CN-121995182-A - Insulation monitoring method and equipment for low-voltage power network

CN121995182ACN 121995182 ACN121995182 ACN 121995182ACN-121995182-A

Abstract

The application discloses an insulation monitoring method and insulation monitoring equipment for a low-voltage power grid, which are used for synchronously acquiring two paths of analog signals of zero sequence voltage and zero sequence current of the power grid by specially configuring a PT opening triangular part and a zero sequence current transformer for the 400V low-voltage power grid, transmitting the analog signals to an acquisition processing circuit module, converting the analog signals into the zero sequence voltage and zero sequence current digital signals carrying vector phase angle digital quantity information through low-voltage filtering and analog-to-digital conversion processing, transmitting the digital signals to an MCU micro controller module, calculating and separating the digital signals through a built-in data analysis processing sub-module, acquiring the values of zero sequence current resistance components and capacitive components, and judging whether insulation hidden danger or capacitive capacitance interference exists in a circuit based on the values of the two components. The application can collect zero sequence electric signals with high precision, weaken distributed capacitance interference and realize accurate detection and early warning of early potential insulation hidden trouble in a low-voltage power grid.

Inventors

ZHANG GENGYONG
SHI XINGYE
YAN BAIHUI
HUANG GUODONG
WEN TING
ZHANG RONGHUI
CHEN WEI
Xu Guohang
WEN HANGUAN
HE ZHENHUA
YU XICHENG

Assignees

南方电网绿能科技(广东)有限公司

Dates

Publication Date: 20260508
Application Date: 20260409

Claims (10)

1. The insulation monitoring method for the low-voltage power network is characterized by comprising the following steps of: Collecting a zero-sequence voltage analog signal through a PT opening triangular part configured on a 400V low-voltage power grid, and synchronously collecting a zero-sequence current analog signal through a zero-sequence current transformer configured on the 400V low-voltage power grid; the acquisition processing circuit module is used for carrying out low-voltage filtering on the zero-sequence voltage analog signal and the zero-sequence current analog signal, and carrying out analog-to-digital conversion processing on the low-voltage filtering to obtain a zero-sequence voltage digital signal and a zero-sequence current digital signal containing vector phase angle digital quantity information; Calculating and separating the zero sequence voltage digital signal and the zero sequence current digital signal through a data analysis processing sub-module in the MCU micro controller module to obtain values of a zero sequence current resistance component and a zero sequence current capacitance component; based on the zero sequence current resistive component and the value of the zero sequence current capacitive component, judging whether the low-voltage power network circuit has potential insulation hidden danger or capacitive interference or not comprises the following steps: Setting a multi-level low-threshold early warning standard for the zero sequence current resistance component, monitoring whether the absolute value of the zero sequence current resistance component reaches the multi-level low-threshold early warning standard, simultaneously monitoring the increasing trend of the zero sequence current resistance component, and judging that the 400V electric power grid has middle-early potential insulation hidden trouble if the absolute value reaches the standard or shows a monotonically increasing trend, wherein the thresholds of the multi-level low-threshold early warning standard are lower than the upper limit of the warning threshold specified by the residual current type electric fire monitoring detector, or, And monitoring whether the real-time value of the zero sequence current capacitive component is suddenly changed relative to the capacitive capacitance baseline value, and if so, judging that the low-voltage power network circuit has capacitive capacitance interference.
2. The insulation monitoring method of a low-voltage power grid according to claim 1, wherein the primary side of the PT-opening triangular part is connected with A, B, C three-phase voltage of the low-voltage power grid in a distributed manner, the secondary side of the PT-opening triangular part is not provided with an extraction port corresponding to the phase voltage, and only the opening of the PT-opening triangular part is provided with a zero-sequence voltage output port through which the zero-sequence voltage analog signal is output.
3. The method of claim 2, wherein a reverse amplification setting is adopted for a PT transformation ratio in the PT-opening delta element, so as to convert a millivolt level zero sequence voltage vector value in the low-voltage power grid into a large voltage vector value, and the PT transformation ratio comprises 1:5.
4. The insulation monitoring method of the low-voltage power grid according to claim 1, wherein a zero sequence voltage sampling processing subunit is arranged in the acquisition processing circuit module, and a signal amplifying sub-circuit is arranged in the zero sequence voltage sampling processing subunit alone, and is used for amplifying a weak zero sequence voltage analog signal with millivolt level in the low-voltage power grid.
5. The method for monitoring the insulation of the low-voltage power grid according to claim 1, wherein an electric energy metering chip is arranged in the acquisition processing circuit module, the calculation precision of the zero-sequence voltage analog signal and the zero-sequence current analog signal is improved through the electric energy metering chip, and meanwhile, the workload of a software program of the MCU microcontroller module is reduced.
6. The method for monitoring the insulation of the low-voltage power grid according to claim 1, wherein the data analysis processing submodule of the MCU microcontroller module calculates and separates to obtain values of a zero-sequence current resistive component and a zero-sequence current capacitive component, and the method comprises the steps of carrying out vector separation on the zero-sequence voltage digital signal and the zero-sequence current digital signal by utilizing phase characteristics that the zero-sequence current resistive component is in-phase with the zero-sequence voltage and the zero-sequence current capacitive component is advanced by 90 degrees to obtain effective values of the zero-sequence current resistive component and the zero-sequence current capacitive component.
7. The insulation monitoring method of the low-voltage power grid according to claim 1, wherein the data analysis processing sub-module of the MCU micro-controller module further comprises integrating the zero-sequence voltage digital signal and the zero-sequence current digital signal for time after obtaining the values of the zero-sequence current resistive component and the zero-sequence current capacitive component, and obtaining a zero-sequence voltage time integration parameter and a zero-sequence current time integration parameter of each time period.
8. The low-voltage power grid insulation monitoring method according to claim 7, wherein the analysis processing is performed again based on the zero-sequence voltage time integral parameter and the zero-sequence current time integral parameter to obtain a zero-sequence current resistive component time integral parameter and a zero-sequence current capacitive component time integral parameter, and the potential insulation hidden danger state of the low-voltage power grid line is further judged by combining the integral parameters.
9. A low voltage grid insulation monitoring device, comprising: PT opening triangular parts are used for collecting zero sequence voltage analog signals of a 400V low-voltage power grid; The zero sequence current transformer is used for synchronously collecting zero sequence current analog signals of the 400V low-voltage power grid; The acquisition processing circuit module is in communication connection with the PT opening triangular component and the zero sequence current transformer, performs low-voltage filtering and analog-to-digital conversion on the zero sequence voltage analog signal and the zero sequence current analog signal, and outputs a zero sequence voltage digital signal and a zero sequence current digital signal containing vector phase angle digital quantity information; The MCU microcontroller module is in communication connection with the acquisition processing circuit module, a data analysis processing sub-module is arranged in the MCU microcontroller module, and a man-machine interface module and a communication module are connected to the exterior of the MCU microcontroller module; The data analysis processing sub-module is used for calculating and separating the zero sequence voltage digital signal and the zero sequence current digital signal to obtain the values of the zero sequence current resistance component and the zero sequence current capacitance component; the data analysis processing submodule is further configured to determine whether a potential insulation hidden danger or capacitive interference exists in the low-voltage network line based on the values of the zero-sequence current resistive component and the zero-sequence current capacitive component, where the data analysis processing submodule includes: Setting a multi-level low-threshold early warning standard for the zero sequence current resistance component, monitoring whether the absolute value of the zero sequence current resistance component reaches the multi-level low-threshold early warning standard, simultaneously monitoring the increasing trend of the zero sequence current resistance component, and judging that the 400V electric power grid has middle-early potential insulation hidden trouble if the absolute value reaches the standard or shows a monotonically increasing trend, wherein the thresholds of the multi-level low-threshold early warning standard are lower than the upper limit of the warning threshold specified by the residual current type electric fire monitoring detector, or, And monitoring whether the real-time value of the zero sequence current capacitive component is suddenly changed relative to the capacitive capacitance baseline value, and if so, judging that the low-voltage power network circuit has capacitive capacitance interference.
10. The insulation monitoring device for the low-voltage power network according to claim 9, wherein the MCU microcontroller module transmits the detection value, the analysis result of the insulation hidden trouble and the early warning information to the man-machine interface module, and performs local display through the man-machine interface module, and the MCU microcontroller module transmits the data information to the communication module, and performs external remote communication through the communication module.

Description

Insulation monitoring method and equipment for low-voltage power network Technical Field The application relates to an insulation monitoring technology of a power system, in particular to a method for monitoring insulation of a power grid and equipment for monitoring insulation of the power grid. Background In the prior art, detection of electrical insulation hidden trouble of a three-phase four-wire system low-voltage power grid mainly depends on a residual current protection technology. Residual current protection is used as a mandatory standard configuration in the field of personal safety protection of low-voltage TN systems, and can effectively prevent electric shock accidents and electric fires, but the residual current protection essentially belongs to isolated parameters in the electric field, lacks residual voltage concepts corresponding to the isolated parameters, cannot acquire the related information of resistive insulation and capacitive insulation of a three-phase loop through a phase angle relation, is difficult to effectively identify and separate capacitive capacitance interference, and cannot perform refined analysis on the development state of the potential insulation hazard. The zero sequence voltage and the zero sequence current are used as the electrical parameters appearing in pairs, which are important basis for evaluating the insulation state of the power grid, the high voltage is usually converted into the low voltage signal through a voltage transformer in a medium-high voltage power grid system, the three-phase PT is used for connecting the three-phase PT into an open triangle structure to collect the zero sequence voltage, and the zero sequence current is collected by means of the zero sequence current transformer. However, for a 400V/380V power grid system, due to the limitation of economy and functional requirements, the prior art generally adopts a mode of directly measuring three-phase voltage and current to acquire signals, and a special PT opening triangular component, a zero sequence current transformer and other hardware acquisition devices are not configured. The zero sequence voltage and zero sequence current parameters are often obtained through indirect calculation through digital algorithm theory such as a three-phase voltage and phase current symmetrical component method, and the zero sequence current value generated by the grounding accident is large, and a protection mechanism can be triggered without additional hardware. The algorithm has obvious precision defects, particularly in the running process of a low-voltage power network, the interference on the ground distributed capacitance current (capacitive component) can seriously mask relatively weak medium-early potential resistive potential insulation hidden danger signals, so that the resistive component and the capacitive component are difficult to effectively identify and separate in the prior art, the accurate identification capability for capacitive capacitance interference is lacking, meanwhile, a multistage low-threshold monitoring mechanism is not established in the prior art, mutation monitoring cannot be carried out based on a baseline value, the medium-early potential weak insulation hidden danger signals are difficult to capture, and the growing trend of hidden danger cannot be tracked. Meanwhile, the sensitivity of the zero sequence current protection in a low-voltage TN system is only an ampere level, the influence of normal unbalanced current and capacitance current must be avoided, the requirement of quick cutting off of the ampere level required by personal safety cannot be met, the application range of the zero sequence current protection is limited to upstream positions such as a transformer, a bus section and the like, and real-time monitoring of early potential insulation hidden danger in a branch line cannot be realized. Therefore, the existing low-voltage power grid insulation detection technology lacks high-precision zero-sequence voltage and zero-sequence current hardware acquisition means, is severely interfered by distributed capacitance current, cannot realize effective identification and separation of capacitive capacitance interference, does not establish a multi-level low-threshold monitoring, baseline value comparison and abrupt change monitoring mechanism, and cannot accurately detect the middle-early potential insulation hidden danger state, and cannot effectively monitor the growth trend of hidden danger, so that the power supply system has the insulation hidden danger which is not found in time for a long time, operation and maintenance personnel cannot easily take targeted intervention measures before an accident, and the risk of the security accident caused by the insulation hidden danger is increased. Disclosure of Invention The application aims to provide a low-voltage power grid insulation monitoring method and low-voltage power grid insulation monitoring equipment, whi