Megger DET3 Series User manual

NEW PRODUCT LAUNCH
Megger Limited PWS / Nov 06
DET4TC/R launch
Sales guide
M
Me eg gg ge er r D DE ET T4 4T TC C a an nd d D DE ET T4 4T TC CR R
2
2, ,3 3 a an nd d 4 4 P Po ol le e E Ea ar rt th h T Te es st te er rs s
The latest additions to the DET Earth testing range.
Providing a solution to every
earth testing challenge

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DET4TC/R Launch
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Table of Contents
PRODUCT FAMILY ....................................................................... 3
DET4TC/R Selection Chart........................................................... 3
NEW – Professional Earth Testing Kit........................................ 4
THIS PRODUCT IS USED FOR? .................................................. 5
WHY?............................................................................................. 5
THIS PRODUCT IS USED BY? ..................................................... 6
TECHNICAL OVERVIEW .............................................................. 7
Principle of Operation .................................................................. 8
FEATURES, ADVANTAGES AND BENEFITS ........................... 10
ORDERING INFORMATION........................................................ 11
COMPETITOR ANALYSIS .......................................................... 11
DET4TC/R Verses Fluke 1623 ...............................................................................12
DET4TC/R Verses Fluke 1625 ...............................................................................13
DET4TC/R verses Metrel M2124C.........................................................................14
Appendix A.................................................................................. 15
Application Guide .................................................................................15
The “ART” of earth electrode testing ............................................15
Just a little aside ..........................................................................................16
Megger gets down to earth with “ART”...............................................16
Don’t underestimate the power of “ART” ...........................................18
The problem with Spheres of Influence..............................................19
We all like “ART” but sometimes it’s misunderstood ....................21
Some resistance to ART ..........................................................................22
The Best Application of “ART” ...............................................................22
“STAKELESS” Earth Electrode Testing .....................................23
Incorrect use of Stakeless testing.........................................................25
The Best Application of “Stakeless” testing......................................26

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DET4TC/R Launch
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PRODUCT FAMILY
The new products are additions to the DET3 and 4 contractor series of earth testers,
launched about a year ago.
The instruments utilises the same rubber armoured, IP54 rated case as the DET3
and is supplied in a tough blow moulded case together with test leads and spikes.
The structure of the new instruments is as follows:
DET4TC 2, 3 & 4 pole earth testers with ART and Stakeless testing
capability
DET4TCR 2, 3 & 4 pole, rechargeable, earth testers with ART and
Stakeless testing capability.
DET4TC+Kit 2, 3 & 4 pole earth testers with ART and Stakeless testing,
complete with ICLAMP and VCLAMP.
DET4TCR+Kit 2, 3 & 4 pole, rechargeable, earth testers with ART and
Stakeless testing, complete with ICLAMP and VCLAMP.
The new DET4 range replaces the complete DET5/4 range, which has an intended
obsolescence date of 30th June 2007.
The complete contractor series of Earth testers can now be summarised by the
following chart:
DET4TC/R Selection Chart
Where does the name come from?
D E T 4T C R
Digital Earth Tester 4 Terminal Clamp Rechargeable
Feature Sub-feature DET3T
A
DET3TD DET3TC DET4TD DET4TC DET4TCR
Display Analog
✔
Digital ✔✔✔✔✔
Back light
✔✔
Earth Tests 2 Pole ✔✔✔✔✔✔
3 Pole (Fall of potential)
✔✔✔✔✔✔
4 Pole (Soil resistivity) ✔✔✔
Selective (ART) capability
✔✔✔
Stakeless (2 clamps) ✔✔
Earth Resistance Range 0.01 to 2kΩ
✔✔✔✔
0.01 to 20kΩ ✔✔
Earth Voltage Range 0-100V
✔✔✔✔✔✔
Earth Current Range 0.5mA to 19.9A ✔✔✔
Supply Alkaline batteries
✔✔✔✔✔
Rechargeable batteries ✔

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DET4TC/R Launch
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NEW – Professional Earth Testing Kit
To complement the launch of the new DET4TC/R a new Professional Earth Testing
Kit will be available shortly.
The new kit is innovative, high quality and comes supplied in a tough hard carry case
similar to the instrument carry case.
The kit consist of the following:
• Four twist in auger style test spikes
• Four test leads (2 x 50m, 2 x 30m)
o Supplied on four reels with test lead wind in while mounted on test
spike feature.
o Reels have innovative test lead brushing feature to clean while
winding in.
• Tape measure
Kit part number: 6320-245

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THIS PRODUCT (DET4TC/R) IS USED FOR?
This product is used for both soil resistivity testing (4 pole) and earth electrode (2 and
3 pole) testing. Methods such as ART allow earth electrodes to be tested without
disconnection. The addition of Stakeless testing will allow testing of electrode where
the use of test stakes is impractical.
WHY?
• Soil resistivity testing. (4 pole)
o Used to locate the best lowest resistance location for a new earth
system.
o Obtain earth resistance values required to design the earth system
o Geophysics – locating changes in geology
• Earth Electrode testing (2, 3 pole)
o Earth electrode / system resistance must be low and reliable. Why?
• To ensure enough current to flow in fault conditions to ensure
the circuits’ protective device trips out in time. Failure to trip or
trip too slowly can result in expensive damage to equipment,
fire or serious injury.
• Lightning strike protection.
• Improve equipment performance by reducing noise levels.
• Static electricity dissipation.
• Prevent dangerously high step or contact voltages present
during fault or high load conditions, another safety issue.
o Earth systems require testing both immediately after installation, and
at regular intervals thereafter as part of a maintenance program.
• ART – Attached Rod Technique
o This method is an additional feature used when performing the
standard 3 pole method when testing earth electrode resistance.
o The main problem associated with testing an electrode resistance is
the requirement to disconnect it. This is because the test current from
the instrument will flow, not just down the electrode being tested, but
also through any other parallel paths. E.g. other electrodes in the
system or back through the building earth.
• ART uses a clamp to measure only the current flowing down
the electrode being tested; the instrument then uses this
measurement to calculate the resistance of electrode.

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• Stakeless Test – Look no test spikes!
o Although the 3-pole method is the traditional method of test earth
electrode resistance, it relies on driving auxiliary test spikes into the
ground, which is not always practical. Imagine trying to drive spikes in
inner city concrete jungles, and locations such as cable cellars
beneath sub stations.
o Another ideal application for this test is measuring electrode
resistance on lightning protection system on buildings.
• The stakeless method utilises two clamps. One to induces
current into the circuit the other the measure the resulting
amount.
• The measurement taken is the resistance of a loop, including
that of the electrode under test.
• The reading will not directly compare to the 3-pole method due
to the additional elements in the reading. However the
readings will always be optimistic and should be repeatable,
ideal for monitoring the earth electrode condition over time.
• Stakeless measurements made in 4-pole mode allow all test
lead resistances to be ignored.
In summary, with the addition of ART and Stakeless testing, DET4TC/R is an
excellent replacement for the DET5/4. The DET4TC/R provides real additional
benefits to the customer in terms of ease of use and the ability to take measurements
in situations the DET5/4 cannot.
Provided with this sales guide in appendix A, is a applications note giving detailed
information on how to use ART and Stakeless testing. This will give valuable
assistance to customers, allowing them to fully understand and get the most from
these test methods.
Further, more detailed information on earth testing may be found on the Megger
Earth/ground micro site. http://www.megger.com/us/story/Index.php?ID=125
THIS PRODUCT IS USED BY?
• Electrical contractors,
• Utilities, Maintenance
• Railways
• Repair Organisations (Industrials),
• Telecoms and Datacoms installers.
• Specialist grounding/earthing companies and consultants.
• Petro-chemical companies
• Service providers

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TECHNICAL OVERVIEW

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DET4TCR
The instrument and display layout are identical with the exception of the 12V input for
battery charging.
Principle of Operation
The principal of operation is fully described in the User Guide, a copy of which has
been provided as part of the launch pack. However since the DET4TCR is replacing
the DET5/4, just the pertinent parts covering the additional ART and Stakeless
capabilities have been reproduced in this document.
Principle of operation (three-terminal resistance measurement using
ART)
The classic three-terminal test method has a disadvantage, namely that the electrode
under test must be disconnected from the system it is supposed to protect in the
event of a power system fault. The reason for this is that the injected test current will
take all possible routes to ground and not all of it will necessarily flow through the
electrode under test. In this case, the instrument will make a reading
of the entire earthing network, not just the individual electrode.
By using a current transducer (the Megger ICLAMP) to measure the current flowing
through the electrode under test as a fraction of the total test current injected, the
instrument can determine the individual resistance. This arrangement is shown in
Figure 7.

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In this configuration, the injected test current I splits along two paths into I1 (flowing
into the connected earthing system) and I2 (flowing into the electrode under test, i.e.
I=I1+I2. The resistance of the electrode under test is calculated as R=V/I2 or R=V/(I-
I1). The current transducer (ICLAMP) measures I2 and feeds this value back to the
instrument.
Principle of operation (two-clamp stakeless resistance measurement)
In this example, the electrode under test is connected to a network of other
electrodes. It is either impractical or unsafe to disconnect an individual electrode for
testing. Also, there might be insufficient space to perform a classic three-terminal
resistance measurement. The stakeless test method using both VCLAMP and
ICLAMP can be used to obtain a measurement for the electrode under test.
A defined test voltage is injected into the system using the VCLAMP, inducing a
current, I, to flow and be measured by the ICLAMP. The model shown in Figure 8
can be simplified to the resistance of the electrode under test, Rx and the resistance
of the other electrodes in parallel, i.e. R1 || R2 || … || Rn. Therefore, the current
induced by the test voltage is I=V/[Rx+(R1 || R2 || … || Rn)]. It follows that as the
resistance of the other electrodes in parallel approaches zero, then the resistance
measured, approaches the value of the electrode under test.

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DET4TC/R Launch
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FEATURES, ADVANTAGES AND BENEFITS
DET4TC/R
F: Tough rubber armoured IP54 rated instrument case.
A: Case can withstand knocks, and the outdoor environments experienced when
earth testing.
B: Instrument will last a long time, and will be ready to test when required.
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F: Supplied in tough blow moulded carry case.
A: Keeps instrument, test leads, spikes, and optional clamps together and
protected.
B: Helps prevent loss of accessories, also makes ideal ‘tray’ to put the
instrument on when testing. Saves having to lay the instrument directly onto
muddy ground.
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F: Supplied with calibration certificate, test leads and spike kit.
A: Nothing more to buy to start testing.
B: Saves time having to source separate leads and spikes. No waiting for
calibration to be carried out. No hidden costs. Convenient.
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F: Back light
A: Easy to read in low light environments
B: Easier to operate when not having to use a torch to be able to read the
display.
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F: ‘Attached Rod Technique’ capability, ART.
A: With the addition of an ICLAMP the instrument is able to take 3 or 4 pole
measurements of earth electrodes without disconnecting them.
B: Saves both time and aggravation having to undo rusted connections. No need
to shut down supply to ensure safety.
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F: ‘Stakeless’ testing capability.
A: No need to drive test spikes in ground to perform measurement.
B: Allows testing in areas when driving test spike is impossible. E.g. Sub station
cable cellars, or when testing lightning protection in concreted locations.
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F: One button operation with automatic noise check and automatic P and C
spike resistance check.
A: Easy to operate.
B: Little time required learning operation, and time saved not having to spend
considerable time troubleshooting poor connections etc.
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F: User selectable output voltage – 25V or 50V
A: 25V required for testing agricultural environments
B: The ability to test in agricultural locations as per IEC61557-5. 25V will not
harm livestock.
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F: 40V Pk to Pk Noise rejection
A: Able to make accurate measurements with up to 40V peak to peak (ground
voltage) between the potential terminals.
B: Can be used in most locations with ground noise such as sub-stations, near
transformers etc.