Megger LT300 User manual

LT300 High current loop tester

User guide

GSAFETY WARNINGS

■Safety Warnings and Precautions must be read and

understood before the instrument is used. They must be

observed during use.

■The earth loop impedance test creates a temporary low resistance

path between live and earth for the duration of the test. This is

particularly hazardous with both an instrument and an installation

fault.

Working practices and hazard avoidance must take care of this

risk

■Continuity of protective conductors and earthed equipotential

bonding of new or modified installations must be verified before

carrying out an earth fault loop impedance tests.

■Circuit connections and exposed metalwork of an installation or

equipment under test must not be touched in case of the

presence of hazardous touch voltages

■Do not leave the instrument connected to the mains supply when

not in use.

■Ensure that hands remain behind guards of probes/clips when

testing.

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

■Test leads, probes and crocodile clips must be in good order,

clean and with no broken or cracked insulation.

■The battery cover must be in place whilst conducting tests.

■Some national safety authorities recommend fused leads for

voltage measurement on high energy systems. If RCD or Loop

tests are made it may cause the fuse to rupture, and so they must

be used with caution on voltage testing.

NOTE

THE INSTRUMENT MUST ONLY BE USED BY SUITABLY

TRAINED AND COMPETENT PERSONS.

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 inadvertent

short circuits

Symbols used on the instrument:

FCaution: risk of electric shock

GCaution: refer to accompanying notes

tEquipment protected throughout by Double Insulation

(Class II)

cEquipment complies with relevant EU Directives

Equipment complies with ‘C tick’ requirements

Lid open/closure

1. Open lid by lifting up front panel tab (1).

2. Fold-away underneath instrument (2 & 3) and click into retaining

slot (4).

N1337

Digital Display Layout

Operation

Important:

Operational voltage range of the LT300 is:

50 V to 550 V.

Operational frequencies of the LT300 are:

16 Hz, 33 Hz, 50 Hz/60 Hz, 125 Hz and 400 Hz (400 V @ 16 Hz).

Auto-Power down:

The instrument will switch off automatically after 4 minutes of no

use. To switch on again press the TEST button or change range.

Test lead check:

Only use the specified test leads. The test leads supplied have an

internal resistance of 0.06 Ω.The LT300 allows for this so accurate

measurements are obtained at the probe tips.

Before each use of the instrument, inspect the test leads, prods and

crocodile clips to confirmthat their condition is good, with no

damaged or broken insulation.

On test leads fitted with an outlet plug and flying leads, never

connect test probes, clips, pins or other objects to the 3 lead plugs

because of the danger of electrocution. These leads should only be

used by a competent person.

Supply Category rating:

The LT300 is designed for use on 300 V CAT IV Phase to Earth and

Temperature

warning Fuse

blown Terminal

voltage

>330 V

Noise

symbol Low battery

warning

System Frequency

550 V Phase to Phase applications (400 V @ 16 Hz).

Loop Testing

Select either the 20 Ωor 200 Ωmeasurement range

depending on:

1. The required measurement resolution 0.01 Ω(20 Ωrange) or

0.1 Ω(200 Ωrange).

2. The anticipated loop resistance.

3. The required test current taken from the Voltage/Resistance table

below.

Test current varies with supply voltage:

20 Ωrange: 200 Ωrange:

@ 550 V supply = 27 A @ 550 V supply = 2.7 A

@ 230 V supply = 12 A @ 230 V supply = 1.2 A

@115 V supply = 6.0 A @ 115 V supply = 0.6 A

@50 V supply = 3 A @ 50 V supply = 0.3 A

Phase-Earth loop measurement

This test is designed for non-RCD protected circuits.

The loop tester will operate over a supply voltage of: 50 V to

550 V (400 V @ 16 Hz).

1. Set the instrument to the 20 Ωrange for 0.01 Ωresolution or the

200 Ωrange for 0.1 Ωresolution. Display will show 000 V~

2. Connect the RED (PHASE) lead to the RED socket on the

instrument and the GREEN (EARTH) lead to the GREEN/BLUE

socket (alternatively use the Mains plug test lead Red and Green

connections).

3. Connect the RED lead to Phase and the GREEN lead to Earth (or

connect the mains plug to the wall socket).

4. The supply voltage is displayed and the appropriate system

frequency indicator displayed.

5. Within 5 seconds the loop test starts automatically and the

measured loop value is displayed.

The test can be repeated by pressing the [TEST] button.

Bonded Metalwork Testing

Repeat the above test but with the Green lead connected to the

exposed metalwork.

Phase-Neutral loop measurement

1. Connect the RED (PHASE) lead to the RED socket on the

instrument and the GREEN (EARTH) lead to the GREEN/BLUE

socket (alternatively use the mains plug test lead RED and BLUE

connections).

2. Connect the RED lead to Phase and the GREEN lead to Neutral (or

connect the mains plug to the wall socket).

3. The supply voltage is displayed and the appropriate system

frequency indicator displayed.

4. Within 5 seconds the loop test starts automatically and the

measured loop value is displayed.

The test can be repeated by pressing the [TEST] button.

Phase-Phase loop impedance

1. Connect the RED (PHASE) lead to the RED socket on the

instrument and the GREEN (EARTH) lead to the GREEN/BLUE

socket.

2. Connect the RED lead to Phase1 and the GREEN lead to Phase 2.

3. The supply voltage is displayed and the appropriate system

frequency indicator displayed.

4. The results are displayed as per Phase - Neutral testing above.

Warning indicators

Over range

If the measured loop impedance exceeds the full scale value, the

display will show “>1.” . This is displayed if:

1. Measurement >19.99 Ωon the 20 Ωrange or >199.9 Ωon the

200 Ωrange. OR

2. A dangerous voltage has been detected on the protective earthing

conductors or bonded metalwork during test. This is normally

due to poor or faulty earthing system.

Over-voltage

The warning triangle will FLASH if the input voltage exceeds 330 V.

This is advisory.

If the voltage exceeds 550 V the warning triangle will be permanently

displayed. Remove source of over-voltage immediately.

Overheating

The thermometer symbol will flash if the instrument is getting hot.

Overheating is shown by a permanently displayed symbol.

Testing is inhibited when the temperature symbol indicator is on.

Voltage Measurement

The voltmeter is designed for AC applications only, up to 550 V

(400 V @ 16 Hz)

Frequency indicators

The frequency indicator shows the system frequency the circuit is

using. It is intended as a guide only. For accurate frequency

measurement a suitable test instrument should be used.

Nominal frequency bands are:

15 Hz to 18 Hz 40 Hz to 70 Hz 260 Hz to 490 Hz

Additional frequency Bands:

33 Hz (29 Hz to 37 Hz) 125 Hz (100 Hz to 142 Hz)

The appropriate indicator is displayed for the supply system

frequency. Testing is only possible when one of the indicators is

displayed.

Battery replacement

Low battery voltage is indicated by the symbol in the display.

When displayed, loop testing is still possible however the voltmeter

accuracy may be affected.

Toreplace batteries switch off instrument and disconnect test leads

from the circuit under test.

Remove the battery cover and replace the batteries. Use 8 x 1.5 V AA

(LR6) Alkaline dry cells or NiMH rechargeable cells. Do not mix old

and new batteries.

Warning: OBSERVE CORRECT POLARITY.Incorrect battery

polarity could cause batteries to leak and damage the instrument.

Fuse replacement

Ablown fuse is indicated by the fsymbol in the display.

To replace the fuse remove battery cover and replace fuse

with type:

7A(F) HBC 50 kA 600 V.

Cleaning: Disconnect the instrument and wipe with a clean cloth

dampened with soapy water or Isopropyl Alcohol (IPA).

SPECIFICATION

Only values with tolerances or limits are guaranteed data. Values

without tolerances are for information only.

Service error is less than ±30% from 0.4 Ωto 200 Ω

16 Hz 50/60 Hz 400 Hz

Voltage measurement

Range: 0Vto 550 V (400 V @ 16 Hz)

Accuracy: ±5% ±2 V

Range: 16 Hz to 400 Hz

Loop Impedance measurement Phase to Earth

Supply: 50 V to 300 V (400 V @ 16 Hz)

Loop impedance measurement Phase to Phase

Supply: 50 V to 550 V (400 V @ 16 Hz)

When testing close to the source transformer, a system phase angle

of 18° will cause an additional error of -5%. A system phase angle of

30° will cause an error of -16%.

Nominal test currents :

20 Ωrange 200 Ωrange

@ 550 V supply = 27 A @ 550 V supply = 2.7 A

@ 230 V supply = 12 A @ 230 V supply = 1.2 A

@ 115 V supply = 6.0 A @ 115 V supply = 0.6 A

@50 V supply = 3 A @ 50 V supply = 0.3 A

Loop accuracy 20 Ωrange: 0to 19.99 Ω±5% ±0.03 Ω

Loop accuracy 200 Ωrange:0to 199.9 Ω±5% ±0.5 Ω

Frequency: 16 Hz, 33 Hz, 50/60 Hz, 125 Hz, 400 Hz

Loop ranges: in accordance with EN 61557-3

Environmental

Operating Range: -10°C to +60°C

Operating Humidity: 90% RH at +40°C max.

Storage Range: -25°C to +70°C

Environmental protection: IP54 weatherproof

Battery: 8x1,5 V cells IEC AA (LR6) alkaline or NiMH rechargeable

Battery Life: 60 hours

Fuse: 7A (F) 600 V, 32 x 6 mm HBC 50 kA minimum

Dimensions: 203 mm x 148 mm x 78 mm

Weight: 980 gms

Safety

Meets the requirements of EN61010-1, 300 V Cat IV phase to earth

and 550 V Phase to Phase applications. Refer to safety warnings

supplied.

E.M.C

In accordance with IEC61326 including amendment No.1

Loop accuracy

Complies with the following parts of EN61557; Electrical safety in

low voltage systems up to 1000 V a.c. and 1500 V d.c.- Equipment for

testing, measuring or monitoring of protective measures:

Part1 - General Requirements Part3 - Loop resistance

Megger Limited

Archcliffe Road, Dover

Kent CT17 9EN England

T+44 (0)1 304 502101

F+44 (0)1 304 207342

Euksales@megger.com

Megger

Z.A. Du Buisson de la Couldre

23 rue Eugène Henaff

78190 TRAPPES France

T+33 (0)1 30.16.08.90

F+33 (0)1 34.61.23.77

Einfos@megger.com

Megger Pty Limited

Unit 26 9 Hudson Avenue

Castle Hill

Sydney NSW 2125 Australia

T+61 (0)2 9659 2005

F+61 (0)2 9659 2201

Eausales@megger.com

Megger Limited

110 Milner Avenue Unit 1

Scarborough Ontario M1S 3R2

Canada

T+1 416 298 9688 (Canada only)

T +1 416 298 6770

F +1 416 298 0848

Ecasales@megger.com

Megger products aredistributed in 146 countries worldwide.

This instrument is manufactured in the United Kingdom.

The company reserves the right to change the specification or design

without prior notice.

Megger is a registered trademark

Part No. LT300_6172-969_UG_en_V02 0107

www.megger.com

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