Join us for an electrifying webinar that dives deep into the capabilities of the new Fluke GFL-1500 ground fault locator! Whether you're new to ground fault troubleshooting or a seasoned pro, this session will sharpen your skills with a review of essential terminology, an overview of the GFL-1500 hardware, and a walkthrough of its powerful functions and modes. Discover how to locate ground faults with confidence and learn insider tips and tricks to maximize your efficiency in the field. Don’t miss this chance to elevate your ground fault troubleshooting game!

1. GFL-1500
Ground Fault Locator

2. • Review basic terms used with the GFL-1500
• Overview of the hardware
• Discuss functions and modes
• How to trace a signal using the GFL-1500
• Learn some tips & tricks
Learning Objectives

3. • VOC = Open circuit voltage
• Voltage of a module or string of modules as measured from positive to negative
• VPE = Voltage as measured from positive to earth (ground)
• VNE = Voltage as measured from negative to earth (ground)
GFL-1500 Terms

4. Parasitic Capacitance in Solar Arrays
• Capacitance: A stored electrical
charge between the module and
its surroundings
• Especially grounded support
structures like racking
• Impacts ground fault
measurements by introducing
additional leakage current paths
• Can cause false positives or
obscure real ground faults
during testing
• Leads to high capacitance result
in analyze function

5. Hardware Overview

6. Ground Fault Detection Basics
• Analyze the system
• Measure voltage to identify if a fault is present
• Trace the fault
• Inject a signal into the system
• Transmitter
• Follow the signal to the fault
• Receiver
• Signal tracing clamp

7. Transmitter Features
High visibility graphic LCD
display with front light
Adjustable audio
feedback button
Info button allows users to
estimate what module
number is closest to the fault
CAT III 1500 V /
CAT IV 600 V
rated lead inputs
Fault Tracing function
with audio-visual guidance
along the fault path
Mapping function
to identify and map
string layout
Mode button to adjust trace signal
amplitude and whether signal is sourced
from the array or from the transmitter
Analyze function tests for
the presence of a ground fault
Open Circuit function
to locate breaks in wiring

8. Receiver Features
CAT III 1500 V /
CAT IV 600 V rated
Sensitivity setting
Signal strength
Visual fault tracing indicator
Frequency of the flash is
proportional to signal strength
Adjust receiver sensitivity
Change display brightness
Adjust mode
Adjust volume
Mode indicators
Tip Sensor, open, breaker

9. Signal Tracing Clamp Features
Rated for use on insulated
conductors up to 1500 V
Hold button
Segment LCD display
Bandpass filter
Display MIN, MAX, or AVG
Backlight
Hold 2 sec for
flashlight

10. Functions & Modes

11. • Measures voltage
• Open circuit – positive to negative
• Positive to earth
• Negative to earth
• If there’s a fault, estimates fault resistance
• Not an insulation resistance test
• Results provided in a range
• ~<5 kΩ, ~10 kΩ, ~50 kΩ, ~100 kΩ, ~500 kΩ, ~>1 MΩ
• No resistance value is provided if high capacitance and
high resistance are detected
Analyze Function
“FAULT” displays
when resistance
is below 10kΩ

12. Analyze Function – Possible Results
Hard fault:
Found voltage to
ground and low
resistance, move to
Fault Function
No fault detected:
High resistance,
No voltage to ground.
Fault tracing
unnecessary
High resistance fault:
Found voltage to
ground with high
resistance, move to
Fault Function. If
unclear results, try
reducing fault
resistance
High resistance
& capacitance:
Transmitter is
unable to determine
if fault is present.
Tracing may provide
inconclusive results

13. • If voltage to ground is detected, pressing INFO
button will ask for module quantity, and estimate
fault location
• Location is based on voltage measurements
• May give location between two modules
• May be between three modules I.E. 3 - 5
Analyze Function – INFO
Homerun Fault Fault Between Modules

14. • Injects a traceable signal into the system
• Use the receiver or signal tracing clamp to
follow the signal
• Sends the signal from the negative
terminal to the fault
• Sends the signal from the positive
terminal to the fault
Fault Function

15. Open Function
• Injects a signal on a circuit to find a break
• The circuit MUST be isolated from
other circuits
• Remove conductors and attach directly to transmitter
• Or isolate the circuit using fuses
• Can use high or low signal modes
• Only the receiver works with the open function
• Must select open mode on the receiver
• Can’t use the signal tracing clamp
• There’s no current flowing in the circuit

16. Map Function
• Injects a traceable signal to locate
isolated circuits
• Can use receiver or signal tracing clamp
• Auto is default signal mode
• Will switch between array and unit based on
voltage present
• If signal is too strong, switch to low
signal mode
• Only available in array mode
• Signal will go to any complete circuit
connected to positive and negative
terminals of the transmitter!
One string isolated, signal only on that string

17. • Press MODE button on transmitter to change signal mode
• Hold MODE button for >2 seconds to switch between high/low
• Array – Signal comes from the array being tested
• Default mode for fault function
• Requires >30 VDC from the array to function
• Array mode won’t work with open function
(no voltage present)
• Increases battery life by almost 100%, ~15 hr battery life
• Unit – Signal comes from the transmitter
• Default mode for open function
• Use when no array voltage is present
• Reduces battery life, ~8 hr battery life
Signal Modes – Array and Unit
Array
Unit

18. • Auto – Automatically switches between array and unit
• Default mode for map function
• Automatically selects array (>30 V) or unit (<30 V) modes
based on voltage
• May lead to unreliable results in systems with high capacitance
• Especially when using Fault Function
• High/Low
• Array mode
• High: 30mA, good for low resistance faults
• Low: 6mA, better for high resistance faults
• Unit mode
• High: 120mA fault & map, 100mA open
• Low: 30mA open function only
Signal Modes – Auto and High/Low
Array High Array Low
Auto

19. Should I Transmit from the Positive or the Negative?
• Transmitting on a circuit with >30 V allows array mode
• Homerun faults will only have voltage on one side
• In most cases, transmit on the side with highest voltage
to ground (from Analyze Function)
• Transmitting on the polarity with no voltage may be the
shortest path to the fault
• What is isolated?
• Opened positive fuses, can’t transmit on positive
• Which to use depends on your workflow, system design,
and preferences
• If one doesn’t work well, try the other

20. Transmitting with isolated circuits
• Isolate strings by opening fuses on one
side
• Transmit on the other polarity
• Use receiver or clamp to follow signal
• If you transmit on isolated busbar
(positive in this diagram) you’ll get no
signal
Fault

21. Fault
Transmitting without isolating circuits
• Don’t open fuses, signal everywhere
• Use clamp on pairs of wires to locate current imbalance

22. Tracing a Signal
Using the GFL-1500

23. • String inverter, central inverter, trunk bus
systems
• The DC system design influences
GFL-1500 workflows
• Knowing where the signal goes helps find
faults and reduces confusion
• The GFL-1500 is very flexible
• Inject signal on negative or positive
• It fits many workflows
• Can make signal tracing complicated or confusing
DC Topology Matters

24. • All of the following methods work with
the Fault Function
• Open and Map Functions only work
with isolated circuits
• Testing on a single isolated string
Or
• Connect to bus bars but isolate a string by
opening all the fuses except the circuit
being tested
Functions

25. • Turn the inverter off or isolate the equipment to be tested by disconnecting
both positive and negative conductors
• The DC system must be ungrounded!
Before Testing

26. • Red lead to positive
• Black lead to negative
• Green lead to ground
• Could be ground bar or any
grounded metal part
• Can use MC4 test leads
or alligator clips
• Inject on either polarity
• Narrows signal path
• Easier to trace to fault
Setting up the Tool – To a Single String
Red and black test
leads connected to
positive and negative
ends of the PV string
Green test lead
connected to grounded
metal component

27. Setting up the Tool – To a Busbar
• Similar workflow in a combiner box or inverter
• Red test lead to positive busbar
• Black test lead to negative busbar
• Green test lead to ground (earth)
• Inject signal on either polarity
• Pay attention to what’s
bussed together
• Fuses allow you to
isolate strings
Red test lead
connected to
positive busbar
Black test lead
connected to
negative busbar
Fuses on positive
and negative
Fuses on
positive only
Green test lead
connected to
ground busbar

28. • MPPT = Maximum power point tracking
• Usually two strings per input
• Can’t test all circuits, they’re separate
• Inverter may indicate MPPT input with the issue
• Potential test procedure
• Test voltage to ground on each MPPT with a multimeter
• Identify string or MPPT input with ground fault
(voltage to ground)
• Unwire and test individual strings with GFL-1500
Setting up the Tool – Inverter with Multiple MPPT Inputs

29. Setting up the Tool – To an External Connector
• Similar workflow in a combiner box or inverter
• May be able to use GFL-1500 without opening box
• Open disconnect to isolate equipment
• Test for current before opening connectors!
• Remove one pair of wires (+ and – of one string)
• Can also use TLPV2 MC4 Y test leads
• Analyze that string, if no fault move to next step
• Connect GFL-1500 to open ports from removed string
• Run analyze, if fault is found, use fault function
• Use clamp around pairs of conductors exiting box
• Identify pair with current, that’s the faulted string
• Disconnect that string, transmit on that string only to trace
the fault using receiver or signal tracing clamp
Connectors on
outside bottom
of box
Open pair of
connectors, connect
GFL-1500 here

30. Setting up the Tool – To a Trunk Bus System
• Set up transmitter at DC disconnect
• Run analyze, if fault found, move to fault function
• Use clamp or receiver to trace to mold block with
the fault
• Identify string with fault and isolate that string
• Move transmitter to isolated string
• Follow signal to fault
Mold block with
string connections
Large DC
disconnect

31. Module Level Power Electronics (MLPE)
• Types: Microinverters, DC optimizers, rapid shutdown devices
• GFL-1500 may not work with this equipment
• Check with the equipment manufacturer
• GFL signal may damage electronic devices
• Most MLPE disconnect when inverter is off
• Especially DC optimizers and rapid shutdown devices

32. • Many faults are on buried cable
• Use the clamp or receiver before and after the cable goes underground
• If the signal is different on each end, the fault is underground
• Receiver and clamp are unable to pinpoint faults on underground cables
Underground Faults

33. • Use the clamp or receiver to verify the signal
at the transmitter leads
• The higher the resistance, the harder the fault
is to trace
• Reduce resistance: test during wet conditions, move
tracker into faulted position
• Use LOW signal strength: lower current is easier to
pass through high resistance faults
• Audio alert changes based on transmit mode
• If the audio alert changes, system conditions changed
• Check connections if you lost voltage from the array
Tips & Tricks

34. • Signal is on multiple strings or across the array
• May be caused by leakage from capacitance
• Don’t use receiver, use clamp with BP function on
• May be due to multiple ground faults in the system
• Isolate individual circuits, trace separately
• Make sure the Green lead has a low-
resistance bond to the ground
• Make sure alligator clip pierces metal coatings
• Faulty equipment grounding may cause testing errors
• Update the transmitter firmware via TruTest
More Tips & Tricks

35. Questions?
Please send any questions you have right
now using the question box in your webinar
controls.
After the webinar, if you think of any more
questions, please feel free to contact me via
email
Katarina Ost: katarina.ost@transcat.com
For related product information, go to:
www.transcat.com/brand/fluke-store