Demoboard Exercises MA 2067 User Manual
Contents
1. 32 Line impedance measurement 6 Line impedance measurement Background of measurement Line impedance is important for supplying electrical equipment The line impedance Zune Z Zn Zt consists of Be Ze line conductor B Zi cosa neutral conductor M Zi transformer The measurement of line impedance is important for Checking the effectiveness of installed overcurrent disconnection devices Locating of too high excessive line impedance that causes too high voltage drop between power transformer and a load Similar to Zune iS Zuine uine In this case Z of second line replaces Zn Faults bad contacts corrosion or improper installation design are the most often reason for too high line impedances and wrong installed fuses Safety conditions are checked by measuring line impedance Zine or Rune e g prospective short circuit current Ipc Limit currents and impedance usually depend on fuse type size and required trip out time Line resistance or line impedance can be measured The resistance measurement returns only the resistive part of the loop The impedance measurement considers the inductive part too In general impedance measurement is preferred if the measurement is performed close to the transformer or on the installation with high rated currents In this case the contribution of the inductive part is relatively high 33 Line impedance measurement Exercise No 6 1 Line impedance and prospectiv2. Demoboard Exercises MA 2067 User Manual Version 1 0 Code No 20 750 236 Se METREL Table of content Conductor continuity measurement 3 Exercise No 1 1 Conductor continuity measurement general 4 Exercise No 1 1 Conductor continuity measurement Demoboard 5 Insulation resistance measurement ss sssnnnnnnnnns 7 Exercise No 2 1 Insulation resistance measurement general 8 Exercise No 2 1 Insulation resistance measurement Demoboard 9 Earth resistance measurements sn nssnenessnsnnnnne 11 Exercise No 3 1 Earth resistance measurement two wire method general 12 Exercise No 3 1 Earth resistance measurement two wire method Demoboard e 14 Exercise No 3 2 Earth Resistance Measurement three wire method general 16 Exercise No 3 2 Earth Resistance Measurement three wire method Demoboard 065 17 Exercise No 3 3 Earth Resistance Measurement current clamp method general 19 Exercise No 3 3 Earth Resistance Measurement current clamp method Demoboard 20 Exercise No 3 4 Earth Resistance Measurement two current clamp method general 22 Exercise No 3 4 Earth Resistance Measurement two current clamp method Demoboard 23 Earth resistivity measurement neanmeanmnnnenmneennnneataennnennnnnantunce 25 Exercise No 4 1
3. Earth resistivity measurement general 26 Exercise No 4 1 Earth resistivity measurement Demoboard 27 Fault loop impedance measurement ss sssnnnnnnee 29 Exercise No 5 1 Fault loop impedance and current measurement in TN system genereal 30 Exercise No 5 1 Fault loop impedance and current measurement in TN system Demoboard 31 Line impedance measurement nsssnnenssneneensssnsnnnce 33 Exercise No 6 1 Line impedance and short circuit current measurement general 34 Exercise No 6 1 Line impedance and short circuit current measurement Demoboad n 0 n 35 Measurement of RCD paramate lS s sccccsesseneeeeeeeeeeeeeeeneeseeeeeeeeeseeeeeeeeeaseeneeeeseeneeseeeees 37 Exercise No 7 1 Testing of installed RCD general 38 Exercise No 7 1 Testing of installed RCD Demoboard cccccccececeeeeeeeeeeeeeeeeaeeees 40 Leakage current measurement sssnnnnssneneesssensnnnne 42 Exercise No 8 1 Leakage current measurement with current clamp general 42 Exercise No 8 1 Leakage current measurement with current clamp Demoboard ssnnssnsennne 43 Phase rotation TOS viisstacacesacdedecceannmientieewieteastiarsd ve baled dian dnauabendusloaivatwiuanadiaadeddeitanadeiiees 45 Exercise No 9 1 Phase Rotation Test general ccceeeeeeeecceeeeeeeeeeeeeneeeeeeeeeeeeneeseens 45 Exercise No
4. 9 1 Phase Rotation Test Demoboard 2 0 2 0 eee eeeeeeeeeeeee eter eeeeenteeeeeeeeeeeeeeeaes 46 Conductor continuity measurement 1 Conductor continuity measurement Background of measurement Automatic trip out of mains voltage in case of present hazardous contact voltage is one of the most common protection methods used on electric mains installations The disconnection device installed for this purpose must trip out or blow But one of basic requirements at this type of protection is low impedance connection of accessible metal parts to grounding system Measurements of continuity are carried out when testing connections between electric conductors protection earth conductors and appliances protection earth conductors and grounding system etc Resistance between two metal parts which are connected together by potential equalizing conductor must be Re Resistance between two accessible metal parts connected together using additional potential equalizing conductor Des Conventional touch voltage limit 50 V betas Current which assures tripping out protection device namely la lan oo for residual current protection devices RCDs Eh nominal working current of overcurrent protections fuses In case of RCD protection devices is equal to nominal differential current while in case of overcurrent protection devices fuses la is the current which causes melting and thus blowing of involved fuse within 5 s the curre
5. BG Resistance of Lightning systems LR1 and LR2 The following errors can be simulated 12 Too high earth resistance of Basic Grounding system approx 250 Q 13 Too high earth resistance of Lightning system 1 additional resistance of approx 100 Q The 250 value is too high for the RCD lan 0 3 A in switchboard 1 If both lightning rods are connected parallel to the Basic Grounding total resistance will meet safety requirement for the RCD regardless of switch S13 Example with demoboard In this example RCD operation test in switchboard S1 is shown Demoboard setup Condition Notes 12 OFF Earthing resistance ca xy O Normal condition 12 ON Earthing resistance ca 250 O Too high contact voltage Switch board 1 RCD fuses ON Mains voltage on Jumper M4 ON RCD protected installation Jumper 1 OFF TT system Jumper 2 OFF Conn 1 OFF To exclude separate Conn 2 OFF lighting system from the earthing system 40 Measurement of rcd paramaters 41 Leakage current measurement 8 Leakage current measurement Background of measurement Leakage and fault currents are caused by appliance EMC filters and because of non ideal insulation resistances in appliances and installation Leakage currents increase with the size of installation and number of devices connected to it If the sum of these currents exceeds the expected level they can cause different troubles like tripping of
6. accessible metal parts and PE conductors is one of the most important requirements when protecting electric installations Well earthing will result in automatic trip out of mains voltage in case of a fault Maximal allowed earth resistances depend on type of earthing working earthing protection earthing or lightning earthing and installation TN TT Earthing is also necessary measure when protecting electric installations against overvoltages There are different earth resistance measurement methods that can be carried out using two thre and four wire and or with current clamp s Two wire test system is used in case there is no place to drive auxiliary test rods is used in place without aux test rods driving possibility and a well grounded auxiliary terminal is available When measuring earth resistance in TT system of installation the power transformer s working earthing neutral conductor N can be used as one The method is applicable also when measuring earth resistance on open connection of parallel lightning system at bigger buildings Three wire test system is the only choice if measuring earthing resistance and there is no well earthed auxiliary terminal available The measurement is performed with two earthing probes Four wire test system is similar to the three wire one Its advantage is that it is not influenced by the contact resistance between measuring terminal and tested item Current clamp test system is suitable whe
7. on that basis If necessary two line conductors must be exchanged between each other in order to reverse the phase rotation Exercise No 9 1 Phase Rotation Test general Measuring connection Measuring procedure Set VOLTAGE or ROTARY FIELD function Connect item under test to instrument Notes The instruments check the line line voltages and phase delays between them Result is correct if all three voltages are present of approximately same size and in correct phase order First phase rotation on the reference mains outlet needs to be measured where behavior of a specific machine e g direction of phase rotation is known The direction should be noted Measurement should to be repeated on an unknown mains outlet and both results compared If necessary reverse the phase rotation 45 Phase rotation test Regulations Specifications for rotary field measurements are defined in IEC EN 61557 7 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Documentation For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Exercise No 9 1 Phase Rotation Test Demoboard MI 2067 Example with demoboar
8. panel AUXrod1 AUXrod2 which enable measurements using three and four wire test system The following earth resistances can be measured using the demonstration board Resistance of Basic Grounding system BG Resistance of Lightning earthing system LR1 and LR2 The following errors can be simulated 12 Too high earth resistance of Basic Grounding system approx 250 Q 13 Too high earth resistance of Lightning system 1 additional resistance of approx 100 Q 17 Earthing resistance measurements Example with demoboard Example on figure below shows measurement of earthing resistance of the demoboard lighting system The instrument is connected to simulated earthing probes AUXrod1 H AUXrod2 S and lighting rod 1 Demoboard Condition Notes setup 13 OFF Resistance of lightning Normal condition system ca 3 O 13 ON Resistance of lightning Fault in lighting system Faulty rod can system ca 9 Q be found with one clamp method or with disconnection and measuring individual rods Conn1 ON To include complete lighting system Conn2 ON Jumper2 OFF To exclude other earthing terminals 18 Earthing resistance measurements Exercise No 3 3 Earth Resistance Measurement current clamp method general Measuring connection In the example below the lighting system consists of more parallel connected earth bars To measure earthing resistance of individual rods instrument terminals mu
9. to regulatives Documentation The continuity test is one of the standard tests for verification of electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place operator of the test instrument etc Measurement results must be placed into appropriate columns of the final test report Conductor continuity measurement Regulations Requirements for continuity measurements are defined in IEC EN 61557 4 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Exercise No 1 1 Conductor continuity measurement Demoboard MI 2067 Simulation of faults with demoboard Demonstration board enables to set eight different faults concerning low ohm connections which can be freely combined enabling the user of the board to set a large number of fault combinations Setting switches S4 to S11 to fault position unacceptably high resistance is included into the tested loop resistance R lt 1 Q in all loops in case switches are not in fault position The following high resistances over limit can be activated 11 Main Potential Equalizing Collector MPE Heat installation S10 MPE Gas installation S9 MPE Protection Earth Collector 2 EC2 S8 Protection Earth Collector 1 EC1 PE terminal at three
10. Even relatively small currents are dangerous if resistance to earth and equipotential bonding are relatively high Typical fault reasons are deteriorated insulation dirt moisture filter capacitors etc Function of RCD In TN system fault and leakage currents flow from live conductors to protection earth conductor and then through PEN conductor to neutral terminal of power transformer The RCD must trip out if the leakage fault current exeeds its nominal current IFAULT LEAKAGE lt lan It must be assured that the fault and leakage currents do not cause touch voltages higher than conventional safety limit of 50 25 V ZLoop lan lt Uc Impedances in TN systems are usually much lower than allowed for example impedance of fault loop protected by RCD protection device with rated differential current of 30 mA could be as high as 1666 Q while actual values are lower than 2Q In TT system fault currents supplied by line voltage flow through the fault to protection earth conductor PE and then to ground via system earthing resistance The current is droved to grounding system of power transformer and thus to neutral terminal of the transformer Total impedance of the fault loop consists of more serial impedances where the major part presents global resistance of earthing system other impedances are negligible in comparison with this resistance Following condition must be fulfilled Re lan s Uc where Reis global earthing resista
11. N usually does not trip an RCD However the trip limit may be exceeded because of leakage current flowing to the PE protective conductor or capacitive connections between L and PE conductors This must be considered as a leakage problem and not as a problem of the RCD itself Regulations Specifications for RCD testing requirements in TN TT systems are defined in IEC EN 61557 6 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Maximum allowed disconnection times for RCDs are defined in IEC EN 60755 IEC EN 61008 and IEC EN 61009 Measurement of rcd paramaters Documentation RCD operation and contact voltage test are one of the standard verification tests for electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place etc Measurement results must be placed into appropriate columns of the final test report Exercise No 7 1 Testing of installed RCDs Demoboard MI 2067 Simulation of faults with demoboard Two switchboards on demonstration board are RCD protected The RCD operation can be checked on Outlets 1 2 and 3 phase outlet If TT system is selected different values of resistances to earth can be set to check the effectiveness of the installed RCD Resistance of Basic Grounding system
12. RCDs If the installation protective measures are improper excessive leakage and fault currents can result in dangerous contact voltages in the system Leakage currents can be easily measured with high quality current clamps Exercise No 8 1 Leakage current measurement with current clamp general Measuring connection CA _ Ce O Fr BES 8 Transformer k SH Rw 0 Leakage current measurement Measuring procedure Set CURRENT function Set TRMS CURRENT subfunction some models Set limit value Connect current clamp After pressing START key test the instrument measures the TRMS value of current flowing through the clamp Notes The clamp current measurement could be influenced by near EM fields caused by high load currents in line conductors large metal surfaces on high voltage in fuse cabinets etc Some types of electronic devices frequency converters etc can produce DC leakage currents DC currents are not detected with AC current clamps Only special current clamps declared as leakage clamps are suitable for this measurement Regulations There is no special regulation for measuring leakage current in installations so far Documentation For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place etc Me
13. asurement results must be placed into appropriate columns of the final test report Exercise No 8 1 Leakage current measurement with current clamp Demoboard MI 2067 Simulation of faults with demoboard Demonstration board has prepared several connections for current clamp measurements In switch board S2 washing machine currents can be measured via three prepared loops PE conductor current of washing machine can be increased with switch S8 The leakage current is too small to trip out the RCD in both cases Example with demoboard The example shows the washing machine leakage current measurement Demoboard setup Condition Notes S8 OFF Appliance leakage ca xy Q Normal condition S8 ON Appliance leakage ca 250 Q Appliance fault Switch board 2 Mains voltage on RCD fuses ON 43 Leakage current measurement 44 Phase rotation test 9 Phase rotation test Background of measurement In practice we often deal with the connection of three phase loads motors and other electro mechanical machines to three phase mains installation Some loads ventilators conveyors motors electro mechanical machines etc require an exact phase rotation and some may even be damaged if the rotation is reversed This is why it is advisable to test phase rotation before connection is made The test instrument compares all three line line voltages concerning amplitude and phase delay Phase rotation is determined
14. ator clamp and measured with the leakage clamp 22 Earthing resistance measurements 1 U source N R GEN CLAMP E I LEAK CLAMP USOURCE voltage of internal AC source NGEN CLAMP number of turns of generating current clamp LEAK CLAMP current through the leakage clamp Note Distance between clamps must be at least 30cm Noise signals that are flowing through the measured earth can disturb the results For a measuring loop resistance higher than 200 the leakage clamp current become too small to obtain accurate results METREL instruments automatically detect too low clamp current and noise signals Regulations There is no special regulation for two clamp measuring method but it will be recommended in new IEC 60364 6 Documentation For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place etc Measurement results must be placed into appropriate columns of the final test report Exercise No 3 4 Earth Resistance Measurement two current clamp method Demoboard MI 2067 Simulation of faults with demoboard Demonstration board enables measurements of earth resistance using two current clamp The following earth resistances can be measured using the demonstration board Resistance of Basic Grounding system BG Sum of resistances of Lig
15. auxiliary test rods in Q The soil included in the measurements depends on the distance between the measuring probes Homogenity of soil eg evaluation of soil structure in different depths can be evaluating by changing the distance a Relation between distance and measured depth can be found in appropriate METREL documents Only instruments equipped with four test terminals and internal generator can perform this measurement 25 Earth resistivity measurement Exercise No 4 1 Earth resistivity measurement general Measuring connection oe Measured portion Measured portion Measuring procedure Set EARTH function Set EARTH p subfunction Set test parameters distance between rods Set test limit Place the probes and connect them to the instrument After pressing START key test signal is applied between H and E terminals Current starts to flow through the measured earthing resistance The instrument measures test voltage between S and ES E terminals After that the instrument internally reconnects the AC generator V and A meter to measure the probe resistances 26 Earth resistivity measurement Note Resistance of current H E and voltage S ES probes must be considered If too high the results are impaired Relation between distance between and depth of measured soil layer must be known METREL instruments check the probe resistances and for eventual noise during each
16. d Demonstration board if connected to 3 phase mains system enables measurement of 3 phase rotation at incorporated 3 phase outlet 46
17. e and prospective fault current measurement in TN system Demoboard MI 2067 Simulation of fault with demoboard Demonstration board enables measurements of fault impedance at the following loops Lamp 1 Lamp 2 3 phase motor 3 phase outlet computer system protection earth collector 2 gas installation and hot water installation In above listed loops unacceptably high resistance can be simulated setting switches S4 to S11 to fault position The following values of fault loop impedance can be set S4 current loop L1 PE of computer system gt 20 Q S5 current loop L1 PE of lamp 2 approx 2 7 Q S6 current loop L1 PE of 3 phase motor approx 3 3 Q S7 current loop L1 PE of lamp 1 gt 20 Q S8 current loop L1 PE of 3 phase outlet gt 3 4 Q S9 current loop L1 Protection earth collector 2 approx 2 2 Q 10 current loop L1 Gas installation approx 3 3 O 11 current loop L1 Hot water installation approx 3 3 Q 31 Fault loop impedance measurement Example with demoboard Demoboard setup Condition Notes Sxy OFF Resistance of basic earthing system Normal condition ca O Sxy ON Resistance of basic earthing system Fault ca O JMP1 ON To simulate TN system Switch board xy Mains voltage on trip lock RCD fuses ON test method recommended Jumper M4 ON Switch board xy Mains voltage on standard RCD OFF fuses test method recommended ON Jumper M3 ON
18. e short circuit current measurement general Measuring connection e494 20 460 00 065 O OA OD eS O1 Measurement procedure Set LINE function Set test parameters if applied fuse type size trip out time If test parameters are applied test limit is set automatically Connect item under test After pressing START key test instrument loads the voltage between L and N terminals and measures loaded and unloaded voltages The result is obtained by following formula simplified form R U UNLOADED U oapen LINE U R LOADED LOAD If phase delay is measured loop impedance Zine can be calculated Zune Rune joLune Notes Specified accuracy of line measurement is valid only if the mains voltage is stable during the measurement In general this is not a big problem since the test current is high ZLINE LINE Can be measured on 3 phase outlet only in the case of 3 phase connection of the demoboard 34 Line impedance measurement Regulations Specifications for earthing resistance measurements are covered in IEC EN 61557 3 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Documentation Line impedance is one of the standard verification tests for electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements l
19. easurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Regulations Requirements for earth resistance measurements are defined in IEC EN61557 5 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Exercise No 3 1 Earth resistance measurement two wire method Demoboard MI 2067 Simulation of faults with demoboard Demonstration board enables measurements of earth resistance using two three four wire system as well as current clamp system The following earth resistances can be measured using the demonstration board Resistance of Basic Grounding system BG Resistance of Lightning earthing systems LR1 and LR2 14 Earthing resistance measurements The following errors can be simulated 12 Too high earth resistance of Basic Grounding system approx 250 Q 13 Too high earth resistance of Lightning system 1 additional resistance of approx 100 Q Example with demoboard Example on figure below shows a two wire measurement of global earthing resistance of the demoboard building TT system is set The test instrument is connected between N mains conductor J1 and main potential equalizer MPE N supply connection of demoboard is used as auxiliary terminal Demobard setup Demoboard setup Condition Notes 12 OFF Re
20. ement Demoboard MI 2067 Demonstration board enables to set seven different faults concerning insulation resistance which can be freely combined enabling the user of the board to set a large number of fault combinations Setting switches S16 to S22 to fault position unacceptably low insulation resistance are simulated 16 Outlet 3 switch board S3 phase conductor L1 neutral conductor N 17 Outlet 3 switch board S3 phase conductor L1 protection earth conductor PE 18 Washing machine phase conductor L1 floor via metal housing 19 Washing machine phase conductor L1 protection earth conductor PE 20 3 phase motor phase conductor L1 protection earth conductor PE 21 3 phase outlet phase conductor L2 neutral conductor N 22 3 phase outlet phase conductor L1 phase conductor L2 Insulation resistance measurement Example with demoboard Example on figure below shows insulation resistance test between phase conductor and main potential equalizer MPE in switch board S1 Demobard setup Demoboard setup Condition Notes S20 OFF Insulation L1 PE gt 500 MQ normal condition S20 OFF Insulation L1 PE lt 0 5 MQ Fault on motor in L1 RCD 300mA OFF to disconnect mains Jumper4 ON Fuses 1 to 4 ON to include complete wiring 10 Earthing resistance measurements 3 Earth resistance measurements Background of measurement Correct earthing of
21. eter is connected between S and E Renu Re R Ro Cpe La ea R R R R lt lt Re SO Rma ER g Ross RER Ry R RollRe lt lt Re SO Rowse Re Isolation EL 4s p 13 Earthing resistance measurements Measuring procedure Set EARTH function Set EARTH 2 3 4W subfunction some models Set test limit Connect item under test After pressing START key test signal is applied between H and E terminals Current starts to flow through the measured earthing resistance The instrument measures test voltage between S connected with E and ES connected with E terminals and current The earthing resistance result is calculated from both results After that the instrument internally reconnects the AC generator V and A meter to measure the probe resistances In the two wire test probes are not used so the measured probe resistances must be ca 0 Q Notes f mains N conductor is used during the resistance test eventual voltage noise can influence the results To obtain correct results it must be assured that the resistance at the auxiliary terminal is small compared to the measured resistance Documentation Global and local earthing resistances are one of the standard tests for verification of electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the m
22. htning earthing system LR1 and LR2 The following errors can be simulated 12 Too high earth resistance of Basic Grounding system approx 250 Q 13 Too high earth resistance of Lightning system 1 additional resistance of approx 100 Q 23 Earthing resistance measurements Example with demoboard Example on figure below shows measurement of demoboard building basic grounding system Measured loop consists of Earthing of mains transformer N conductor and PE conductor on which demoboard is connected Earthing resistance of demoboard building s basic grounding system Demoboard Condition Notes setup 12 OFF Resistance of basic earthing system normal condition ca 10 O 12 ON Resistance of basic earthing system Fault on system earthing prolongation ca 250 O connection wire JMP1 ON to simulate TN system JMP2 OFF To exclude lighting system 24 Earth resistivity measurement 4 Earth resistivity measurement Background of measurement Earth resistivity measurement is usually carried out when testing structure of soil in order to use this information for further designing of earthing system length and deepness of earth rods Usually Wenner s method is used for the measurement Earth resistivity is calculated as follows p 2 n a R where Dhakiri earth resistivity in Qm d a distance between two test rods in m Rise measured value of resistance between P1 and P2
23. ike type of the measurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Exercise No 6 1 Line impedance and prospective short circuit current measurement Demoboard MI 2067 Simulation of fault with demoboard Demonstration board enables measurements of line impedance at the following current loops switch board S1 Outlet 1 and 3 phase outlet switch board S2 Outlet 2 switch board S3 Outlet 3 In above listed current loops unacceptably high resistance can be simulated setting switches S1 to S3 to fault position The following values of line impedance can be set S1 current loop L3 N at 3 phase outlet gt 10 Q S2 current loop L1 N at outlet 2 gt 10 Q S3 current loop L1 N at outlet 1 gt 10 Q current loop L1 N at outlet 3 100 continuously present regardless of switches Example with demoboard Demoboard setup Condition Notes Sxy OFF Line impedance ca Q normal condition Sxy ON Line impedance ca Q fault Switch board xy mains voltage on RCD fuses ON Jumper M4 ON 35 Line impedance measurement 36 Measurement of rcd paramaters 7 Measurement of RCD paramaters Background of measurement RCD protection switches are used to protect users of electric appliances against electric shock caused by fault and leakage currents in the installation
24. instrument A series of measurements must be performed to get proper data about soil structure and homogenity Regulations Specifications for earthing resistance measurements are covered in IEC EN61557 5 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Documentation For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Exercise No 4 1 Earth resistivity measurement Demoboard MI 2067 Simulation of fault with demoboard Demonstration board enables to set four different distances between auxiliary rods so four different resistances between test terminals P1 and P2 can be measured It is important to know that earth resistivity will always be the same in all four cases as the measurements are meant to be done at the same homogenous soil The following values of resistance R and distances a can be selected using switches 14 and 15 S14 off S15 off a 1m R 20 Q S14 on S15 off a 3m R 6 7 Q S14 off S15 on a 10m R 2Q 14 on S15 on a 12m R 1 67 Q Example with demoboard Example on figure below shows typical soil resistivity measurement The instrument terminals are connected to simulated earthing
25. isturb the results 16 Earthing resistance measurements METREL instruments automatically check the probes resistances during test The three wire test method can performed with three or four wires terminals H S E or H S E ES connected If measuring with three wires the contact resistance of E probe is added to the result and must therefor be low With the four wire connection the contact resistance between E probe and tested metal surface is excluded from the result with help of ES terminal Regulations Specifications for earthing resistance measurements are covered in IEC EN61557 5 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Documentation Global and local earthing resistances are one of the standard verification tests for electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Exercise No 3 2 Earth Resistance Measurement three wire method Demoboard MI 2067 Simulation of faults with demoboard Demonstration board enables measurements of earth resistance using two three four wire system as well as current clamp system There are two auxiliary test terminals on front
26. models Set test parameters test voltage and limit Connect item under test After pressing START key test voltage is applied to test leads and thus to the object under test The instrument calculates the value of insulation resistance on base of measured voltage and current At the end of test the tested items is discharged Notes Mains voltage must be switched off during the test Other fuses and switches should be closed to include all for safety relevant parts f electrical loads lamps equipment are connected to the mains the installation test between L and N terminal can usually not be carried out This must be considered Tested items must be discharged after the test with high voltage DC voltage The measuring instruments do this automatically Documentation The insulation test is one of the standard tests for verification of electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Regulations Requirements for insulation resistance measurements are defined in IEC EN61557 2 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Exercise No 2 1 Insulation resistance measur
27. n measuring earth resistances of individual earthing rods in an earthing system The earthing rods do not need to be disconnected Two current clamp test system is used when measuring earth resistances of grounding rods cables etc under earth connections etc It is especially suitable in urban area 11 Earthing resistance measurements Exercise No 3 1 Earth resistance measurement two wire method general Measuring connection EXAMPLE1 In this example the N conductor is is used as the auxiliary test terminal The earthing resistance of the transformer and resistance of N conductor must be small compared to the measured resistance DS O O IEN R 9 Most of measuring instruments are without ES terminal In this case voltmeter is connected between S and E Transformer SOLAR RE R amp O Measured portion U Earthing resistance measurements EXAMPLE 2 In this example parallel connection of resistances R1 R2 R3 and R4 is used as auxiliary test terminal As independent auxiliary test terminals the following systems can be used too Gas installation system Railway rail system Water installation system metal etc It is assumed that the resistance of the auxiliary test terminal is small compared to the measured resistance gt ES OC Qu amp 4 A KW Most of measuring instruments are without ES terminal In this case voltm
28. nce in Q he nominal differential current of RCD less limit contact voltage 50V or 25 V RCD parameters RCD test parameters test current shape size must be set correctly before the test Disconnection time tan and actual disconnection currents I are measured A complete analysis of the proper operation of installed RCD includes disconnection times tan at 2 1 and 5 lan contact voltage test Limit values are defined in appropriate standards and are usually inbuilt in measuring equipment 37 Measurement of rcd paramaters Exercise No 7 1 Testing of installed RCDs general Measuring connection EXAMPLE 1 In that example RCD test in a TN system is shown 8 i ay D O O START CSS Yoe TE INE ZL O4 RU A Transformer AAPA 38 Measurement of rcd paramaters EXAMPLE 2 In that example RCD test in a TT system is shown N O EN va 200 a Transformer Measurement procedure Set RCD function Set RCD subfunction tAN IA AUTO Uc RS Set test parameters IAN multiplikator RCD type test current starting polarity Test limit is set automatically Connect item under test After pressing START key test the instrument drives test fault current from phase terminal to PE terminal The instrument can measure actual trip out current trip out time at nominal tripout current contact voltage Notes The measurement of contact voltage and IA
29. nt is to be found in appropriate table for a certain type of fuse At automatic installation fuses is the current which ensures reliable tripping out involved automatic fuse at B type of automatic installation fuses is equal to 5 x In at C type la is equal to 10 x h etc Conductor continuity measurement Exercise No 1 1 Conductor continuity measurement general START RADOMA D TeS a CHANGE y R e MPE main potential equilizing e Local potential equilizing Z O e PE terminals at mains outlets e Heat or gas installation e Water installation e Lamp and appliance housings e Lightning system e Local potential equilizing a J l N z YV Measuring procedure Set CONTINUITY function Set LOWQ 200mA subfunction Set test parameters and limits Calibrate test leads if necessary Connect item under test After pressing START key the test current flows through the object under test The instrument measures voltage drop and test current and calculates resistance R Polarity of test current is automatically exchanged the instrument measures voltage drop and test current and calculates R Final result is the average value of R and R Notes During the measurement mains voltage must be switched off Resistance of measuring leads must be compensated before test CONTINUITY 7 mA is intended for fast continuity checks This test is does not conform
30. phase outlet S7 EC1 Casing of LAMP 1 S6 EC1 Casing of 3 phase motor S5 EC2 Casing of LAMP 2 S4 EC3 Accessible metal parts of computer system Example with demoboard Example on figure below shows measurement of continuity between main potential equalizer MPE and local protection earthing collector EC2 Demobard setup Demoboard setup Condition Notes S9 OFF Continuity MPE EC2 lt 0 40 normal S9 ON Continuity MPE EC2 gt 2 0 Q fault Other settings Conductor continuity measurement Insulation resistance measurement 2 Insulation resistance measurement Background of measurement Appropriate Insulation Resistance between live parts and accessible conductive parts is a basic safety parameter that protects against direct or indirect contact of the human body with mains voltage Insulation resistance between live parts which prevents short circuits or leakage currents is also important High fault leakage currents can cause fire especially if they spark In general insulation decreases with age dirty moisture etc On electrical installations insulation resistance shall be measured between Phase conductors Phase and PE conductors Phase and neutral conductors Neutral and PE conductors On electrical appliances insulation resistance shall be measured between Phase connected together and PE conductors Phase connected together and accessible conduc
31. probes C1 H P1 S P2 ES and C2 E 27 Earth resistivity measurement Demoboard setup Condition Notes S14 ON OFF 1 67 Q to 20 Q as in table above To simulate behavior of 15 ON OFF results in homogenous soil 28 Fault loop impedance measurement 5 Fault loop impedance measurement Background of measurement In TN system all accessible metal parts are connected to neutral conductor N via protection earth conductors PE and thus to ground by means of earthing system of power transformer Safety conditions are checked by measuring loop impedance Zi oop or Rioop and calculating prospective fault current lpfc The fault loop impedance Zioop Zit Zpe Zyre Zt consists of A PRE phase conductor E Lp ieee protection earth conductor in building a ZNPE common neutral protection earth conductor from mains transformer to building a Z ees transformer The prospective fault current is calculated from lPrc Ulpe Zioop with m Uribe rated fault loop voltage Overcurrent disconnection device must be designed to trip out in case of an earth fault i e short circuit of line to earth PE Limit currents and impedance depend on selected fuse type size and required trip out time Where TN installation is protected with a RCD special measuring techniques are used to avoid tripping out the RCD during the test Allowed values of fault loop impedance resistance depend on re
32. quired trip out time which can be found in appropriate literature In TT system all accessible metal parts are connected to basic grounding system of the building via protection earth conductor PE Safety conditions are checked by measuring earth resistance RE The fault loop impedance Zioop Z Ze Zr Zer consists of ie te sateen phase conductor BZ Linie global earthing of building PE conductor in building A S earthing of supply system mn ZT transformer 29 Fault loop impedance measurement RCD devices are usually used as protection elements in TT system In case of short circuit or a high leakage current between phase and PE conductor contact voltage occures on accessible metal parts The voltage must stay below 50 V 25 V for aggravating conditions otherwise the RCD must trip out Exercise No 5 1 Fault loop impedance and prospective fault current measurement in TN system general Measuring connection O AEN QU 1 X 3 OL O E o CONTINUITY ZUNE TD RCD Measurement procedure Set LOOP function Select LOOP test method some instruments standard or trip lock Set test parameters if applied fuse type size trip out time If test parameters are applied test limit impedance or prospective fault current is set automatically Connect item under test After pressing START key test instrument loads the installation between L and PE terminals and measures loaded and
33. sistance of basic grounding Normal condition system ca 3 O 12 ON Resistance of basic grounding Fault in main earthing system ca 250 Q connection M2 ON To perform global earthing of building J1 OFF To set TT system J2 OFF To exclude lighting system from result 15 Earthing resistance measurements Exercise No 3 2 Earth Resistance Measurement three wire method general Measuring connection Most of measuring instruments are without ES terminal In this case voltmeter is connected between S and E gt 5 d U Measured portion d diagonal distance of building lt _ lt Measuring procedure Set EARTH function Set EARTH 2 3 4 W subfunction some models Set test limit Connect item under test After pressing START key test signal is applied between H and E terminals Current starts to flow through the measured earthing resistance The instrument measures test voltage between S and ES E terminals and current The earthing resistance result is calculated from both results After that the instrument internally reconnects the AC generator V and A meter to measure the probe resistances Note Resistance of current H and voltage S probes must be considered If too high the results are impaired Distances probe probe and probe object must be at least 5 times larger than the diagonal size of tested item Noise signals that flow through the measured earth can d
34. st be connected to earthing system and to two auxiliary test rods according to the figure below That way the instrument can calculate either total earthing resistance EARTH function or only the resistance of a certain earth bar using EARTH 1CLAMP function Most of measuring instruments are without ES terminal In this case voltmeter is connected between S and E Oo P R R EARTH CLAMP iti 4 ar E postan Oe ro ee Current probe Re R1 ll R2ll Rn 7 7 a7 7 y SSS std R R R R d diagonal distance of building Measuring procedure Set EARTH function Set EARTH 1CLAMP subfunction Set test limit Connect item under test After pressing START key test signal is applied between H and E terminals Current starts to flow through the measured earthing resistance The instrument measures test voltage between S and ES E terminals and current through the clamp The selective earthing resistance is calculated from both results U V meter k I Clamp 19 Earthing resistance measurements After that the instrument internally reconnects the AC generator V and A meter to measure the probe resistances The overall earthing resistance and probe resistances are available subresults Note Resistance of current H and voltage S probes must be considered If too high the results are impaired Distances probe probe and probe object must be at least 5 times larger than the diagonal size of tes
35. stem 1 additional resistance of approx 100 Q 20 Earthing resistance measurements Example with demoboard Example on figure below shows measurement of earthing resistance of lighting rod 1 The lighting system consists of lighting rods 1 and 2 The instrument is connected to simulated earthing probes AUX rod1 H AUX rod2 S and lighting rod 2 Current clamp are connected to CONN1 Demoboard setup Condition Notes 13 OFF Resistance of lightning rod ca O Normal condition 13 ON Resistance of lightning system Fault on earhing rod ca 100 Q Conn2 ON To simulate earthing Conn1 ON system with two rods 21 Earthing resistance measurements Exercise No 3 4 Earth Resistance Measurement two current clamp method general Measuring connection EXAMPLE 1 In this example the measurement of system earthing in building performed with earthing probe in TN system is shown Measured loop consists of earthing of mains transformer N conductor and system earthing of building The earthing resistance of the transformer and resistance of N conductor must be small compared to the measured resistance Transformer RO Measuring procedure Set EARTH function Set EARTH 2CLAMP subfunction Set test limit Connect both current clamps and item under test After pressing START key test signal is applied between H and E terminals Test signal is driven through the measured loop with the gener
36. ted item Noise signals that are flowing through the measured earth can disturb the results Noise currents that are flowing through the measured earthing rod can disturb the results In large systems with many rods only a small portion of the measuring current is flowing through the clamp If the clamp current is too small the results are impaired METREL instruments check automatically the probe resistances and for eventual noise during test Regulations Specifications for earth resistance measurements are defined in IEC EN61557 5 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Documentation For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place operator etc Measurement results must be placed into appropriate columns of the final test report Exercise No 3 3 Earth Resistance Measurement current clamp method Demoboard MI 2067 Simulation of faults with demoboard Demonstration board enables measurement of two separate earth resistances of Lightning system as each of the two lightning earth bars is equipped with an appropriate clamp connection The following errors can be simulated 12 Too high earth resistance of Basic Grounding system approx 250 Q 13 Too high earth resistance of Lightning sy
37. tive parts Typical measurement voltages and minimal allowed insulation resistances 100 Vire 0 100 MOQ Telecommunication installations 250 Vins 0 250 MQ Extra low voltage electric installations 500 Vue 0 500 MQ Low voltage electric installations UN lt 500 V floor and wall resistances insulation resistances of switch boards etc Electrical equipment and accessories 1000 V 1 000 MQ Low voltage electric installations Un gt 500 V floor and wall resistances insulation resistances of switch boards etc Insulation resistance measurement Exercise No 2 1 Insulation resistance measurement general Measuring connection EXAMPLE 1 Standard measuring connection e Phase conductor against lamp housing e Phase conductor against appliance housing e Phase conductor against PE conductor e Live conductors between each other ON co oe e Coax cable shield against middle conductor Isolation of gas installation Floor resistance Wall resistance Conductors between each other in switchbox O OO Q wT Oe 2 EXAMPLE 2 Some METREL instruments can perform the insulation tests L PE N PE L N test in one step Relais circuit Examples e All conductors between each other on socket e All conductors between each other in switchbox Insulation resistance measurement Measuring procedure Set INSULATION function Set INSULATION subfunction LPE LN NPE ALL some
38. unloaded voltages The result is obtained by following formula simplified form R U UNLOADED U toanen LOOP U toanen Rios If phase delays are measured loop impedance Zoop can be calculated Zioop RLoop joLroop 30 Fault loop impedance measurement Notes Specified accuracy of loop impedance measurement is valid only if mains voltage is stable during the measurement If RCD is installed it is likely that it will trip during the standard test In modern loop testers alternative measuring functions can be selected that will not trip the RCD trip lock etc In general this measurements are more influenced by unstable mains voltage than the standard one There are huge differencies in the accuracy and noise immunity of trip lock methods between different producers Regulations Specifications for loop impedance measurements are covered in IEC EN 61557 3 General requirements for equipment for testing safety of electrical installation are defined in IEC EN 61557 1 Documentation Loop impedance is one of the standard verification tests for electrical installations For measurements at a certain test object final test report is to be done containing all parameters of the measurements like type of the measurement type and serial number of the test instrument test place etc Measurement results must be placed into appropriate columns of the final test report Exercise No 5 1 Fault loop impedanc
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