Megger LT300 Manual de usuario

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.

CAT II - Measurement category II:

Equipment connected between the electrical outlets and the user’s

equipment.

CAT III - Measurement category III:

Equipment connected between the distribution panel and the

electrical outlets.

CAT IV - Measurement category IV:

Equipment connected between the origin of the low-voltage

mains supply and the distribution panel.

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:

F Caution: risk of electric shock

GCaution: refer to accompanying notes

tEquipment protected throughout by Double Insulation

(Class II)

c Equipment 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).

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 confirm that 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

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

Temperature

warning

Fuse

blown

Terminal

voltage

>330 V

Noise

symbol

Low battery

warning

System Frequency

Loop Testing

Select either the 20 Ω or 200 Ω measurement range

depending on:

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

0.1 Ω (200 Ω range).

2. The anticipated loop resistance.

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

table below.

Test current varies with supply voltage:

20 Ω range: 200 Ω range:

@ 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 Ω range for 0.01 Ω resolution or

the 200 Ω range for 0.1 Ω resolution. 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

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 Ω on the 20 Ω range or >199.9 Ω on the

200 Ω range. 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.

To replace 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.

16 Hz 50/60 Hz 400 Hz

Fuse replacement

A blown fuse is indicated by the fsymbol in the display.

To replace the fuse remove battery cover and replace fuse with

type:

7 A (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 Ω to 200 Ω

Voltage measurement

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

Accuracy: ±2% ±3 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 Ω range 200 Ω range

@ 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 Ω range: 0 to 19.99 Ω ±5% ±0.03 Ω

Loop accuracy 200 Ω range: 0 to 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: 8 x 1,5 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 IEC61326-1

Operational uncertainties: Refer to www.megger.com

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

Declaration of Conformity

Hereby, Megger Instruments Limited declares that radio equipment

manufactured by Megger Instruments Limited described in this user

guide is in compliance with Directive 2014/53/EU.

Other equipment manufactured by Megger Instruments Limited

described in this user guide is in compliance with Directives

2014/30/EU and 2014/35/EU where they apply.

The full text of Megger Instruments EU declarations of conformity

are available at the following internet address: megger.com/

eu-dofc.

LT300

Hochstrom-Schleifenprüfgerät

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