product overview

Cables above 35kV mainly use single core cables with metal protective layers. Due to the hinge between the metal sheath of a single core cable and the magnetic field lines generated by the alternating current in the core wire, a high induced voltage appears at both ends. Therefore, appropriate grounding measures need to be taken to keep the induced voltage within the safe voltage range (usually not exceeding 50V, and not exceeding 100V when safety measures are in place). Usually, the metal protective layer of short circuit single core cables is grounded directly at one end and grounded at the other end through a gap or protective resistor; The metal protective layer of long single core cables adopts a three-phase segmented cross interconnection method with both ends grounded. Regardless of the grounding method used, good insulation of the protective layer is necessary. When the insulation of the cable protective layer is damaged, it will cause the metal sheath to be grounded at multiple points, resulting in a circulating current in the protective layer, increasing the loss of the sheath and affecting the current carrying capacity of the cable. In severe cases, it may even cause the cable to overheat and burn out. At the same time, it is also very important to ensure good grounding of the direct grounding point of the metal layer sheath of high-voltage cable lines. If the grounding point cannot be effectively grounded for various reasons, the potential of the cable metal sheath will sharply rise to several thousand volts or even tens of thousands of volts, which can easily break through the outer sheath of the cable and continue to discharge at the breakdown point, causing the temperature of the outer sheath of the cable to rise or even ignite.

The IM5000C 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.

IM5000 C uses GSM or RS485 as the communication method. Suitable for multi-point grounding fault monitoring of single core cables above 35kV.

system composition

The online monitoring of cable sheath circulation is achieved by the IM5000C cable sheath comprehensive monitoring device host, current transformer, 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:

Functional Features

The main functional characteristics of the device are as follows:

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;

Real time anti-theft cutting monitoring of cable sheath grounding;

The monitoring time interval can be set;

Alarm parameters and whether corresponding monitoring parameters are allowed to generate alarms can be set;

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 ground current during the cycle, and alarm processing;

Real time monitoring and statistics of the ratio of grounding current to load during the cycle, and alarm processing;

Real time monitoring and statistical analysis of the rate of change in single-phase ground current during the cycle, and alarm processing;

● 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;

Real time measurement device input voltage;

All monitoring data have time labels to ensure data uniqueness;

All monitoring sensors can be configured according to user requirements;

Multiple data transmission interfaces: RS485 interface, GPRS, GSM SMS, can simultaneously use one or more data transmission modes;

● Support remote maintenance and upgrades;

Adopting low-power design, supporting multiple power inputs: CT induction power supply, AC-DC power supply, and battery power supply;

All use industrial grade components with good reliability and stability;

Unit type fully enclosed structure design, easy to install, all components adopt locking measures, good anti vibration performance, and easy replacement and disassembly;

Supports IP68 protection level.

Detecting parameters

communication interface

RS485 interface

Baud rate: 2400bps, 9600bps, 19200bps. Data length can be set to 8 bits; Starting position: 1 position; Stop position: 1 position;

Verification: No verification;

GSM/GPRS interface

Working frequency band: 4 frequencies, 850 MHz/900 MHz/1800 MHz/1900 MHz;

GSM short messages in both Chinese and English; GPRS class 10， The maximum downlink rate is 85.6 kbit/s, and the maximum uplink rate is 42.8 kbit/s. It supports TCP/IP, FTP, and HTTP protocols.

Working power supply

Characteristics of AC power supply:

Voltage: 85~265VAC;

Frequency: 47~63Hz;

Power: ≤ 8W

Battery power characteristics:

Voltage: 6VDC

Capacity: determined based on the duration of battery power supply