eSpace IAD
Troubleshooting
3 Common Troubleshooting Methods
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
When an electrical device is leaking because of some faults, personnel and devices could
be exposed to the risk of electric shock. The PGND is provided to connect the electrical
device house to the ground to prevent electric shock.
Lighting protection ground
Lightning production ground deals with the protection of buildings and other structures
due to direct damage from lightning.
Working ground
Working ground is to connect an electrical circuit to the ground as required by the
normal work or fault location.
In a ground system, a ground electrode is buried in the earth and is connected to a ground
conductor by a connector. The ground conductor connects to the ground bar or device houses.
If multiple devices connect to the same ground electrode by conductors, a ground bar is
required and the ground bar should be installed near to the ground electrode. The conductors
from different devices must be connected to the ground bar separately.
Test Principles
The ground impedance is mainly affected by the following variables:
Depth of the ground electrode
Diameter and length of the ground electrode
Number of ground electrodes
Around geographical environment (plain, slop, or ditch)
Soil humidity
The 3-pole Fall of Potential method is used to test the ground impedance. The method is as
follows:
Position two ground stakes in the soil in a straight line on one side of the ground electrode (X),
equidistant from one another. The stake (Y) is 20 m away from the ground electrode and stake
(Z) is 40 m away from the ground electrode. The potential difference between X and Y and
the current between X and Z are measured by a tester. Using Ohm's Law (V=IR), the tester
automatically calculates the impedance.
Precautions
The ground impedance changes with the season, weather, and soil humidity. Generally,
the ground impedance tested in autumn is more precise.
Before testing the PGND impedance, disconnect the ground cable from the device.
If a ground electrode is severely rusty or corroded, polish the electrode and then test the
impedance.
Before testing the working ground (single-point ground), verify that the ground cable is
connected to the device properly. If they are not connected, you cannot perform test; if
the connection is abnormal, the test result is not accurate.
Select a suitable test point because the test results on different points may vary greatly. If
there is no available test point, you can remove the original ground conductor if
necessary and connect a jumper cable that is easy to test.
Prevent noise interference. If the current in the ground connector circuit is large, the test
result will be inaccurate or even the impedance cannot be tested and noise may be
displayed on the tester.
Normally, the PGND and working ground impedance of devices is less than 4 ohms and the
lightning protection ground impedance of high buildings is less than 10 ohms. If the ground
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