Online Detection System For Grounding Resistance

The online grounding resistance detection system can monitor the connection between the grounding lead line of the storage tank and the grounding network in real time, and the grounding resistance value of the grounding network of the storage tank discharging lightning current to the ground. If the resistance value exceeds the standard, the alarm can be generated. In addition, the historical data analysis can predict the performance parameter change and corrosion of the grounding resistance, and provide maintenance suggestions. The system consists of two products, the lead-down metal loop resistance data collector and the earth network grounding resistance data collector, and the main controller and the host computer platform constitute a complete intelligent online monitoring system of grounding resistance.

■ Lead the metal loop resistance data collector offline

The downlead connects the tank wall to the grounding network. The downlead metal loop resistance data collector is installed on the tank grounding lead line to monitor the connection between the downlead line and the storage tank and between the downlead line and the grounding main line below the ground to ensure the smooth discharge channel.

Non-explosion-proof type	Explosion proof type

▲ Lead-down metal loop resistance data collector installation diagram

Technical parameter 

● Shell material: die-cast aluminum alloy

● Explosion-proof class: Ex db [iaGa] IIC T6Gb

● Impulse discharge current resistance: more than 100KA (10/350uS waveform)

● Communication mode: RS-485, Moudus protocol

● Protection level: IP66

● Measuring range and accuracy: 0~100Ω, ±1mΩ

■ Earth network grounding resistance data collector

The grounding network of the storage tank is also called the grounding device, and the lightning flow is discharged into the ground through the grounding network, and its ground resistance value is the standard to measure the good grounding of the storage tank. The ground network data collector can monitor the resistance between the ground network and the ground in real time. It is composed of the main controller and the permanent auxiliary pole. The plasma grounding element is used to construct a permanent auxiliary pole, and the high frequency pulse current is used to measure the impact impedance of the ground network. The detection accuracy and installation difficulty are better than the three-pole method.

Technical parameter

● Supply voltage: DC24V

● Measuring range: 0--100Ω

● Measurement pulse frequency: 1500Hz

● Current: 3mA

● Auxiliary body: copper plasma grounding body

■ Main control unit

The main control unit is a control device in the earth resistance online monitoring system, which is used to collect the resistance values measured by each sub-control unit (under lead loop resistance data collector and earth network resistance data collector). It is an intermediate device between the field device and the upper computer system, and has functions such as data display, resistance value exceeding the alarm, parameter setting, and power supply for the sub-control.

Technical parameter

● Explosion-proof class: Ex db llB T6 Gb

● Working voltage and output: AC220V input DC24V output

● Communication mode: RS-485

● Display mode: LCD display

● Alarm mode: sound and light alarm

● Load quantity: ≤40 sub-control devices

● Protection grade: IP65

● Communication distance: RS485 mode ≤1KM, can expand optical fiber communication, communication distance of 10KM

● Earth resistance alarm value: adjustable, factory default 4Ω

▼ Application results of earth resistance online monitoring system

01. In the process of installing the earth resistance online monitoring system in a petrochemical company, the "false" lead down line on its storage tank was identified by our company's equipment, and the hidden danger of lightning protection was successfully found.		02. During the site leveling operation of a commercial storage warehouse, the connection between the multi-root lead down line and the ground main line was torn off by the excavator, and our company's equipment found a total of 11 lead down line fracture points.		03. The contact resistance of a petrochemical substation is seriously exceeded because of corrosion at the break card of the ground lead line.

▲ Ground resistance monitoring system host computer display interface