Megger LT310 Manuale utente

LT300 Series

Earth Loop Testers

USER MANUAL

GSAFETY WARNINGS

■Safety Warnings and Precautions must be read and understood before the instrument is used. They must be observed during use.

■Continuity of protective conductors and earthed equipotential bonding of new or modified installations must be verified before carrying out an earth

fault loop impedance or RCD tests.

■Do not leave the instrument connected to the mains supply when not in use.

■Circuit connections and exposed metalwork of an installation or equipment under test must not be touched.

■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.

■National Safety Authorities may recommend the use of fused test leads when measuring voltage on high-energy systems.

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

■Voltage indicator LED’s cannot reveal a N-PE supply reversal.

■When making a 2 wire measurement with the 3 wire lead set, for safety reasons the balck test lead should be connected together with the green test lead.

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.

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.

Frequency Hz (LT320 and LT330) 16

Phase sequence (LT320 and LT330) 16

Test result storage (LT330 only) 17

Replacing batteries and fuses 18

Low battery warning symbol 18

To replace batteries 18

Fuse blown indication 19

Auto power down 19

Preventive maintenance 20

Technical specification 20

Basic and service errors 22

Accessories and equipment 23

Repair and Warranty 24

Symbols used on the instrument are:

GCaution: refer to accompanying notes

tEquipment protected throughout by Double

Insulation (Class II)

cEquipment complies with current EU directives.

Equipment complies with ‘C tick’ requirements

CONTENTS

Safety warnings 3

Introduction 4

General description 5

Case contents 7

LCD display 6

Front panel 6

Connection panel 7

Lid open/closure 7

Preparations for use 8

Batteries 8

Preliminary test lead check 8

General operating instructions 8

Display warning symbols 8

Setup procedure 9

Reverse polarity or line/neutral swapping 9

Test leads 9

Test lead connection. 10

LED indicators 10

Loop testing 11

Non-tripping loop test [No Trip] 11

Hi current loop test [Hi] 11

Phase-Earth loop impedance (not at a power socket): 12

Phase-Neutral or Phase-Phase loop impedance 12

Prospective fault current display [PFC] 12

Error messages 12

Possible sources of error 13

maxZ (LT320 only) 14

Deriving R1 + R2 (LT320 and LT330) 14

Voltage measurement 15

Phase to earth voltage measurement 15

Phase to Phase voltage measurement (LT320 and LT330) 15

N13117

Feature LT310 LT320 LT330

3 Phase safe ■■■

Large clear display ■■■

Backlight ■■

Battery status indication ■■■

Auto power down ■■■

Fuse blown indication ■■■

L-N-E polarity indicators ■ ■ ■

Voltmeter range 500V ■■■

Frequency measurement ■■

Phase rotation indicator ■■

Reverse polarity operation

(some models only) ■■■

Locking test button ■■■

3 wire no trip loop test ■■■

2 wire high loop test ■■■

Phase-Phase loop test ■■

PFC display ■■■

INTRODUCTION GENERAL DESCRIPTION

Thank you for purchasing the Megger Earth Loop Impedance Tester.

For your own safety and to get the maximum benefit from your

instrument, please ensure that you read and understand the following

safety warnings and instructions before attempting to use the instruments.

This user manual describes the operation and functions of the following

LT300 series of Loop Impedance Testers:

LT310

LT320

LT330

The LT300 series test instruments have

the following features

Please complete the warranty card and return it to Megger as soon as

possible to help us reduce any delays in supporting you should the need

arise.

Carton contents LT310, LT320 and LT330

1 x LT300 series loop tester

1 x 3 wire test lead with prods with clips

1 x Plug ended test lead

8 x AA (LR6) batteries (fitted in instrument)

1 x Warranty card

1 x Certificate of test

1 x Calibration certificate

1 x CD containing user manual

1 x Quick start guide

1 x Download Manager CD (LT330 only)

CASE CONTENTS

Feature LT310 LT320 LT330

Max Zs display ■■

R1+R2/ZRef switch ■■

Plug ended test lead ■■■

3 wire ended test lead

probe/croc clip ended ■■■

Calibration certificate ■■■

IEC61010-1 300V CATIII ■■■

EN61557 ■ ■ ■

Test result storage ■

USB download ■

LCD DISPLAY FRONT PANEL

LT300 Series test lead connections

LT320 and LT320

LT310

LT330 additional controls

Memory control keys:

STORE: Store initiates the storing of a test result.

LAST/NEXT: Selects the type of location; ie job, distribution

board, circuit, phase etc.

ESC: Aborts a save at any time.

OK: Final operation to save the result.

▲Selects the job, db, circuit number; ie

▼01,02,03 etc

Lid open/closure

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

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

(4).

Neutral or 2nd

phase connection

USB

connection

(LT330 only)

Single or 3 phase

Single phase connection only

Mains plug test

lead

Maximum 300 V phase

to earth allowed Maximum 300 V phase

to earth allowed

Maximum 500 V across

terminals

PREPARATIONS FOR USE (ALL INSTRUMENTS) GENERAL OPERATING INSTRUCTIONS

Tests lock

The LOCK Lindicates when the [Hi] current loop test range is locked

ON.

It is activated by holding down the Llock button, and pressing the

[TEST] button. When activated, the [Hi] current loop resistance

measurement will start when the instrument is connected to a voltage.

The test lock remains on for 30 seconds, after which it resets to off.

Test inhibit

The following conditions may cause the instrument to inhibit testing:

Out of range supply voltage

If an out of range voltage or frequency exists on the circuit under test,

or on a very noisy mains supply, testing will be automatically inhibited.

Overheating

Repetitive loop testing generates heat within the instrument. If this

heat becomes excessive the instrument will warn the operator and

prevent further testing until the instrument has had a chance to cool

down.

Fuse Blown

A fuse blown will prevent the instrument from making further tests.

The fuse indicator will be displayed.

Default voltmeter

The default voltmeter automatically operates in all test modes, indicating

connection to a live system.

Auto power-down

To extend battery life the instrument will automatically switch off six

minutes after the last operation.

The instrument can be switched off manually by selecting [OFF] with the

Batteries

The Megger LT300 series instruments are supplied with batteries fitted.

When batteries become exhausted, refer to page 18, battery replacement.

Warning: Do not switch the instrument on with the battery cover

removed.

Preliminary test lead check

Functional verification

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

and crocodile clips to confirm that their condition is good, with no

damaged or broken insulation.

rotary switch, or switched back on again by pressing the [TEST] button.

Backlight operation (LT320 and LT330)

The LT320 and LT330 LCD display may be backlit, to allow readings to be

seen in adverse lighting conditions. The backlight function can be selected

at any time while the instrument is switched on by pressing the

BACKLIGHT Jbutton.

The backlight function will switch off automatically 15 seconds after the

instrument has finished testing.

Display warning symbols

GRefer to user manual.

Any time the warning triangle is displayed the operator should refer to the

user manual for further information.

LRange lock

Displayed at any time the [TEST] button is locked in the on position.

Battery condition indication. Refer to page 18.

fFuse blown indicator, appears when an instrument fuse has failed.

Refer to page 17.

>280V Displayed on the LT310 indicates a supply voltage in excess of that

allowed is present.

>480V Displayed on the LT320 indicates a supply voltage in excess of that

allowed is present.

hot Indicates the instrument needs to cool down before it can continue

loop testing

Noise on the circuit under test may affect the reading

Setup procedure

Reverse polarity or line/neutral swapping

This feature is only available on the following models

LT310-EN-SC LT320-EN-SC

LT310-FR-SC LT320-FR-SC

LT310-DE-SC LT320-DE-SC

LT310-ES-SC LT320-ES-SC

LT310-IT-SC LT320-IT-SC

LT310-NL-SC LT320-NL-SC

LT310-NO-SC LT320-NO-SC

The set-up menu allows the user to change the way the instrument

behaves when testing on a supply with Line and Neutral connections

swapped. Tests may be permitted or prohibited.

To select Polarity reversal acceptance or rejection:

1. With the instrument switched OFF, hold down the [TEST] button and

turn the range knob to any ON position.

2. Keep the button held down until the instrument displays the ‘SET’

warning.

3. Now release the [TEST] button.

4. Press the [TEST] button again to view the current setting for

line/neutral swapping.

5. The display shows ‘L+L’ (instrument will perform tests with L & N

swapped) or ‘L+N’ (instrument will not perform tests with L & N

swapped).

6. Press the [LOCK] button or the PFC button to change the setting.

7. Press the [TEST] button to exit from the set-up menu.

Application

This instrument may be connected live to earth or between live conductors

of systems that have a rated voltage of 300V a.c. rms to earth and an

installation (overvoltage) Category III or lower.

This means that the instrument may be connected to any fixed wiring of a

building installation, but not to primary supply circuits such as overhead

cables. To maintain user safety and ensure accurate measurements, only use

the test leads supplied or by Megger Limited.

LED indicators

Three RED led indicators show circuit connection status when correctly

connected to a live circuit. These are for indication purposes only and

should not be relied upon as a indication of the presence of a hazardous

voltage.

Test leads

All test leads form part of the measuring circuit of the instrument and must

not be modified or changed in any way, or be used with any other electrical

instrument or appliance.

The mains plug test lead supplied with the Megger tester is a test lead that

forms part of the measuring circuit of the instrument. The overall length of

this lead must not be altered. If the power cord plug is not suitable for your

type of socket outlets, do not use an adapter. You may change the plug once

only by cutting the cord as close to the plug as possible and fitting a suitable

plug.

The colour code of the cord is:

Earth (Ground) Yellow/Green

Neutral Blue

Phase (Line) Brown

Note: A plug severed from the power cord must be destroyed, as a plug

with bare conductors is hazardous in a live socket outlet.

Test lead connection

The supplied test leads should be connected to the appropriate sockets on

the rear of the instrument marked L0 and L1, or to the 3 way test socket.

Standard test probes and crocodile clips are supplied for connection to the

circuit under test.

The test lead supplied with the LT310, LT320 and LT330 provides connection

for 2 wire testing or 3 wire testing, using the 3 wire (red, black and green)

lead set (6220-782)

all instruments all instruments LT320/LT330

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