Comprehensive online monitoring device for cable sheath

Introduction

The LHDL1908 cable sheath comprehensive online monitoring device adopts the principle of circulating current method, which means that under normal circumstances (i.e. one point grounding), the circulating current on the metal sheath of a single core cable is extremely small, mainly capacitive current. However, once the metal sheath is grounded at multiple points and forms a loop with the ground, the circulating current increases significantly, and in severe cases, it can reach more than 90% of the main current. Real time monitoring of metal sheath circulation and its changes can achieve online monitoring of multi-point grounding faults in single core cable metal sheaths, thereby timely and accurately detecting grounding faults, fundamentally avoiding cable accidents, and ensuring the safe and reliable operation of cables.
LHDL1908 uses GSM or RS485 as the communication method and is suitable for multi-point grounding fault monitoring of single core cables above 35kV.

System Composition

The online monitoring of cable sheath circulation is implemented by the LHDL1908 cable sheath comprehensive monitoring device host, current transformers, temperature and anti-theft cutting sensors, etc. The open-ended current transformer is installed on the grounding wire of the cable sheath and is converted into a secondary signal before being introduced into the monitoring device. The temperature sensor is used to monitor the temperature of the cable, and the anti-theft cutting sensor is used to monitor the theft of the circulating grounding wire.

The composition of the comprehensive online monitoring system for cable sheath is shown in the following figure:

Features

Real time monitoring of the protective layer grounding current, total grounding current, and operating current of any phase main cable of three-phase cables;
Real time monitoring of three-phase cable temperature and anti-theft cutting monitoring of cable sheath grounding;
◎ Monitoring time intervals can be set according to user requirements;
◎ Alarm parameters can be set according to user requirements and whether corresponding monitoring parameters are allowed to generate alarms;
Calculate the maximum, minimum, and average values within the set time period;
Real time monitoring and statistical analysis of the maximum and minimum values of single-phase grounding current, the ratio of grounding current to load, and the rate of change of single-phase grounding current during the cycle, and conducting
Alarm handling;
◎ Measurement data can be sent at any time specified;
When one or more monitoring parameters are specified to trigger an alarm, an alarm message can be sent to the designated mobile phone;
The system structure configuration is flexible, and all monitoring sensors can be added or removed according to user requirements;
Multiple data transmission interfaces: RS485 interface GPRS/CDMA；
◎ Supports IP66 protection level.

Main technical indicators of the system