A method for calculating cable head temperature rise threshold of ring main unit and a fault early warning system

Abstract

A kind of ring main unit cable head temperature rise threshold calculation method and fault early warning system, method includes: step 1, under non-fault condition, carry out constant current steady temperature rise test, obtain test current and its corresponding test measured steady temperature rise;Step 2, based on test current and test measured steady temperature rise, construct about ring main unit cable head load current temperature rise threshold calculation model;Step 3, real-time acquisition ring main unit cable head load current I0And temperature rise τ W‑I0 , substitute temperature rise threshold calculation model, obtain the temperature rise threshold τ max‑I0 under this load current I0;Step 4, compare according to ring main unit cable head measured temperature rise τ W‑I0 And temperature rise threshold τ max‑I0 , carry out early fault judgment.The present application provides the calculation method of ring main unit cable head temperature rise threshold under different load currents, according to load current, the temperature rise threshold of this part can be calculated, by comparing ring main unit cable head temperature rise actual measurement value and its temperature rise threshold, ring main unit cable head temperature rise fault can be predicted in advance.

Description

Technical Field

[0001] This invention belongs to the field of online temperature monitoring and prediction technology for high-voltage electrical equipment, and more specifically, relates to a method for calculating the temperature rise threshold of cable heads in ring main units and a fault early warning system. Background Technology

[0002] During long-term operation of ring main unit cable heads, conductive components may overheat due to aging, surface oxidation and corrosion, loose connections, loose bolts, or excessive contact resistance, seriously affecting the safe operation of the equipment and the power grid. Therefore, manufacturers aim to prevent malfunctions by installing online temperature monitoring devices at the ring main unit cable heads to monitor real-time temperature changes and maintain normal and reliable equipment operation.

[0003] Currently, the technology for real-time online temperature measurement of cable heads in ring main units is relatively mature, and it can reliably obtain temperature rise data of the cable heads in real time. When the measured temperature rise exceeds the standard limit, a fault alarm is triggered. Existing technical document 1 (CN219627222U) provides a fully sensing intelligent fusion ring main unit, which can continuously monitor the temperature rise data of the cable heads and trigger an alarm for the temperature rise in real time.

[0004] However, in actual engineering, the magnitude of the load current flowing through the cable head of the ring main unit depends on the line load. Under normal circumstances, the load current is lower than the rated current. At this time, even if the equipment has a contact fault, its temperature rise value does not exceed the standard limit. Therefore, the shortcoming of the existing technical document 1 is that temperature monitoring alone cannot achieve early fault warning. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for calculating the temperature rise threshold of cable heads in ring main units and a fault early warning system.

[0006] The present invention adopts the following technical solution. The first aspect of the present invention provides a method for calculating the temperature rise threshold of cable heads in ring main units, comprising the following steps:

[0007] Step 1: Under non-fault conditions, conduct a constant current stable temperature rise test to obtain the test current and its corresponding measured stable temperature rise.

[0008] Step 2: Based on the test current and measured stable temperature rise obtained in Step 1, construct a temperature rise threshold calculation model for the load current of the cable head of the ring main unit.

[0009] Step 3: Real-time acquisition of the load current I0 and temperature rise τ of the ring main unit cable head. W-I0 Substituting the values ​​into the temperature rise threshold calculation model obtained in step 2, the temperature rise threshold τ under the load current I0 is calculated. max-I0 ;

[0010] Step 4: Compare the measured temperature rise τ of the ring main unit cable head. W-I0 and the temperature rise threshold τ under the load current I0 max-I0 To enable early fault diagnosis.

[0011] Preferably, step 1 includes:

[0012] Step 1.1: Obtain the rated load current of the cable head of the ring main unit, referred to as the rated current I. r Based on rated current I r The set multiple should include at least two test currents;

[0013] Step 1.2: Under different test currents set in Step 1.1, after the temperature rise reaches a steady state, the test current and the corresponding measured stable temperature rise of the ring main unit cable head are collected.

[0014] Preferably, in step 1.1, the test current is selected from either 1.1 times the rated current or 0 to 1.0 times the rated current.

[0015] Preferably, step 2 includes:

[0016] Step 2.1: Based on the test current and measured stable temperature rise obtained in Step 1, fit a mathematical model of the stable temperature rise with respect to the load current of the cable head of the ring main unit;

[0017] Step 2.2: Based on the mathematical model of stable temperature rise with respect to the load current of the cable head of the ring main unit constructed in Step 2.1, and taking into account the safety margin, construct a calculation model for the temperature rise threshold with respect to the load current of the cable head of the ring main unit.

[0018] Preferably, in step 2.1, the mathematical model for the stable temperature rise with respect to the load current of the ring main unit cable head is expressed by the following formula:

[0019] τ W =a·I b (1)

[0020] In the formula:

[0021] τ W This indicates a stable temperature rise;

[0022] a represents the first fitting coefficient, and b represents the second fitting coefficient;

[0023] I represents the load current of the cable head of the ring main unit;

[0024] In step 2.2, the calculation model for the temperature rise threshold of the load current at the cable head of the ring main unit is expressed by the following formula:

[0025]

[0026] In the formula:

[0027] τ max Indicates the temperature rise threshold;

[0028] N indicates the temperature rise limit specified in the standard at 1.1 times the rated current;

[0029] The stable temperature rise test value is the product's current at 1.1 times the rated current.

[0030] I r Indicates the rated current.

[0031] Preferably, step 2 further includes step 2.3, constructing fault conditions, conducting a temperature rise test, and verifying the effectiveness of the temperature rise threshold calculation model obtained in step 2.2;

[0032] Step 2.3 includes:

[0033] Manufacturing a ring main unit cable head contact fault, based on rated current I r Set the multiple, set the test current;

[0034] Under the test current, after the temperature rise of the cable head of the ring main unit reaches a steady state, the test current and the corresponding measured stable temperature rise are collected.

[0035] If the measured stable temperature rise exceeds the temperature rise threshold under any load current, the model is valid; otherwise, return to step 2.2 to correct the temperature rise threshold calculation model.

[0036] Preferably, in step 2.3, the test current is 1.1 times the rated current, 1 times the rated current, 0.8 times the rated current, and 0.6 times the rated current.

[0037] Preferably, for phases A, B, and C, a calculation model for the temperature rise threshold of the load current at the cable head of the ring main unit is constructed respectively.

[0038] Preferably, step 4 includes:

[0039] If the load current I0 is not less than 1.1 times the rated current I r The measured temperature rise τ W-I0 The temperature rise standard limit for the cable head of the ring main unit or the temperature rise threshold τ under the load current I0. max-I0 Compare with the smaller one to make early fault detection;

[0040] If the load current I0 is less than 1.1 times the rated current I r The measured temperature rise τ W-I0 Temperature rise threshold τ under this load current I0 max-I0 If the temperature rise exceeds the threshold, an alarm will be triggered for a temperature rise fault.

[0041] A second aspect of the present invention provides a ring main unit cable head fault early warning system, comprising a method for calculating the temperature rise threshold of the ring main unit cable head, including:

[0042] The ring main unit cable head load current acquisition module is used to collect the load current and temperature rise of the ring main unit cable head in real time.

[0043] The data processing module is used to receive real-time collected load current data of the cable heads of the ring main unit, substitute it into the built-in temperature rise threshold calculation model, and calculate the temperature rise threshold under the current load current.

[0044] The fault early warning module is used to compare the measured temperature rise τ of the cable head in the ring main unit. W-I0 and the temperature rise threshold τ under the load current I0 max-I0 It can perform early fault diagnosis and output early warning results.

[0045] The beneficial effect of this invention is that, compared with the prior art, this invention calculates the temperature rise threshold under the corresponding load current based on the load current of the ring main unit cable head, and performs early fault judgment by comparing the temperature rise threshold with the actual temperature rise, effectively realizing early warning and predicting potential faults in the ring main unit cable head in advance. Attached Figure Description

[0046] Figure 1 This is a flowchart of the calculation method for the temperature rise threshold of the cable head in a ring main unit and a fault early warning system;

[0047] Figure 2 These are the temperature rise threshold curve, stable temperature rise curve, and standard-specified temperature rise limit for the cable heads of ring main units. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0049] like Figure 1 As shown, Embodiment 1 of the present invention provides a method for calculating the temperature rise threshold of cable heads in ring main units, including the following steps:

[0050] Step 1: Under non-fault conditions, conduct a constant current stable temperature rise test to obtain the test current and its corresponding measured stable temperature rise.

[0051] In a preferred but non-limiting embodiment of the present invention, step 1 specifically includes:

[0052] Step 1.1: Obtain the rated load current of the cable head of the ring main unit, referred to as the rated current I. r Based on rated current I r The test current is set by a predetermined multiple. Preferably, the test current is selected from either 1.1 times the rated current or within the range of 0 to 1.0 times the rated current.

[0053] Step 1.2: Under the test current set in Step 1.1, after the temperature rise reaches a steady state, collect the test current and the corresponding measured stable temperature rise of the ring main unit cable head.

[0054] Furthermore, stable temperature rise was collected in phases A, B, and C.

[0055] It is understandable that when current flows through a conductor, a current heating effect is generated. Over time, the temperature of the conductor surface continuously rises until it stabilizes. The difference between the conductor surface temperature and the ambient temperature is the temperature rise. A steady-state temperature rise means that the temperature of the cable head in the ring main unit remains constant within a set time period.

[0056] In an exemplary but non-limiting embodiment of the present invention, the rated current I is selected. r Apply 1.1 times the rated current I to the 630A ring main unit. r and 0.8 times the rated current I r The temperature rise test data is shown in Table 1 below:

[0057] Table 1 Temperature rise test data

[0058]

[0059] Step 2: Based on the test current and measured stable temperature rise obtained in Step 1, construct a calculation model for the temperature rise threshold of the load current of the ring main unit cable head.

[0060] In a preferred but non-limiting embodiment of the present invention, step 2 specifically includes:

[0061] Step 2.1: Based on the test current and measured stable temperature rise obtained in Step 1, fit a mathematical model of the stable temperature rise with respect to the load current of the ring main unit cable head, specifically expressed by the following formula:

[0062] τ W =a·I b (1)

[0063] In the formula:

[0064] τ W This indicates a stable temperature rise;

[0065] a represents the first fitting coefficient, and b represents the second fitting coefficient;

[0066] I represents the load current of the cable head of the ring main unit.

[0067] Furthermore, mathematical models for the stable temperature rise in relation to the load current at the cable head of the ring main unit are fitted for phases A, B, and C, respectively.

[0068] In the above-described exemplary but non-limiting embodiments of the present invention, the stable temperature rise fitting relationship is shown in Table 2 below:

[0069] Table 2. Fitting Relationship of Stable Temperature Rise

[0070]

[0071]

[0072] Step 2.2: Based on the mathematical model of stable temperature rise with respect to the load current of the ring main unit cable head constructed in Step 2.1, and taking into account the safety margin, a calculation model for the temperature rise threshold with respect to the load current of the ring main unit cable head is constructed, specifically expressed by the following formula:

[0073]

[0074] In the formula:

[0075] τ max Indicates the temperature rise threshold;

[0076] N indicates the temperature rise limit specified in the standard at 1.1 times the rated current;

[0077] The stable temperature rise test value is the product's current at 1.1 times the rated current.

[0078] I r Indicates the rated current.

[0079] It is worth noting that Formula (2), as a calculation model for the temperature rise threshold of the load current of the cable head of the ring main unit, takes into account the temperature rise limit stipulated by national and industry standards, and provides a safety margin for the temperature rise design of the cable head of the ring main unit.

[0080] Furthermore, for phases A, B, and C, calculation models for the temperature rise threshold of the load current at the cable head of the ring main unit are constructed respectively.

[0081] In the above-described exemplary but non-limiting embodiments of the present invention, the mathematical models for the temperature rise threshold under different load currents are shown in Table 3 below:

[0082] Table 3 Mathematical models of temperature rise threshold under different load currents

[0083]

[0084] In a further preferred but non-limiting embodiment of the present invention, step 2 further includes step 2.3: constructing fault conditions, conducting a temperature rise test, and verifying the effectiveness of the temperature rise threshold calculation model obtained in step 2.2. Specifically, step 2.3 includes:

[0085] Manufacturing a ring main unit cable head contact fault, based on rated current I r The test current is set as a multiple of the rated current. Preferably, the test current is 1.1 times the rated current, 1 times the rated current, 0.8 times the rated current, and 0.6 times the rated current.

[0086] Under the test current, after the temperature rise of the cable head of the ring main unit reaches a steady state, the test current and the corresponding measured stable temperature rise are collected.

[0087] If the measured stable temperature rise exceeds the temperature rise threshold under any load current, the model is considered effective. Furthermore, if the temperature rise of the ring main unit cable head exceeds its corresponding temperature rise threshold under any load current, the temperature rise test at 1.1 times the rated current will definitely fail. In other words, this invention accurately judges temperature rise faults through a temperature rise warning curve, enabling "early" fault detection and effective early warning. It can provide early warnings under low load conditions, effectively preventing accidents.

[0088] If step 2.3 fails the verification, return to step 2.2 and rebuild the temperature rise threshold calculation model for the load current of the ring main unit cable head.

[0089] In the above-described exemplary but non-limiting embodiments of the present invention, electrical contact fault conditions are created at the cable heads of phases A and C, and 1.1I is carried out. r I r 0.8I r and 0.6I r Table 4 below shows a comparison of the temperature rise test values ​​and the temperature rise threshold under current-induced temperature rise test conditions and contact fault conditions.

[0090] Table 4 Comparison of Temperature Rise Test Values ​​and Temperature Rise Thresholds under Contact Fault Conditions

[0091]

[0092] Step 3: Real-time acquisition of the load current I0 and temperature rise τ of the ring main unit cable head. W-I0 Substituting the values ​​into the temperature rise threshold calculation model obtained in step 2, the temperature rise threshold τ under the load current I0 is calculated. max-i0 .

[0093] Step 4: Compare the measured temperature rise τ of the ring main unit cable head. W-I0 and the temperature rise threshold τ under the load current I0 max-I0 To enable early fault diagnosis.

[0094] In a preferred but non-limiting embodiment of the present invention, step 4 includes:

[0095] If the load current I0 is not less than 1.1 times the rated current I r The measured temperature rise τ W-I0 The temperature rise standard limit for the cable head of the ring main unit or the temperature rise threshold τ under the load current I0. max-I0 The smaller one is compared to the larger one to make early fault detection.

[0096] If the load current I0 is less than 1.1 times the rated current I r The measured temperature rise τ W-I0 Temperature rise threshold τ under this load current I0 max-I0 If the temperature rise exceeds the threshold, an alarm will be triggered for a temperature rise fault.

[0097] Embodiment 2 of the present invention provides a ring main unit cable head fault early warning system, which implements the calculation method for the temperature rise threshold of the ring main unit cable head described in Embodiment 1, including:

[0098] The ring main unit cable head load current acquisition module is used to collect the load current and temperature rise of the ring main unit cable head in real time.

[0099] The data processing module is used to receive real-time collected load current data of the cable heads of the ring main unit, substitute it into the built-in temperature rise threshold calculation model, and calculate the temperature rise threshold under the current load current.

[0100] The fault early warning module is used to compare the measured temperature rise τ of the cable head in the ring main unit. W-I0 and the temperature rise threshold τ under the load current I0 max-I0 It can perform early fault diagnosis and output early warning results.

[0101] It is worth noting that ring main units (RMMs) are crucial electrical devices in power systems. As power networks demand increasingly higher power quality, the reliability requirements for RMMs also rise. Excessive temperature rise at the cable heads of RMMs directly impacts the safe and stable operation of the equipment. Overheating is a continuously evolving process; if left uncontrolled, it will escalate, causing insulation failure and ultimately equipment burnout. By installing online temperature monitoring devices at the cable heads of RMMs to monitor real-time temperature changes, and using the calculation method and fault early warning system proposed in this invention, faults can be prevented in advance, ensuring the normal and reliable operation of the equipment.

[0102] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for calculating the temperature rise threshold of cable heads in a ring main unit, characterized in that, Includes the following steps: Step 1: Under non-fault conditions, conduct a constant current stable temperature rise test to obtain the test current and its corresponding measured stable temperature rise. Step 2: Based on the test current and measured steady-state temperature rise obtained in Step 1, fit a mathematical model of the steady-state temperature rise with respect to the load current of the ring main unit cable head, expressed by the following formula: In the formula: τ W Indicates stable temperature rise; a represents the first fitting coefficient, b represents the second fitting coefficient; I represents the load current of the ring main unit cable head; Based on the mathematical model of the stable temperature rise with respect to the load current of the ring main unit cable head, and taking into account the safety margin, a calculation model for the temperature rise threshold of the load current of the ring main unit cable head is constructed, expressed by the following formula: In the formula: τ max Indicates the temperature rise threshold; N The standard specifies the temperature rise limit at 1.1 times the rated current; The stable temperature rise test value is the product's current at 1.1 times the rated current. I r Indicates the rated current; Step 3: Real-time acquisition of load current at the cable heads of the ring main unit I 0 and temperature rise τ W-I0 Substituting the values ​​into the temperature rise threshold calculation model obtained in step 2, the load current is calculated. I Temperature rise threshold below 0 τ max-I0 ; Step 4: Compare the measured temperature rise of the cable heads in the ring main unit. τ W-I0 and the load current I Temperature rise threshold below 0 τ max-I0 To enable early fault diagnosis.

2. The method for calculating the temperature rise threshold of cable heads in a ring main unit as described in claim 1, characterized in that: Step 1 includes: Step 1.1: Obtain the rated load current of the cable head of the ring main unit, referred to as the rated current. I r Based on rated current I r The set multiple should include at least two test currents; Step 1.2: Under different test currents set in Step 1.1, after the temperature rise reaches a steady state, the test current and the corresponding measured stable temperature rise of the ring main unit cable head are collected.

3. The method for calculating the temperature rise threshold of cable heads in a ring main unit as described in claim 2, characterized in that: In step 1.1, the test current can be selected from either 1.1 times the rated current or 0 to 1.0 times the rated current.

4. The method for calculating the temperature rise threshold of cable heads in a ring main unit as described in claim 1, characterized in that: Step 2 also includes constructing fault conditions, conducting temperature rise tests, and verifying the effectiveness of the obtained temperature rise threshold calculation model, including: Manufacturing a ring main unit cable head contact fault, based on rated current I r Set the multiple, set the test current; Under the test current, after the temperature rise of the cable head of the ring main unit reaches a steady state, the test current and the corresponding measured stable temperature rise are collected. If the measured stable temperature rise exceeds the temperature rise threshold under any load current, the model is valid; otherwise, return to the steps of constructing the temperature rise threshold calculation model for the load current of the ring main unit cable head, and correct the temperature rise threshold calculation model.

5. The method for calculating the temperature rise threshold of cable heads in a ring main unit as described in claim 4, characterized in that: The test currents are 1.1 times the rated current, 1 time the rated current, 0.8 times the rated current, and 0.6 times the rated current.

6. The method for calculating the temperature rise threshold of a ring main unit cable head as described in any one of claims 1 to 3, characterized in that: For phases A, B, and C, respectively, calculation models for the temperature rise threshold of the load current at the cable head of the ring main unit are constructed.

7. A method for calculating the temperature rise threshold of a ring main unit cable head as described in any one of claims 1 to 3, characterized in that: Step 4 includes: If the load current I 0 Not less than 1.1 times the rated current I r The measured temperature rise τ W-I0 Compared with the standard limit for temperature rise of cable heads in ring main units or the load current. I Temperature rise threshold below 0 τ max-I0 Compare with the smaller one to make early fault detection; If the load current I 0 Less than 1.1 times the rated current I r The measured temperature rise τ W-I0 With the load current I Temperature rise threshold below 0 τ max-I0 If the temperature rise exceeds the threshold, an alarm will be triggered for a temperature rise fault.

8. A ring main unit cable head fault early warning system, operating the calculation method for the temperature rise threshold of the ring main unit cable head as described in claims 1-6, characterized in that, include: The ring main unit cable head load current acquisition module is used to collect the load current and temperature rise of the ring main unit cable head in real time. The data processing module is used to receive real-time collected load current data of the cable heads of the ring main unit, substitute it into the built-in temperature rise threshold calculation model, and calculate the temperature rise threshold under the current load current. The fault early warning module is used to compare the measured temperature rise of the cable heads in the ring main unit. τ W-I0 and the load current I Temperature rise threshold below 0 τ max-I0 It can perform early fault diagnosis and output early warning results.

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