Biddle DET62D_UG 电路图.pdf

DIGITAL EARTH TESTER MEGGERDET62D User Guide MeterCenter www.MeterC (800) 230-6008 NOTE THE INSTRUMENT MUST ONLY BE USED BY TRAINED AND COMPETENT PERSONS. GENERAL DESCRIPTION. The MEGGER DET62D Digital Earth Tester is a compact portable instrument designed to measure earth electrode resistance quickly and accurately. Powered by six LR6 battery cells, the instrument is very robust and has a tough case moulded in ABS plastic. The instrument uses the three-terminal method of measurement in which the X terminal is connected to the earth electrode under test, and the C and P terminals are connected to Current and Potential test spikes. Test frequency is 128 Hz to avoid problems from electrical mains Noise. Test leads and auxiliary electrode test spikes can be supplied as part of an earth testing field accessory kit which is available as an option. SAFETY WARNINGS Warnings and precautions must be read and understood before the instrument is used. They must be observed during use. The earth spikes, test leads and their terminations must not be touched if an installation earth-fault can arise, unless adequate precautions are taken. The DET62D must be disconnected while its battery cells are changed. Replacement fuses must be of the correct type and rating. Special precautions are necessary when live earths may be encountered. Isolation switches and fuses are needed in this situation. When working near high tension systems, rubber gloves and shoes should be worn. RadioFans.CN 收音机爱 好者资料库 DET62D FEATURES CIRCUIT CONDITION WARNING INDICATORS IF ANY OF THE WARNING INDICATION LEDS ARE ILLUMINATED, A WARNING ALERT ARROW IS DISPLAYED . HIGH CURRENT SPIKE RESISTANCE (Rc) During a test, if the resistance of the Current circuit is too high for accurate measurement, the Rc LED automatically illuminates. This may be caused by an open circuit, poor test lead connections, or excessive resistance of the soil near the electrode under test and / or the remote Current spike. Whatever the cause of the symbols appearance, it should be cleared before a test can be regarded as valid. Moistening the soil around the Current spike; re-siting the spike in a new position or using more than one spike may solve the problem. HIGH POTENTIAL SPIKE RESISTANCE (Rp) If the resistance of the Potential circuit is too high for an accurate measurement, the Rp LED automatically illuminates. This may be caused by an open circuit, poor test lead connections, or excessive resistance of the soil near the electrode under test and / or the remote Voltage spike. Whatever the cause of the symbols appearance, it should be cleared before a test can be regarded as valid. Moistening the soil around the Voltage spike; re-siting the spike in a new position or using more than one spike may solve the problem. EXCESSIVE NOISE INTERFERENCE (NOISE / BRUIT) During a test, if the interference voltage in the earth being measured is beyond the level that can be rejected by the Instrument, the NOISE LED will illuminate. Valid measurements cannot be made in this condition, and the solution may be to wait until the interference has subsided. Alternatively, choose a new position for the two remote test spikes, by re-siting them at right angles to their first position; still in a straight line, and try again. XPC ESH EARTH TESTER EARTH TESTER R D D The 312digit liquid crystal display shows all test resistance results directly in or k, with the decimal point automatically Warning LEDs (accompanied with Warning Alert arrow) indicate any excessive resistance in the Current circuit, or the Potential circuit (both usually caused by a high test spike resistance) and any excessively Noisy earth environment Single push button operation. All other functions are automatic Low battery voltage indicator If the resistance under test exceeds 2 k, an over-range symbol appears (1 as left hand digit, with a decimal point) Battery compartment cover Range indicators Electrode under test terminal Potential test spike terminal Current test spike terminal Case protected to IP54 Warning Alert arrow RadioFans.CN 收音机爱 好者资料库 APPLICATIONS The principal application of the DET62D is in the testing of single or small earth electrodes by the 3 terminal test technique. The instrument will directly measure the resistance to earth of an earth electrode, in the presence of electrical mains supply noise in the soil, provided it is not excessive. The instrument may also be used equally well for the testing of Continuity of conductors; conduit coupling joints etc. MEASURING METHOD - 3 TERMINAL RESISTANCE MEASUREMENT A measured current is passed between the electrode under test X, and the remote Current electrode C. The voltage drop between X, and the remote potential electrode P is measured. The resistance of the electrode under test is then the voltage between X and P, divided by the current flowing between X and C, provided there is no overlap of the resistance areas of the electrodes. The resistance area is where the incremental resistance is still significant, owing to localised current flows. V By Ohms Law: R = I THE FALL OF POTENTIAL METHOD This is the basic method for measuring the resistance of earth electrode systems. It is most useful on small single or double earth electrode systems. To obtain a reliable measurement with the Fall-of-Potential method the Current spike must be far enough away from the Earth electrode. In general, reliable results may be expected if the distance between the Current spike and the Electrode under test is at least ten times the maximum dimension of the electrode system, e.g. 30 m for a 3 m electrode system. Both possess resistance areas, and if they are positioned too close together their resistance areas will overlap. The optimum position for the Potential spike will be located between these resistance areas. To locate this point the Potential spike is moved between X and C, and readings are taken at each location. The more readings that are taken, the more accurate the final resistance reading will be. Test results are plotted, on a curve. The optimum position is the point on the curve where reading variation is minimal. Provided there is reasonable homogeneity of the soil, the distance apart is adequate, and the straight line of the electrodes is maintained, the shape of the curve will ideally be as shown. OPERATION INITIAL TEST SET UP AND CONNECTIONS 1. Connect a short lead from the Earth electrode to be tested to the instrument terminal X (E) (The resistance of this lead will be included in the measurement). 2. Insert the Current test spike into the ground 30 to 50 metres away from the Earth electrode to to be tested. Connect this spike to the instrument terminal C (H). 3. Insert the Potential test spike into the ground midway between the Current test spike and the Earth electrode, and in direct line with them both. Connect this spike to the instrument terminal P (S). 4. When running the test leads out to each remote electrode, avoid laying the wires too close to each other. ? ? ? ? A V XPC Auxiliary Current Electrode Auxiliary Potential Electrode Electrode Under Test CURRENT SOURCE Resistance Areas (Not Overlapping) Auxiliary Current Electrode C H Electrode Under Test X E Auxiliary Potential Electrode P S XPC ESH EARTH TESTER EARTH TESTER R D D RadioFans.CN 收音机爱 好者资料库 OPERATION LIVE EARTH SAFETY PRECAUTIONS It is preferable that the earth electrode to be tested is first isolated from the circuit it is protecting, so that only the earth is measured and not the complete system. When this is done, the circuits and equipment must be de-energised. If however this is not possible, the earth electrode should be duplicated so that when it is disconnected for test purposes, the other one provides the necessary circuit protection. The following safety precautions are essential when working near high tension systems where any unintentional Live earths may be encountered between the site earth and remote earths established for test purposes. A Live earth is one that carries current from the mains supply, or could do so under fault conditions. 1.All persons involved must be trained and competent in isolation and safety procedures for the system to be worked on. They must be clearly instructed not to touch the earth electrode; test spikes; test leads, or their terminations if any Live earths may be encountered. It is recommended that they wear appropriate rubber gloves, rubber soled shoes, and stand on a rubber mat. 2.The P (S) and C (H) terminals should be connected through a double pole isolation switch, the rating of which will cope with the maximum fault voltage and current. The isolation switch must be open whilst any personal contact is made with the remote test spikes,or the connecting leads, e.g. when changing their position. Note: If a fault occurs while a test is being made the instrument may be damaged. Incorporating fuses at the isolation switch, rated at 100 mA, and able to cope with the maximum fault voltage will provide some protection for the instrument. TEST PROCEDURE FOR EACH MEASUREMENT Connect the instrument terminals to the respective earth electrode and test spikes. See Initial Test Set Up and Connections. 1. Press the push button. This will begin the test sequence and include the circuit condition, and noise monitoring. The instrument will automatically switch Off after 30s of inactivity. Alternatively, press the Test push again to switch Off. 2. Check the circuit condition warning LEDs. If any adverse conditions are indicated, the cause should be rectified (to prevent a false reading), before the test continues. Note: If the Current spike resistance is too high for the required measurement range, the instrument will autorange to a range which can tolerate a higher Current spike resistance. This results in a loss of resolution. 3. If conditions for the test are satisfactory, the display will stabilise, and the reading given may be accepted. 4. Several individual readings are taken, in order to locate the Potential spike in its optimum position, relative to the Current spike and the Electrode under test. Measurements are plotted and the Plateau region of the curve is identified to confirm the real resistance value. 5. Calculate the average of ALL measurements which lie on the horizontal plateau of the curve. 6. If the maximum deviation from the average of all measurements is better than 5%, then their average may be taken as the resistance to earth of the electrode under test. Note: To determine X (E) terminal lead resistance, firmly connect the lead to the X (E) terminal, and its free end to the P (S) terminal. Firmly connect terminals P (S) and C (H) together with a short length of lead. Press the push button, and note the reading of the instrument. This is the resistance value of X (E) terminal lead ONLY. If desired, subtract this value from the overall measured resistance. CONTINUITY TESTING The instrument will measure metallic resistances of low inductance or capacitance. The circuit under test MUST be switched off, de-energised and isolated before the test is made. Firmly connect terminals P and C together with a short length of lead, and connect a short test lead from these terminals and another from X terminal. Connect these two test leads across the test points, press the push button, and note the instrument reading. Due to the inherent high accuracy of the instrument, and the low resistance to be measured, contact resistance between the test lead clips and the conduit could be a factor in the measured value. Contact and test lead resistance should therefore be kept as low as possible. BATTERY INSTALLATION It is advisable that new battery cells are available before embarking on a test sequence, as it can be extremely inconvenient if the battery life expires while a field test is in progress. Caution: Whenever battery cells are being fitted or replaced, there should be no connections to the instrument terminals. The cover to the battery compartment lifts off the front of the instrument, and is held in position by two captive screws in the base of the instrument. To fit or replace battery cells, loosen the two captive screws, and lift away the cover. Fit new cells as indicated on the battery compartment moulding. Replace the cover and tighten the securing screws. To avoid damage by leaking electrolyte, do not leave cells fitted in an instrument which will remain unused for extended periods of time. SPECIFICATION Earth Resistance Ranges: 00,0to199,9 0,00kto 1,999 k Accuracy (23C 2C):2% of reading 3 digits. Total service error 5% of reading 3 digits Test Frequency:128 Hz 0,5 Hz Test Current:200 range 1 mA a.c.(r.m.s.) (constant throughout a range)2 k range 100A a.c.(r.m.s) Interference Effect: 40 V 1V (peak to peak) at 50 Hz; 60 Hz; 200 Hz or16 2 3Hz in the Potential circuit will typically have a effect of 1% on the reading obtained. If the Noise LED is not showing, the maximum error will not exceed 2%. Max. Current Loop Resistance:The loop resistance that will introduce an additional 1% error is: 200 range 40k 2 k range 400k Max.Voltage Probe Resistance:An additional error of typically 1% will be introduced for a resistance of 75k. If the Rp LED is not showing, the maximum error will not exceed 2%. Max. Output Voltage:50 V. Display:31/2digit LCD. Maximum reading 1999 Environment Protection: IP54. Temperature Effect:<0,01% /C over the temperature range -5C to +55C Temperature Range:Operating-15C to +55C Storage-40C to +70C (without batteries) Humidity:Operating90% RH max. at 45C Storage70% RH max. at 55C Flash Test:3 kV a.c. Voltage Withstand:240 V a.c. applied between any two terminals (In the event of a system fault) Power Supply:6 x 1,5V alkaline battery cells IEC LR6 Instrument accuracy range:6 V to 10 V. Typical battery life: 700 x 15 second tests Reduction of battery life will occur at low temperatures Fuses: Internal 100 mA ceramic 20 mm x 5 mm IEC 127/1 (for current source protection) Internal 100 mA ceramic HBC 20 mm x 5mm IEC127/1 (for potential protection) Compliance With Standards:BS 7430 (1992)BS7671 (1992)Limiting Value Curve (VDE 0413) VDE 0413 (1982)NFC 15-100 IEC 364 Safety:The instrument meets the requirements for safety to IEC1010-1(1995),EN61010-1(1995) E.M.C.The instrument meets EN 5008-1 and EN50082-1(1992) Dimensions:38 mm x 153 mm x 70 mm Weight:0,82 kg Cleaning:Wipe the disconnected instrument with a clean cloth dampened with soapy water or isopropyl alcohol (IPA) 1 2 5 10 20 50 100 200 10 20 50 100 200 500 1000 2000 Limiting Value of Earth System Test Specification () Indicated Resistance V Limiting Values 1 2 5 10 20 50 100 200 10 20 50 100 200 500 1000 2000 Maximum Value to be indicated by the Meter () 2k Range 200 Range 200 Range 2k Range FONCTIONNEMENT La mthode de “chute de potentiel” Il sagit de la mthode fondamentale de mesure de la rsistance des circuits