Kyoritsu Electrical Instruments Works, Ltd. KEW 4140 User manual

INSTRUCTION MANUAL
DIGITAL LOOP/PFC/PSC TESTER
ＫＥＷ 4140
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CONTENTS
1.SafeTesting ･･･････････････････････････････････････････ 1
2.InstrumentsLayout･･････････････････････････････････････ 3
3.Accessories････････････････････････････････････････････ 6
4.Features･･･････････････････････････････････････････････ 7
5.Specification･･･････････････････････････････････････････ 8
5.1MeasurementSpecification･･････････････････････････ 8
5.2OperatingError･････････････････････････････････････ 9
5.3GeneralSpecification･･････････････････････････････10
5.4AppliedStandards･････････････････････････････････10
6.PreparationforMeasurement････････････････････････････11
7.LOOP/PSC/PFCTest ･････････････････････････････････12
7.1
PrinciplesofMeasurementofFaultLoopImpedanceandPFC  ･12
7.2
PrinciplesofMeasurementofLineImpedanceandPSC ･16
7.3OperatingInstructionsforLOOPandPSC/PFC･･･････17
7.3.1InitialChecks････････････････････････････････････17
7.3.2MeasurementOfLOOPAndPSC/PFC･････････････18
7.3.3ContentsonSubDisplay･･････････････････････････18
8.PhaseRotationTest･･･････････････････････････････････22
9.Volts･････････････････････････････････････････････････23
10.BackLight･･･････････････････････････････････････････23
11.Auto-Test････････････････････････････････････････････23
12.BatteryReplacement･･････････････････････････････････24
13.Servicing････････････････････････････････････････････25
14.CaseandStrapAssembly･････････････････････････････26
The KEW4140 incorporates Anti Trip Technology (ATT) which
electronically bypasses RCDs when performing loop impedance
tests.ThissavestimeandmoneybynothavingtotaketheRCD
outofthecircuitduringtestingandisasaferproceduretofollow.
WiththeATTfunctionenabled,atestof15mAorlessisapplied
betweenline&earth.
ItenablesloopimpedancemeasurementswithouttrippingRCDs
ratedat30mAandabove.
Please read this instruction manual carefully before using this
equipment.
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1. Safe Testing
Electricity is dangerous and can cause injury and death. Always
treat it with the greatest of respect and care. If you are not quite
sure how to proceed, stop and take advice from a qualified person.
This instruction manual contains warning and safety rules which
must be observed by the user to ensure safe operation of the
instrument and retain it in safe condition. Therefore, read through
these operating instructions before using the instrument.
IMPORTANT:
1This instrument must only be used by a competent and trained
person and operated in strict accordance with the instructions.
KYORITSU will not accept liability for any damage or injury
caused by misuse or non-compliance with the instructions or with
the safety procedures.
2 It is essential to read and to understand the safety rules contained
in these instructions. They must always be observed when using
the instrument.
The symbol #indicated on the instrument means that the user
must refer to the related sections in the manual for safe operation of
the instrument. Be sure to carefully read instructions following each
symbol #in this manual.
#DANGER is reserved for conditions and actions that are likely
to cause serious or fatal injury.
#WARNING is reserved for conditions and actions that can
cause serious or fatal injury.
#CAUTION is reserved for conditions and actions that can
cause a minor injury or instrument damage.
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#DANGER
●Thisinstrumentisdesignedtoworkindistributionsystems
where the line to earth has a maximum voltage of 300V 50/60Hz
and for some ranges where line to line has a maximum voltage
of 500V 50/60Hz.
Be sure to use it within this rated voltage.
●Whenconductingtestsdonottouchanyexposedmetalwork
associated with the installation. Such metalwork may become
live for the duration of the test.
●
For safety reasons only use accessories (test leads, probes,
cases, etc) designed to be used with this instrument and
recommended by KYORITSU. The use of other accessories is
prohibited as they are unlikely to have the correct safety features.
●Whentesting,alwaysbesuretokeepyourfingersbehindthe
finger guards on the test leads.
#WARNING
●
Never open the instrument case (except for battery replacement
and in this case disconnect all leads first) because dangerous
voltages are present. Only fully trained and competent electrical
engineers should open the case. If a fault develops, return the
instrument to your distributor for inspection and repair.
●Iftheoverheatsymbol appears in the display disconnect the
instrument from the mains supply and allow to cool down.
●
If abnormal conditions of any sort are noted (such as a faulty
display, unexpected readings, broken case, cracked test leads,
etc) do not use the tester and return it to your distributor for repair.
●Neverattempttousetheinstrumentiftheinstrumentoryour
hand is wet.
#CAUTION
●Duringtestingitispossiblethattheremaybeamomentary
degradation of the reading due to the presence of excessive
transients or discharges on the electrical system under test.
Should this be observed, the test must be repeated to obtain a
correct reading. If in doubt, contact your distributor.
●Useadampclothanddetergentforcleaningtheinstrument.Do
not use abrasives or solvents.
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2. Instrument Layout
1. Front View
Fig.2-1
Name Operation
①Display(LCD) --
②Test Switch Start measurements.
③BackLightSwitch Switches on/off the Back light of
theDisplay(LCD)
④L-PEATTONSwitch Select“L-PEATTON”function
⑤L-PEATTOFFSwitch
Select“L-PEATTOFF”function
⑥L-N/L-LSwitch Select“L-N/L-L”Function
⑦DISPSwitch ChangethecontentsonSub
Display
⑧
VOLTS/FREQUENCYSwitch Select"VOLTS/FREQUENCY" function
⑨PHASEROTATIONSwitch
Select"PHASEROTATION"function
⑩PowerSwitch PowerSwitch
(Pressdownforatleast1sec.)
④ ⑥ ⑤
①
②
③
⑦
⑧
⑨
⑩
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2. Input Terminal
Fig.2-2
①Terminal Names for :
LOOP,VOLTS
L:Line
PE:ProtectiveEarth
N:Neutral(forLOOP)
②Terminal Name for L1:Line1
PHASEROTATION L2:Line2
L3:Line3
3.LCD
Fig.2-3
②
①
Sub Display
Main Display
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List of Display Message
Battery symbol
Displayedwhenthemeasuredvaluesexceedthe
displayable range.
(over-range)
e.g.Thedisplayshows“>1999Ω”ataLOOPtestwhen
atestresultexceeds1999Ω.
Displayedwhen“L-PEATTON”functionisselectedto
indicate ATT is on.
TheLCDindicates“L-PE”when“L-PEATTON”or
“ATTOFF”isselectedand“L-N/L-L”when“L-N/L-L”is
selected.
IndicatingwhatthevaluesdisplayedontheSubDisplay.
Temperature monitor for internal resistance, available
atLoop,PSC/PFCfunction.Furthermeasurementsare
suspended until the“ ”symboldisappears.
Measuringsymbol(LOOPfunction)
L-N>20Ω Alert:Presenceof20ΩormorebetweenLine
‐
Neutral at
ATT ON measurement
Caution:Presenceofnoiseinthecircuitundertest
during ATT measurement. ATT function should be
disabled to continue measurements.
nEHv
Caution:PresenceofhighvoltagebetweenNEUTRAL-
EARTH during ATT measurement. ATT function should
be disabled to continue measurements.
WiringcheckforLOOPfunction
DisplayedatPHASEROTATIONcheck
Correctphasesequence:displayed mark.
Reversed phase sequence : displayed mark.
no
PHASE
ROTATION
Appears to indicate wrong connection
atPhaseRotationcheck.
LOOP WhenontheLOOPfunction,supply
may have been interrupted.
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3. Accessories
1.MainTestLead(Model7218)
Fig.3-1
2.DistributionBoardTestLead(Model7246)
Fig.3-2
3.SoftCaseModel9156…x1
4.StrapBeltModel9155…x1
5.Battery…x6
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4. Features
TheKEW4140LOOP/PFC/PSCtesterperformsthreefunctionin
one instrument.
1Loopimpedancetester
2 Voltage tester
3Phaserotationtester
TheKEW4140havethefollowingfeatures:
ATT (Anti Trip Technology) ATT enables a measurement without
trippingtheRCDswiththerated
residual current of 30mA or more.
Wiringcheck ThreeWiringsymbolsindicateif
the wiring of the circuit under test is
correct.
Over temperature protection Detectsoverheatingoftheinternal
resistor displaying a warning symbol
() and automatically halting further
measurements.
Auto power off Automatically switches the instrument
off after a period of approximately 10
minutes.
The Auto power off mode can only be
cancelled by switching the instrument
on again.
BackLight Poweredoffautomaticallywhen 2
min pass after the last operation.
SUBDisplay PFC,PSCandL-NLOOPresistance
valuesarealsomeasuredatLOOP
L-PEtestanddisplayedontheSub
Display.
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5. Specification
5.1 Measurement Specification
LoopImpedance
Function
(Operating Voltage)
Rated Voltage
Range
(Auto-Ranging)
NominalTestCurrent
at0ΩExternalLoop:
Magnitude/Duration
(＊1)
Accuracy
Guaranteed Voltage
Range
L-PE
ATT OFF
(100〜280Ｖ)
(45〜65 Hz)
230V(50／60Hz) L-PELOOP:
20Ω:0.00-19.99Ω
200Ω:20.0-199.9Ω
2000Ω:200-1999Ω
PFC/PSC:
2000A
：
0-1999A
20kA
：
2.00-19.99kA
L-PE:
20Ω
:
6A/20ms
200Ω
:
2.3A/20ms
2000Ω
:
15mA/250ms
L-N:
6A/20ms
±(3%rdg+4dgt)
(＊2)
230 V (+10%/-15%)
(50/60 Hz)±1%
ATT ON
(100〜280Ｖ)
(45〜65 Hz)
230V(50／60Hz) L-PELOOP:
20Ω:0.00-19.99Ω
200Ω:20.0-199.9Ω
2000Ω:200-1999Ω
PFC/PSC:
2000A
：
0-1999 A
20kA
：
2.00-19.99 kA
(L-N<20Ω)
L-N:6A/60ms
N-PE:10mA
/approx. 5s
±(3%rdg+6dgt)
(＊2)
230 V (+10%/-15%)
(50/60 Hz)±1%
L-N/L-L
(100〜500Ｖ)
(45〜65 Hz)
L-N
：
230V(50/60Hz)
L-L
：
400V(50/60Hz) L-N/L-LLOOP:
20Ω:0.00-19.99Ω
PSC:
2000A
：
0-1999 A
20kA
：
2.00-19.99 kA
20Ω:6A/20ms
L-N
：
±(3%rdg+4dgt)
L-L
：
±(3%rdg+8dgt)
(＊3)
L-N
：
230 V (+10%／-15%)
L-L
：
400V(+10%／-15%)
(50／60 Hz)±1%
＊1: at 230V
＊2:AccuracyofL-NLOOPdisplayedontheSubDisplayis
synchronizedwiththeoneatL-N/L-Lfunction.
PSC/PFCAccuracyisderivedfrommeasuredloopimpedance
specification and measured voltage specification.
＊3:PSCAccuracyisderivedfrommeasuredloopimpedance
specification and measured voltage specification.
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PHASEROTATION
Rated
Voltage Remarks
50〜500V
45~65Hz
Correctphasesequence:displayed“1.2.3”and mark
Reversedphasesequence:displayed“3.2.1”and mark
Volts
Range DisplayRange Guaranteed
VoltageRange Accuracy
500V Volt：0 〜 525V
Frequency：40.0 〜 70.0Hz 25 〜 500Vrms 45 〜 65Hz Volt：±(2%rdg+4dgt) Frequency：±(0.5%rdg+2dgt)
Possiblenumberoftestswithfreshalkalinebatteries.
LOOP/PFC/PSC :Approx.3000timesmin(ATT)
VOLT/PHASEROTATION :Approx.100H.
5.2 Operating error
LoopImpedance(EN61557-3)
FUNCTION Operating range compliant
withEN61557-3operatingerror
Maximum percentage
operating error
L-PE 0.40~1999Ω ±30%
L-N/L-L 0.40~19.99Ω
The influencing variations used for calculating the operating error
are denoted as follows;
Temperature : 0 ℃and 35 ℃
Phaseangle :Ataphaseangle0°to18°
Systemfrequency :49.5Hzto50.5Hz
System voltage : 230V+10%-15%
Supplyvoltage :6.8Vto10.35V
Harmonics :5%of3rdharmonicat0°phaseangle
5%of5thharmonicat180°phaseangle
5%of7thharmonicat0°phaseangle
D.Cquantity :0.5%ofthenominalvoltage
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5.3 General specification
Instrument dimensions 84X184X133mm
Instrument weight:- 860g(includingbatteries.)
Reference conditions Specifications are based on the following
conditions except where otherwise stated:-
1.Ambienttemperature:23±5°C:
2.Relativehumidity45%to75%
3.Position:horizontal
4.ACpowersource230V,50Hz
5.DCpowersource:9.0V
6. Altitude up to 2000m, Indoor use
Battery type Six 1.5V AA batteries
Useofalkalinebatteries(LR6)is
recommended.
Operating temperature
and humidity.
-10to +50°C,relativehumidity85%orless,
no condensation
Storage temperature
and humidity
-20to +60°C,relativehumidity75%orless,
no condensation
5.4 Applied standards
Instrument operating IEC/EN61557-1,3,7,10
Standard
Safety standard IEC/EN61010-1
CATIII(300V)-Instrument
IEC/EN61010-031
CATII(250V)-TestLeadModel7218
CATIII(600V)-TestLead7246
Protectiondegree IEC60529IP54
EMC EN 61326
This manual and product may use the following symbols adopted
from International Safety Standards;
CAT.III Measurementcategory”CATIII”appliesto;Primaryelectrical
circuitsoftheequipmentConnecteddirectlytothedistribution
panel, and feeders from the distribution panel to outlets.
EquipmentprotectedthroughoutbyDOUBLE
INSULATIONorREINFORCEDINSULATION;
#Caution(refertoaccompanyingdocuments)
Earth Ground
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6. Preparation for Measurement
CheckofBatteryvoltage
(1)See“12.Batteryreplacement”andinstallbatteriesinKEW4140.
(2)PressthePowerswitchonKEW4140foratleast1sectopower
on the instrument.
*Powerswitchisactivatedonlywhentheswitchispressedfor1
sec or more.
Presstheswitchforatleast1sectopowerofftheinstrument.
(3)Power onKEW4140andchecktheBatterysymboldisplayed
at the upper left on the LCD. When the displayed battery level
is lowest ( ), the installed batteries will be exhausted soon.
Replacethebatterieswithreferenceto“12.Batteryreplacement”
to continue further tests.
WhentheBatterysymbolisempty ( ), battery level is
lower than the lower limit of the working voltage. In this case,
accuracies of the measured values aren’t assured. Replace the
batteries with new ones.
The empty Battery symbol ( ) is displayed and warning
buzzer sounds for 2 sec when powering on the instrument with
exhausted batteries.
Batteries to be used
Use of alkaline batteries is recommended. Battery level may not
be recognized properly when alkaline batteries aren’t used.
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7. LOOP/ PSC/PFC Test
7.1 Principles of measurement of fault loop impedance and PFC
If an electrical installation is protected by over-current protective
devices including circuit breakers or fuses, the earth loop
impedance should be measured.
In the event of a fault the earth fault loop impedance should be
low enough (and the prospective fault current high enough) to
allow automatic disconnection of the electrical supply by the circuit
protection device within a prescribed time interval. Every circuit
must be tested to ensure that the earth fault loop impedance value
does not exceed that specified or appropriate for the over-current
protectivedeviceinstalledinthecircuit.TheKEW4140takes a
current from the supply and measures the difference between the
unloaded and loaded supply voltages. From this difference it is
possible to calculate the loop resistance.
TT System
For a TT system the earth fault loop impedance is the sum of the
following impedances;
●Impedanceofthepowertransformersecondarywinding.
●Impedanceofthephaseconductorresistancefromthepower
transformer to the location of the fault.
●Theimpedanceoftheprotectiveconductorfromthefaultlocation
to the earth system.
●Resistanceofthelocalearthsystem(R).
●Resistanceofthepowertransformerearthsystem(Ro).
The figure below shows (dotted line) the Fault loop impedance for
TT systems.
Fig.7-1
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AccordingtotheInternationalStandardIEC60364,forTTsystems
the characteristics of the protective device and the circuit resistance
shall fulfill the following requirements:
Ra x Ia ≤ 50V Where:
RaisthesumoftheresistancesinΩofthelocalearthsystemand
the protective conductor for the exposed conductive parts.
50 is the maximum safety touch voltage limit (it can be 25V in
particular cases like construction sites, agricultural premises, etc.).
Ia is the current causing the automatic disconnection of the
protective device within the maximum disconnecting times required
byIEC60364-41:
-200msforfinalcircuitsnotexceeding32A(at230/400VAC)
-1000 ms for distribution circuits and circuits over 32A (at 230 /
400VAC)
The compliance with the above rules shall be verified by:
1) Measurement of the resistance Ra of the local earth system by
LooptesterorEarthtester.
2) Verification of the characteristics and/or the effectiveness of the
RCDassociatedprotectivedevice.
GenerallyinTTsystems,RCDsshallbeusedasprotectivedevice
and in this case, Ia is the rated residual operating current I△n. For
instanceinaTTsystemprotectedbyaRCDthemaxRavaluesare:
Rated residual operating current I△n 30 100 300 500 1000 (mA)
RA(with touch voltage of 50V) 1667 500 167 100 50 (Ω)
RA(with touch voltage of 25V) 833 250 83 50 25 (Ω)
Shown below is a practical example of verification of the protection by
RCDinaTTsystemaccordingtotheinternationalStandardIEC60364.
Fig7-2
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Forthisexamplethemaxpermissiblevalueis1667Ω(RCD=30mA
and contact voltage limit of 50 V). The instruments reads 12.74Ω,
thustheconditionRA≤50/Iaisrespected.However,considering
that the RCD is essential for protection, it must be tested (Please
refertoRCDTESTSsection).
TN System
For TN systems the earth fault loop impedance is the sum of the
following impedances.
●Impedanceofthepowertransformersecondarywinding.
●Impedanceofthephaseconductorfromthepowertransformerto
the location of the fault.
●Impedance of the protective conductor from the fault location to
the power transformer.
The figure below shows (dotted line) the Fault loop impedance for
TN systems.
Fig.7-3
AccordingtotheInternationalStandardIEC60364,forTN
system the characteristics of the protective device and the circuit
impedance shall fulfill the following requirement:
Zs x Ia ≤ Uo Where:
Zs is the Fault loop impedance in ohm.
Uo is the nominal voltage between phase to earth (typically 230V
ACforbothsinglephaseandthreephasecircuits).
Ia is the current causing the automatic disconnection of the
protective device within The maximum disconnecting times required
byIEC60364-41thatare:
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-400msforfinalcircuitsnotexceeding32A(at230/400VAC)
-5sfordistributioncircuitsandcircuitsover32A(at230/400VAC)
The compliance with the above rules shall be verified by:
1)MeasurementofthefaultloopimpedanceZsbyLooptester.
2) Verification of the characteristics and/or the effectiveness of the
associated protective device. This verification shall be made:
-for circuit-breakers and fuses, by visual inspection (i.e. short time
or instantaneous tripping setting for circuit-breakers, current rating
and type for fuses);
-f o r RCDs,byvisualinspectionandtestusingRCDtesters
recommending that the disconnecting times mentioned above are
met(PleaseseeRCDTESTsection).
ForinstanceinaTNsystemwithnominalmainsvoltageUo=230
V protectedbyGeneralpurposegGfusesorMCBs(Miniature
CurrentBreakers)requiredbyIEC898/EN60898,theIaandmax
Zs values could be:
ProtectionbygGfuses
with Uo of 230V
ProtectionbyMCBswithUoof230V
(Disconnectiontime0.4and5s)
Rating
(A)
Disconnection
time 5s
Disconnection
time0.4s
Characteristic
B
Characteristic
C
Characteristic
D
la(A) Zs(Ω) la(A) Zs(Ω) la(A) Zs(Ω) la(A) Zs(Ω) la(A) Zs(Ω)
617 13.5 38 8.52 30 7.67 60 3.83 120 1.92
10 31 7.42 45 5.11 50 4.6 100 2.3 200 1.15
16 55 4.18 85 2.7 80 2.87 160 1.44 320 0.72
20 79 2.91 130 1.77 100 2.3 200 1.15 400 0.57
25 100 2.3 160 1.44 125 1.84 250 0.92 500 0.46
32 125 1.84 221 1.04 160 1.44 320 0.72 640 0.36
40 170 1.35 -- -- 200 1.15 400 0.57 800 0.29
50 221 1.04 -- -- 250 0.92 500 0.46 1000 0.23
63 280 0.82 -- -- 315 0.73 630 0.36 1260 0.18
80 403 0.57 -- --
100 548 0.42 -- --
The most complete loop testers or Multifunction testers also
havetheProspectiveFaultcurrentmeasurement.Inthiscase,
ProspectiveFaultcurrentmeasuredwithInstrumentsmustbe
higher than the tabulated Ia of the protective device concerned.
BelowisapracticalexampleofverificationoftheprotectionbyMCB
inaTNsystemaccordingtotheinternationalStandardIEC60364.
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Fig.7-4
MaxvalueofZsforthisexampleis1.44Ω(MCB16A,characteristic
C),theInstrumentreads1.14Ω(or202AonFaultcurrentrange)it
meansthattheConditionZsxIa≤Uoisrespected.
InfacttheZsof1.14Ωislessthan1.44Ω(ortheFaultcurrentof
202 A is more than Ia of 160A).
In other words, in case of fault between phase and earth, the wall
sockettestedinThisexampleisprotectedbecausetheMCBwill
trip within the disconnection time required.
7.2 Principles of the measurement of line impedance and PSC
The method for measuring Line – neutral impedance and line-line
impedance is exactly the same as for earth fault loop impedance
measurement with the exception that the measurement is carried
out between line and neutral or line and line.
Prospectiveshortcircuitorfaultcurrentatanypointwithinan
electrical installation is the current that would flow in the circuit if no
circuit protection operated and a complete (very low impedance)
short circuit occurred. The value of this fault current is determined
by the supply voltage and the impedance of the path taken by the
fault current. Measurement of prospective short circuit current can
be used to check that the protective devices within the system will
operate within safety limits and in accordance with the safe design
of the installation. The breaking current capacity of any installed
protective device should be always higher than the prospective
short circuit current.
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Fig.7-5
7.3. Operating instructions for LOOP and PSC/PFC
7.3.1 Initial Checks: to be carried out before any testing
1. Preparation
Always inspect your test instrument and lead accessories for
abnormalityordamage:IfabnormalconditionsexistDONOT
PROCEEDWITHTESTING.Havetheinstrumentcheckedby
your distributor.
(1)OperatethePowerswitchandturnontheinstrument.(Pressthe
Powerswitchforatleast1sec.)
Pressanyofthefollowingswitchestoselectafunction.
・
L-PEATTON:forLine–Earthloopimpedancetests(withATTon)
・L-PEATTOFF:forLine–Earthloopimpedancetests
・L-N/L-L:forline-neutralorline–lineloopimpedancetests
●ATT enables a measurement without tripping the RCDs with the
rated residual current of 30mA or more.
(2)InserttheTestLeadintotheinstrument.(Fig.7-6)
Fig.7-6
2. Wiring Check
Aftertheconnection,ensurethatthesymbolsforWiringcheckon
theLCDareinthestatusindicatedinFig.7-6beforepressingthe
test switch.
I f thestatusofthesymbolsforWiringcheckdifferfromFig.7-6
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orsymbolisindicatedontheLCD,DONOTPROCEEDAS
THEREISINCORRECTWIRING.Thecauseofthefaultmustbe
investigated and rectified.
3. Voltage Measurement
Whentheinstrumentisfirstconnectedtothesystem,itwill
display the line-earthVoltage (L-PEATT ON /ATT OFF) orline-
neutralvoltage(L-N/L-L)whichisupdatedevery1s.Ifthisvoltage
isnotnormalorasexpected,DONOTPROCEED.
7.3.2 Measurement of LOOP and PSC/PFC
a. Measurement at Mains Socket Outlet
Connectthemainstestleadtotheinstrument.Insertthemoulded
plugofmainstestleadintothesockettobetested.(seeFig.7-8)
Carry out the initial checks
Pressthetestswitch.Abeepwillsoundasthetestisconducted
andthevalueofLoopimpedancewillbedisplayed.
b. Measurement at the distribution board
ConnectthedistributionboardleadModel7246totheinstrument.
b-1.Measurement of Line – Earth Loop Impedance and PFC
ConnectthegreenPEleadoftheModel7246totheearth,the
blue N lead to the neutral of the distribution board and the red
Lleadtoone‘line’ofthedistributionboard.(SeeFig.7-9)
b-2.Measurement of Line – Neutral Loop Impedance and PSC
Connecttheblue N leadoftheModel7246totheneutral
ofthedistributionboard,theredLleadtoonelineofthe
distributionboard.(SeeFig.7-10)
b-3.Measurement of Line – Line Loop Impedance and PSC
ConnecttheblueNleadoftheModel7246tothelineof
thedistributionboard,theredLleadtoanotherlineofthe
distributionboard.(SeeFig.7-11)
Carry out the initial checks
Pressthetestswitch.Abeepwillsoundasthetestisconducted
andthevalueofloopimpedancewillbedisplayed.When
disconnecting from the distribution board, it is good practice to
disconnect the line first.
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