CN-118033258-B - Calculation method of ring main unit cable head temperature rise threshold and fault early warning system

CN118033258BCN 118033258 BCN118033258 BCN 118033258BCN-118033258-B

Abstract

A calculation method of a ring main unit cable head temperature rise threshold and a fault early warning system are provided, wherein the method comprises the steps of 1, under a non-fault condition, conducting constant current stable temperature rise test to obtain test current and corresponding test actual measurement stable temperature rise, 2, constructing a temperature rise threshold calculation model related to ring main unit cable head load current based on the test current and the test actual measurement stable temperature rise, 3, collecting ring main unit cable head load current I 0 and temperature rise tau W‑I0 in real time, substituting the temperature rise threshold calculation model to calculate the temperature rise threshold tau max‑I0 under the load current I 0 , and 4, comparing and judging faults in advance according to the ring main unit cable head actual measurement temperature rise tau W‑I0 and the temperature rise threshold tau max‑I0 . The invention provides a calculation method of a temperature rise threshold value of a ring main unit cable head under different load currents, wherein the temperature rise threshold value of the position can be calculated according to the load currents, and the temperature rise fault of the ring main unit cable head can be predicted in advance by comparing an actual temperature rise measured value of the ring main unit cable head with the temperature rise threshold value thereof.

Inventors

LU DEPENG
SU JINLIANG
HAN DONG
LI CHUANQIANG
ZONG QINGSEN
HUANG JING
QIU JIEYUN
WANG DAYAN
WANG FURUN
ZHANG PEIJIE

Assignees

南瑞智能配电技术有限公司

Dates

Publication Date: 20260512
Application Date: 20231229

Claims (8)

1. The calculation method of the ring main unit cable head temperature rise threshold is characterized by comprising the following steps of: step 1, under a non-fault condition, performing a constant current stable temperature rise test to obtain a test current and a corresponding test actual measurement stable temperature rise; step 2, based on the test current and the test actual measured stable temperature rise obtained in the step 1, fitting a mathematical model of the stable temperature rise about the load current of the cable head of the ring main unit, and expressing the mathematical model by the following formula: wherein: τ W represents stable temperature rise, a represents a first fitting coefficient, b represents a second fitting coefficient, and I represents load current of a cable head of the ring main unit; Based on the mathematical model of the stable temperature rise about the load current of the cable head of the ring main unit, a safety margin is considered, and a temperature rise threshold calculation model about the load current of the cable head of the ring main unit is constructed and expressed by the following formula: wherein: Tau max represents a temperature rise threshold value, and N represents a temperature rise limit value under the condition that 1.1 times of rated current is regulated by a standard; The stable temperature rise test value is 1.1 times of rated current of the product; I r represents a rated current; Step 3, collecting the load current I 0 and the temperature rise tau W-I0 of the cable head of the ring main unit in real time, substituting the load current I 0 and the temperature rise tau W-I0 into the temperature rise threshold calculation model obtained in the step 2, and calculating to obtain a temperature rise threshold tau max-I0 under the load current I 0 ; And 4, comparing the measured temperature rise tau W-I0 of the cable head of the ring main unit with a temperature rise threshold tau max-I0 under the load current I 0 , and judging the fault in advance.
2. The method for calculating the temperature rise threshold of the cable head of the ring main unit according to claim 1, wherein the method comprises the following steps: the step 1 comprises the following steps: Step 1.1, obtaining a rated value of a load current of a cable head of a ring main unit, namely rated current I r , and setting at least two test currents based on a set multiple of the rated current I r ; and step 1.2, under the different test currents set in step 1.1, the cable head of the ring main unit collects the test current and the corresponding test actual measurement stable temperature rise after the temperature rise is in a steady state.
3. The method for calculating the temperature rise threshold of the cable head of the ring main unit according to claim 2, wherein the method comprises the following steps: In the step 1.1, the test current is 1.1 times of rated current and is optionally selected from a test current within a range of 0-1.0 times of rated current.
4. The method for calculating the temperature rise threshold of the cable head of the ring main unit according to claim 1, wherein the method comprises the following steps: Step 2 also includes constructing fault conditions, performing a temperature rise test, verifying validity of the obtained temperature rise threshold calculation model, including: Manufacturing a ring main unit cable head contact fault, and setting test current based on a set multiple of rated current I r ; the cable head of the ring main unit is under test current, and after the temperature rise is in a steady state, the test current and the corresponding test actual measurement steady temperature rise are collected; If the measured stable temperature rise exceeds the temperature rise threshold under any load current, the model is effective, otherwise, the step of constructing the temperature rise threshold calculation model about the load current of the cable head of the ring main unit is returned, and the temperature rise threshold calculation model is corrected.
5. The method for calculating the temperature rise threshold of the cable head of the ring main unit according to claim 4, wherein the method comprises the following steps: the test currents are 1.1 times rated current, 1 time rated current, 0.8 time rated current and 0.6 time rated current.
6. A method for calculating a temperature rise threshold of a cable head of a ring main unit according to any one of claims 1 to 3, wherein: and respectively constructing temperature rise threshold calculation models related to the load current of the cable head of the ring main unit aiming at A, B and C three phases.
7. A method for calculating a temperature rise threshold of a cable head of a ring main unit according to any one of claims 1 to 3, wherein: step 4 comprises: If the load current I 0 is not less than 1.1 times of rated current I r , comparing the actually measured temperature rise tau W-I0 with the standard temperature rise limit value of the cable head of the ring main unit or the smaller one of temperature rise thresholds tau max-I0 under the load current I 0 , and performing early fault judgment; If the load current I 0 is smaller than 1.1 times of rated current I r , the measured temperature rise tau W-I0 is compared with a temperature rise threshold tau max-I0 under the load current I 0 , and if the temperature rise threshold is exceeded, the temperature rise fault is alarmed.
8. A ring main unit cable head fault early warning system, and a calculation method for a ring main unit cable head temperature rise threshold according to claims 1-6, comprising: the ring main unit cable head load current acquisition module is used for acquiring the ring main unit cable head load current and temperature rise in real time; The data processing module is used for receiving the load current data of the cable head of the ring main unit acquired in real time, substituting the load current data into a built-in temperature rise threshold calculation model, and calculating to obtain a temperature rise threshold under the current load current; And the fault early warning module is used for comparing the actually measured temperature rise tau W-I0 of the cable head of the ring main unit with the temperature rise threshold tau max-I0 under the load current I 0 , judging the fault in advance and outputting an early warning result.

Description

Calculation method of ring main unit cable head temperature rise threshold and fault early warning system Technical Field The invention belongs to the technical field of high-voltage electrical equipment temperature on-line monitoring and prediction, and particularly relates to a calculation method of a ring main unit cable head temperature rise threshold value and a fault early warning system. Background In the long-term operation process of the cable head of the ring main unit, the conductive part generates heat due to aging, surface oxidation corrosion, loose connection, loose fastening bolts or overlarge contact resistance, and the safety operation of equipment and a power grid is seriously influenced. Therefore, manufacturers hope to prevent faults in advance by installing an on-line temperature measuring device at the cable head part of the ring main unit and monitoring real-time temperature change state parameters so as to keep the equipment to normally and reliably operate. At present, the real-time online temperature measurement technology of the cable head of the ring main unit is relatively mature, the temperature rise data of the cable head of the ring main unit can be reliably obtained in real time, and fault alarm is carried out when the measured temperature rise exceeds the standard regulation limit value. Prior art document 1 (CN 219627222U) provides a full-perception intelligent fusion ring main unit, which can continuously monitor temperature rise data of a cable head and alarm the temperature rise in real time. 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, and the load current is generally lower than the rated current, and even if the equipment has a contact fault, the temperature rise value of the equipment does not exceed the standard regulation limit value, so that the disadvantage of the prior art document 1 is that early fault early warning cannot be realized by singly performing temperature monitoring. Disclosure of Invention In order to solve the defects in the prior art, the invention provides a calculation method of a ring main unit cable head temperature rise threshold and a fault early warning system. The invention adopts the following technical scheme. The first aspect of the invention provides a calculation method of a ring main unit cable head temperature rise threshold, which comprises the following steps: step 1, under a non-fault condition, performing a constant current stable temperature rise test to obtain a test current and a corresponding test actual measurement stable temperature rise; step 2, constructing a temperature rise threshold calculation model of the ring main unit cable head load current based on the test current and the test actual measurement stable temperature rise obtained in the step 1; Step 3, collecting the load current I 0 and the temperature rise tau W-I0 of the cable head of the ring main unit in real time, substituting the load current I 0 and the temperature rise tau W-I0 into the temperature rise threshold calculation model obtained in the step 2, and calculating to obtain a temperature rise threshold tau max-I0 under the load current I 0; And 4, comparing the measured temperature rise tau W-I0 of the cable head of the ring main unit with a temperature rise threshold tau max-I0 under the load current I 0, and judging the fault in advance. Preferably, step 1 comprises: Step 1.1, obtaining a rated value of a load current of a cable head of a ring main unit, namely rated current I r, and setting at least two test currents based on a set multiple of the rated current I r; and step 1.2, under the different test currents set in step 1.1, the cable head of the ring main unit collects the test current and the corresponding test actual measurement stable temperature rise after the temperature rise is in a steady state. Preferably, in step 1.1, the test current is optionally a test current within a range of 1.1 times of rated current and 0 to 1.0 times of rated current. Preferably, step 2 comprises: Step 2.1, fitting a mathematical model of the stable temperature rise relative to the load current of the cable head of the ring main unit based on the test current and the test measured stable temperature rise obtained in the step 1; And 2.2, based on the mathematical model of the stable temperature rise constructed in the step 2.1 on the load current of the cable head of the ring main unit, considering the safety margin, and constructing a temperature rise threshold calculation model on the load current of the cable head of the ring main unit. Preferably, in step 2.1, the mathematical model of the stable temperature rise with respect to the load current of the cable head of the ring main unit is expressed by the following formula: τW＝a·Ib (1) wherein: τ W represents a steady temperature rise; a represents a first fitting coefficient, b represents a second fitt