Cable Fault Location Online Monitoring System
System architecture
The system is suitable for fault location and monitoring of 10kV and above voltage grade cables. The cable fault location online monitoring system adopts hierarchical structure design, which consists of three parts: front-end data acquisition, back-end data processing and data access. The system can conveniently, timely and effectively monitor the status of the running cable and locate the fault accurately.
According to the specific structure of cable network, it is an effective way to install the cable fault location device on the main trunk cable and the feeder branch cable of the ring cabinet, and realize the distributed traveling wave location and line selection of fault.
The fault location system of distribution and power supply cable realizes the online monitoring of power supply cable of ring network by using the systematic method of high-speed transient traveling wave online monitoring and network topology analysis, and can locate, select and warn the fault of power supply cable of urban ring network. The specific method is to install the cable fault traveling wave ranging device on the main dry cable and the feeder cable respectively, collect the weak transient signal of the cable before the failure to each fault traveling wave ranging device, analyze and process the signal through the fault traveling wave ranging device, and then send the signal to the background of the system. System background through waveform analysis automatic warning and through the two-end ranging technology automatically calculate the distance of the fault point, through the system background to indicate the location of the fault point, and the feeder branch cable to achieve line selection function.
1）System function
Fault location: the system adopts the double-terminal automatic ranging technology to achieve the double-terminal ranging of the main loop cable of the loop network. The fault location is indicated on the background interface of the system, and the fault location is marked. The fault location accuracy can reach ±1.7m.
Fault line selection: real-time monitoring of the cable transient current changes in each branch, according to the principle of traveling wave line selection and ring network topology structure to determine the ring network cabinet and the ring network cabinet in the fault line.
Fault warning: the system uses the transient traveling wave sign of instantaneous fault to monitor the insulation state of cable according to the phenomenon that the insulation state of cable after instantaneous grounding is closer to permanent fault, so as to ensure that the system can reliably warn before the permanent grounding fault occurs.
Circulation monitoring: For some single-core cables in the urban ring network, the system can monitor the insulation of the outer sheath of the line, draw the circulation curve, and alarm the cable with abnormal insulation of the outer sheath.
Power failure protection: The power module in the fault travelling wave ranging device is in a hot backup state. When the power supply fails, the fault travelling wave ranging device can work continuously for 2-3h to ensure the integrity of data collected at the moment of power failure.
History storage: realize real-time storage information, historical data query, alarm information printing, etc.
2) System technical indicators
Monitoring device size: 260mm*340mm*88mm
Current sampling frequency: 50MHz*8 channels
Voltage sampling frequency: 100KHz*4 channels
High frequency monitoring: 50MHz*8 channels high-speed sampling, can monitor 8 cables at the same time
Circulation monitoring (single core cable) : 10KHz*8 channels acquisition, can monitor 8 cables at the same time
System positioning accuracy: ±1.7m
System line selection accuracy: ≥95%
GPS/ Optical fiber/Beidou Punctuality accuracy: 20ns
Cloud service (optional) : Aliyun
Power consumption: 10 w or less
Communication interface: 4G wireless communication/network port *2/ optical port *2
Power supply mode: AC/DC 110-220V /DC 15-60V /CT Coupling power (starting current > 30A)
Power failure hold time: ≥8h
Average trouble-free working time MTBF: ≥ 5000h
System upper computer: master station or cloud
3) System structure
1, Cable fault location online device
Cable fault location online device is composed of main control unit (CPU module), high-speed signal data acquisition unit (DAU module), GPS/ optical fiber/Beidou punctuality module, 4G/ optical fiber/network communication module, power management module and other parts. Cable fault precise location device obtains transient traveling wave current signal through high-frequency sensor. At the same time, on the premise that the on-site conditions are available, Ua, Ub, Uc, power frequency voltage signals and zero-sequence components can be added to be used as auxiliary conditions for locating and warning high-voltage cable fault points, and to provide data support for background operation.
2, Sensor: high frequency signal acquisition sensor is divided into high frequency shielding layer sensor and high frequency core wire sensor:
High-frequency shielded layer sensor: the sensor is installed on the grounding line of the metal shielded layer of the monitored cable (Figure 1) and is responsible for monitoring the transient electrical wave signal of the tested cable. The sensor is fixed on the shielded cable in a consistent direction, and it should be noted that insulation treatment is required before installing the sensor on the shielded line.
High-frequency core-wire sensor: The sensor is installed on the monitored cable body. Each monitoring point is equipped with three sensors (FIG. 2), which are responsible for monitoring the transient electrical wave signal of the cable under test. The sensor is connected with the acquisition unit through multi-core shielded wire.
Contact Now
