MeihekouNDGZDW-II Distributed Fault Monitoring Device for Transmission Lines

1. System Functions

Transmission lines that traverse mountains and valleys are highly susceptible to trip‑outs caused by a variety of natural factors, including lightning, pollution, vegetation, and wind‑induced galloping. Each such incident can damage insulators, conductors, and other equipment, creating safety risks for system operation. Therefore, promptly and accurately locating fault points and carrying out timely repair and maintenance of the lines is a critical task.

Traditional methods for locating line faults present numerous challenges: First, they require line operators to be thoroughly familiar with the line and its underlying documentation and to possess substantial experience. Second, during daylight hours, strong solar illumination can render arc‑flash discharges difficult to detect or unstable, posing a significant risk of injury to maintenance and other personnel; at night, additional lighting and vehicle support are also necessary. Relying solely on operator experience is insufficient to address unexpected, random faults. Furthermore, constrained by operational procedures, once a ground fault has not yet been fully identified, the allowable two‑hour time limit is often reached, forcing an emergency outage that complicates the search for the root cause and further prolongs the time required to resolve the fault and restore power. This issue is particularly pronounced in areas characterized by long transmission lines, complex right-of-way conditions, and poor transportation access.

The online monitoring system for fault location on high-voltage transmission lines features a core component: a monitoring terminal mounted directly on the transmission line. This terminal can capture, at close range, transient traveling-wave signals generated during a fault, identify the fault type, and, using mathematical formulas, determine the precise location of the fault.

• Product Features:
• Online operation: installed directly on the power line; provides high-precision localization of the fault‑trip section and location.
• Fault identification: Capable of detecting ground faults and short circuits, and able to distinguish between transient faults and permanent faults.
• Time reference: Built-in GPS module and temperature-compensated crystal oscillator, with a time error of no more than 0.1 µs.
• Information Transmission: Utilizes 4G communication to transmit equipment status information and captured fault data to the central station in real time.
• Built-in dual-channel high-precision AD conversion chip;
• It features built-in dual Rogowski coils for simultaneous monitoring of power-frequency current and fault current.
• Supports web-based viewing of work status;
• Supports SMS text messages and WeChat alerts;

2. Technical Parameters

• Fault section location reliability: ≥99%
• Fault location error: ≤300 m
• Accuracy of fault identification between lightning-induced and non-lightning-induced faults: ≥95%
• Lightning strike/counterstrike identification accuracy: ≥90%
• Direct lightning strike detection accuracy: ≥90%
• Fault tripping alarm time: ≤5 min
• Fault diagnosis and alarm time: ≤30 min
• Traveling Wave Current Measurement

1. Frequency response range of the traveling-wave current sensor: 1 kHz to 10 MHz
2. Traveling-wave current sampling rate: ≥2 MHz
3. Single-conductor traveling-wave current measurement range: 5 A to 5000 A (peak)
4. Continuous recording duration of traveling-wave current: ≥1000 μs
5. Traveling-wave current measurement time‑parameter error: ±5% ±5 A (linear range)
6. Traveling-wave current measurement error: ≤10%

• Power-frequency fault current measurement

1. Frequency response range of the fault current sensor: 1 Hz to 1 kHz
2. Fault current sampling rate: ≥4 kHz
3. Single-conductor power-frequency current measurement range: 4 A to 5000 A (RMS)
4. Continuous fault current recording duration: ≥500 ms

e) Fault current measurement error: ±5% ± 2 A (linear range)

• Minimum operating current of the AC line: ≤15 A
• Maximum operating current of the AC line: ≤1500 A;
• Short-time withstand current capacity: 30 kA/2 s;
• System time calibration accuracy: ≤0.1 μs;
• Operating temperature range: -40°C to 70°C;
• Mean Time Between Failures of the monitoring terminal: not less than 25,000 hours;
• Communication method: 4G;
• Power supply method: integrated power‑coupling and solar‑panel system; minimum conductor load current: ≤15 A.
• Wind resistance: Withstands winds up to 150 km/h without loosening.
• Protection rating: IP65

3. System Composition

The online monitoring system for fault location on high-voltage transmission lines consists of two main components: hardware and software.

• 3.1 Hardware Composition

The hardware component of the system consists of a monitoring server and several line‑fault location devices. The line‑fault location devices are connected to the server via a 4G link. The monitoring terminals are mounted on the overhead conductors and are powered by lithium batteries and current transformers. The monitoring server may be a dedicated server provided by provincial utilities or a standard computer configured by the user.

3.1.1 Line Fault Location Device

The fault‑location device is equipped with a built-in main control board, data‑acquisition circuitry, a 4G network communication module, a charging‑management circuit, and a battery, and it provides the following functions:

1. Actively upload its operational status and the measured power-frequency current at the configured intervals.
2. It monitors line current changes in real time and, upon detecting a sudden current surge—such as from lightning strikes or short circuits—sends the acquired current data to the backend for processing.
3. It features sleep and wake functions to conserve power.
4. It features self-diagnosis and self-recovery capabilities.
5. Supports alarm triggering and alarm threshold configuration;
6. Supports remote reset;
7. Supports network‑based parameter configuration (including modifying and querying the server’s IP address and port);
8. Supports password setting and substation number configuration.
9. Supports clock synchronization and time query.

3.1.2 Monitoring Server

The monitoring server is a computer deployed at the remote monitoring center, running monitoring software that accesses the Internet to obtain data collected by the fault‑location device. The monitoring software provides functions such as displaying, analyzing and processing, storing, and printing reports based on the acquired line current data.

• 3.2 Software Composition

The monitoring software may be either a standardized solution developed by State Grid or China Southern Power Grid, or it may be the “High-Voltage Transmission Line Online Monitoring System” application developed by our company. Its main functions are as follows:

1. It features real-time passive reception and active query capabilities for monitoring and tracking data.
2. It features a remote function for setting the data acquisition cycle.
3. It features automatic time synchronization.
4. It features terminal device status monitoring.
5. Equipped with an alarm notification function;
6. The alarm notification will provide the precise geographic location of the alarmed measurement point, the point’s name, and the detailed timestamp of the current alarm.
7. It features device management and storage services.
8. This system’s software platform can operate in either B/S or C/S mode.
9. Multi‑mode remote monitoring: remote web access and client‑side system control;
10. Statistically process, analyze, and export the monitored data; select different measurement points and time periods as needed, and present the results in various reports, charts, and other formats.

Its operating interface is shown in the figure below.