Megger MIT510/2 User manual

M
MIT510/2
5kV Digital Insulation Tester
USER MANUAL

2
NOTE
THE INSTRUMENT MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS.
Users of this equipment and/or their employers are reminded that National 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 inadvertent short circuits. Where the assessments
show that the risk is significant then the use of fused test leads may be appropriate.
GSAFETY WARNINGS
Safety Warning must be observed during use.
nThe circuit under test must be switched off, de-energised, isolated and checked to be safe before insulation test connections are made. Make sure the
circuit is not re-energised whilst the instrument is connected.
nCircuit connections must not be touched during an insulation test.
nAfter completing a test, capacitive circuits must be completely discharged before disconnecting the test leads. Capacitive charges can be lethal.
nTested items should be firmly shorted out with a shorting link, after discharge, until required for use. This is to guard against any stored dielectric
absorption charge subsequently being released thereby raising the voltage to potentially dangerous levels.
nThe voltage indicator and automatic discharge features should be regarded as additional safety features and not a substitute for normal safe working
practice.
nIt is rare, but in certain circumstances, breakdown of the circuit under test may cause the instrument to terminate the test in an uncontrolled manner,
possibly causing a loss of display while the circuit remains energised. In this event, the unit must be turned off and the circuit discharged manually.
nTest leads, including crocodile clips, must be in good order, clean and with no broken or cracked insulation.
nThe instrument should not be used if any partof it is damaged.
nInsulation testing in wet weather conditions might be hazardous. It is recommended that this instrument is not used in these circumstances. If this is
unavoidable, the user must takeall necessary precautions.
nThis instrument is not intrinsically safe and must not be used in hazardous atmospheres.

Symbols used on the instrument are:
FCaution: risk of electric shock
GCaution: refer to accompanying notes
tEquipment protected throughout by Double
Insulation (Class II)
cEquipment complies with current EU directives.
Terms used in this manual
The word must is used to indicate that the instructions following should
be followed under all circumstances. Failure to follow these instructions
could result in damage to the instrument and / or a hazard to the operator.
The word should is used to indicate that the instructions indicate best
practice.
Cleaning
Disconnect the instrument and wipe it with a clean cloth slightly damped
with soapy water or Isopropyl alcohol (IPA).
CONTENTS
3
Safety warnings 2
Cleaning 3
Introduction 4
Power lead and charging 4
Instrument controls and indicators 5
Power On/Off button 6
Test voltage sand tbuttons 6
Test start/stop button 6
Ω/I button 6
Bbutton 6
High voltage warning LED 6
Line input present LED 7
Test terminals 7
Guard terminal 7
Factory programming socket 7
Battery bar graph 8
Voltage at terminals 8
Timer indicator 8
Digital display 8
Analogue display 8
Capacitance display 9
Time constant 9
Measurements above 100 GΩ9
Circuit block diagram 10
Specification 10
Accessories 12
Repair and Warranty 13

If the power lead supplied is not suitable for your type of mains outlet, do
not use an adaptor. Always use a power lead fitted with the correct plug.
NB: A plug severed from the power lead is a hazard if plugged into a live
socket. Severed plugs must be destroyed immediately.
The instrument is fitted with a two-pin IEC60320 power inlet. Most power
leads are made with three-core cable so the ground connection will not
be used.
Power lead cable colour coding:
International USA
Earth/Ground Yellow/Green Green
Neutral Blue White
Live (Line) Brown Black
If using a fused plug ensure it is fitted with a 3 Amp fuse.
The instrument can be powered from 95 - 240 V rms, ±10% 50/60Hz.
With power connected the battery will charge as long as a test is not in
progress. The Power On/Off button has a green LED which illuminates
when mains power is present.
For best battery lifetime, charge the battery after each use. A completely
exhausted battery will take 14 hours to recharge.
INTRODUCTION POWER LEAD AND CHARGING
4
The MIT510/2 is a compact microprocessor controlled high voltage d.c.
insulation tester, powered by internal rechargeable battery or mains
supply. A comprehensive LCD display shows resistance, current,
capacitance, voltage and timer measurements digitally, with resistance
being shown in analogue as well.
Features include:
nResistance or current measurement- front panel selectable
nResistance measurement range - 10 kΩto 15 TΩ
nFront panel selectable test voltages - 250 V, 500 V, 1000 V, 2500 V, 5000 V
nIncremental timer (minutes & seconds) – measures during test
nLoad capacitance measurement – displayed at end of a test
nLCD backlight – front panel selectable
nBattery level/charging indicator
nMains (line) input presence LED
nHigh voltage warning flashing LED shows when greater than 50 V
present on test leads
nHigh voltage warning LCD "flash" shows when greater than 50 V
present on test leads
n8hours continuous testing on full charge.

8. Tostop the test press TEST button.
9. Timer will stop.
10. Analogue display shows insulation resistance.
11. Digital display shows resistance or current selected by pressing Ω/I
button.
12. Load capacitance will be calculated and displayed after the end of
the test.
13. Time-constant will be displayed after the end of the test.
INSTRUMENT CONTROLS AND INDICATORS
5
1. Check connections to load - see SAFETY WARNINGS
2. To turn on, press Power On/Off button and release after display
responds. The instrument first will perform a self-check during which
Ini is displayed. After Ini disappears the instrument is ready for use.
3. Check voltage at terminals display to be sure the load is safe to
energise.
4. Set test voltage required with Vsand Vtbuttons.
5. To start a test, press TEST button and release after red LED shows. If
external voltage at terminals <50 V, testing starts.
6. TEST button red LED and display warning symbols will flash during a
test to show high voltage present at terminals.
7. Timer will count up from zero during test.
Voltage at terminals
Battery level
Warning
voltage at
terminals
Digital
display
Timer
Analogue
display
Warning
voltage at
terminals
Capacitance display
Time constant

Power On/Off button
The instrument will only turn on if this button is pressed, held and then
released when the display responds. The instrument will not turn on if the
button is released before the display responds, or if the button is held
down for too long. This is a safety feature to prevent the instrument being
inadvertently turned on.
The instrument is turned off either by pressing the button again, or if the
instrument is running on the battery, by timing out after 10 minutes of
inactivity.
Upon switching the instrument on the display will first show ‘Ini’ while it
undergoes a self-checking routine. When Ini disappears, the instrument is
ready for use.
Test voltage sand tbuttons
Using these buttons one of five test voltages can be selected: 250 V, 500 V,
1kV, 2.5 kV, and 5 kV. The selected voltage is shown on the display.
If there is an external voltage greater than 50 V on the test leads, the high
voltage warning indicators are flashed, and the display shows this voltage
instead. The instrument will not perform a test if this voltage is greater
than 50 V.
During a test the display shows the actual voltage on the test leads. If the
test voltage is changed during a test, the new test voltage will be displayed
briefly.
When the test has stopped, the display continues to show the voltage
present on the test leads. Pressing either test voltage sor tbutton will
then display the test voltage immediately before the end of the test.
Test start / stop button
Atest will only start if this button is pressed, held and then released as
soon as the red high voltage warning indicator LED lights. The LCD and
red LED high voltage warning indicators flash when the test starts.
Atest will not start if the button is released before the red LED shows, or
pressed continuously for longer than 5 seconds. This is a safety feature to
prevent a test being started inadvertently.
The presence of a voltage greater than 50 V on the test leads is indicated
with flashing high voltage warning indicators. Testing is disabled if the
external voltage exceeds 50 V.
Testing will stop if the test start / stop button is pressed again.
When a test has finished, the instrument will discharge the load, which
may take some time. The operator must always check the load has been
discharged before touching the test leads.
Ω/I button
Pressing this button toggles the digital display between the insulation
resistance and current.
Bbutton
Pressing this button toggles the display backlight on and off.
High voltage warning LED
This is a red LED next to the TEST button on the front panel. The LED
flashes when the voltage on the test inputs exceeds 50 V.
6

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. The display will show ‘FUS’ if the internal guard terminal fuse is
found to have blown. The instrument must be switched off to clear the
message before further testing is permitted. The fuse should be replaced
by an authorised repairer.The instrument may be used in the mean time if
the guard terminal not used. Refer to notes regarding measurements
above 100 GΩon page 9.
Factory programming socket
This is a 9 pin socket under the hinged cover and is not for customer use.
Line input present LED
This is a green LED next to the power On/Off button on the front panel. It
is illuminated whenever the mains power is connected.
Test terminals
There are three test terminals marked +, - and G. These terminals are
designed to accept only the test leads supplied. Shutters across the
terminals prevent accidental ingress of dirt and other objects. Test lead
plugs interlock with the shutters and are released by rotating the test lead
plug a quarter turn.
The Guard terminal is explained below and is only used in cases where
surface leakage currents need to be eliminated. Most measurements use
just the + and – terminals. The instrument’s internal voltage generator
drives the + terminal with respect to the – terminal, current being
measured in the – terminal.
Guard terminal
For basic insulation tests and where there is little possibility of surface
leakage affecting the measurement, it is unnecessaryto use the guard
terminal i.e. if the insulator is clean and there are unlikely to be any adverse
current paths. However in cable testing for example, 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’.
7

8
instrument will not perform a test. The high voltage warning indicators
flash, and the beeper sounds, to warn of the hazard until the external
voltage becomes less than 50 V.
When testing, the voltage displayed is the voltage present at the test
terminals of the instrument. If the test voltage is changed, by pressing
either of the test voltage sand tbuttons during a test, the new test
voltage is displayed momentarily.
After testing, the voltage displayed is the voltage present on the terminals.
To see what the voltage was immediately prior to the end on the test,
press either test voltage sor tbuttons.
Timer indicator
The timer shows minutes and seconds. At the start of a test the timer will
start from zero and at the end of a test it will stop. The duration of the last
test remains on the display until another test is started.
Digital Display
The digital display shows the resistance or current being measured during
a test. The Ω/I button toggles between the two. After a test the display
shows the last measurement made until the timer or voltage test settings
are changed or the test start/stop button is pressed.
Analogue display
This simulates an analogue meter movement to give the user a better
"feel" for how a measurement is progressing. The analogue display shows
resistance only.
Battery bar graph
This is a battery symbol on the LCD display comprising 4 pairs of
segments. The battery is monitored continuously when the instrument is
turned on. The charge remaining in the battery is shown in the table
below.
Fully charged battery
50% charged battery
Tests cannot be started, and the batterymay fail
at any time.
Symbol flashes when there is not enough charge
for a test. The instrument then turns itself off
When mains power is present the indicator shows the battery is being
charged by animating the segments of the bar graph.
Voltage at terminals
The test voltage will default to that selected in the previous test. If the
instrument has been switched off since the previous test, the test voltage
defaults to 250 V.
If there is an external voltage greater than 50 V present, this will be
displayed regardless of changes made to the test voltage. In this case the

Capacitance display
At the end of a test the capacitance of the circuit under test is calculated
and displayed. After a test the display shows the last measurement made
until the Vs, Vt,or TEST buttons are pressed.
Time constant:
At the end of a test the time constant of the circuit under test is calculated
and displayed. After a test the display shows the last measurement made
until the Vs, Vt,or TEST buttons are pressed.
Measurements above 100 GΩ
Measurements up to 100 GΩcan be made without any special precautions,
assuming that the test leads are reasonably clean and dry. The guard lead
can be used to remove the effects of surface leakage if necessary. When
measuring resistances above 100 GΩ, the test leads should not be allowed
to touch each other, or any other object since this will introduce leakage
paths. Sharp points at the test lead connections should also be avoided
since this will encourage corona discharge.
The output is isolated, and so will float relative to ground such that the
positive terminal is at plus half of the test voltage, and the negative terminal
is at minus half of the test voltage with respect to ground. Leakages
therefore occur between the positive terminal and ground, between the
negative terminal and ground, and directly between the positive and
negative terminals. These leakages have a significant effect and can occur
through the air itself.
If the guard lead is connected to ground, then since the negative terminal
is at the same voltage as the guard terminal, the leakage into the negative
terminal will be considerably reduced. This will improve accuracy because
the current flowing into the negative terminal is measured by the
instrument and used to calculate resistance. This technique is only
permissible if the item under test is isolated from ground. “Isolated” in
this context means insulated by a resistance of at least 5 MΩfor the
positive terminal, or at least 10 kΩfor the negative terminal.
Conversely, if the positive terminal is grounded, then the negative terminal
will be at a voltage equal to the test voltage relative to ground, which will
result in an increase in leakage current, and worsening of measurement
accuracy.
When making measurements above 100 GΩtherefore, the user should
ground the Guard Lead where possible, otherwise parallel leakage paths
may occur.
Alternatively, screened leads are available as an optional accessory from
Megger. The lead to the negative terminal is fully screened. The screen is
plugged into the Guard terminal, diverting any stray leakage currents. This
considerably improves measurements made with a floating output, where
the leads might touch each other or anything other than the test piece.
9
+Test V
2
-Test V
2
Ground
+-
+Test V 0V
Ground
Guard
+-

10
Voltage input range
85-265 V rms, 50/60Hz, 60 VA
Battery life
Typical capacity is 6 hours continuous testing at 5 kV with a 100 MΩload
Test voltages
250 V, 500 V, 1000 V, 2500 V, 5000 V
Accuracy (23°C, 5 kV)
±5% @ 1 TΩ
±20% @ 10 TΩ
Guard
2% error guarding 500 kΩleakage with 100 MΩload
Display range
Digital display (3 digits) 10 kΩto 15 TΩ
Analogue display 100 kΩto 1 TΩ
Short circuit/charge current
3mA @ 5 kV
Capacitor charge time
<3 seconds per µF at 3mA to 5 kV
Capacitor discharge time
<120 ms per µF to discharge from 5000 V to 50 V
Capacitance measurement (500 V minimum test voltage)
10 nF to 50 µF (dependent on test voltage)
Capacitance measurement accuracy (23°C)
±5% ±5 nF
Circuit block diagram
For 5 kV instruments C1 = 47 nF, R1 = 50 kΩ, R2 = 40 kΩ
For 10 kV instruments C1 = 15 nF, R1 = 156 kΩ, R2 = 110 kΩ
SPECIFICATION
100 MΩ
R1 R2
C1
Volts
Fuse
Cable
under
test
+
+
-
-
G
Discharge
resistance
Current
Ref
Voltage
control
Current
Limit
High
voltage
source