Megger MGFL 100 User manual

MGFL 100
Ground fault locator
5 Commonwealth Ave
Woburn, MA 01801
Phone [phone]
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com

MGFL100
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The information presented in this manual is believed to be adequate for the intended use of the product. If the product
or its individual instruments are used for purposes other than those specified herein, confirmation of their validity
and suitability must be obtained from Megger. Refer to the warranty information below. Specifications are subject to
change without notice.
WARRANTY
Products supplied by Megger are warranted against defects in material and workmanship for a period of two years
following shipment. The warranty is void in the event of abuse (failure to follow recommended operating procedures)
or failure by the customer to perform specific maintenance as indicated in this manual.
Valley Forge Corporate Center
2621 Van Buren Ave
Norristown, PA 19403-2329
610-676-8500 (Telephone)
610-676-8610 (Fax)

Contents
Section Description Page
1.0 Introduction ..............................................................................................................................................4
1.1 Purpose of Manual .................................................................................................................................4
1.2 Audience...................................................................................................................................................4
1.3 Items received ..........................................................................................................................................5
2.0 Safety ........................................................................................................................................................6
3.0 Technical specifications ...........................................................................................................................7
4.0 Connections and Controls ......................................................................................................................9
4.1 Transmitter connections .........................................................................................................................9
4.2 Transmitter controls and displays ..........................................................................................................9
4.3 Receiver connections...............................................................................................................................10
4.4 Receiver controls and displays................................................................................................................10
5.0 MGFL100 Operations ..............................................................................................................................10
5.1 Locating a fault on ungrounded DC systems.......................................................................................12
5.2 Locating a ground fault on IT grounded systems................................................................................13
5.3 Locating a ground fault on TT grounded systems ..............................................................................20
6.0 Setting voltage and current limits.........................................................................................................25
7.0 Replacement parts...................................................................................................................................26
8.0 Maintenance ............................................................................................................................................27
8.1 General .....................................................................................................................................................27
8.2 Receiver Battery Replacement ...............................................................................................................28
8.3 Transmitter Battery Replacement..........................................................................................................28
9.0 Sales and Manufacturing Sites...............................................................................................................29
Table of contents
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Section 1.0 Introduction
Thank you for your purchase of the Megger MGFL100 Ground Fault Locator. Be assured that your unit has been
designed with emphasis on reliability, simplicity and ease of use. It will provide you with the information you need to
locate various types of ground faults.
Section 1.1 PURPOSE OF THIS MANUAL
This document is the operator manual for the Megger MGFL100 Ground Fault Locator. It provides a description of the
operation of the unit as well as installation and operating instructions. Read this manual before installing or using the
equipment. Special emphasis should be placed on all safety discussions.
Section 1.2 AUDIENCE
This manual is written for technical personnel who are familiar with the various measurements performed by volt
meters and current meters and have a general understanding of their use and operation. Such personnel should also be
thoroughly familiar with the hazards associated with the use of this equipment and should have received proper safety
training.
If you find any discrepancies in the MGFL100 or have any comments, please send them to Megger via fax, e-mail or
phone.
Megger
Valley Forge Corporate Center
2621 Van Buren Avenue
Norristown, PA, 19403
Attn: Customer Service
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1.0 Introduction

Section 1.3 Items Received
Qty Description Image
1 MGFL100 Transmitter
1 MGFL100 Receiver
1 Transmitter Output Cable
1 Current Clamp (CT)
1 Sync Cable
Optional Capacitive Pick Up
Optional Active mini CT NEED CLASS 3 PRODUCT
Optional AC Filter NEED CLASS 3 PRODUCT
Section 1.4 Overview
The MGFL100 is a ground fault locator that is intended to be used to locate ground faults up to 400K ohms on online
ungrounded DC systems. With use of the optional AC Filter the MGFL100 can also be used to locate ground faults up
to 400K ohms on online IT grounded AC systems. The MGFL100 receiver can also be placed in a mode that will allow it
to trace 60Hz and 50Hz currents on TT grounded systems with ground faults.
www.megger.com MGFL100 5
1.3 Items received

Section 1.5 Definitions
This section defines the terms used throughout this manual.
Term Definition
Impedance The AC and DC components of the ground fault on the circuit being measured, when the sync
cable or Capacitive Pick Up is not used. When the sync cable or Capacitive Pick Up are used the
term will refer to the actual resistance (The DC component only) of the ground fault on the circuit
being measured.
Capacitance The leakage capacitance present in the circuit being measured.
Fault Current The current delivered by the transmitter, used for tracing the fault.
Reactive Current The portion of the fault current drawn by the capacitive portion of the circuit.
Transmitter The part of the MGFL100 that provides the fault current and the direct measurement of the
resistance and capacitance of the circuit.
Receiver The part of the MGFL100 that measures the fault current and reactive current of the circuit.
Capacitive Pick
Up
The accessory that when connected between the receiver and the circuit being measured allows
the receiver to measure the reactive current of the circuit.
Sync Cable The cable that is connected between the transmitter and receiver that allows the receiver to
measure the reactive current of the circuit, without the need for the Capacitive Pick Up
CT The current transformer or current clamp that connects to the receiver.
Active Mini CT A battery powered miniature current clamp used to measure the fault current. This miniature
current clamp fits in tight locations and on small wires.
AC Filter Box The filter box that is placed between the transmitter and the IT grounded AC system. The box
blocks the AC current from damaging the transmitter.
Section 2.0 Safety
Warnings and Safety Precautions
WARNING!
Death, serious injury, or fire hazard could result from improper use/installation of this instrument. Read
and understand this manual before installing this instrument.
Installation of this instrument MUST be performed in compliance with the National Electric Code and any additional
safety requirements applicable to your installation.
Installation, operation and maintenance of this instrument MUST be performed by qualified personnel only. The
National Electrical Code defines a qualified person as one familiar with the construction and operation of the
equipment and the hazards involved.
Safety Precautions
The following safety precautions MUST be taken whenever the instrument is installed.
Wear safety glasses and insulated gloves when making connections to power circuits
Hands, shoes, floor/ground must be dry when making any connection to a powered line
These warnings and safety precautions are to be used where appropriate when following instructions in this manual.
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1.5 Definitions

CAUTION!
The equipment could be impaired from improper use. Read the complete manual before use.
WARNING!
The equipment should not be used while its battery door is removed or if there is any visible damage
to the case or if the hardware holding the unit together has been loosened.
Section 3.0 Technical Specifications
SPECIFICATIONS REFERENCE 25ºC (77ºF)
TRANSMITTER
Working Voltage 600 VDC max using fused test leads.
Output Voltage Range 0.0 to 50.0 V RMS
Output Frequency 5.12 Hz
Output Current 0 to 160 mA RMS
Output Power 5 Watts
Display LCD, TN, Positive, Reflective Size: 0.4” high digits Format: Seven
segment with decimal points Digits: 3.5
DC Voltage Measurement Range 0.0 VDC to 600 VDC
Accuracy ±5% of reading ± 2 Least Significant Digits
Speed of Measurement < 3 seconds
Display Resolution 0.0 VDC to 199.9 VDC / 200 VDC to 600 VDC Auto-ranging
Resistance Measurement Range 0.0 kΩ to 400 kΩ
Resolution 0.1 kΩ (< 175.0 kΩ), 1 kΩ (> 199.9 kΩ)
Accuracy (±10 ± 280 x RC) % ± 1 Least Significant Digit
Speed of Measurement < 3 seconds
Display Resolution 0.0 kΩ to 199.9 kΩ / 199.9 kΩ to 400 kΩ Auto-ranging
Capacitance Measurement Range 0.00 μfd to 19.99 μfd
Resolution 0.01 μfd
Accuracy ±20% ± (.0027 / R) fd ± 1 Least Significant Digit
Speed of Measurement < 3 seconds
AC Voltage Measurement Range 0.0 V RMS to 50.0 V RMS
Resolution 0.1 V RMS
Accuracy ±5% of reading ± 2 Least Significant Digit
Speed of Measurement < 3 seconds
AC Current Measurement Range 0.0 mA RMS to 160 mA RMS
Resolution 0.1 mA RMS
Accuracy ±5% of display ± 2 Least Significant Digit
Response time < 3 seconds
Voltage limit Password protected programmable from 0 to 50V
Current limit Password protected programmable from 0 to 160mA
Battery Type Four Li-Ion Protected Cells (18650)
Run Through Time Up to 4 hours
Charge Time < 8 hours
Battery Status Indication LED, Red / Amber / Green
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3.0 Technical specifications

RECEIVER
Visual Alarm Range Selectable - 30% / 40% / 50% / 60% / 70% of reference.
Audio Alarm Range Selectable - 30% / 40% / 50% / 60% / 70% of reference.
Receiver Filter Range Selectable 5.12Hz or 50 / 60Hz
Save Saves Total Current, Resistive Current and Reactive Current
Recall Recalls Total Current, Resistive Current and Reactive Current
Display LCD, TN, Positive, Reflective Size: 0.4” high digits, Format: Seven
segment with decimal points, Digits: 3.5
Resistive Current Measurement Range 0.00 mA to 160 mA
Resolution 0.01 mA (< 19.99 mA), 0.1 mA (> 19.99 mA)
Accuracy ±5% of reading ± 0.01 x IC ± 2 Least Significant Digits
Speed of Measurement < 3 seconds
Capacitive Current Measurement Range 0.00 mA to 160 mA
Resolution 0.01 mA (< 17.50 mA), 0.1 mA (> 19.99 mA)
Accuracy ±5% of reading ± 0.01 x IR ± 2 Least Significant Digit
Speed of Measurement < 3 seconds
Battery Type Six AA alkaline cells. (Eveready EN91, or equivalent).
AC Power Adapter 90 to 264Vac 47 – 63Hz.
Run Through Time Up to 4 hours
Battery Status Indication Visual: LED, Red / Amber / Green
PHYSICAL
Transmitter Size 36.1 x 30.5 x 19.5 cm (14.2” x 12.0” x 7.65”)
Transmitter Weight 6.00 kg (13.2 lbs). (with batteries installed)
Receiver Size 22.1 x 10.4 x 5.1 cm (8.7” x 4.1” x 2.0”)
Receiver Weight 1.00 kg (2.2 lbs) (with batteries installed)
ENVIRONMENTAL
Operating Temperature -10°C to +50°C.
Storage Temperature -20°C to 60°C
Humidity 95% Relative Humidity, Non-Condensing
IP Rating 51 when closed
ALTITUDE
<2000 meters 600V CAT IV
2000-4000 meters 600V CAT III / 300V CAT IV
SAFETY
Insulation
Safety Standard IEC61010
CAT Rating IV @ 600V
STANDARDS COMPLIANCE
Conducted EMI Immunity IEC 61000-4-6 at 3V (150kHz to 80 MHz) Performance Criterion A
Radiated EMI Immunity IEC 61000-4-3 at 10V/m (80 MHz to 1 GHz), 3V/m (1.4 GHz to 2.0 GHz)
and 1 V/m (2.0 GHz to 2.7 GHz) Performance Criterion A
ESD Immunity IEC 61000-4-2 with 4 kV contact discharges and 8 kV air discharges.
Performance Criterion B
Conducted EMI Emissions When operating
using external power adapter
CISPR 11 Group 1 class A.
Radiated EMI Emissions CISPR 11 Group 1 class A.
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3.0 Technical s[pecifications

Shock MIL-STD-810G method 516.6
Drop test MIL-STD-810G method 516.6
Static Rigidity IEC 61010-1 section 8.2.1
Impact IEC 61010-1 section 8.2.2
Vibration MIL-STD-810G method 514.6 Annex C
Loose Cargo MIL-STD-810G method 514.6 category 5.
*Full Accuracy Specification guaranteed 0ºC to 50ºC
Section 4.0 Connections and Controls
Section 4.1 Transmitter Connections
Section 4.2 Transmitter Controls and Displays
Battery String Connections
Red to positive side of string
Green to earth ground
Black to negative side of string
Safety Earth
Connection
Capacitive Sync Connection
Battery Compartment
AC - DC Power
Adapter
Positive Voltage and
Resistanve Display
Negative Voltage and
Capacitance Display
Negative Output
ON/OFF
Current Output
Display
Voltage Output
Adjust
Voltage Output
Display
Power
ON/OFF
Positive Output
ON/OFF
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4.0 Connections and controls

Section 4.3 Receiver Connections
The current clamp plugs into the CT inputs.
The sync cable will plug into the “SYNCH” input.
Section 4.4 Receiver Controls and Displays
Battery test button:
Press to view the status of the
receiver batteries. (Red should be
replaced)
IT indicator: When lit this indicates the
displayed value is total current.
Alarm indicator: Lights when the receiver
locates the circuit with the fault.
Save LED: Lights during save operation.
Power On / Off: Press button to
power the unit on and off.
Function button: Press button to
deactivate the low pass filter in
order to trace 50/60Hz current. Recall button: Press to recall saved values.
Alarm knob: Selects alarm level
and audio / visual alarm.
Save button: Press to save values displayed
on screens.
Section 5.0 MGFL100 Operations
Section 5.1 Locating ground faults on ungrounded DC systems
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4.3 Receiver connections

Before operating
Verify the battery in the transmitter is fully charged,
if the unit is to be operated off of battery.
Turn on the transmitter and verify the battery
indicator displays a fully charged battery
Verify the receiver batteries are good.
.
Fresh battery in the active mini CT if using NEED CLASS 3 PRODUCTx
Connection
Connect the green safety earth cable from the safety
ground on the unit to earth.
This can be a pipe or conduit that is tied to earth or an
earth stake or equivalent.
Connect the green terminal to earth.
This can be a pipe or conduit that is tied to earth or an
earth stake or equivalent.
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5.1 Locating ground faults on ungrounded DC systems

Connect the black terminal to the negative side of the
battery string.
Connect the red terminal to the positive side of the
battery string.
GCAUTION
Do not connect the equipment across voltages that exceed 600Vdc. This could cause damage to the unit.
WARNING!
Use only the provided fused test leads for connection to the battery.
WARNING!
Wear proper PPE equipment when connecting the unit. Do not place the transmitter on unstable surfaces or
on the batteries or battery rack.
If operating the transmitter off of AC then plug the
power adapter into transmitter as shown.
Then plug the power adapter into an AC outlet.
The power outlet must be from 90 to 264Vac 47 – 63Hz.
If powering off of battery the AC adapter is not required.
A fully charged battery should last approximately 4 hours.
After the MGFL100 is connected follow the procedure below.
Step 1: Turn ON the MGFL100 transmitter and allow it to boot up.
During boot up the following sequence will take place.
All LED’s will display “1888” for 3 seconds.
The firmware version will be displayed on the lower left Voltage Display and the build on the right.
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5.1 Locating ground faults on ungrounded DC systems

After the boot up is complete:
View the positive and negative voltages as displayed in the top displays.
The display with the lower voltage indicates the side of the string with the ground fault.
Step 2: Press the appropriate output button based on the side of the string that has the fault.
If the positive voltage reads lower than the negative voltage then press the “+” button.
If the negative voltage reads lower than the positive voltage then press the “-” button.
A count down will ensue while the isolation caps charge up.
Once the countdown is compete.
Turn the voltage adjustment knob clockwise until the voltage reads approximately 10V.
NOTE: If a low impedance fault to earth is present you may see the current rising while the voltage does not. In this
case adjust the voltage knob until the current display indicates approximately 10 to 25mA.
Note the readings on the top displays.
The left display will indicate the resistive value of the fault.
The right display will indicate the capacitance on the circuit.
Problem: No readings are displayed.
If OL is displayed for the resistive reading then this can indicate a high impedance fault. Continue raising the voltage
until a sable reading is shown.
There is no problem if the capacitive reading displayed is 0.00. This just means there is minimal stray capacitance on
the circuit.
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5.1 Locating ground faults on ungrounded DC systems

Step 3: Connect the receiver:
Connect the current clamp to the receiver and place the current
clamp around either the positive or negative output lead.
Whichever one is outputting the current to the fault.
Connect the sync cable between the receiver and transmitter
Note the readings on the displays.
The top display will indicate the current the fault is drawing.
The lower display will indicate the reactive current drawn by stray capacitance on the circuit.
It is the actual fault current on the top display that will be traced.
Step 4: Press the SAVE button on the receiver.
This will save 3 values.
The total current being drawn by the circuit.
The resistive current being drawn by the fault. (The fault current)
The reactive current being drawn by stray capacitance.
These values can be recalled by pressing the recall button on the receiver.
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5.1 Locating ground faults on ungrounded DC systems

Set the alarm level on the receiver to 50%. This can be either a visual only alarm or a visual and audio alarm, depending
on how it is set
If there are multiple panels then perform the procedure below. If there is only one panel skip to step 6.
Step 5: Place the CT around the wires going into each panel. (Do not disconnect the sync cable)
If the alarm is set to 50% then it will trigger if it sees a fault current in excess of 50% of the saved value.
Locate the panel drawing the fault current.
Problem: The measured value on the receiver will not stabilize.
This may indicate a level of low frequency noise on the circuit. Place the CT around both the positive and return wires
of each circuit. This will cancel out any noise on the system.
Problem: More than 1 panel indicates fault current.
This may indicate that there are multiple faults. View the fault current on the top display of the receiver for each panel.
Identify the panel drawing the highest level of fault current. This is the panel where to start the tracing process.
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5.1 Locating ground faults on ungrounded DC systems

Problem: No panels indicate fault current.
There may be multiple faults on various circuits. Lower the alarm level on the receiver from 50% to a lower value
then repeat the measurements. If no fault can be identified then the fault is before the panels. Begin tracing from the
batteries to the panels.
Step 6: Once the panel is identified, remove the cover of the panel in order to expose the circuit wires.
Place the CT around the each wires of each circuit in the panel. (Do not disconnect the sync cable)
Problem: More than 1 circuit indicates fault current.
This may indicate that there are multiple faults. View the fault current on the top display of the receiver for each panel.
Identify the circuit drawing the highest level of fault current. This is the circuit where to start the tracing process.
Problem: No circuits indicate fault current.
There may be multiple faults on various circuits. Lower the alarm level on the receiver from 50% to a lower value
then repeat the measurements. If no fault can be identified then the fault is before the panel. Begin tracing from the
batteries to the panel.
Once the circuit is identified the tracing of the fault can begin.
Step 7: Tracing the ground fault.
Be sure to have a schematic of the circuit being traced.
If using Capacitive Pick Up go to section on using the capacitive pick up.
Not using Capacitive Pick Up.
Disconnect the sync cable from the receiver.
The receiver will now only display the total current drawn by the circuit on the top display. This will be inclusive of both
the fault current and any current drawn by stray capacitance.
The alarm will now be triggered when the measured current exceeds the selected percentage of total current.
Push the recall button and note the value of the total current.
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5.1 Locating ground faults on ungrounded DC systems

Using the schematic of the circuit, start tracing the fault current through the circuit.
Move the current clamp down the circuit to trace the fault.
If the fault current is displayed on the top display of the receiver then the fault is still downstream.
If the fault current is no longer displayed on the top screen of the receiver then you have passed the fault. Use this
technique to narrow down the location of the fault until it is located.
Problem: The fault current splits along 2 different paths.
This may be due to 2 separate faults or it may be due to stray capacitance on the circuit. If you have a Capacitive Pick
Up connect it to the receiver using the sync cable. Then place both the current clamp and the Capacitive Pick Up on the
same line. The receiver will now display the fault current on the top display and leakage current on the bottom display.
Continue tracing on the circuit that is drawing the most fault current, as shown on the top display.
If you do not have a Capacitive Pick Up then you can do the same procedure above by moving the transmitter and
connecting the sync cable between the transmitter and the receiver.
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5.1 Locating ground faults on ungrounded DC systems

Problem: The Current Clamp is too large to get around the cable.
Use the active mini CT to measure the fault current on the small insulated cables. Be sure the CT has a good battery.
Since the active CT has a different size core the fault current measurement may not exactly match the larger CT. It
is recommended to re-establish a reference value by placing the active mini CT on the last point measured and then
pressing the SAVE button on the receiver. Note the saved value.
CAUTION!
Once fault is found turn off transmitter before clearing fault. Failure to do so, could trip a breaker.
Using Capacitive Pick Up.
Disconnect the sync cable from the transmitter and connect it to the Capacitive Pick Up.
Connect the Capacitive Pick Up ground cable to earth.
Then place both the current clamp and the Capacitive Pick Up on the same line. This needs to be an insulated wire. The
receiver will now display the fault current on the top display and leakage current on the bottom display. If the value
of the fault current on the top display exceeds the value of the leakage current on the bottom display then a real fault
exists on the cable. If the leakage current on the bottom display exceeds the fault current on the top display then the
cable has stray capacitance.
The alarm will trigger when the fault current exceeds the percentage set on the receiver.
Only trace the paths with the real fault current.
Push the recall button and note the total values of the fault current and reactive current.
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5.1 Locating ground faults on ungrounded DC systems

Using the schematic of the circuit, start tracing the fault current through the circuit.
Move the current clamp down the circuit to trace the fault.
If the fault current is displayed on the top display of the receiver then the fault is still downstream.
If the fault current is no longer displayed on the top screen of the receiver then you have passed the fault. Use this
technique to narrow down the location of the fault until it is located.
Problem: The Current Clamp is too large to get around the cable.
Use the active mini CT to measure the fault current on the small insulated cables. Be sure the CT has a good battery.
Since the active CT has a different size core the fault current measurement may not exactly match the larger CT. It
is recommended to re-establish a reference value by placing the active mini CT on the last point measured and then
pressing the SAVE button on the receiver. Note the saved value.
CAUTION!
Once fault is found turn off transmitter before clearing fault. Failure to do so, could trip a breaker.
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5.1 Locating ground faults on ungrounded DC systems

Section 5.2 Locating a ground faults on IT grounded systems
Connection
Connect the green safety earth cable from the safety
ground on the unit to earth.
This can be a pipe or conduit that is tied to earth or an
earth stake or equivalent.
Connect the green terminal to the AC Filter box input.
Connect the red terminal to the AC Filter box input.
Connect the output of the AC Filter between earth and
the IT circuit with the ground fault.
CAUTION!
Do not connect the equipment across voltages that exceed 600Vdc. This could cause damage to the unit.
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5.2 Locating a ground faults on IT grounded systems