GROUND RESISTANCE TESTER E N G L I S H User Manual Z Y X
Contents
1. 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 Ground Resistance Tester Model 3620 17 4 4 Ground Resistance Measurement Procedure 3 Point A 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 Procedure e Disconnect shorting link between Y and Z C2 P2 e Connect X to the ground rod to be tested Connect Y P2 to the central electrode e Connect Z C2 to the outer electrode Depress the Measure button to measure ground resistance A NOTE When performing a test this light will initially come on for approxi mately three seconds until the nominal test voltage is reached and then the light will go out if all indications are normal 7 ee s GROUND RESISTANCE TESTER MODEL 3620 Z Electrode Y Electrode D Alligator Clips Ground Rod VVVVY 10 3rd 10 2nd Measurement _ Measurement Ground Rod Y Electrode Z Electrode x 66389 z i T T 0 52 627 9 100 of distance i j i between X and Z Figure 82. 18 Ground Resistance Tester Model 3620 45 2 Point Measurement Simplified Measurement A NOTE This is an alternative method to three point measurement when an excellent 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 test lead resistances will also be included in the measurement and should be deducted from the final measurement This method is not as accurate as three point methods 62 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 used as a standard procedure but rather as a backup in tight areas Procedure Short Y and Z P2 C2 e Connect X to ground rod to be measured e Connect Z to an electrode Measure as in the three point method Grounding conductor Auxiliary rod Y Z shorted Utility pole GROUND RESISTANCE TESTER MODEL 3620 ar Butt plate Figure 9 Ground Resistance Tester Model 3620 19 4 6 Continuity Measurement Connect the shorting strip between Y P2 and Z C2 Continuity measurement is made with two leads one from
3. 1962 These safety warnings are provided to ensure the safety of per sonnel and proper operation of 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 sys tems are no exception Use extreme caution when using the instrument around ener gized electrical equipment Never attempt to use the instrument to twist or pry the ground electrode or ground wire away from the equipment being grounded AEMC Instruments considers the use of rubber gloves to be 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 Ground Resistance Tester Model 3620 1 1 International Electrical Symbols This symbol signifies that the instrument is protected by double or rein forced 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 b
4. Ground Electrode Figure 6 Now consider Figure 7 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 reading 2 5 10 etc Ground Auxiliary Auxiliary Electrode Potential Current Under Test Electrode Electrode ee A EE SS 62 of D 38 of D l Effective OH 4 y i ie eae ape sm e sects a l Resistance Areas Do Resistance of Not Overlap 1 is l Auxiliary Current Electrode Resistance Resistance of Earth Electrode Distance from Y to Ground Electrode Figure 7 16 Ground Resistance Tester Model 3620 4 3 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
5. 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 or 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 24 Ground Resistance Tester Model 3620 EJAEMC INSTRUMENTS 09 08 99 MAN 100152 v11 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
6. button and press again after the fault has been corrected Occasionally a stray voltage above 6VDC may also set off this light Check the leads for a possible solution 2 2 3 X Y High Noise This LED signals the presence of excessive noise approximately 13V peak in the voltage circuit between 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 Ground Resistance Tester Model 3620 7 Galvanometer Pointer If the pointer stops on the right side this indicates that you mea sured more than 1000Q over ranging condition or that the circuit is open If the pointer stops on the left side this indicates that you mea sured less than 0 5Q This may also indicate that the X and Y rods or the X and Z rods were inverted e Check the connections 23 Fault Indicator Tips And Solutions The LED indicators show excessive electrode resistance and or excessive transient noise and or stray current In the event of an incorrect measurement indication Improve the quality of the connection to earth of auxiliary ground electrodes Y and Z Z is the most likely source of problems caused by excessive electrode resistance e Check connections for continuity between leads and electrodes e Be sure that electrodes are properly inserted they should be buried as much as possible If high electrode resistance still exists after properly inse
7. 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 500 ft 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 carrying 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 25Q Calibration Checker Cat 2130 59 Tape Measure AEMC 100 ft Cat 2130 60 Ground Tester Video Workbook Set Cat 2130 64 Set of 2 T Shaped Auxiliary Ground Electrodes Cat 2135 39 Fuse Set of 5 0 1A gt 250V 0 25 x 1 25 Cat 2970 12 Ground Resistance Tester Model 3620 5 CHAPTER 2 PRODUCT FEATURES 21 Control Features O OI GQ N GROUND RESISTANCE TESTER MODEL 3620 X Z Fault E X Y Hi Resistance X Y Hi Noise Press To arer TO USER MANUAL Measure ri FAULT WARNING LIGHT PLANATION
8. 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 sur rounding 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 12 Ground Resistance Tester Model 3620 4 2 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 and Z is measured by an ammeter By Ohm s Law E RI or R E l 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 2 A NOTE Terminals X and Xv are shorted together in three point measurement Ground Resistance Tester Model 3620 13 4 2 1 Position of the Auxiliary Electrodes in Measurements The go
9. 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 25Q 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 resistance 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 a transmission line or in small substations In some regions resistances of 5Q 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 resistanc
10. E GROUND RESISTANCE 3 6 2 0 TESTER gt GROUND RESISTANCE TESTER MODEL 3620 X Z Fault C X Y Hi Resistance L X Y Hi Noise Press To REFER TO USER MANUAL Measure FOR FAULT WARNING LIGHT EXPLANATIONS EJAEMC User Manual INSTRUMENTS Set SS Sa Se SS Se Statement of Compliance Chauvin Arnoux Inc d b a AEMC 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 3620 Please fill in the appropriate date as indicated Date Received Date Calibration Due Chauvin Arnoux Inc d b a AEMC Instruments INSTRUMENTS www aemc com ee ee ee ee Table of Contents 1 INTR0DUCTI0N 3 1 4 International Electrical Symbols a 4 1 2 Definit
11. S Figure 1 Press to measure button Input terminal X C1 Input terminal Y P2 Shorting link Input terminal Z C2 Display 7 Zero adjustment screw 8 Low battery indicator 9 X Y hi noise indicator 10 X Y hi resistance indicator 11 X Z fault indicator Ground Resistance Tester Model 3620 2 2 Fault Indicator LEDs The three LED indicators described below confirm the correct measure ment being taken if none of them are lit 2 2 1 X Z Fault This LED signals that the voltage between terminals X and Z exceeds 30V peak There are five possible causes the resistance 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 e when the reading is under 0 5Q needle on the left of the scale A NOTE When performing a test this light will initially come on for approxi mately three seconds until the nominal test voltage is reached and then the light will go out if all indications are normal 2 2 2 X Y High Resistance This LED signals that the resistance in the voltage circuit between X and Y is too high approximately 50kQ or that the circuit may be open Flashing will continue throughout the measurement even if the resistance drops below the threshold for example after reconnecting or lowering auxiliary rod resistance In this case you must release the push
12. X the other from Y Z P2 C2 push the Press To Measure button to mea sure Figure 10 47 How to Use 250 Calibration Checker The calibration checker has a resistance of 25Q The procedure to use the calibration checker is as follows Loosen the X Y and Z terminals Insert the resistor as shown in Figure 11 Tighten down the terminals X Y and Z e Push down the Press to Measure button e 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 best if the shorting link is connected between Y and Z C Jf GROUND RESISTANCE TESTER MODEL 3620 CO X Z Fault XY HiResistance O XY Hi Noise Frese Ta REFER TO USER MANUAL Measure FOR FAULT WARNING LIGHT EXPLANATIONS INSTRUMENTS J Figure 11 20 Ground Resistance Tester Model 3620 CHAPTER 5 MAINTENANCE 51 Warning A Please make sure that you have already read and fully understand the WARNING section on page 3 For maintenance use only specified factory replacement parts To avoid electrical shock do not attempt to perform any servicing unless you are qualified to do so To avoid electrical shock and or damage 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 open
13. al 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 WEY YA Z Effective Resistance Areas Overlapping Resistance Reading Variation 100 of Distance Between X amp Z Figure 3 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 4 Effective Resistance Areas No Overlap Resistance 100 of Distance Between X amp Z Figure 4 14 Ground Resistance Tester Model 3620 43 Measuring Resistance of Ground Electro
14. des 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 Figure 5 GROUND RESISTANCE TESTER MODEL 3620 crauna Strip TAME ST 4 Ss Y Electrode Z Electrode SS S S z F Alligator Clips 4Z pps tas nt E Ground Rod VET FLIT 177171 147 y AAY a in rr BER 777 E a WINS ES oes rid BER eae WR 4 ele Figure 5 Consider Figure 6 which shows the effective resistance areas concentric shells of the ground electrode X and of the auxiliary current electrode Z The resistance 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 Ground Resistance Tester Model 3620 15 Ground Auxiliary Auxiliary Electrode Potential Current Under Test Electrode Electrode Overlapping Effective Resistance Areas Q c s A N x Distance from Y to
15. e 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 Ground Resistance Tester Model 3620 11 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 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 Poten tial
16. echsupport aemc com www aemc com NOTE Do not ship Instruments to our Foxborough MA address Ground Resistance Tester Model 3620 23 Limited Warranty The Model 3620 is warranted to the owner for a period of one year from the date of original purchase against defects in manufacture This lim ited warranty is given by AEMC Instruments not by the distributor from whom it was purchased This warranty is void if the unit has been tam pered with abused or if the defect is related to service not performed by AEMC Instruments For full and detailed warranty coverage please read the Warranty Coverage Information which is attached to the Warranty Registration Card if enclosed or is available at www aemc com Please keep the Warranty Coverage Information with 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 Service 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
17. gt en 1 2 Cat I Cat Il Cat Ill Cat IV 1 3 In conformity with WEEE 2002 96 EC Definition of Measurement Categories For measurements on circuits not directly connected to the AC supply wall outlet such as protected secondaries signal level and limited energy circuits For measurements performed on circuits directly connected to the electrical distribution system Examples are measurements on household appliances or portable tools For measurements performed in the building installation at the distribution level such as on hardwired equipment in fixed installation and circuit breakers For measurements performed at the primary electrical supply lt 1000V such as on primary overcurrent protection devices ripple control units or meters 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 equip ment appears to be damaged file a claim immediately with the carrier and notify your distributor at once giving a detailed description of any damage Save the damaged packing container to substantiate your claim Ground Resistance Tester Model 3620 1 4 Ordering Information Ground Resistance Tester Model 3620 Cat 2114 90 Includes soft carrying case batteries and a user manual Ground Resistance Tester Model 3620 Kit 150 ft Cat 2135 10 Includes gr
18. hat 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 support 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 t
19. ing the case 5 2 Cleaning A WARNING 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 53 Replacing the Battery To replace the batteries e Loosen the two fastening screws on the battery compartment cover which is located on the bottom of the case See Figure 12 e Remove the battery compartment cover to gain access to the eight 1 5V AA batteries Replace with new batteries and reassemble the instrument Ground Resistance Tester Model 3620 21 5 4 Replacing the Safety Fuse To replace the fuse A WARNING Do not replace the fuse when the instrument is connected e 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 e 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 WARNING DISCONNECT INSTRUMENT FROM ALL INPUTS BEFORE OPENING CASE Battery Compartment Fastening Fastening Screw Screw Figure 12 22 Ground Resistance Tester Model 3620 Repair and Calibration To ensure that your instrument meets factory specifications we recommend t
20. ion of Measurement Categories 4 1 3 Receiving Your Shipment u u 4 1 4 Ordering Intorfimati iu u u E 5 14 1 Kits Accessories and Replacement Parts 5 PRODUCT FEATURES 6 2 1 Control Features sienne u a aaa sas asas sss 6 2 2 Fault Indicator LEDs a 7 2 27 REZ PAUNS tes uu kusam ia uma Tisa qta uiisqa ata 7 2 2 2 X Y High Resistance oerrinne 7 2 2 3 XY High NOSS ic nn tia tel aces n E a aa 7 2 3 Fault Indicator Tips And Solutions 8 SPEGIFICATIONS UU M A u 9 3 1 Electrical sm cecctehatitietetidentitensdddetecte bad geuntdneceeanahd heentteasalecteade 9 2 Mechanical us um u uu n h una E i aaa aaa E 9 3 3 Environmental u n u N pa a ua ay ass 10 3 4 Safety Specifications T 10 OPERATION 11 4 1 Ground Resistance Values 11 4 22 Ground Resistance Testing Principle 13 4 2 1 Position of the Auxiliary Electrodes in Measurements 14 4 3 Measuring Resistance of Ground Electrodes 62 Method 15 4 3 1 Auxiliary Electrode Spacing 17 4 4 G
21. ound 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 user manual and warranty card Ground Resistance Tester Model 3620 Kit 300 ft Cat 2135 11 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 user manual and warranty card Ground Resistance Tester Model 3620 Kit 500 ft Cat 2135 11 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 user manual and warranty card 1 4 1 Kits Accessories and Replacement Parts Test Kit for 3 Point Testing 150 ft 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 300 ft Cat 2135 36 Includes two 300 ft color coded leads on spools red blue two 100 ft color coded
22. round Resistance Measurement Procedure 3 Point 18 4 5 2 Point Measurement Simplified Measurement 19 4 6 Continuity Measurement a 20 4 7 How to Use 250 Calibration Checker 20 5 MAINTENANCE 21 Beds Warming ees n yanin aad sali Dya m cats gal mu akna 21 9 2 Cleaning Asien ne alice isco Gee habia 21 5 3 Replacing the Battery u u 21 5 4 Replacing the Safety Fuse 22 Repair and Calibration r 23 Technical and Sales Assistance 23 himilediWamanyu u u D u tb A ass 24 Warranty Repas u u S ba aS aa waku ow 24 CHAPTER 1 INTRODUCTION AN WARNING It should be impressed on all personnel that a 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
23. rting 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 shift and test again A NOTE Accuracy may be affected by auxiliary ground rod Ry Rz resistance levels and by stray signal levels earth currents 8 Ground Resistance Tester Model 3620 CHAPTER 3 SPECIFICATIONS 3 1 Electrical Measurement Range 0 5 to 1000Q Test Current 10mA Operating Frequency 128Hz square wave Accuracy 5 of Reading 0 1 of galvanometer scale length Auxiliary Electrode Influence Rz 3000 times the reading up to 50kQ Ry 50kQ Voltage Withstand Unit is fuse protected In the event of a system fault the units can with stand 250Vrms with spikes of 3000VAc or 1000VDc Power Source Eight 1 5V AA batteries Alkaline recommended Battery Life 1680 15 second measurements approx Low Battery Indicator If the Low Battery indicator lights up the batteries are losing power The available operating time remaining is 80 15 second measurements approx Fuse Protection High breaking capacity 0 1A gt 250V 0 25 x 1 25 Accuracies and specifications are given for an ambient temperature of 23 C 3K RH of 45 to 55 battery power at 8V auxiliary resis
24. tance at the measurement terminals lt 200Q no stray voltage and a magnetic field from 0 to 40A m 3 2 Mechanical Dimensions 8 7 x 5 4 x 5 9 220 x 136 x 150mm Weight 2 9 Ibs 1 3kg Ground Resistance Tester Model 3620 9 Connection Color coded terminals accept spade lugs with minimum gap of 6mm or standard 4mm banana jacks Meter Movement Pivot movement Scale 3 1 77mm white scale with black pointer 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 Storage Temperature 40 to 158 F 40 to 70 C 0 to 90 RH with batteries removed Relative Humidity 20 to 90 maximum 3 4 Safety Specifications C O Electrical EN61010 1 Cat lll Pollution degree 2 24V Electromagnetic Compatibility Emission EN 50081 1 Immunity EN 50082 1 All specifications are subject to change without notice 10 Ground Resistance Tester Model 3620 CHAPTER 4 OPERATION 41 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 25 or less to ground shall be augmented by one additional electrode of any of the types specified by 250 52 A 4 through A
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