here.

[0067] The creation point of the technical scheme of the application lies in the logical action process of the man-machine interface, the parameter management module, the fault diagnosis module and the data sampling module and the specific diagnosis process of the diagnosis method.

[0068] 3. Process of the diagnosis method:

[0069] The detailed diagnosis process of the fault diagnosis is shown in the figure. Figure 3

[0070] Step 1) Start the device;

[0071] Step 2) Read the rated current of the switch loop, the overcurrent tripping set value, the cable temperature limit value, the statistical period and other parameters;

[0072] Step 3) Real-time scan the sampling data of the switch to be measured and the cable, and perform cyclic storage of the sampling data;​

[0073] Step 4) Determine whether the switch trips by reading the sampling data; if not, return to Step 3); if yes, proceed to the next step;

[0074] Step 5) Determine whether the switch overflows by reading the sampling data; if yes, return to Step 3); if not, proceed to the next step;

[0075] Step 6) Determine whether the cable temperature is over limit by reading the sampling data; if not, return to Step 3); if yes, proceed to the next step;

[0076] Step 7) Determine that the switch tripping fault is due to loose cable joint;

[0077] Step 8) Record the fault cause;

[0078] Step 9) Push the alarm information through the human-machine interface.

[0079] Wherein:

[0080] (1) The criterion for switch tripping is that the effective value average of three-phase voltage on the bus side is > U N * 0.85 within the tripping statistical time Tn1, and the effective value average of line side voltage is < U N * 0.1 within the tripping statistical time Tn1;

[0081] The tripping statistical time Tn1 can be set, and the default is 5 seconds; U N is the rated working voltage, and U N = 220V.

[0082] (2) The criterion for switch overflow is that the effective value average of three-phase current of the switch is < I cri within the overflow statistical time Tn2 before the switch trips;

[0083] Wherein I cri is the user-set switch tripping current constant value, and the overflow statistical time Tn2 can be set, and the default is 5 seconds.

[0084] (3) The criterion for cable temperature over limit is that the temperature average of three-phase cable is > T cri within the over-temperature statistical time Tn3 before the switch trips,

[0085] Wherein T cri is the user-set cable temperature limit value; the over-temperature statistical time Tn3 can be set, and the default is 5 minutes.

[0086] The technical scheme of the application can conveniently and concisely determine whether the switch loop tripping power failure is caused by the cable head loosening and over-temperature when the switch power is off, and provide on-site fault indication, can be installed on the low-voltage power distribution loop of the power distribution station and the box-type substation, realize the timely discovery of the "over-temperature capacity reduction" phenomenon, early warning, and avoid the occurrence of larger accidents caused by the "over-temperature capacity reduction" fault.

[0087] The application can be widely used in the fault monitoring or operation management field of the 0.4kV low-voltage power distribution loop of the power distribution station and the box-type substation.

Claims

1. A low-voltage distribution circuit cable head looseness fault diagnosis device, characterized in that: four bus voltage sensors are arranged on the bus side of the switch under test, on the three-phase power supply incoming bus and the neutral line, and the output ends of each bus voltage sensor are respectively connected to the bus side voltage sampling input end of the fault diagnosis device; the fault diagnosis device monitors the three-phase alternating current voltage signals and the neutral line voltage signal on the bus side of the switch under test through the bus voltage sensors, as the voltage sampling input of the fault diagnosis device; a line side voltage sensor is arranged on any one phase of the switch under test, and the output end of the line side voltage sensor is connected to the corresponding line side voltage sampling input end of the fault diagnosis device; the fault diagnosis device monitors the voltage signal of any one phase on the line side of the switch under test through the line side voltage sensor, as the fault judgment trigger signal of the fault diagnosis device when the switch circuit is powered off; four temperature sensors are respectively arranged on the A, B, C, N four-wire cables on the switch line side, and the output ends of the four temperature sensors are respectively connected to the temperature sampling input end of the fault diagnosis device; the fault diagnosis device monitors the temperature signal of the cable on the switch line side through the temperature sensor; the fault diagnosis device at least includes a man-machine interface, a parameter management module, a fault diagnosis module and a data sampling module; the data sampling module collects the monitoring data of the bus side voltage, the line side voltage, the line side current and the cable temperature on the line side through external sensors; the parameter management module is used for storing the device setting parameters and cyclically storing the monitoring data collection; the user sets the device setting parameters through the man-machine interface; the fault diagnosis module obtains the real-time sampling parameters, combines the setting parameters set by the user, makes a fault diagnosis judgment when the switch is powered off, and returns the judgment result to the man-machine interface for display; the low-voltage distribution circuit cable head looseness fault diagnosis device collects the bus side voltage, the line side voltage, the line side current and the cable temperature data on the line side, judges and identifies whether the switch circuit tripping power failure is caused by cable head looseness and overtemperature, provides on-site fault indication, is installed on the low-voltage distribution circuit of the distribution station and the box-type substation, realizes the timely discovery of the "overtemperature capacity reduction" phenomenon, gives an early warning, and avoids the occurrence of larger accidents caused by the "overtemperature capacity reduction" fault; the low-voltage distribution circuit cable head looseness fault diagnosis device diagnoses the low-voltage distribution circuit cable head looseness fault according to the following steps: step 1) starting the device; step 2) reading the switch circuit rated current, overcurrent tripping setting, cable temperature limit value, statistical period and other parameters; step 3) real-time scanning of the sampling data of the switch under test and the cable, and cyclically storing the sampling data; step 4) judging whether the switch trips by reading the sampling data; if not, returning to step 3); if yes, proceeding to the next step; step 5) judging whether the switch overflows by reading the sampling data; if yes, returning to step 3); if not, proceeding to the next step. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Step 6) whether the cable temperature is over limit by reading the sampling data; if the cable temperature is not over limit, return to step 3); if the cable temperature is over limit, proceed to the next step; Step 7) determine that the cause of the switch tripping is the cable joint loosening; Step 8) record the cause of the failure; Step 9) push the alarm information through the man-machine interface.

2. The low-voltage power distribution circuit cable head looseness fault diagnostic device of claim 1, wherein The fault diagnosis device collects bus side voltage, line side voltage, line side current, line side cable temperature data, and when the switch power failure occurs, judges and identifies whether the switch loop tripping power failure is caused by cable head loosening and over temperature, realizes the timely discovery of the "over temperature capacity reduction" fault.

3. The low-voltage power distribution circuit cable head looseness fault diagnostic device of claim 1, wherein The fixed value parameter at least includes the rated current of the switch loop, the overcurrent tripping action current, the cable temperature limit value, the tripping statistical time constant, the overcurrent statistical time constant and the over temperature statistical time constant.

4. The low-voltage power distribution circuit cable head looseness fault diagnostic device of claim 1, wherein The fault diagnosis device accesses the three-phase alternating current voltage signal and the neutral line voltage signal of the bus side of the switch loop to be tested through the bus voltage sensor, as the voltage sampling input of the device, and also provides the working power supply for the device.

5. The low-voltage power distribution circuit cable head looseness fault diagnostic apparatus according to claim 1, characterized in that The statistical period includes the tripping statistical time, the overcurrent statistical time and the over temperature statistical time.

6. The diagnostic method of the low-voltage power distribution circuit cable head looseness fault diagnostic apparatus according to claim 1, characterized by The criterion for judging whether the switch appears tripping is that: In the trip statistical time Tn1, the average value of the effective value of the three-phase voltage on the bus side > U N *0.85, and the average value of the effective value of the voltage on the line side < U N *0.1; The trip statistic time Tn1 can be set, and the default is 5 seconds; U N The working voltage is the rated value, U N =220V.

7. The diagnostic method of the low-voltage power distribution circuit cable head looseness fault diagnostic apparatus according to claim 1, characterized by The criterion for judging whether the switch appears overcurrent is that: In the overcurrent statistical time Tn2 before the switch trips, the average value of the effective value of the three-phase current of the switch is < I cri ; I cri The switch trip current value set for the user, the overcurrent statistical time Tn2 can be set, the default is 5 seconds.

8. The diagnostic method of the low-voltage power distribution circuit cable head looseness fault diagnostic apparatus according to claim 1, characterized by The criterion for judging whether the cable appears temperature over limit is that: In the over-temperature statistical time Tn3 before the switch trips, the average temperature of the three-phase cable > T cri ; Tn1 cri Cable temperature limit set by user; over-temperature statistical time Tn3 can be set, default is 5 minutes.

9. The diagnostic method of the low-voltage power distribution circuit cable head looseness fault diagnostic apparatus according to claim 1, characterized by The diagnosis method collects bus side voltage, line side voltage, line side current, line side cable temperature data, judges and identifies whether the switch loop tripping power failure is caused by cable head loosening and over temperature, realizes the timely discovery of the "over temperature capacity reduction" phenomenon, and gives early warning.

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