Megger MFM 10-M User manual

1
MFM 10-M
Sheath Fault Location System
USER GUIDE
Issue: B (12/2022) - EN
Article number: 128313372

2

Consultation with Megger
3
Consultation with Megger
The present system manual has been designed as an operating guide and for reference.
It is meant to answer your questions and solve your problems in as fast and easy a way
as possible. Please start with referring to this manual should any trouble occur.
In doing so, make use of the table of contents and read the relevant paragraph with great
attention. Furthermore, check all terminals and connections of the instruments involved.
Should any question remain unanswered or should you need the help of an authorized
service station, please contact:
Megger Limited Megger Germany GmbH (Baunach)
Archcliffe Road
Kent CT17 9EN
T: [phone]
F: [phone]
E: [e-mail]
Dr.-Herbert-Iann-Str. 6
D - 96148 Baunach
T: [phone] – 0
F: [phone]
E: [e-mail]
Megger Germany GmbH (Radeburg) Megger USA
Röderaue 41
D - 01471 Radeburg / Dresden
T: [phone] – 0
F: [phone]
E: [e-mail]
Valley Forge Corporate Centre
2621 Van Buren Avenue
Norristown, PA 19403 USA
T: [phone]
F: [phone]
Megger
All rights reserved. No part of this handbook may be copied by photographic or other means unless Megger
have before-hand declared their consent in writing. The information in this document is subject to change without
notice and should not be construed as a commitment by Megger. Megger cannot be made liable for technical or
printing errors or shortcomings of this handbook. Megger also disclaims all responsibility for damage resulting
directly or indirectly from the delivery, supply, or use of this matter.

Terms of Warranty
4
Terms of Warranty
Megger accept responsibility for a claim under warranty brought forward by a customer
for a product sold by Megger under the terms stated below.
Megger warrant that at the time of delivery Megger products are free from manufacturing
or material defects which might considerably reduce their value or usability. This warranty
does not apply to faults in the software supplied. During the period of warranty, Megger
agree to repair faulty parts or replace them with new parts or parts as new (with the same
usability and life as new parts) according to their choice.
This warranty does not cover wear parts, lamps, fuses, batteries and accumulators.
Megger reject all further claims under warranty, in particular those from consequential
damage. Each component and product replaced in accordance with this warranty
becomes the property of Megger.
All warranty claims versus Megger are hereby limited to a period of 12 months from the
date of delivery. Each component supplied by Megger within the context of warranty will
also be covered by this warranty for the remaining period of time but for 90 days at least.
Each measure to remedy a claim under warranty shall exclusively be carried out by
Megger or an authorized service station.
This warranty does not apply to any fault or damage caused by exposing a product to
conditions not in accordance with this specification, by storing, transporting, or using it
improperly, or having it serviced or installed by a workshop not authorized by Megger. All
responsibility is disclaimed for damage due to wear, will of God, or connection to foreign
components.
For damage resulting from a violation of their duty to repair or re-supply items, Megger
can be made liable only in case of severe negligence or intention. Any liability for slight
negligence is disclaimed.
Since some states do not allow the exclusion or limitation of an implied warranty or of
consequential damage, the limitations of liability described above perhaps may not apply
to you.

Contents
5
Contents
Consultation with Megger.......................................................................................... 3
Terms of Warranty...................................................................................................... 4
Contents ..................................................................................................................... 5
1Safety Instructions ...................................................................................... 7
1.1 Basic Notes ................................................................................................... 7
1.2 General Safety Instructions and Warnings ..................................................... 8
2Technical Description.................................................................................10
2.1 System Description.......................................................................................10
2.2 Technical Data .............................................................................................12
2.3 Connections, Controls and Display ...............................................................13
3Commissioning...........................................................................................14
3.1 Electrical Connection: Typical Procedure ......................................................15
3.2 Electrical Connection: Special Applications ...................................................17
4Operation ....................................................................................................21
4.1 Switching On the System..............................................................................21
4.2 General Operation ........................................................................................21
4.3 Security Mechanisms....................................................................................23
4.4 System Settings............................................................................................24
4.5 Operating Modes ..........................................................................................25
4.5.1 Testing the Insulation - ..........................................................................25
4.5.2 Prelocating a Fault - ...............................................................................27
4.5.3 Pinpointing a Sheath Fault - ....................................................................29
4.5.4 Burning - .................................................................................................31
4.6 Concluding the Test......................................................................................33
5Processing Log Data ..................................................................................34
6Updating the Firmware ...............................................................................35
7Maintenance and Care................................................................................36

Safety Instructions
7
1Safety Instructions
1.1 Basic Notes
This handbook contains basic instructions for the commissioning and operation of the
MFM 10-M. For this reason, it is important to ensure that the manual is always available
to authorised and trained personnel. Operating personnel should read the manual
thoroughly. The manufacturer will not be held liable for any injury or damage to personnel
or property through failure to observe the safety precautions contained in this handbook.
The specific standards and regulations in each country must also be observed.
Important instructions concerning personnel, operational and technical safety are marked
in the text as follows:
Symbol Description
WARNING
Indicates a potential danger of an electric shock that may result in fatal or
serious injury.
CAUTION
Indicates a potential danger that may lead to slight or moderate injury.
The notes contain important information and useful tips for using the
system. Failure to observe them can render the measurement results
useless.
It is important to observe the generally applicable electrical regulations of the country in
which the device will be installed and operated, as well as the current national accident
prevention regulations and internal company directives (work, operating and safety
regulations).
After working on the system, it must be voltage-free and secured against reconnection as
well as having been discharged, earthed and short-circuited.
Use genuine accessories to ensure system safety and reliable operation. The use of other
parts is not permitted and invalidates the warranty.
This system and its peripheral equipment may only be operated by trained or instructed
personnel. Anyone else must be kept away.
The system may only be installed by an authorised electrician. DIN VDE 0104 (EN 50191),
DIN VDE 0105 (EN 50110) and the German accident prevention regulations (UVV) define
an electrician as someone whose knowledge, experience and familiarity with the
applicable regulations enables him to recognise potential hazards.
Repair and maintenance work may only be performed by Megger or authorised service
partners. Megger recommends having the system tested and maintained at a Megger
service centre once a year.
Megger also offers its customers on-site service. Please contact your service centre as
needed.
Safety precautions
Labelling of safety
instructions
Working with products
from Megger
Operating staff
Repair and
maintenance

Safety Instructions
8
This device is designed for industrial use according to EN 55011. When used at home it
could cause interference to other equipment, such as the radio or television.
The interference level from the line complies with the limit curve B (living area), the
radiation level complies with the limit curve A (industrial area). Once the living area is
sufficiently far away from the planned area of operation (industrial area), equipment there
will not be impaired.
1.2 General Safety Instructions and Warnings
The operating safety is only guaranteed if the delivered system is used as intended.
Incorrect use may result in danger to the operator, to the system and the connected
equipment.
The MFM 10-M must only be operated while being properly installed in the test van.
The thresholds listed in the technical data may not be exceeded under any circumstances.
Condensation during the operation of Megger products may result in danger to persons
and devices through voltage arc-over. Prevent condensation before and during the
measuring mode by cooling the measuring systems sufficiently. The operation of Megger
products in direct contact with water, aggressive substances and inflammatory gases and
vapours is prohibited.
The MFM 10-M is built to be robust and can withstand the stresses it can expect to be
subjected to in demanding everyday use. Nevertheless, it is a precision measuring device
which needs to be treated with the appropriate care. This applies in particular to the
connection cable and the clamps, which play an important role in ensuring the device
remains safe while the results of measurements remain precise.
The system may only be operated whilst it is in perfect working condition. In the event of
damage, irregularities or malfunctions that cannot be resolved with the assistance of the
operating instructions, the system must be shut down immediately and labeled
accordingly. In such an event, the relevant management must be informed. Please
contact Megger Service immediately, to eliminate the malfunction. The system may only
be started up again once the malfunction has been eliminated.
Five safety rules
The five safety rules must always be followed when working with HV (High Voltage):
1. De-energise
2. Protect against re-energising
3. Confirm absence of voltage
4. Earth and short-circuit
5. Cover up or bar-off neighbouring energised parts
Using cardiac pacemaker / defibrillator
Physical processes during operation of high voltage may endanger
persons wearing a cardiac pacemaker or defibrillator
when near these high
voltage facilities.
Electromagnetic
radiation
Use only as intended
Procedure in the event
that the device
malfunctions

Safety Instructions
9
Fire fighting in electrical installations
•According to regulations, carbon dioxide (CO2) is required to
be used as extinguishing agent for fighting fire in electrical
installations.
•
Carbon dioxide is electrically non conductive and does not leave
residues. It is safe to be used in energized facilities as long as
the minimum distances are maintained. A CO2fire extinguisher
must be always available within electrical installations.
•If, contrary to the regulations, any other extinguishing agent is
used for fire fighting, this may lead to damage at the electrical
installation. Megger disclaims any liability for consequential
damage. Furthermore, when using a powder extinguisher near
high-voltage installations, there is a danger that the operator of
the fire extinguisher will get an electrical shock from a voltage
arc-over (due to the powder dust created).
•It is essential to observe the safety instruction on the
extinguishing agent.
•Applicable is DIN VDE 0132.
WARNING
Be careful when working with high voltage
Working on high voltage systems and equipment – especially in non-
stationary operation – requires particular care and safety-
conscious
action on the part of test personnel. VDE regulations 0104 on setting up
and operating electrical test systems, as well as EN 50191 and national
standards and regulations must be strictly adhered to.
•The System generates a dangerous voltage of up to 10. This is
supplied via a HV connection cable to the test object.
•The test system may not be operated without supervision.
•Never fail to use safety equipment or put it out of operation.
•To prevent dangerous charge accumulation, earth all metal parts in
the vicinity of the high voltage equipment.
•When high voltage is shut off, the cable under test is discharged by
an internal discharge device. This discharge device is designed for a
maximum test object capacity in compliance with the technical data.
This value must not be exceeded. The discharge device may
otherwise become damaged and charge may remain in the test
object. The cable must therefore always be discharged in
accordance with the applicable safety regulations, e.g. discharged
using a discharge rod and then be shorted before the danger zone is
accessed.

Technical Description
10
2Technical Description
2.1 System Description
For power cables and particularly for cables in the field of telecommunication, an
undamaged cable sheath is an exceptionally important prerequisite to avoid serious cable
faults which would influence the quality of supply. The conservation of the value of a cable
is also determined by the attention paid to the condition of the sheath. Irrespective of the
tests and diagnoses of the core insulation, the early recognition and elimination of sheath
faults has a stabilising effect on the operational quality of a cable system.
The sheath fault location system MFM 10-M was developed for this purpose. This device
is used for the general measurement of insulating cable sheaths and, due its numerous
applications, is regarded as the universal device for these measuring requirements.
Accordingly, the MFM 10-M permits in the easiest way the testing of cable sheaths and
prelocation and pinpointing of cable sheath faults.
To detect sheath faults, the MFM 10-M works in test mode with a voltage of up to 10 kV
(negative polarity), which also permits cables with a thicker outer sheath to be tested.
The prelocation of a detected fault takes place using the voltage drop method, in which
the current, voltage and resistance before and after the fault location are determined and
considered in relation to the cable length. The necessary measuring and calculation steps
take place automatically and, after a few seconds, the distance to the fault is displayed.
Due to the bipolar measurement, falsifying thermoelectric and galvanic influences can be
detected and mathematically eliminated.
The available current of up to 750 mA also enables the “burning” of difficult sheath faults,
if necessary.
For sheath fault pinpointing, the device provides several possibilities. One of these is a
pulsed DC output voltage, which is used in combination with an earth fault locator as the
ESG to locate the sheath fault by the step voltage method. A second method is to pinpoint
the fault with a so-called A-Frame while the MFM 10-M transmits a low frequency (3 or
4.8 Hz) signal.
Intended use
Function

Technical Description
11
The MFM 10-M combines the following features in a single device:
•Easy and comfortable operation via rotary encoder (EasyGo) and touch screen
•Bipolar measurement
•Prelocation by means of the voltage drop method with a direct measurement of
resistance
•Burning mode with manual control of the output voltage, selectable current limit
and up to 750 mA of continuous output current (max. 5 minutes)
•Pinpointing with pulsed DC voltage
•Fully automatic measurement
•Independent from the resistance of supplementary wires and test leads
•Detection of incorrect hook-up to cable under test
•Fault locating of high resistive faults inside cables
•Detection, storage and data recording of fast processes (wipers, breakdowns)
•Logging and log data export to Easyprot software via USB
•Integrated discharge with active overload protection
•Wide range input for the voltage supply
The scope of delivery of the system includes the following:
•MFM 10-M
•2 x measuring leads (incl. aligator clips), 0.5 m
•USB flash drive with Easyprot software
•Manual
Check the contents of the package for completeness and visible damage right after
receipt. In the case of visible damage, the device must under no circumstances be taken
into operation. If something is missing or damaged, please contact your local sales
representative.
The following optional accessories can also be ordered from Megger Sales:
Accessory Description Item number
Connection set for HV
cable terminations
Connection set with 8 larger connection
clamps (e.g.
for HV cable terminations) and
connection cables 2 m in length (for the
wiring at the far end of the cable)
118308004
Features
Scope of delivery
Check contents
Optional accessories

Technical Description
12
2.2 Technical Data
The MFM 10-M has the following parameters:
Parameter Value
Output voltage 0 … 10 kV DC, bipolar
Output current 750 mA at 0.4 kV,
200 mA at 0.5 … 1.5 kV,
60 mA at 5 kV,
30 mA at 10 kV
Maximum permitted capacity of
the test object
10 µF
Test voltage 0 … −10 kV
Prelocation
•Method
•Measuring accuracy
Voltage drop method (fully automatic)
±0,1%
Pinpointing
•Voltage
•Duty cycle
•Pulse rates
0 … -10 kV DC, pulsed
selectable
0.5:1 / 1:2 / 1.5:0.5 / 1.5:3.5
4,8 Hz („vLoc“ A-frame of VivaxMetrotech)
3 Hz („SFL2“ A-frame of Metrotech)
Power supply (rated voltage) 88 V … 264 V, 50 / 60 Hz
Power consumption max. 500 VA
Display 320 x 240 pixel LCD, LED backlight
Interfaces USB port
Memory 2 GB flash memory for system and user data
Data logging with a USB stick
Operating temperature −25 °C ... +55 °C
Storage temperature −40 °C ... +70 °C
Operating humidity max. 93% relative humidity
Dimensions (W x H x D) 483 x 266 x 420 mm
Weight 17 kg
Protection class (according to
IEC 61140 (DIN VDE 0140-1))
I (protective earthing)
Protection rating (according to
IEC 60529 (DIN VDE 0470-1))
IP40

Technical Description
13
2.3 Connections, Controls and Display
The MFM 10-M has the following connections, controls and display:
Element Description
Touch-screen display
USB port
On/off push-button
HV “interlock” key switch
“HV ON” push-button
“HV OFF” push-button
Rotary encoder

Commissioning
14
3Commissioning
WARNING
Safety instructions for commissioning
•
The safety guidelines for the operation of mobile testing systems often
differ from one network operator to another and are frequently subject
to national regulations (such as the German BGI 5191). Before the
measurement session, find out what the applicable guidelines are and
follow the rules set out therein precisely, in respect of the organisation
of work and the commissioning of the mobile test system.
•While setting up the test van, the instructions and safety precautions
contained in the respective manual must be observed.
•Before connecting the test object, always follow the general safety
instructions and the five safety rules in particular (see page 8).
•When setting up and connecting the device, make sure that it does
not impair the function of any other systems or components. If other
systems and components have to be modified in order to set up and
operate the device, be sure to reverse these actions when the work is
finished. Always take the special requirements of these systems and
components into account and only carry out work on them after
consulting and obtaining approval from whoever is in charge of them.
•All cables which are out of operation and not tested must be shorted
and earthed.
•The protective earth connection of the test van must always be
connected to a suitable earthing point (e.g. station earth).
•Since the voltage applied to the test object can assume values that
pose a risk of incidental contact, the cable ends must be shielded in
accordance with VDE 0104 to avoid this. When doing so, be sure to
take all cable branchings into account.

Commissioning
15
3.1 Electrical Connection: Typical Procedure
The following figure shows the simplified connection diagram:
Although the illustrated complex connecting method is only required when
prelocating a fault, it works for all operating modes. Under certain conditions
also simplified / special connecting methods can be applied (see page 17).
Connection diagram
Observe position / order

Commissioning
16
Connect the system in the following order:
Step Description
1 Establish the protective earth connection and the auxilliary earth connection of
the test van.
For detailed instruction on how to establish the connections, please
refer to the test van’s operating manual.
2 Unwind the cable from the special MFM 10-M cable reel.
3 Connect the yellow connection lead to the earthing busbar of the cable
system that is to be tested.
4 Connect the black connection lead to the shield of the cable that is to be
tested.
5 The prelocation using the voltage drop method requires two healthy auxiliary
conductors.
Connect the white connection lead to the phase conductor of the cable that is
to be tested.
Connect the green connection lead to the phase conductor (auxiliary
conductor) of an additional cable that is part of the system.
Instead of the phase conductor, an intact shield can also serve as the
auxiliary conductor.
6 At the far end of the cable, connect the auxiliary conductors with the shield of
the cable that is to be tested.
To achieve optimal results during prelocation, you should use
separate connection clamps to connect the auxiliary conductors to the
shield.
Make sure the contact is of good quality (remove or clean any dirt or
corroded surfaces).
7 As the output voltage is applied between shield and earth, the earthing of the
shields and the auxiliary conductors must be removed!
If there are any voltage transformers, they must be separated from the test
object. Make also sure that there is no indirect contact to earth, e.g. through
joints.
8 Connect power supply (power grid or generator system) to the test van.
For detailed instruction on how to establish power supply, please
refer to the test van’s operating manual.
Procedure

Commissioning
17
3.2 Electrical Connection: Special Applications
If the MFM 10-M is only to be used in testing, burning or pinpointing mode, an
auxiliary conductor is not necessarily needed. Accordingly, in these operating modes, the
wiring at the far cable end can be omitted while all connecting leads except of the yellow
one have to be connected to the conductor under test as shown in the picture below:
When testing cable systems for which the probability of a fault is very low, all conductors
to be tested can be bridged and tested in a single step, without having to reconnect.
In this procedure, the capacity of the measured object is the sum of the capacities of all
the connected conductors and, of course, must not exceed the maximum capacity of 10
µF! If the test result indicates that one of the conductors is affected by leakage fault, the
electrical connection must be corrected and each conductor individually tested.
Simplified connection
methods

Commissioning
18
This method of prelocating a fault should only be used when absolutely unavoidable, e.g.
when no second, fault-free auxiliary conductor is available.
The precision will be impaired in the same way as the simple Murray loop bridge is
impaired by the effects of the contact resistances, but should remain comparatively
higher.
Furthermore, the auxiliary conductor must be fault-free. It is connected as follows:
For this type of prelocation, the double cable length must be entered!
If both conductors are not of the same type (cross section, conductor material,
length), they should be treated like a mixed cable with two sections (with the
faulty conductor being the first section) during prelocation.
Prelocation using one
auxiliary conductor only

Commissioning
19
Using the MFM 10-M, it is possible to locate non-earthed faults in inner conductors. In MV
cables with standard cross sections in particular, faults with a fault resistance of several
MΩ can be prelocated to within a few metres.
In these cases (especially on very high-impedance inner conductor faults) the correct
connection method has a significant effect on the accuracy of the measurement.
For a fault between the inner conductor and the shield, the faulty cable and the fault-free
auxiliary conductor (green / white) must be connected as follows:
For a fault between two adjacent inner conductors of a multicore cable, the yellow
connection cable must be connected to the second, faulty inner conductor which must, in
turn, be connected to earth.
Prelocation of non-
earthed inner
conductor faults
Observe position / order
Observe position / order

Commissioning
20
Under certain circumstances, prelocation can also be performed on a spooled cable which
allows the MFM 10-M to be connected directly to both ends of the cables.
To prelocate an inner conductor fault, the cables only have to be connected to the two
faulty conductors as shown in the following illustration (shield/inner conductor or inner
conductor/inner conductor):
Prelocating a sheath fault, in contrast, requires a conductive sheath with is used as a
return conductor for the fault current. The yellow connection cable must, in this case, be
connected to the earthed outer sheath. The contact for the conductive sheath must be
established very carefully (e.g. using copper mesh tape which is looped tightly around the
sheath several times and pressed securely in place using pipe clamps or cable ties).
The reference point for the measured fault distance is the end of the cable to
which the yellow line is connected.
For this application, the conductive outer sheath of the cable is used as a return path for
the fault current. Accordingly, the outer sheath must be earthed at as many places as
possible to ensure the fault current can flow out of the pipe and into the ground. An earth
point like this can e.g. be established with the aid of copper mesh tape (see above).
Prelocation when there
is direct access to both
ends of the cable
Prelocation for cables
with a conductive outer
layer installed in pipes
Observe position / order