CN-121978586-A - Virtual connection fault positioning method for relay protection secondary circuit

CN121978586ACN 121978586 ACN121978586 ACN 121978586ACN-121978586-A

Abstract

The invention discloses a virtual connection fault positioning method of a relay protection secondary circuit, which comprises the steps of connecting a controllable load disturbance device in series in the relay protection secondary circuit, arranging distributed voltage acquisition units at a plurality of key nodes of the secondary circuit, enabling load current of the secondary circuit to jump from reference current to preset test current through the controllable load disturbance device, synchronously acquiring voltage values of corresponding monitoring nodes through the distributed voltage acquisition units before and after each step load current is applied, calculating dynamic voltage drop of each monitoring node, extracting contact resistance characteristic parameters corresponding to each monitoring node based on response relation of the dynamic voltage drop and the step load current, calculating virtual connection indexes of each monitoring node, comparing the virtual connection indexes with preset thresholds, judging whether virtual connection faults exist in the corresponding monitoring nodes, and positioning specific positions of the virtual connection faults aiming at the identified virtual connection nodes.

Inventors

ZHAN PENG
Zhao yingfeng
HUANG YUBAO
LI JIJUN
Mu Jielei
LU YUNJIANG
ZANG YONGGANG
WU YONGZHI
CAI YANG
LV JIAJUN
ZHU BIN
WANG YUNFEI
WANG XINXING
LU WENTAO

Assignees

云南联合电力开发有限公司
华能澜沧江水电股份有限公司

Dates

Publication Date: 20260505
Application Date: 20260225

Claims (10)

1. A virtual connection fault positioning method of a relay protection secondary circuit is characterized by comprising the following steps: s1, a controllable load disturbance device is connected in series in a relay protection secondary circuit, and distributed voltage acquisition units are arranged at a plurality of key nodes of the secondary circuit; s2, periodically applying step load current through the controllable load disturbance device to enable the load current of the secondary circuit to jump from a reference current to a preset test current; S3, synchronously acquiring voltage values of corresponding monitoring nodes through each distributed voltage acquisition unit before and after each step load current application, and calculating dynamic voltage drops of each monitoring node; s4, extracting characteristic parameters of contact resistance corresponding to each monitoring node based on the response relation between the dynamic voltage drop and the step load current; s5, calculating virtual connection indexes of all monitoring nodes according to the contact resistance characteristic parameters, comparing the virtual connection indexes with a preset threshold value, and judging whether virtual connection faults exist in the corresponding monitoring nodes; And S6, aiming at the identified virtual connection node, calculating the voltage gradient anomaly coefficient between the virtual connection node and the adjacent monitoring node, and combining the topology information of the relay protection secondary circuit to locate the specific position of the virtual connection fault point.
2. The method according to claim 1, wherein in the step S2, the controllable load disturbance device comprises a power electronic switching device, a current detection unit and a PWM control circuit, wherein the PWM control circuit realizes accurate control of load current by adjusting a turn-on duty ratio of the power electronic switching device, the current detection unit monitors loop current in real time and feeds back the loop current to the PWM control circuit to form closed loop control, and the step load current is applied in a periodic triggering manner, wherein each period comprises a reference current phase, a current jump process and a test current phase.
3. The method according to claim 1, wherein in the step S3, the distributed voltage acquisition unit adopts a multi-channel synchronous sampling architecture, voltage sampling of each monitoring node is triggered by a unified clock signal, and the method for calculating the dynamic voltage drop includes: identifying a steady-state voltage section before step load current is applied, and calculating the average value of the steady-state voltage section as an initial voltage; Identifying a steady-state voltage section after step load current is applied, and calculating the average value of the steady-state voltage section as final-state voltage; and calculating the difference value between the initial voltage and the final voltage as a dynamic voltage drop, and recording complete time domain waveform data from the beginning of current jump to the time when the voltage reaches a stable state.
4. The method according to claim 1, wherein the characteristic parameters of the contact resistance in the step S4 include a linearity deviation coefficient, a voltage drop fluctuation coefficient and a response delay time, and wherein the extracting method of each parameter includes: When the linearity deviation coefficient is extracted, corresponding dynamic voltage drops are respectively obtained under two different current levels of the reference current and the test current, the ratio of the two dynamic voltage drops to the ratio of the two load currents is calculated, and the nonlinear characteristics of the contact resistance are quantified by comparing the deviation degree of the two ratios; When the voltage drop fluctuation coefficient is extracted, carrying out statistical analysis on a voltage drop time sequence of a test current stage, calculating a standard deviation of the time sequence, and carrying out normalization processing on the standard deviation and a mean value of the time sequence to obtain dimensionless parameters reflecting the dynamic fluctuation characteristic of the contact resistance; When the response delay time is extracted, starting timing from the moment when the load current generates step transition, identifying the moment when the voltage drop curve enters a stable state, and taking the difference between the two moments as the response delay time, wherein the judgment criterion of the stable state is that the voltage change rate is continuously lower than a preset threshold value.
5. The method of claim 4, wherein the linearity deviation coefficient The calculation formula of (2) is as follows: Wherein, the Representing reference current The corresponding dynamic voltage drop is determined by, Representing test current The corresponding dynamic voltage drop is determined by, The reference current value is indicated and the reference current value, Indicating the value of the test current.
6. The method according to claim 4, wherein in the step S5, the calculation of the virtual connection index H adopts a multidimensional feature weighted fusion algorithm, and a specific calculation formula is: Wherein, the 、、 Is a weight coefficient and meets the normalization condition; For the normalized linearity deviation coefficient, the linearity deviation coefficient is obtained by Divided by a preset maximum deviation threshold Obtaining; For normalized voltage drop fluctuation coefficient, by dividing the voltage drop fluctuation coefficient Divided by a preset maximum fluctuation threshold Obtaining; for normalized response delay time, by delaying the response time Divided by a preset maximum delay time Obtained.
7. The method according to claim 6, wherein in the step S5, a multi-level judgment mechanism is established according to the virtual connection index H, and specifically includes: Setting a normal connection threshold And severe virtual connect threshold ; When imaginary connection index Below the normal connection threshold When the monitoring node is in a normal connection state, the monitoring node is judged; When imaginary connection index Between normal connection threshold Threshold value of severe virtual connection When the node is in the slight virtual connection state, the system generates an early warning record and marks the node to be focused; When imaginary connection index Above the severe virtual joint threshold And when the corresponding monitoring node is judged to be in a serious virtual connection state, the system triggers a fault alarm mechanism and starts a fault positioning process.
8. The method according to claim 1, wherein in the step S6, the voltage gradient abnormality coefficient is The calculation method of (1) is as follows: Wherein, the Representing the monitoring node with the largest virtual joint index, Representation of Is provided with a plurality of monitoring nodes adjacent to the upstream of the monitoring node, Representation of Downstream adjacent monitoring nodes of (a); 、、 Representing the dynamic voltage drops corresponding to the three nodes, respectively.
9. The method according to claim 1, wherein in the step S1, the arrangement of the key nodes follows the topology structure of the secondary circuit, and specifically comprises a first monitoring node at the outlet end of the protection device, a second monitoring node at the terminal block of the protection screen, a third monitoring node at the inlet side of the operation box, a fourth monitoring node at the outlet side of the operation box, a fifth monitoring node at the middle junction box of the cable, a sixth monitoring node at the inlet side of the terminal box of the switch equipment, a seventh monitoring node at the two ends of the coil of the operation mechanism and an eighth monitoring node; the distributed voltage acquisition unit acquires signals by adopting a non-contact voltage sensor or a high-impedance voltage probe, wherein the non-contact voltage sensor detects potential distribution around a wire based on an electric field coupling principle, the input impedance of the high-impedance voltage probe is at least three orders of magnitude higher than the impedance of a measured loop, and the distributed voltage acquisition unit is connected with a data processing center through an optical fiber communication network to realize high-speed transmission and time synchronization of data of each monitoring node.
10. A relay protection secondary circuit virtual connection fault location system for implementing the method of claims 1-9, comprising: The controllable load disturbance module is used for periodically applying step load current to ensure that the load current of the relay protection secondary circuit transits between the reference current and the test current; The distributed voltage acquisition module is used for synchronously acquiring the voltage of each monitoring node based on a unified clock source and acquiring the voltage value of each monitoring node before and after the step load current is applied; the characteristic extraction module is used for calculating the dynamic voltage drop of each monitoring node and extracting a contact resistance characteristic parameter based on the response relation between the dynamic voltage drop and the step load current, wherein the contact resistance characteristic parameter comprises a linearity deviation coefficient, a voltage drop fluctuation coefficient and response delay time; The virtual connection identification module is used for carrying out normalization processing on the characteristic parameters of the contact resistance, calculating virtual connection indexes of all monitoring nodes by adopting a multidimensional characteristic weighting fusion algorithm, and judging whether virtual connection faults exist according to a preset threshold value; the fault positioning module is used for calculating a voltage gradient anomaly coefficient aiming at the identified virtual connection node and positioning the specific position of the virtual connection fault point by combining the secondary circuit topology information.

Description

Virtual connection fault positioning method for relay protection secondary circuit Technical Field The invention relates to the technical field of relay protection of power systems, in particular to a virtual connection fault positioning method of a relay protection secondary circuit. Background The relay protection secondary loop is a key link of safe operation of the power system, wherein the virtual connection fault refers to the phenomenon of abnormal increase of contact resistance caused by poor contact of connection points such as terminals, binding posts and the like. Virtual connection faults have typical dynamic characteristics, are well contacted under light load or static state, but are expressed as dynamic fluctuation of contact resistance when load current is increased or environment is changed, so that misoperation or refusal of the protection device is caused. The existing secondary loop fault detection technology mainly comprises a static voltage and current monitoring based method for judging faults through monitoring steady-state electric quantity of a loop, a signal injection based method for injecting test signals into the loop and analyzing response characteristics, and an intelligent sensor tag based method for positioning faults through distributed sensor nodes. The technologies are mainly designed aiming at fault types such as open circuit, short circuit, grounding and the like, and have obvious defects in detecting virtual connection faults. The main defect of the prior art is that the dynamic change characteristic of the contact resistance cannot be effectively identified by adopting a static monitoring or single excitation mode. The nature of virtual connection fault is that the contact resistance presents nonlinear response along with load current, the static monitoring method can only acquire electrical parameters under specific working conditions and cannot capture dynamic characteristics of the contact resistance, and the signal injection method can apply test excitation, but mostly adopts constant current or constant voltage signals, lacks step change process, and is difficult to extract nonlinear response characteristics of the contact resistance. Disclosure of Invention The invention mainly aims to provide a virtual connection fault positioning method for a relay protection secondary circuit. Another object of the present invention is to provide a virtual connection fault positioning system for a relay protection secondary circuit. In order to achieve the above objective, an embodiment of a first aspect of the present invention provides a method for positioning virtual connection faults of a relay protection secondary circuit, including: s1, a controllable load disturbance device is connected in series in a relay protection secondary circuit, and distributed voltage acquisition units are arranged at a plurality of key nodes of the secondary circuit; s2, periodically applying step load current through the controllable load disturbance device to enable the load current of the secondary circuit to jump from a reference current to a preset test current; S3, synchronously acquiring voltage values of corresponding monitoring nodes through each distributed voltage acquisition unit before and after each step load current application, and calculating dynamic voltage drops of each monitoring node; s4, extracting characteristic parameters of contact resistance corresponding to each monitoring node based on the response relation between the dynamic voltage drop and the step load current; s5, calculating virtual connection indexes of all monitoring nodes according to the contact resistance characteristic parameters, comparing the virtual connection indexes with a preset threshold value, and judging whether virtual connection faults exist in the corresponding monitoring nodes; And S6, aiming at the identified virtual connection node, calculating the voltage gradient anomaly coefficient between the virtual connection node and the adjacent monitoring node, and combining the topology information of the relay protection secondary circuit to locate the specific position of the virtual connection fault point. In one embodiment of the invention, in the step S2, the controllable load disturbance device includes a power electronic switching device, a current detection unit and a PWM control circuit, where the PWM control circuit implements accurate control of load current by adjusting a turn-on duty ratio of the power electronic switching device, the current detection unit monitors loop current in real time and feeds back the loop current to the PWM control circuit to form closed loop control, and application of the step load current adopts a periodic triggering manner, and each period includes a reference current stage, a current jump process and a test current stage. In one embodiment of the present invention, in the step S3, the distributed voltage acquisition unit adopts a multi-channel synch