AEMC 3640 Ground Resistance Tester Manual PDF
Contents
1. u uu u 11 3 5 uuu u ice eit eere uds 12 4 OPERATIOIN 13 4 1 Grounding Electrode 13 4 1 1 Effect of Ground Electrode Size and Depth oni RESISTANCE ii oed cora ele ro i Ra eden 15 4 1 2 Effects of Soil Resistivity on Ground Electrode cibum 16 4 1 3 Factors Affecting Soil 17 4 1 4 Effect of Ground Rod Depth on Resistance 19 Digital Ground Resistance Tester Model 3640 and 4610 1 4 2 Ground Resistance Values 21 4 3 Ground Resistance Testing Principle 23 4 3 1 Position of Auxiliary Electrodes in Measurements 24 4 4 Measuring Resistance of Ground Electrodes 6296 Method 25 4 4 1 Auxiliary Electrode Spacing 27 4 5 Ground Resistance Measurement Procedure 3 Point 28 4 6 Multiple Electrode 29 4 7 2 Point Measurement Simplified Measurement 31 4 8 Continuity Measurement eee 32 4 9 Soil Resistivity Measurements Model 4610 Only 33 4 10 Soil Resistivity Measurement Procedure 42. Effective Resistance Areas Overlapping Resistance I Io 1 1 e 8 lt E X Y Distance Figure 9 On the other hand if the auxiliary potential rod Y is located outside of the effective resistance areas as Y is moved back and forth the reading variation is minimal The readings taken should be relatively close to each other and are the best values for the resistance to ground of the ground X The readings should be plotted to ensure that they lie in a plateau region as shown in Figure 10 x lal Effective Resistance ME Areas No Overlap I I _ Resistance X Y Distance Figure 10 24 Digital Ground Resistance Tester Model 3640 and 4610 4 4 Measuring Resistance of Ground Electrodes 62 Method The 62 method has been adopted after graphical consideration and after actual test It is the most accurate method but is limited by the fact that the ground tested is a single unit This method applies only when all three electrodes are in a straight line and the ground is a single electrode pipe or plate etc as in Figures 11 and 12 Model 3640 Ground 5 Strip Y Electrode Z Electrode 10 3rd 10 2nd J Measurement L ou Measurement Ground Rod Y Electrode Z Electrode 2 0 52 62 72 100 of distance between X and Z Figure 11 Model 4610 GROUND RES
3. Figure 15 WARNING Use extreme caution when disconnecting the ground connection from the rest of the circuit Current may be flowing and a dangerous potential could exist between the disconnected wires Xand Xv C1 P1 are shorted Disconnect shorting link between Y and Z C2 P2 Connect X to the ground rod to be tested Connect Y P2 to the central electrode Connect Z C2 to the outer electrode Depress the Measure button to measure ground resistance 28 Digital Ground Resistance Tester Model 3640 and 4610 4 6 Multiple Electrode System A single driven ground electrode is an economical and simple means of making a good ground system but sometimes a single rod will not provide sufficient low resistance and several ground electrodes will be driven and connected in parallel by a cable Very often when two three or four ground electrodes are used they are driven in a straight line When four or more are used a hollow square con figuration is used and the ground electrodes are still connected in parallel and equally spaced Figure 16 In multiple electrode systems the 6296 method electrode spacing may no longer be applied directly The distance of the auxiliary electrodes is now based on the maximum grid distance e g in a square the diagonal in a line the total length A square having a side of 20 ft will have a diagonal of approximately 28 ft DIAGONAL IVNOS VIG Figure 16 Digital Gro
4. DIGITAL GROUND RESISTANCE TESTERS GROUND RESISTANCE TESTER MODEL 3640 L3 X Z Fault C Xv Y Hi Resistance Xv Y Hi Noise REFER TO USER MANUAL AUTORANGING FOR FAULT WARNING LIGHT Press To EXPLANATIONS Measure GROUND RESISTANCE TESTER MODEL 4610 C X Z Fault C Xv Y Hi Resistance Di Li Li Li Xv Y Hi Noise Lt Li ECL Q AUTORANGING REFER TO USER MANUAL FOR FAULT WARNING LIGHT Press To EXPLANATIONS Measure AEMC AEMC User Manual INSTRUMENTS Statement of Compliance Chauvin Arnoux Inc d b a AEMCS Instruments certifies that this instrument has been calibrated using standards and instruments traceable to international standards We guarantee that at the time of shipping your instrument has met its published specifications An NIST traceable certificate may be requested at the time of purchase or obtained by returning the instrument to our repair and calibration facility for a nominal charge The recommended calibration interval for this instrument is 12 months and begins on the date of receipt by the customer For recalibration please use our calibration services Refer to our repair and calibration section at www aemc com Serial Catalog Model 3640 4610 Please fill in the appropriate date as indicated Date Received Date Calibration Due Chauvin Inc d b a AEMC Instruments INSTRUMENTS WWW aemc
5. shift and test again Display of 0 00 Xv and Y are short circuited Display of 0 X and Z or Xv and Y rods are reversed NOTE Accuracy may be affected by auxiliary ground rod Ry Rz resistance levels and by stray signal levels earth currents Digital Ground Resistance Tester Model 3640 and 4610 9 CHAPTER 3 SPECIFICATIONS 3 1 Electrical Measurement Ranges Auto ranging 0 to 20000 Range 200 2000 20000 Measurement 0 to 19 990 20 to 199 90 200 to 19990 Resolution 10mQ 100mQ 10 Test Current 10mA 1mA 0 1mA Accuracy 2 of Reading 1ct 5 of Reading 3cts Open Voltage 42V peak Operating Frequency 128Hz square wave Max Auxiliary Rod Resistance Range 200 2000 20002 Current Circuit 30kO 50 Voltage Circuit 50kQ Response Time Approximately 6 seconds for a stabilized measurement Interference Models 3640 amp 4610 are designed to reject high levels of interference voltage DC 50 60Hz harmonics DC voltage in series with X 20V AC voltage in series with Y 13V peak AC voltage in series with Z 32V peak Accuracies and specifications are given for an ambient temperature of 23 3 RH of 45 to 55 battery power at 8V auxiliary resistance at the measurement terminals 2000 no stray voltage and a magnetic field from 0 to 40A m Power Source Eight 1 5V AA batteries Alkaline recommended Battery Life 1800 15 secon
6. 2 Select apparent resistivity on P scale 3 Lay straightedge on R and P scale and allow to intersect with K scale Mark K scale point Lay straightedge on K scale point and DIA scale and allow to intersect with D scale 6 Point on D scale will be rod depth required for resistance on R scale 20 Digital Ground Resistance Tester Model 3640 and 4610 4 2 Ground Resistance Values NEC 2008 article 250 56 regarding the resistance of rod pipe and plate electrodes states that if the rod pipe or plate does not have a resistance of 25Q or less to ground shall be augmented by one additional electrode of any of the types specified by 250 52 A 4 through A 8 Where multiple rod pipe or plate electrodes are installed to meet the requirements of the section they shall not be less than 6 feet apart FPN The paralleling efficiency of rods longer than 8 feet is improved by spacing greater than 6 feet apart The National Electrical Code NEC states that the resistance to ground shall not exceed 250 This is an upper limit and guideline since much lower resistance is required in many instances How low in resistance should a ground be An arbitrary answer to this in ohms is difficult The lower the ground resis tance the safer and for positive protection of personnel and equipment it is worth the effort to aim for less than one ohm It is generally impractical to reach such a low resistance along a distribution system or
7. Point 34 4 11 How to Use 250 Calibration Checker 36 5 MAINTENANCIE 37 Warning tator eet eae e REP 37 5 2 Cleanirig eon e o teet e ER ied serito ne 37 5 3 Replacing the 37 5 4 Replacing the Safety 38 Repair and CGalibratiori reto ret Renee at ident endete 39 Technical and Sales Assistance sss 39 Limited Warranty 2 2 dee on Led 40 Warranty Repalls 3 2 40 2 Digital Ground Resistance Tester Model 3640 and 4610 CHAPTER 1 INTRODUCTION N WARNING N It should be impressed on all personnelthata lethal potential can exist between the station ground and a remote ground if a system fault involving the station ground occurs while tests are being made Since one of the objects of tests on a station ground is the establishment of the location of an effectively remote point for both current and potential electrodes the leads to the electrodes must be treated as though a possible potential could exist between these test leads and any point on the station ground grid excerpted from IEEE Std 81 1962 These safety warnings are provided to ensure the safety of personnel and proper operation o
8. Screw Screw Figure 24 38 Digital Ground Resistance Tester Model 3640 and 4610 Repair and Calibration To ensure that your instrument meets factory specifications we recommend that it be scheduled back to our factory Service Center at one year intervals for recalibration or as required by other standards or internal procedures For instrument repair and calibration You must contact our Service Center for a Customer Service Authorization Number CSA This will ensure that when your instrument arrives it will be tracked and processed promptly Please write the CSA on the outside of the shipping container If the instrument is returned for calibration we need to know if you want a standard calibration or a calibration traceable to N I S T Includes calibration certificate plus recorded calibration data Ship To Chauvin Arnoux Inc d b a AEMC Instruments 15 Faraday Drive Dover NH 03820 USA Phone 800 945 2362 Ext 360 603 749 6434 Ext 360 Fax 603 742 2346 or 603 749 6309 E mail repair aemc com Or contact your authorized distributor Costs for repair standard calibration and calibration traceable to N I S T are available NOTE You must obtain a CSA before returning any instrument Technical and Sales Assistance If you are experiencing any technical problems or require any assistance with the proper operation or application of your instrument please call mail fax or e mail our technical s
9. batteries carrying bag and user manual Ground Resistance Tester Model 3640 Kit 300 ft Cat 2135 14 Includes ground tester two 300 ft color coded leads on spools red blue two 100 ft color coded leads hand tied green black four T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure batteries carrying bag and user manual Ground Resistance Tester Model 3640 Kit 500 ft Cat 2135 15 Includes ground tester two 500 ft color coded leads on spools red blue two 100 ft color coded leads hand tied green black one 30 ft lead green four T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure batteries carrying bag and user manual Ground Resistance Tester Model 4610 Cat 2114 94 Includes soft carrying case batteries and a user manual 4 Digital Ground Resistance Tester Model 3640 and 4610 Ground Resistance Tester Model 4610 Kit 150 ft Cat 2135 16 Includes ground tester two 150 ft color coded leads on spools red blue one 30 ft lead green two T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure batteries carrying bag and user manual Ground Resistance Tester Model 4610 Kit 300 ft Cat 2135 17 Includes ground tester two 300 ft color coded leads on spools red blue two 100 ft color coded leads hand tied green black four T shaped
10. Digital Ground Resistance Tester Model 3640 and 4610 21 changes utilizing non metallic pipes and insulating joints have made this method of obtaining a low resistance ground questionable and in many instances unreliable Ground rods of course will be required in high voltage transmission lines where maximum resistance of 15 ohms is recommended and in distribu tion lines where maximum resistance of 25 ohms is preferred All electri cal systems constructed in accordance with the National Electrical Code should not exceed 25 ohms The measurement of ground resistances may only be accomplished with specially designed test equipment Most instruments use the Fall of Potential principle of alternating current AC circulating between an auxiliary electrode and the ground electrode under test the reading will be given in ohms and represents the resistance of the ground electrode to the surrounding earth AEMC Instruments has also recently introduced a clamp on ground resistance tester Note The National Electrical Code and NEC are registered trademarks of the National Fire Protection Association 22 Digital Ground Resistance Tester Model 3640 and 4610 4 3 Ground Resistance Testing Principle Fall of Potential 3 Point Measurement Three point measurement is used to measure resistance to ground of ground rods and grids The potential difference between rods X and Y is measured by a voltmeter and the current flow between rods X a
11. Factors Affecting Soil Resistivity Two samples of soil when thoroughly dried may become in fact very good insulators having a resistivity in excess of 109 ohm centimeters The resistivity of the soil sample is seen to change quite rapidly until approxi mately twenty percent or greater moisture content is reached Moisture content Resistivity O cm by weight Top Soil Sandy Loam 0 gt 109 gt 109 2 5 250 000 150 000 5 165 000 43 000 10 53 000 18 500 15 19 000 10 500 20 12 000 6 300 30 6 400 4 200 Table 2 The resistivity of the soil is also influenced by temperature Table 3 shows the variation of the resistivity of sandy loam containing 15 296 moisture with temperature changes from 20 to 15 C In this temperature range the resistivity is seen to vary from 7 200 to 330 000 ohm centimeters Digital Ground Resistance Tester Model 3640 and 4610 17 Temperature Resistivity ec F Q cm 20 68 7 200 10 50 9 900 0 32 water 13 800 0 32 ice 30 000 5 23 79 000 45 14 330 000 Table 3 Because soil resistivity directly relates to moisture content and temper ature it is reasonable to assume that the resistance of any grounding system will vary throughout the different seasons of the year Such varia tions are shown in Figure 6 below Since both temperature and moisture content become more stable at greater distances below the surface of
12. IN perra Concentric LLL 1 DLE Maa Shells of Ill QAM M NEN ORC RUN EASL Lv P ol t m N Z E i SRL me d Figure 3 Digital Ground Resistance Tester Model 3640 and 4610 13 C The only component remaining is the resistance of the surround ing earth The electrode can be thought of as being surrounded by concentric shells of earth or soil all of the same thickness The closer the shell to the electrode the smaller its surface hence the greater its resistance The farther away the shells are from the electrode the greater the surface of the shell hence the lower the resistance Eventually adding shells at a distance from the grounding electrode will no longer noticeably affect the overall earth resistance surrounding the electrode The distance at which this effect occurs is referred to as the effective resistance area and is directly dependent on the depth of the grounding electrode In theory the ground resistance may be derived from the general formula Length Resistance Resistivit esistance esistiVity X Area r This formula clearly illustrates why the shells of concentric earth decrease in resistance the farther they are from the ground rod Thickness of Shell R Resistivity of Soil x Area In the case of ground resistance uniform earth or soil resistivity through out the volume is assumed although this is seldom the case in nat
13. ISTANCE TESTER MODEL 4610 Ground 5 bd Strip EN Y Electrode Z Electrode N Alligator Clips 4 H 7 Ground Rod Wil HT NE 7 WA 7 Sri NN 2 Figure 12 Consider Figure 13 which shows the effective resistance areas concentric shells of the ground electrode X and of the auxiliary current electrode Z Theresistance areas overlap If readings were taken by moving the auxiliary potential electrode Y towards either X or Z the reading differentials would be great and one could not obtain a reading within a reasonable band of tolerance The sensitive areas overlap and act constantly to increase resistance as Y is moved away from X Digital Ground Resistance Tester Model 3640 and 4610 25 Ground Auxiliary Auxiliary Electrode Potential Current Under Test Electrode Electrode X Y 2 Overlapping Effective Resistance Areas Resistance Distance from Y to Ground Electrode Figure 13 Now consider Figure 14 where the X and Z electrodes are sufficiently spaced so that the areas of effective resistance do not overlap If we plot the resistance measured we find that the measurements level off when Y is placed at 62 of the distance from X to Z and that the readings on either side of the initial Y setting are most likely to be within the established tolerance band This tolerance band is defined by the user and expressed as a percent of the initial read
14. TESTER MODEL 4610 7 D Press To FOR FAULT WARNING LIGHT Measure Figure 2 1 Press to Measure button 7 Display 2 Input terminal X C1 8 Low battery indicator 3 Input terminal Xv P1 9 Xv Y high noise indicator 4 Input terminal Y P2 10 Xv Y high resistance indicator 5 Ground resistance shorting link 11 X Z fault indicator 6 Input terminal Z C2 Digital Ground Resistance Tester Model 3640 and 4610 2 3 Fault Indicator LEDs The three indicators described below confirm the correct measurement being taken if none of them are lit 2 9 1 X Z Fault This LED signals that voltage between terminals X and Z exceeds 30V peak There are four possible causes theresistance of the current circuit between X and Z is too high interference voltage in the current circuit is too high the fuse is blown the circuit is open lead not connected 2 3 2 X Y High Resistance 3640 Xv Y High Resistance 4610 This LED signals that the resistance in the voltage circuit between Xv and Y or X and Y is too high approx 50kQ or that the circuit may be open Flashing will continue throughout the measurement even if the resistance drops below the threshold e g after reconnecting or lowering auxiliary rod resistance n this case you must release the push button and press again after the fault has been corrected Occasionally a stray voltage above 6Vpc may also set off this light Check the leads for a possibl
15. a transmis sion line or in small substations In some regions resistances of 50 or less may be obtained without much trouble In others it may be difficult to bring resistance of driven grounds below 100Q Accepted industry standards stipulate that transmission substations should be designed not to exceed one ohm resistance In distribution substations the maximum recommended resistance is 5Q In most cases the buried grid system of any substation will provide the desired resistance In light industrial or in telecommunications central offices 50 is often the accepted value For lightning protection the arresters should be coupled with a maximum ground resistance of 10 These parameters can usually be met with the proper application of basic grounding theory There will always exist circumstances which will make it difficult to obtain the ground resistance required by the NEC When these situations develop several methods of lowering the ground resis tance can be employed These include parallel rod systems deep driven rod systems utilizing sectional rods and chemical treatment of the soil Additional methods discussed in other published data are buried plates buried conductors counterpoise electrically connected building steel and electrically connected concrete reinforced steel Electrically connecting to existing water and gas distribution systems was often considered to yield low ground resistance however recent design
16. ameter of 5 8 1 59cm is required for steel rods and 1 2 1 27cm for copper or copper clad steel rods NEC 2008 250 52 A 5 a b Minimum practical diameter for driving limitations for 10 ft 3m rods are 1 2 1 27cm in average soil 5 8 1 59cm in moist soil 3 4 1 91cm in hard soil or more than 10 ft driving depths 4 1 2 Effects of Soil Resistivity on Ground Electrode Resistance Dwight s formula cited previously shows that the resistance to earth of grounding electrodes depends not only on the depth and surface area of grounding electrodes but on soil resistivity as well Soil resistivity is the key factor that determines what the resistance of a grounding electrode will be and to what depth it must be driven to obtain low ground resistance The resistivity of the soil varies widely throughout the world and changes seasonally Soil resistivity is determined largely by its content of electro lytes consisting of moisture minerals and dissolved salts A dry soil has high resistivity if it contains no soluble salts Resistivity O cm Soil Minimum Average Maximum Ashes cinders brine waste 590 2 370 7 000 Clay shale gumbo loam 340 4 060 16 300 Same with varying proportions of sand and gravel Gravel sand stones with little clay or loam 1 020 15 800 135 000 59 000 94 000 458 000 Table 1 16 Digital Ground Resistance Tester Model 3640 and 4610 4 1 3
17. as been narrowed down to a plot of ground approximately 75 square feet 22 5 m Assume that you need to determine the resistivity at a depth of 15 feet 457 cm The distance between the electrodes must then be equivalent to the depth at which average resistivity is to be determined 15 ft or 450cm Using the more simplified Wenner formula 2 the electrode depth must then be 1 20th of the electrode spacing or 8 22 5cm If the electrode depth is greater than 1 20th of the electrode spacing the following formula must be used 34 Digital Ground Resistance Tester Model 3640 and 4610 4nAR Lay out the electrodes in a grid pattern Figure 22 and connect to the Model 4610 as shown in Figure 21 Proceed as follows Remove the shorting strip between X and Xv Connect all four auxiliary ground electrodes For example if the reading is R 15 P resistivity 27 x R x A A distance between electrodes 450 cm P 6 28 x 15 x 450 42 390 Q cm c G ROUND RESISTANCE TESTER IODEL 4610 15 00 0 Figure 21 Pte dq Y Y Y v vov v do Y Y Y v f Y Y Y Figure 22 Digital Ground Resistance Tester Model 3640 and 4610 35 4 11 How to Use 250 Calibration Checker The calibration checker is good for both the 3640 and 4610 It has a resistance of 25Q The procedure to use the calibration checker is as fo
18. auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure batteries carrying bag and user manual Ground Resistance Tester Model 4610 Kit 500 ft Cat 2135 18 Includes ground tester two 500 ft color coded leads on spools red blue two 100 ft color coded leads hand tied green black one 30 ft lead green four T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure batteries carrying bag and user manual 1 4 1 Kits Accessories and Replacement Parts Test Kit for 3 Point Cat 2135 35 Includes two 150 ft color coded leads on spools red blue one 30 ft lead green two T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure carrying bag Test Kit for 4 Point Testing Cat 2135 36 Includes two 300 ft color coded leads on spools red blue two 100 ft color coded leads hand tied green black four T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure carrying bag Test Kit for 4 Point Testing Cat 2135 37 Includes two 500 ft color coded leads on spools red blue two 100 ft color coded leads hand tied green black one 30 ft lead green four T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure carryi
19. bject to considerable variation of resistiv ity with changes in temperature as shown in Table 5 If salt treatment is employed it is of course necessary to use ground rods which will resist chemical corrosion The Effect of Temperature on the Resistivity of Soil Contining Salt sandy loam 20 moisture salt 5 of weight of moisture Temperature Resistivity Ohm centimeters 20 110 10 142 0 190 5 312 13 1440 Table 5 Such as copper sulfate sodium carbonate and others Salts must be EPA or local ordinance approved prior to use 4 1 4 Effect of Ground Rod Depth on Resistance Digital Ground Resistance Tester Model 3640 and 4610 19 To assist the engineer in determining the approximate ground rod depth required to obtain a desired resistance a device called the Grounding Nomograph may be used The Nomograph shown on the following page indicates that to obtain a grounding resistance of 20 ohms in a soil with a resistivity of 10 000 ohm centimeters a 5 8 OD rod must be driven 20 ft Note that the values indicated on the Nomograph are based on the assumption that the soil is homogeneous and therefore has uniform resistivity Figure 7 The Nomograph value is an approximation Grounding Nomograph Ground Rod Soil Resistivity Rod Depth Rod Diameter Resistance Ohms Ohm centimeters Feet Inches D 100 K R 100 80 DIA 60 40 Figure 7 1 Select required resistance on R scale
20. com ee ee Table of Contents 1 INTRODUCTION 3 1 1 International Electrical 3 1 2 Definition of Measurement Categories 4 1 3 Receiving Your Shipment u 4 1 4 Ordering Information a 4 14 1 Kits Accessories and Replacement Parts 5 2 PRODUCT FEATURES 6 2 1 3640 Control and Connector Identification 6 2 2 4610 Control and Connector Identification 7 2 3 Fault Indicator LEDS eater ede end 8 2 817 XZ Falta E fes 8 2 3 2 X Y High Resistance 3640 Xv Y High Resistance 4610 8 2 3 3 X Y High Noise 3640 Xv Y High Noise 4610 8 2 4 Over range Indication a 9 2 5 Fault LED Indication Tips and Solutions 9 3 SPECIFICATIONS 10 3 1 Electrical uice ee e essc 10 3 2 Mechanical rone P testa 11 3 3 Environmental eret it eee eee ete ede ea 11 3 4 Safety Specifications
21. d as a stan dard procedure but rather as a backup in tight areas See Figure 17 Procedure Short X and Xv C1 P1 Short Y and Z P2 C2 Connect X to ground rod to be measured Connect Z to an electrode Measure as in the three point method Grounding conductor Auxiliary rod Terminals shorted Y Z shorted Ground S level Utility pole GROUND RESISTANCE TESTER MODEL 4610 Ground rod Butt plate K7 57 Figure 17 Digital Ground Resistance Tester Model 3640 and 4610 31 4 8 Continuity Measurement Connect the shorting strips between X and Xv C1 P1 and Y P2 and Z C2 Continuity measurement is made with two leads one from X Xv the other from Y Z P2 C2 push the Measure button to measure Model 3640 GROUND RESISTANCE TESTER MODEL 3640 Press To Measure Figure 18 Model 4610 GROUND RESISTANCE TESTER MODEL 4610 Press To Measure Figure 19 32 Digital Ground Resistance Tester Model 3640 and 4610 4 9 Soil Resistivity Measurements Model 4610 Only Why make soil resistivity measurements Soil resistivity measurements have a threefold purpose First such data are used to make sub surface geophysical surveys as an aid in identifying ore locations depth to bedrock and other geological phenomena Second resistivity has a direct impact on the degree of corrosion in undergr
22. d measurements Low Battery Indicator If the Lo Bat indicator lights up the batteries are losing power The available operating time remaining is 100 15 second measurements approx Fuse Protection High breaking capacity 0 1A gt 250V 0 25 x 1 25 10 Digital Ground Resistance Tester Model 3640 and 4610 3 2 Mechanical Connection Color coded terminals accept spade lugs with minimum gap of 6mm or standard 4mm banana jacks Display 7 segment LCD 71 18mm high 3 1 2 digit 2000cts LCD also indicates overrange test lead shorts and lead reversals Dimensions 8 7 x 5 4 x 5 9 220 x 136 x 150mm Weight 2 9 Ibs 1 3kg Case Heavy duty ABS Colors Case safety yellow Front panel gray Mechanical Shock IEC 68 2 27 Vibration IEC 68 2 6 Drop Test IEC 68 2 32 Case Material UL94 Environmental O ring sealed against dust and water to IP50 3 3 Environmental Operating Temperature 14 to 131 F 10 to 55 C 0 to 90 RH Storage Temperature 40 to 158 F 40 to 70 C 0 to 90 RH with batteries removed 3 4 Safety Specifications C nj Electrical EN 61010 1 CAT III Pollution Degree 2 42V Electromagnetic Compatibility Emission EN 61326 1 Immunity EN 61326 1 Specifications are subject to change without notice Digital Ground Resistance Tester Model 3640 and 4610 11 3 5 Auto ranging The selection of the measurement current is depending on the resistance to measure When the
23. e solution 2 3 3 High Noise 3640 Xv Y High Noise 4610 This LED signals the presence of excessive noise approx 13V peak in the voltage circuit between Xv and Y or X and Y One remedy is to use shielded leads from the instrument to the auxiliary electrodes Connect all the shields to the rod under test 8 Digital Ground Resistance Tester Model 3640 and 4610 2 4 Over range Indication Over range is indicated when the display reads 1 or when the display is blinking and the indicator is lit 2 5 Fault LED Indication Tips and Solutions The LED indicators show excessive electrode resistance and excessive transient noise and or stray current In the event of an incorrect measurement indication e A Improve the quality of the connection to earth of auxiliary ground electrodes Y and Z Zis the most likely source of problems caused by excessive electrode resistance Check connections for continuity between leads and electrodes Be sure that electrodes are properly inserted they should be buried as much as possible If high electrode resistance still exists after properly inserting aux iliary electrodes into the earth try pouring water on and around the auxiliary electrodes This will improve their electrical connec tion to earth If stray currents are suspected one solution to reduce their influ ence is to move both Y and Z electrodes in an arc relative to the X electrode try e g a 90
24. e to the instrument do not get water or other foreign agents into the case Turn the instru ment OFF and disconnect the unit from all circuits before opening the case 5 2 Cleaning A NOTE Disconnect the instrument from any source of electricity Use a soft cloth lightly dampened with soapy water Rinse with a damp cloth and then dry with a dry cloth Do not use alcohol solvents or hydrocarbons 5 3 Replacing the Battery Loosen the two fastening screws on the battery compartment cover which is located on the bottom of the case See Figure 24 Remove the battery compartment cover to gain access to the eight 1 5V AA batteries Replace with new batteries and reassemble the instrument Digital Ground Resistance Tester Model 3640 and 4610 37 5 4 Replacing the Safety Fuse A NOTE Do not replace the fuse when the instrument is connected To replace the fuse Loosen the two fastening screws on the battery compartment cover which is located on the bottom of the case Remove the battery compartment cover to gain access to the fuse holder Replace the fuse with the appropriate replacement 0 1A gt 250V 0 25 x 1 25 and reassemble the instrument ATTENTION NE PAS OUVRIR LE BOITIER AVANT D AVOIR DECONNECTE TOUTES LES ENTREES Fuse Spare Holder Fuse Holders WARNING DISCONNECT INSTRUMENT FROM ALL INPUTS BEFORE OPENING CASE Fastening Compaen Fastening
25. f the instrument The instrument must not be operated beyond its specified operating range Safety is the responsibility of the operator All metal objects or wires connected to the electrical system should be assumed to be lethal until tested Grounding systems are no exception Use extreme caution when using the instrument around energized electrical equipment Never attempt to use the instrument to twist or pry the ground electrode or ground wire away from the equipment being grounded The use of rubber gloves is an excellent safety practice even if the equipment is properly operated and correctly grounded Always inspect the instrument and leads prior to use Replace any defective parts immediately 1 1 International Electrical Symbols This symbol signifies that the instrument is protected by double or reinforced insulation This symbol on the instrument indicates a WARNING and that the operator must refer to the user manual for instructions before operating the instrument In this manual the symbol preceding instructions indicates that if the instructions are not followed bodily injury installation sample and product damage may result Risk of electric shock The voltage at the parts marked with this symbol may be dangerous Ex PE In conformity with WEEE 2002 96 EC Digital Ground Resistance Tester Model 3640 and 4610 3 1 2 Definition of Measurement Categories I For measurements on circui
26. ing X296 5 10 etc Ground Auxiliary Auxiliary Electrode Potential Current Under Test Electrode Electrode X Y 2 g D 62 of D 38 of D Effective lt A gt Resistance EDDIE ene aren Areas Do Not Overlap Resistance of Auxiliary Current Electrode Resistance of Earth Electrode Resistance Distance from Y to Ground Electrode Figure 14 26 Digital Ground Resistance Tester Model 3640 and 4610 4 4 1 Auxiliary Electrode Spacing No definite distance between X and Z can be given since this distance is relative to the diameter of the electrode tested its length the homogeneity of the soil tested and particularly the effective resistance areas How ever an approximate distance may be determined from the following chart which is given for a homogeneous soil and an electrode of 1 in diameter For a diameter of 1 2 reduce the distance by 10 for a diameter of 2 increase the distance by 10 Digital Ground Resistance Tester Model 3640 and 4610 Approximate Distance to Auxiliary Electrodes Using the 62 Method Depth Driven Distance to Y Distance to Z 6 ft 45 ft 72 ft 8 ft 50 ft 80 ft 10 ft 55 ft 88 ft 12 ft 60 ft 96 ft 18 ft 71 ft 115 ft 20 ft 74 ft 120 ft 30 ft 86 ft 140 ft Table 6 27 4 5 Ground Resistance Measurement Procedure 3 Point Z Electrode Y Electrode M N Alligator Clips Ground Rod
27. instrument is turned ON the measurement starts on the smallest current range 100pA If the measurement is between 185 and 1950cts the range stays the same 100 If the measurement is under 185cts the current is multiplied by 10 within 10 max If itis above 1950cts the current is divided by 10 without going under 100p4A This is done to avoid switching back and forth between ranges when you are measuring 1900 It is possible to display 190 0 or 1900 depending the automatic range selection 12 Digital Ground Resistance Tester Model 3640 and 4610 CHAPTER 4 OPERATION 4 1 Grounding Electrode Resistance Figure 3 illustrates a grounding rod The resistance of the electrode has the following components the resistance of the metal and that of the connection to it the contact resistance of the surrounding earth to the electrode the resistance in the surrounding earth specifically A Grounding electrodes are usually made of a very conductive metal copper with adequate cross sections so that overall resistance is negligible B The National Institute of Standard and Technology N I S T has demonstrated that the resistance between the electrode and the surrounding earth is negligible if the electrode is free of paint grease or other coating and if the earth is firmly packed D Ground Rod li p and Clamp Between Rod and Soil LEILI Er NEN NEN NE
28. llows Loosen the X XV 4610 only Y and Z terminals Insert the resistor as shown in Figure 23 Tighten down the terminals X XV 4610 only Y and Z Push down the Press to Measure button Compare the reading on the display to the measurement range provided on the label A NOTE For alignment purposes of the test resistor it is recommended that the shorting links remain connected between X and XV for the Model 4610 and Y and Z for the Models 3640 and 4610 For example if a check was performed on the Model 4610 or 3640 the display should show a reading between 24 150 and 25 850 If so as Figure 23 the instrument is in good working condition AEM 250 CALIBRATION CHECKER 2 250 CALIBRATION CHECKER 3620 3640 4610 4600 3620 3640 4610 4600 18750 31250 24150 25850 24050 25950 18750 31250 24150 25850 24050 25950 NN fL N fL N GROUND RESISTANCE TESTER GROUND RESISTANCE TESTER MODEL 3640 MODEL 4610 INSTRUMENTS y Figure 23 36 Digital Ground Resistance Tester Model 3640 and 4610 CHAPTER 5 MAINTENANCE 5 1 Warning Please make sure that you have already read and fully understand the WARNING section on page 3 To avoid electrical shock do not attempt to perform any servicing unless you are qualified to do so To avoid electrical shock and or damag
29. nd Z is measured by an ammeter By Ohm s Law E RI or R we may obtain the ground electrode resistance R If E 20V and 1A then It is not necessary to carry out all the measurements when using a ground tester The ground tester will measure directly by generating its own cur rent and displaying the resistance of the ground electrode CURRENT SUPPLY AMMETER I VOLTMETER E GROUND AUXILIARY AUXILIARY ELECTRODE POTENTIAL CURRENT UNDER TEST ELECTRODE ELECTRODE Figure 8 A NOTE Terminals X and Xv are shorted together in three point measurement Digital Ground Resistance Tester Model 3640 and 4610 23 4 3 1 Position of the Auxiliary Electrodes in Measurements The goal in precisely measuring the resistance to ground is to place the auxiliary current electrode Z far enough from the ground electrode under test so that the auxiliary potential electrode Y will be outside of the effec tive resistance areas of both the ground electrode and the auxiliary current electrode The best way to find out if the auxiliary potential rod Y is outside the effective resistance areas is to move it between X and Z and to take a reading at each location If the auxiliary potential rod Y is in an effective resistance area or in both if they overlap by displacing it the readings taken will vary noticeably in value Under these conditions no exact value for the resistance to ground may be determined X Y 2 Cy
30. ng bag Test Kit for 3 Point Testing Supplemental for 4 Point Testing Cat 2135 38 Includes two 100 ft color coded leads hand tied green black one 30 ft lead green two T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure carrying bag Set of 2 T Shaped Auxiliary Ground Electrodes Cat 2135 39 Ground Tester Video Workbook Set Cat 2130 64 250 Calibration Cat 2130 59 Tape Measure AEMC 100 ft Cat 2130 60 Fuse Set of 5 0 1A gt 250V 0 25 x 1 25 Cat 2970 12 Order Accessories and Replacement Parts Directly Online Check our Storefront at www aemc com store for availability Digital Ground Resistance Tester Model 3640 and 4610 5 CHAPTER 2 PRODUCT FEATURES 2 1 3640 Control and Connector Identification GROUND RESISTANCE TESTER MODEL 3640 REFER TO USER MANUAL FOR FAULT WARNING LIGHT EXPLANATIONS Figure 1 1 Press to Measure button 6 Display 2 Input terminal X C1 7 Low battery indicator 3 Input terminal Y P2 8 Xv Y high noise indicator 4 Ground resistance shorting link 9 Xv Y high resistance indicator 5 Input terminal Z C2 10 X Z fault indicator 6 Digital Ground Resistance Tester Model 3640 and 4610 2 2 4610 Control and Connector Identification GROUND RESISTANCE
31. ound pipelines A decrease in resistivity relates to an increase in corrosive activ ity and therefore dictates the protective treatment to be used Third soil resistivity directly affects the design of a grounding system and it is to that task that this discussion is directed When designing an extensive ground ing system it is advisable to locate the area of lowest soil resistivity in order to achieve the most economical grounding installation Resistivity measurements are of two types the two point and the four point method The two point method is simply the resistance measured between two points For most applications the most accurate method is the four point method which is used by the AEMC Instruments Model 4610 Ground Tester The four point method as the name implies requires the insertion of four equally spaced and in line electrodes into the test area A known current from a constant current generator is passed between the outermost electrodes The potential drop a function of the resistance is then measured across the two innermost electrodes The Model 4610 is calibrated to read directly in ohms Ove w N GROUND RESISTANCE TESTER MODEL 4610 EXT eesja X electrode Xv electrode Y electrode Z electrode Figure 20 Digital Ground Resistance Tester Model 3640 and 4610 33 4 10 Soil Resistivity Measurement Procedure 4 Poin
32. t Assuming that the objective is low resistivity preference should be given to an area containing moist loam as opposed to a dry sandy area Consid eration must also be given to the depth at which resistivity is required Disconnect the shorting strip from the X and Xv terminals Arrange the electrodes in a straight line Be sure that distances between electrodes are identical e g 3 meters between each electrode See Figure 20 The distance between poles is proportional to the average depth of the soil sample you wish to make The electrodes should be placed at a depth of approximately 6 inches 0 15 meters so that the depth is approximately 1 20th of the distance between electrodes Use leads to connect the X Xv Y and Z electrodes to the respective terminals on the Digital Ground Resistance Tester Press the Measure button Read the resistance level R indicated on the display n the event of difficulties in performing measurements consult the previous instructions concerning ground resistance measurements Apply the following formula in order to determine resistivity p 2nxRxA A 7 distance between electrodes in meters P 7 resistivity in O meters R ohms reading obtained on Model 4610 Example 1 For measurement performed in soil with a high limestone content the reading is R 2250 with A 3 meters P 2r x 2250 x 3m 42399m Example 2 After inspection the area to be investigated h
33. the earth it follows that a grounding system to be most effective at all times should be constructed with the ground rod driven down a considerable distance below the surface of the earth Best results are obtained if the ground rod reaches the water table 80 60 40 Curve 1 20 Curve 2 Cee 5 22 FS BBS 5 2 2 5 Z 22 53 Figure 6 Seasonal variation of earth resistance with an electrode of 3 4 pipe in rather stony clay soil Depth of electrode in earth is 3 ft for Curve 1 and 10 ft for Curve 2 In some locations the resistivity of the earth is so high that low resistance grounding can be obtained only at considerable expense and with an elab orate grounding system In such situations it may be economical to use a ground rod system of 18 Digital Ground Resistance Tester Model 3640 and 4610 limited size and to reduce the ground resistivity by periodically increasing the soluble chemical content of the soil Table 4 shows the substantial reduction in resistivity of sandy loam brought about by an increase in chemical salt content The Effect of Salt Content on the Resistivity of Soil sandy loam moisture content 15 by weight temperature 17 Added Salt Resistivity by weight of moisture Ohm centimeters 0 10 700 0 1 1 800 1 0 460 5 190 10 130 20 100 Table 4 Chemically treated soil is also su
34. ts not directly connected to the AC supply wall outlet such as protected secondaries signal level and limited energy circuits CAT Il For measurements performed on circuits directly connected to the electrical distribution system Examples are measurements on household appliances or portable tools CAT Ill For measurements performed in the building installation at the distribution level such as on hardwired equipment in fixed installation and circuit breakers CAT IV For measurements performed at the primary electrical supply lt 1000V such as on primary overcurrent protection devices ripple control units or meters 1 3 Receiving Your Shipment Upon receiving your shipment make sure that the contents are consistent with the packing list Notify your distributor of any missing items If the equipment appears to be damaged file a claim immediately with the car rier and notify your distributor at once giving a detailed description of any damage Save the damaged packing container to substantiate your claim 1 4 Ordering Information Ground Resistance Tester Model 3640 Cat 2114 92 Includes soft carrying case batteries and a user manual Ground Resistance Tester Model 3640 Kit 150 ft Cat 2135 13 Includes ground tester two 150 ft color coded leads on spools red blue one 30 ft lead green two T shaped auxiliary ground electrodes set of 5 spaded lugs one 100 ft AEMC tape measure
35. und Resistance Tester Model 3640 and 4610 29 Multiple Electrode System Max Grid Distance Distance to Y Distance to Z 6 ft 78 ft 125 ft 8ft 87 ft 140 ft 10 ft 100 ft 160 ft 12 ft 105 ft 170 ft 14 ft 118 ft 190 ft 16 ft 124 ft 200 ft 18 ft 130 ft 210 ft 20 ft 136 ft 220 ft 30 ft 161 ft 260 ft 40 ft 186 ft 300 ft 50 ft 241 ft 340 ft 60 ft 230 ft 370 ft 80 ft 273 ft 440 ft 100 ft 310 ft 500 ft 120 ft 344 ft 550 ft 140 ft 372 ft 600 ft 160 ft 390 ft 630 ft 180 ft 434 ft 700 ft 200 ft 453 ft 730 ft 30 Table 7 Digital Ground Resistance Tester Model 3640 and 4610 4 7 2 Point Measurement Simplified Measurement This is an alternative method to three point measurement when an excel lent ground is already available In congested areas where finding room to drive the two auxiliary ground electrodes may be a problem the two point measurement method may be applied The reading obtained will be that of the two grounds in series Therefore the water pipe or other ground must be very low in resistance so that it will be negligible in the final measurement The lead resistances will also be measured and should be deducted from the final measure ment This method is not as accurate as three point methods 6296 method as it is particularly affected by the distance between the tested electrode and the dead ground or water pipe This method should not be use
36. upport team Chauvin Arnoux Inc d b a AEMC Instruments 200 Foxborough Boulevard Foxborough MA 02035 USA Phone 800 343 1391 508 698 2115 Fax 508 698 2118 E mail techsupport aemc com www aemc com NOTE Do not ship Instruments to our Foxborough MA address Digital Ground Resistance Tester Model 3640 and 4610 39 Limited Warranty The Ground Resistance Testers Model 3640 and 4610 are warranted to the owner for a period of one year from the date of original purchase against de fects in manufacture This limited warranty is given by AEMC Instruments not by the distributor from whom it was purchased This warranty is void if the unit has been tampered with abused or if the defect is related to service not performed by AEMC Instruments Full warranty coverage and product registration is available on our website at www aemc com warranty html Please print the online Warranty Coverage Information for your records What AEMC Instruments will do Ifa malfunction occurs within the one year period you may return the instrument to us for repair provided we have your warranty registration information on file or a proof of purchase AEMC Instruments will at its option repair or replace the faulty material REGISTER ONLINE AT www aemc com Warranty Repairs What you must do to return an Instrument for Warranty Repair First request a Customer Service Authorization Number CSA by phone or by fax from our Ser
37. ure The equations for systems of electrodes are very complex and often expressed only as approximations The most commonly used formula for single ground electrode systems developed by Professor H R Dwight of the Massachusetts Institute of Technology follows R ap In 4L 1 2nL r R resistance in ohms of the ground rod to the earth or soil L grounding electrode length r grounding electrode radius P average resistivity in ohms cm 14 Digital Ground Resistance Tester Model 3640 and 4610 4 1 1 Effect of Ground Electrode Size and Depth on Resistance Size Increasing the diameter of the rod does not materially reduce its resistance Doubling the diameter reduces resistance by less than 1096 100 75 S 50 m 25 0 1 2 58 3 4 1 1 1 4 1 1 2 1 3 4 Figure 4 Depth As a ground rod is driven deeper into the earth its resistance is substantially reduced In general doubling the rod length reduces the resistance by an additional 4096 Resistance in Ohms 5 15 25 35 40 50 60 70 Driven Depth in Feet Ground Resistance Versus Ground Rod Depth Figure 5 Digital Ground Resistance Tester Model 3640 and 4610 15 The NEC 2008 250 52 A 5 requires a minimum of 8 ft 2 4m to be in contact with the soil The most common is a 10 ft 3m cylindrical rod which meets the NEC code A minimum di
38. vice Department see address below then return the instrument along with the signed CSA Form Please write the CSA on the outside of the shipping container Return the instrument postage or shipment pre paid to Ship To Chauvin Arnoux Inc d b a AEMC Instruments 15 Faraday Drive Dover NH 03820 USA Phone 800 945 2362 Ext 360 603 749 6434 Ext 360 Fax 603 742 2346 603 749 6309 E mail repair aemc com Caution To protect yourself against in transit loss we recommend you insure your returned material NOTE You must obtain a CSA before returning any instrument 40 Digital Ground Resistance Tester Model 3640 and 4610 AEMC INSTRUMENTS 05 12 99 MAN 100143 v16 Chauvin Arnoux Inc d b a AEMC Instruments 15 Faraday Drive Dover NH 03820 USA Phone 603 749 6434 Fax 603 742 2346 www aemc com
Download Pdf Manuals
Related Search