Gfl - Searching For Conditions Of Low Insulation On Pv Strings - HT PV-ISOTEST User Manual

6.3. GFL – SEARCHING FOR CONDITIONS OF LOW INSULATION ON PV STRINGS
In GFL (Ground Fault Locator) function, the instrument is capable
indication about the position of a possible single fault of low insulation located in a string of
the installation due, for example, to infiltrations of water or humidity in the junction boxes of
PV modules. The instrument measures input voltages and, according to the unbalance
between V(+) and V(-) with respect to earth, it detects the assumed position of the fault on
the string.
The GFL function allows obtaining correct results ONLY at the following
conditions:
 Test carried out on a single string
dischargers and functional ground connections
 Single fault of low insulation located at any position in the string
 Insulation resistance of the single fault <0.1M
 Due to the random nature of these faults, it is recommended to carry out
the measurements in environmental conditions similar to those in which the
fault was reported
1. Position the cursor onto GFL by using the arrow keys
(,) and confirm with ENTER. The display shows the
screen to the side. The indication "Rp" indicates the
parallel of the insulation resistances of the positive (+)
and negative (-) poles of the string being tested.
2. Use the arrow keys  or  and select the position
"NMOD to set the number of modules of the string being
tested.
3. Use the arrow keys (,) to select a number of modules
between: 4 ÷ 50
4. Use the arrow keys  or  and select the position
"Vtest" to set the test voltage.
5. Use the arrow keys (,) to select one of the following
test voltages (Vnom): 250, 500, 1000, 1500VDC.
compliance with the prescriptions of IEC/EN62446-1 it
is recommended to set the test voltage Vtest≥Vnom
of the system
CAUTION
disconnected from the inverter, any
In
EN - 25
PV-ISOTEST
of providing an
GFL 15/10 – 18:04
R p - - -
V P N V P E
0 V 0 V
10 1500V 0.10M
NMOD Vtest. Lim.
GFL 15/10 – 18:04
R p - - -
V P N V P E
0 V 0 V
10 1500V 0.10M
NMOD Vtest. Lim.
GFL 15/10 – 18:04
R p - - -
V P N V P E
0 V 0 V
10 1500V 0.10M
NMOD Vtest. Lim.
M 
V N E
0 V
M 
V N E
0 V
M 
V N E
0 V