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Kewtech KT41, Инструкция по эксплуатации

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8

2.3 Principles of the measurement of line impedance and 

prospective short circuit current

Line impedance on a single phase system is the impedance
measured between phase and neutral terminals.

Measurement principles for line impedance are exactly the
same as for earth fault loop impedance measurement with the
exception that the measurement is carried out between phase
and neutral.

The protective 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 volt-
age 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.

Содержание KT41

Страница 1: ...KEWTECH KT41 KT42 digital multi function testers Instruction manual ...

Страница 2: ...ake the RCD out of circuit during testing and is a safer procedure to follow The ATT circuits may not by pass some RCDs and this will result in the RCD tripping out as they would with a conventional loop tester Also in the case of high sensi tivity RCDs rated at 10mA or less the ATT circuits may not function If there is doubt as to whether this tester will by pass a particular RCD contact Kewtech ...

Страница 3: ... not touch any exposed metal work This is because the earth has a current flowing through it for the duration of the test approx 20ms 1 4 Never open the instrument case there are dangerous voltages present Only trained competent Electronic engineers should open the case Send the unit to Kewtech if a fault develops 1 5 This instrument is primarily protected by HRC Ceramic fuses Do not attempt to re...

Страница 4: ...n mind However no design can completely protect against incor rect use Electrical circuits can be dangerous and or lethal when a lack of caution or poor safety practice is used Use caution in the presence of voltages above 50V as these pose a shock hazard 1 12 Pay attention to cautions and warnings which will inform you of potentially dangerous procedures 1 13 If at anytime during testing there is...

Страница 5: ... 2 Features and Principles of Measurement 2 1 Features KT42 with ATT avoids the need to by pass most passive RCDs Large high contrast display Auto lock out if test resistor overheats Voltage indication Microprocessor controlled Measures PSC Measure low loop with 0 01Ω resolution High loop ranges permit measurement of ground spikes Bright colour coded LED mains status indicators Distribution board ...

Страница 6: ...er 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 For TN systems the earth fault loop impedance is the sum of the following impedances Imped...

Страница 7: ...V is the maximum voltage limit it may be 25V in certain circumstances Ia is the value of current that causes automatic disconnection of the protective device within 5 sec onds When the protective device is a residual device RCD Ia is the rated residual operating current I n For example in a TT sys tem protected by an RCD the maximum RA values are as fol lows Rated residual operating cur 10 30 100 ...

Страница 8: ...t Zs Uo Ia where Zs is the earth fault loop impedance voltage is the nominal voltage between phase and earth and Ia is the cur rent that causes the automatic disconnection of the protective device within the time stated in the following table Note When the protective device is a residual current device RCD Ia is the rated residual operating current 1 n For instance ina TN system with a nominal mai...

Страница 9: ...G fuse 0 4 seconds The loop tester reads 1 14Ω and conse quently the condition Zs Uo Ia is met Rating Disconnecting time 5s Disconnecting time 4s A Ia A Zs Ω Ia A Zs Ω 6 28 8 2 47 4 9 10 46 5 82 2 8 16 65 3 6 110 2 1 20 85 2 7 147 1 56 25 110 2 1 183 1 25 32 150 1 53 275 0 83 40 190 1 21 320 0 72 50 250 0 92 470 0 49 63 320 0 71 550 0 42 80 425 0 54 840 0 27 100 580 0 39 1020 0 22 ...

Страница 10: ...int 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 volt age 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 w...

Страница 11: ... Nominal test Intrinsic Range range current at 0Ω external accuracy loop Period applied 20Ω 0 00 19 99Ω 25A 20ms 200Ω 0 0 199 9Ω 2 3 40ms 2 rdg 3dgt 2000Ω 0 1999Ω 15mA 280ms Measuring Nominal test Intrinsic Range range current at 0Ω external accuracy loop Period applied 200A 0 0 19 99A 2 3A 40ms 2000A 0 1999 25A 20ms 20kA 0 00 4 00kA 25A 20ms PSC accuracy is derived from the loop impedance accurac...

Страница 12: ... Storage temperature 5 C to 60 C Storage humidity 85 maximum Dimensions 175 x 115 x 85 7mm Weight KT41 500g KT42 700g Maximum altitude 2000m Over range indication OL Input voltage greater than 260V indication VP E Hi Over temperature indication Applied standards Instrument operating standard IEC EN61557 1 IEC EN61557 3 Range Operating range compliant with EN61557 3 operating error 20Ω 0 35 to 19 9...

Страница 13: ...KT42 KT41 Anti trip technology X Loop 0 19 99Ω 0 199 9Ω 0 1999Ω PSC 0 199 9A 0 1999A 0 4 00kA Mains Lead for Sockets KAMP10UK ACC016E ACCEP5 External Earth Probe SLP5 Distribution Board Lead SL16E ATT does not operate on the 2000Ω ranges This manual and product may use the following symbols adopted from International Safety Standards Equipment protected throughout by DOUBLE INSULATION or REINFORCE...

Страница 14: ...12 4 Instrument layout LCD display Test button Main status indication LED Range switch ...

Страница 15: ...13 Test leads LCD display ACCEP5 ACC016E KAMP10UK ...

Страница 16: ... cause of the fault must be investigated and rectified Voltage Measurement When the instrument is first connected to the system it will display the phase earth voltage which is updated every 1s This mode is cancelled the first time the test button is pressed If this voltage is not normal or as expected DO NOT PROCEED NOTE This is a single phase 230V AC instrument and under no circumstances should ...

Страница 17: ...nd you must switch up a range to the 200Ω range 5 2 1 External Earth Probe The phase earth loop impedance of exposed metal work e g pipes conduit etc can be tested using the external earth probe Connect the unit to the socket as normal Plug the external earth probe into the instrument external earth probe socket ensuring the probe is held with fingers behind the finger guard This will break the ea...

Страница 18: ...lay to indicate the input voltage before conducting another test or disconnecting from the distribution board When disconnecting from the distribution board it is good practice to disconnect the phase first c Loop impedance at 3 phase equipment Use the same procedure as b ensuring only 1 phase is connected at a time i e FIRST test red prod to phase 1 black prod to neutral green crocodile clip to e...

Страница 19: ...red phase probe of the ACC016E to the phase of the system the black probe to the neutral of the system and the green crocodile clip to the neutral of the system Carry out the initial checks Press the test button A bleep will sound as the test is conducted and the value of PSC will be displayed Wait for the display to indicate the input voltage before conducting another test or disconnecting the in...

Страница 20: ...iding the need to physically press the test button i e hands free 6 Servicing and Calibration If this tester should fail to operate correctly return it to Kewtech marked for the attention of the Service Department stating exact nature of fault Make sure that a operating instructions have been followed b leads have been inspected c the unit is returned with all accessories Regular re calibration is...

Страница 21: ...ould blow always return the instrument to Kewtech for checking The fuses are special and should only be replaced by equivalent types Returning the product to Kewtech will ensure this If other leads are used then reading may not be true unless they are calibrated with the instrument If this product needs cleaning use a damp cloth to wipe its sur faces DO NOT use strong cleaning agents as these may ...

Страница 22: ...st lead pouch in the following sequence 1 Pass the strap down through the first lug under the case and up through the other lug 2 Slide the shoulder pad onto the strap 3 Feed the strap down through the slots in the back of the test lead pouch 4 Pass the strap through the buckle adjust the strap for length and secure ...

Страница 23: ...KEWTECH Kewtech Corporation Limited 76 St Catherine s Grove Lincoln LN5 8NA www kewtechcorp com Distributor 92 1616 04 03 ...

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