Megger MJ15 Operating Manual

BM15/MJ15
Insulation Testers

USER GUIDE

GUIDE DE L’UTILISATEUR

GEBRAUCHSANLEITUNG

M

GUÍA DEL USUARIO

CONTENTS GUIDE DE L’UTILISATEUR - P.14 GEBRAUCHSANLEITUNG - S.26 GUÍA DEL USUARIO - P.38

Safety Warnings 3

General Description 4

Features and Controls 5

Working with Capacitive Loads 6

Operation

Preliminary Checks 7

Battery Replacement 7

Voltage Measurement 8

Insulation Testing 8

Choice of Test Leads 8

Using the Guard terminal 9

Specification 10

Accessories 12

Repair and Warranty 13

Before using the instrument, follow the separate instructions provided to fit
either the locking or non-locking test button.

If the locking button is fitted, extra care must be taken. See page 6.

Symbols used on the instruments

F Risk of electric shock.
G Caution, refer to accompanying documents
t Equipment protected throughout by Double Insulation

(Class II)

c Equipment complies with current EU Directives

2

GSAFETY WARNINGS

■ ‘Safety Warnings‘ and ‘Working with Capacitive Loads‘ must be read and understood before the instrument is used. Safety

precautions must be observed during use.

■ The circuit under test must be switched off, de-energised and isolated before any test connections are made.

■ Circuit connections must not be touched during a test.

■ On completion of a test, decaying voltage across the terminals is indicated on the display. Capacitive load circuits must be discharged

to below 60 V before disconnecting the test leads.

■ Capacitive load circuits should be shorted with a shorting link after discharge.

■ Remove the test leads from the instrument before opening the battery compartment.

■ Test leads and crocodile clips must be in good order, clean and with no broken or cracked insulation.

■ The instrument should not be used if any part of it is damaged.

■ U.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high energy systems. See ‘Choice of Test

Leads‘.

NOTE

The instruments must only be used by suitably trained and competent persons.

NOTE

Users of this equipment and or their employers are reminded that Health and Safety Legislation requires them to carry out valid risk assessments of

all electrical work so as to identify potential sources of electrical danger and risk of electrical injury such as from inadvertent short circuits. Where the

assessments show that the risk is significant then the use of fused test leads constructed in accordance with the HSE guidance note GS38 ‘Electrical

Test Equipment for use by Electricians’ should be used. See ‘Choice of Test Leads’.

3

GENERAL DESCRIPTION

BM15, and MJ15 testers are completely self contained instruments designed
for high voltage insulation resistance testing in the maintenance and servicing
of rotating plant machinery, transformers, switchgear and industrial
installations.

Tests can be performed at 500 V, 1000V, 2500 V or 5000 V. Insulation measuring
range is 100 kΩ to 20 GΩ and Infinity. Automatic discharge for capacitive
circuits under test is provided and decaying voltage displayed.

A guard terminal can be used to minimise the effects of surface leakage when
carrying out insulation resistance tests.

Tests are initiated by pressing the BM15 ‘Test’ button (or by turning the MJ15
generator handle). Releasing the ‘Test’ button (or ceasing handle rotation)
causes the instrument to default to ac/dc voltmeter mode, with a discharge
resistor internally connected across the terminals. This feature will give
decaying voltage indication following the testing of equipment possessing
capacitance.

The moving coil meter operates a black pointer to display the readings on a
single logarithmic black scale on a white scale-plate for clarity of reading. The
movement is resiliently mounted for field use.

A slide - in ‘Pass Band‘ overlay can be inserted over the display. Appropriate
Pass/Fail bands can be marked on these windows with a permanent marker for
‘Go / No Go’ testing.

BM15 is powered by eight 1,5 V (IEC LR6) cells.

Normal power for the MJ15 is by low voltage, hand cranked, brushless a.c
generator. Fitting the battery container supplied, with eight 1,5 V IEC LR6 cells
gives the instrument a dual (independent) supply capability. Both instruments
are fitted with a battery check range, operated by pressing the ‘Test‘ push
button. Cranking the handle too slowly (<180 RPM) results in an unstable

pointer reading. Excess handle speed cannot harm the instrument as the
output voltage is electronically regulated.

The case is robust, yet light-weight, made from a flame retardant ABS, with a
polycarbonate display window. Mounted on top of the case is a 6 position,
rotary, range selection switch and a ‘Test‘ push button.

Three recessed sockets are provided, and marked ‘+’, ‘-’ and ‘G’. These have
safety covers which open when the plugs are inserted. When inserted into the
sockets, the shrouded test lead plugs lock into position. They are released by
twisting the plug a quarter turn and pulling out.

For this reason, only the test leads supplied or suitable Megger replacement
ones should be used.

Design safety features include:

■ External voltage, a.c. or d.c., displayed.

■ Load automatically discharged at the end of a test, and decaying

voltage displayed.

■ Test leads can lock into the case to prevent accidental disconnection.

4

FEATURES AND CONTROLS

Rotary Selector

Switch

Non Locking Button

(recommended

option)

Generator Handle (MJ15)

Locking Button

(Extra care must

be taken if this

option is chosen.

See page 6)

- Terminal

Guard Terminal

+ Terminal

TO INSERT TERMINAL PLUGS, PUSH IN - TO RELEASE, TWIST A QUARTER TURN AND PULL OUT

5

WORKING SAFELY WITH CAPACITIVE LOADS

G

Circuit connections and the instrument terminals may become

hazardous when connected to Capacitive loads.

1. These instruments are designed to safely charge and discharge
capacitive loads up to 5 µF. To safeguard against malfunction however,
you are advised to take your own precautions when working with
capacitive loads. Remember that when charged, even low value
capacitors can be fatal on contact .

2. Extra care must be taken if the locking Test button is selected.

3. Circuit connections must not be touched when testing.

Do not forget to release a locked Test button and discharge

any capacitance before touching the item under test or

disconnecting the test leads.

4. Care must be taken to prevent capacitive circuits becoming
disconnected during a test, leaving the circuit in a charged state.

5. On completion of a test, the instrument indicates circuit decaying
voltage. Do not disconnect test leads until the load capacitance has
discharged to below 60 V.

6. The voltmeter and automatic discharge feature of the instruments
should be regarded as additional safety features and not a substitute
for normal safe working practice.

7. If any part of the instrument is damaged, it should not be used, but
returned to the manufacturer or an approved service organization for
repair.

6

PRELIMINARY CHECKS

Preliminary Performance Checks

The instrument will operate in any position, but best results are achieved
when the instrument is face up, on a firm level surface. This is particularly true
for hand cranked units to obtain a crank speed of >180 rev/min.

1) If battery cells are fitted, switch to Battery Check range and press the
‘Test‘ push button. Confirm that the pointer settles within the battery
symbol portion of the scale.

2) With the test leads disconnected, set the rotary selector switch to the
appropriate insulation range, press and hold down the ‘Test‘ button,
(or turn the generator handle). The meter pointer should move up the
scale briefly and then return to the ‘∞ ‘ (infinity) position on the scale.
This establishes that there is no leakage through the instrument itself.

3) Check that the test leads and crocodile clips are in good order, clean
and with no broken or cracked insulation. Connect two of the test
leads to the ‘+’ and ‘-’ terminals and ensure that their clips are not
touching anything.

4) Press the ‘Test‘ button again (or turn the generator handle) and
observe the meter pointer. The pointer should rest over the ‘∞‘
position on the scale. If it does not, the test leads may be faulty and
should be inspected more closely for damage. Replace them if
necessary.

5) Connect the test lead clips together, press the ‘Test‘ button (or turn the
generator handle) and observe the meter pointer. The meter should
read ‘0Ω‘. If it indicates infinity or a high resistance value the leads
may be open circuit and should be inspected further. Replace them if
necessary. (Shorting the leads together and obtaining a ‘0 Ω‘ reading
also indicates that the instrument is working).

Battery Replacement

GWARNING

The battery contacts are not isolated from the test leads. Remove the test

leads from the instrument before opening the battery compartment.

The cells are housed in a battery compartment in the base of the instrument.
To change the cells, use a screwdriver to remove the battery cover securing
screws and lift off the battery compartment cover. Observing the correct
polarity as marked on the battery housing, install 8 replacement IEC LR6 (AA)
cells. Replace and secure the battery compartment cover on completion.

7

OPERATION

Voltage measurement

When switched to the ‘V’ position, the instrument measures up to 600 V a.c.
to the specified accuracy of the instrument. DC voltage is also indicated on the
display, but not to the specified accuracy. When not testing (i.e. in standby
mode) and connected to a live circuit, the instruments default to voltmeter (0
to 600 Volts a.c. or d.c.) irrespective of the rotary switch position. Any voltage
present will immediately be shown. Thus indication is given that the item has
not been completely de-energized. The instrument also monitors circuit
discharge when the ‘Test‘ button is released following an insulation test on a
capacitive item, e.g. a long cable.

Insulation Testing

After connecting the test leads to the instrument and carrying out the
Preliminary Performance Checks:

1) Set the selector switch to the required test voltage. Connect the test
leads to the isolated circuit to be tested, as follows:-

(a) For insulation tests to earth (ground):- Connect either test

lead to earth (ground) or the frame of the equipment,and
the other lead to that part of the circuit to be tested.

b) For insulation tests between wires:- Connect a lead to the

core of each of the wires.

2) Press the ‘Test‘ button (or turn the generator handle).

3) The meter pointer will indicate the value of insulation resistance on
the Ω scale.

If a capacitive circuit is tested, the pointer will initially deflect towards 0 Ω and
then gradually rise to its final steady value as the capacitance is charged up to
the output voltage of the tester.

If several successive readings of ∞ (infinity) are obtained, connect the two

farthest ends of the test leads together and carry out a check on the leads. A
0Ω reading should result which double checks that the leads are not
disconnected or broken and therefore, the insulation resistance readings are
correct.

Capacitive circuits automatically discharge through the tester when the ‘Test‘
button is released. Decaying discharge voltage will be indicated on the voltage
scale. Wait a few moments for the voltage to decay to below 60 V before
disconnecting the test leads.

Do not forget to release a locked Test button, and discharge

any capacitance before touching the item under test, or

disconnecting the test leads.

Choice of Test Leads

BM15/MJ15 are supplied with three unfused leads terminated in crocodile
clips. These are the best leads to use for insulation tests on non-live circuits.
The crocodile clips ensure that any capacitive load remains connected until it
is automatically discharged at the end of a test.

GS 38 (UK Safety Authority Guidance Note) advises the use of fused test prods
if the instrument is to be used for making voltage measurements on live, high
energy circuits. These leads are available as an optional extra. See
‘Accessories’.

Fused prods must not be used for insulation testing. If the fuse should
rupture, or the prods lose contact during a test, the system under test would
remain charged without any apparent evidence of danger!

8

Using the Guard terminal (G)

For basic insulation tests and where there is little possibility of surface leakage
affecting the measurement, it is unnecessary to use the guard terminal (if the
insulator is clean and there are unlikely to be any adverse current paths).
However in cable testing, there may be surface leakage paths across the
insulation between the bare cable and the external sheathing due to the
presence of moisture or dirt. Where it is required to remove the effect of this
leakage, particularly at high testing voltages, a bare wire may be bound tightly
around the insulation and connected via the third test lead to the guard
terminal ‘G’.

The guard terminal is at the same potential as the negative terminal. Since the
leakage resistance is effectively in parallel with the resistance to be measured,
the use of the guard causes the current flowing through surface leakage to be
diverted from the measuring circuit. The instrument therefore reads the
leakage of the insulator, ignoring leakage across its surface.

Leakage Path

to ‘+’ve
terminal

to ‘G’
terminal

Tightly bound bare wire

to ‘-’ve
terminal

OPERATION BLOCK DIAGRAM

9

SPECIFICATION

Insulation

Range: 100 kΩ to 20 GΩ (also 0 Ω and ∞ )
Test Voltages (d.c.): 500 V, 1000 V, 2500 V & 5000 V
Test Voltage Accuracy: ±5% of nominal test voltages on 20 MΩ load
Test Voltage Stability: <±1% (180 r.p.m. to 240 r.p.m. MJ15)
Insulation Accuracy see page 11
Short Circuit Current: 1,5 mA ± 0,5 mA
Maximum capacitance of load: 5 µF
Interference Rejection: 1 mA rms at 50 to 60 Hz
Discharge Resistor: <500 kΩ

Voltage

Range: 0 to 600 V a.c. indication of d.c.
Accuracy: see page 11

General

Overload rating: 720 V a.c. or d.c.
Scale Length: 72 mm (96˚)
Power Supply: BM15 8 x LR6 (AA alkaline or rechargeable) cells

MJ15 Low voltage brushless Generator or 8 x LR6 (AA alkaline) cell battery
Battery life: Typically 2000 five second tests at 5 kV on 100 MΩ load
Battery Indicator: Loaded battery test

10

Safety: IEC 61010-1
Non replaceable Fuse: 1 Amp, 250 V, HBC type (F) (20 mm x 5 mm) to IEC 127/1

This fuse protects the instrument against any faults occurring when using rechargable batteries.
E.M.C: IEC 61326-1
Operational uncertainties: Refer to www.megger.com
Temperature Range:

Operating: 0˚C to 30˚C (32˚F to 86˚F) at full specification
Operating: -20˚C† to 50˚C (-4˚F to 122˚F) to temperature coefficient ±0,1% / ˚C
Storage: -25˚C to 65˚C (-13˚F to 149˚F)

Humidity: 90% RH maximum at 40˚C (104˚F)

Dimensions: 220 mm x 160 mm x 115 mm (8,9 in x 6,3 in x 4,5 in)
Weight: BM15 Approx 1.2 kg

MJ15 Approx 1,6 kg, or 1,8 kg with battery holder and cells.

Cleaning: Wipe the disconnected instrument with a clean cloth dampened with soapy water or Isopropyl Alcohol (IPA)

***Relates to transient overvoltage likely to be found in fixed installation wiring.
*Relates to transient overvoltage likely to be found in special equipment or parts of equipment, telecommunication, electronic etc.

† Note: MJ15 will operate as normal by generator at full temperature range

BM15 will require new healthy battery cells to operate as normal at -20˚C

11

ACCESSORIES

SUPPLIED WITH THE INSTRUMENT PART NUMBER

User Guide 6172-209

Battery of 8 x 1,5 V LR6 (AA Alkaline) cells

3 x 3 m HV leads 8101-181

Test Record Card (5 supplied) 6172-111

(U.S. 210949)

Carrying case with lead storage 6420-117

Slide in Pass Band overlay (5 supplied) 6121-401

AVAILABLE AS AN OPTIONAL EXTRA

5 kV Fused Prod Set 6320-240

5 kV Calibration Box - CB101 6311-077

Test Record Card (Pack of 20) 6111-216

PUBLICATIONS

‘A Stitch In Time’ AVTM21-P8B

’Lowdown on HV d.c. Testing’ AVTM22P-1

12

REPAIR AND WARRANTY

The instrument circuit contains static sensitive devices, and care must be taken
in handling the printed circuit board. If the protection of an instrument has
been impaired it should not be used, and be sent for repair by suitably trained
and qualified personnel. The protection is likely to be impaired if, for example,
the instrument shows visible damage, fails to perform the intended
measurements, has been subjected to prolonged storage under unfavourable
conditions, or has been exposed to severe transport stresses.

New Instruments are Guaranteed for 1 Year from the

Date of Purchase by the User.

Note: Any unauthorized prior repair or adjustment will automatically

invalidate the Warranty.

Instrument Repair and Spare Parts

For service requirements for Megger Instruments contact:

Megger Limited or Megger
Archcliffe Road Valley Forge Corporate Center
Dover 2621 Van Buren Avenue
Kent, CT17 9EN. Norristown, PA 19403
England. U.S.A.

Tel: [phone] Tel: [phone]

Fax: [phone] Fax: [phone]

[e-mail] [e-mail]

or an approved repair company.

Approved Repair Companies

A number of independent instrument repair companies have been approved
for repair work on most Megger instruments, using genuine Megger spare
parts. Consult the Appointed Distributor / Agent regarding spare parts, repair
facilities and advice on the best course of action to take.

Returning an Instrument for Repair

If returning an instrument to the manufacturer for repair, it should be sent
freight pre -paid to the appropriate address. A copy of the Invoice and of the
packing note should be sent simultaneously by airmail to expedite clearance
through Customs. A repair estimate showing freight return and other charges
will be submitted to the sender, if required, before work on the instrument
commences.

13

GUIDE DE L’UTILISATEUR - TABLE DES MATIÈRES GEBRAUCHSANLEITUNG - S.26 GUÍA DEL USUARIO - P.38

Avertissements relatifs à la sécurité 15

Description Générale 16

Caractéristiques et Commandes 17

Opérations sur des charges capacitive 18

Exploitation

Vérifications Préliminaires 19

Remplacement des piles 19

Mesure des tensions 20

Essai d’isolement 20

Choix des câbles d’essai 20

Utilisation de la borne de protection 21

Spécifications 22

Accessoires 24

Réparation et Garantie 25

Avant d’utiliser l’instrument, suivre les instructions séparées pour monter soit
le bouton d’essai verrouillable soit le bouton d’essai non verrouillable. Le
bouton d’essai verrouillable exige des soins supplémentaires.

Symboles utilisés sur l'instrument

F Risque de choc électrique
G Consulter le Guide de l'utilisateur
t Équipement entièrement protégé par un isolement

double (Classe II).

c Équipement conforme aux Directives en vigueur de

l'UE.

14

GAVERTISSEMENTS RELATIFS À LA SÉCURITÉ

■ Les Avertissements relatifs à la sécurité et les instructions Opérations sur des charges capacitives doivent être lus et compris

avant d’utiliser l’instrument. Les précautions de sécurité doivent être observées pendant l’usage.

■ Le circuit à tester doit être coupé, désexcité et isolé avant d’effectuer des connexions d’essai quelconques.

■ Les connexions du circuit ne doivent pas être touchées pendant l’essai

■ A la fin de l’essai, la tension de déclin aux bornes est indiquée sur l’affichage. Les circuits à charge capacitive doivent être déchargés

en dessous de 60 V avant de déconnecter les câbles d’essai.

■ Les circuits à charge capacitive doit être court-circuités avec un cavalier de court-circuit après la décharge.

■ Enlever les câbles d’essai de l’instrument avant d’ouvrir le compartiment des piles.

■ Les câbles d’essai et les pinces crocodiles doivent être en bon état, propres et avec un isolement sans cassures ni fissures.

■ L’instrument ne doit pas être utilisé si l’un de ses constituants est endommagé.

■ Les Services de sécurité Britanniques recommandent l’utilisation de câbles d’essai équipés de fusibles pour lade la mesure de la

tension des systèmes à haute énergie. Voir “Choix des câbles d’essai”.

REMARQUE

Seule une personne düment formée et compétente doit se servir de cet instrument.

NOTE

ll est rappelé aux utilisateurs de cet instrument et/ou à leurs employeurs qu’ils doivent évaluer les risques de tous les travaux électriques de manière à

identifier les sources possibles de danger électrique et les risques de blessure tels que ceux des courts-circuits involontaires. Lorsque ces évaluations
indiquent des risques importants, des câbles d’essai équipés de fusibles tels que recommandés par les Services de sécurité Britanniques doivent être

employés. Des sondes équipées de fusibles ne doivent pas être utilisées pour les essais d’isolement. En cas de rupture du fusible ou si les sondes

perdent contact pendant l’essai, le circuit testé peut rester chargé sans aucun signe évident du danger !

15