CPT G-TEST Manual de usuario
G-TEST
接地電阻測試器
使用手冊
33
G-TEST
Microprocessor Controlled Digital Earth Tester
User’s Guide
34
Index
1. Description_______________________________________________________ 35
1.1. Control panel _________________________________________________ 36
1.1.1. Connections and items ______________________________________ 36
1.1.2. Keyboard _________________________________________________ 37
1.1.3. LED's ____________________________________________________ 38
1.2. Measurement ranges ___________________________________________ 38
2. Battery / battery charger ____________________________________________ 39
3. Real time clock and calendar_________________________________________ 40
4. Equipment calibration checking_______________________________________ 40
5. Grounding resistance measurement ___________________________________ 41
5.1. Observations about grounding diffusion systems (GDS) ________________ 42
6. Spurious voltages measurement ______________________________________ 43
7. Soil resistivity measurement _________________________________________ 44
8. Abnormalities indications on the display ________________________________ 46
8.1. Excessively high spurious voltages ________________________________ 46
8.2. Excessively high earth resistance__________________________________ 46
8.3. Excessively high resistance in the auxiliary rods ______________________ 46
8.4. Excessively high soil resistivity____________________________________ 47
9. Exporting data to the computer _______________________________________ 47
10. Printer _________________________________________________________ 48
11. Technical Specifications ___________________________________________ 49
35
1. Description
The G-TEST is a microprocessor controlled earth tester that allows meas-
uring earth resistance and ground resistivity (by Wenner's method), as well
as detecting parasitic voltages that may be present in the ground. Totally
automatic and easy to operate, the G-TEST is suitable to measure earth
systems in power substations, industries, distribution networks, etc., ac-
cording to IEC 61557-5, or to measure soil resistivity in a terrain, in order to
optimize the earth systems project.
Before starting each test, the G-TEST will check if all conditions are within
the appropriate limits and will notify the operator if there are any abnormali-
ties, such as too high interference voltage, too much resistance in the test
spikes, very low test current, etc. If all conditions are normal, the equipment
will automatically select the adequate range and will show the results on the
display.
In order to conveniently test earth systems, the G-TEST allows measure-
ments using test currents with selectable frequency, of 270Hz or 1470Hz.
Measurements in the 270Hz frequency allow to analyse the system behav-
iour when in contact with fault currents of industrial frequency, while those in
the 1470Hz frequency show better the system behaviour when in contact
with electrical currents caused by lightning. Measurements in the higher
frequency also offer high immunity to interference voltages in the soil, what
allows accurate results in often unfavorable conditions.
The G-TEST has memory to store up to 4000 measurements, a built-in
printer and a serial data output that allows to transfer the stored results to a
computer or data logger for later analysis. Practical, lightweight and strong,
the G-TEST is suitable to field use, even under severe weather conditions.
It is powered by a rechargeable battery (220 - 240V charger), and is sup-
plied with all the necessary accessories in a practical auxiliary case.
36
1.1. Control panel
All of the G-TEST buttons, keys, outputs and connections are located on the
panel, and are easily accessible by the operator. The following graphics
show the function of each one of the equipment's items.
1.1.1. Connections and items
!
#
"
$
%
&
'
(
)
HS ES
E
!- Output terminal E
"- Output terminal ES
#- Output terminal S
$- Output terminal H
%- Alphanumeric display
&- Keyboard
'- RS-232 communication port
(- Power supply input
)- Paper feed control
37
1.1.2. Keyboard
*
+
,
-
/
0
1
2
.
3
5
4
6
7
*- ON/OFF switch
+- The printer is active
,- Activates the voltmeter
-- Selects 270Hz frequency
.- Selects the resistivity measurement function
/- Shows the battery charge status on the display
0- Sends stored memory data to a connected computer or data logger
1- Selects 1470Hz frequency
2- Selects the resistance measurement function
3and 4- Increase or decrease the specified distance between rods in a
progression of 1, 2, 4, 8, 16 or 32 meters. It also allows the operator to
select the Rx function, used to check the equipment calibration by using a
standard resistance (ignoring the “distance” parameter, not needed in this
function)
5and 6- Increase or decrease the specified distance between rods in one
meter steps.
7- START key; starts the test.
38
1.1.3. LED's
8
9
:
;
=
<
>
8- The resistance measurement function is selected.
9- The battery charger is operating.
:- The G-TEST is on.
;- The printer is operating.
<- The voltmeter is selected.
=- The resistivity measurement function is selected.
>- A measurement is running.
1.2. Measurement ranges
The G-TEST automatically selects an adequate range when operating,
allowing measurements between 0,01Ωand 20kΩ(resistance), 0,01Ωm
and 50kΩm (resistivity), or voltages between 0 and 60V (when in the volt-
meter function).
39
2. Battery / battery charger
The G-TEST uses a 12V – 2.3Ah rechargeable battery. At the end of its
useful life, the battery must be recycled or disposed of properly, in order to
protect the environment.
Before starting each test, it is recommended to check if the battery has
enough charge. This can be done by pressing the battery status (/) key.
If the battery charge is low, the following message will appear on the dis-
play:
LOW BATTERY
[$ ]
When connected to the power supply, the battery charger will be always
active, even if the G-TEST is off.
Recharge procedure:
Check if the G-TEST is off, and then connect it to the power supply. The
battery charger LED will turn red, and will remain so until the battery is to-
tally recharged. Then, the light will turn to green, and will stay on until the
equipment is disconnected from the power supply.
If the equipment is turned on during the recharge procedure, the display will
show:
Charging
Battery...
During the process, the START7key will be deactivated.
Note: battery slowly loses part of its charge while stored, even whithout
use. Therefore, before using the equipment for the first time, or after a long
period out of use, it may be necessary to recharge the battery.
40
3. Real time clock and calendar
In order to provide an easier identification of each test, the G-Test has a
built-in real-time clock/calendar. Date and time must be adjusted with a PC
software (available at www.cirprotec.com) that sychronizes the equipment
with the PC clock.
4. Equipment calibration checking
By using a standard resistance (Rx), it is possible to test the equipment
calibration. The resistance must be connected to the G-TEST as shown
below:
RX
HS
ES
E
After connecting the resistance, follow these procedures:
•Turn the G-TEST on.
•Select the resistivity function (.).
•In the distance/standard resistance selection function, choose Rx (nomi-
nal standard resistance)
•Press the START7key.
•After 5 seconds, a stable value close to the standard resistance's nominal
value should appear on the display.
•If this is not the case, the equipment accuracy is out of its specification
and must be adjusted by a qualified laboratory.
41
5. Grounding resistance measurement
When turning on the G-TEST, the display will show the opening message,
followed by the parameters Earth Resistance / 3-Pole / 270Hz. These are
the standard functions and frequency; to operate in the 1470Hz frequency,
press the 1470Hz1key.
Insert the auxiliary rods (current rod E3 and voltage rod E2) in the ground.
Using the cables supplied with the equipment, connect the rods to the H$
and S#output terminals, respectively. The grounding system under test
must be connected to E!with the 5 meter cable.
E3 E2
E1
fig. 01
D1
D2
40m cable
20m cable
5m cable
Current
rod Voltage
rod Ground
to be
measured
H
S
ES
E
Press the START7key to start the test. The test number will be shown on
the display, followed by the message “WAIT...”, and after a few moments
the resistance value will appear, as in the following example:
R= 10.01@
3_Pole 270Hz
The result will then be stored on the memory.
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