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Earth testing

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Title: Earth testing


1
Earth testing
  • Practical Earth Testing Techniques and
    Measurement Instruments

2
Practical Earth Testing
  • Content
  • Principles
  • Test Methods
  • Practical Measurement
  • Summary

3
Earth / Ground Basics
What is ground?
A conducting connection, whether intentional or
accidental, between an electrical circuit or
equipment and the earth, or to some conducting
body that serves in place of earth
Ground is a connection to Earth made either
intentionally or accidentally
NFPA 70-2000 (National Fire Protection
Association)
4
Earth / Ground Basics
Why ground?
To protect people and equipment
By dissipating stray energy from Electrical
faults (fuses, breakers etc.) Lightning
strikes Radio Frequency Static discharges
5
Real Examples
Why test? Catch the problem before it happens!
Estimate at least 15 of power quality problems
are related to grounding Lightning strikes on
equipment with poorly maintained protection
systems destroy millions of dollars of equipment
and lost production every year Using ground
testing in a PDM protocol will help prevent
possible dangerous situations and loss of
downtime ( money)
6
Earth / Ground Basics
How do you connect to earth?
Cable or tape
Stake or rod
Earth material
7
Earth / Ground Basics
Spheres of influence
8
Attention! Potential gradients!
Earth / Ground Basics
Umeasure
Potential gradients around the earth electrode
can reduce the accuracy of measurements! The
probe must always be placed outside this area!
Typical distance gt20m
Distance a
Ground Potential Neutral ground, reference
Umeasure
9
Earth / Ground Basics
Types of Grounding Systems
  • Many different types available
  • Choice depends on local conditions and required
    function
  • Simplest form is a single stake
  • Mostly used for
  • Lightning protection
  • Stand alone structures
  • Back-up for utility ground

Ground rod
10
Earth / Ground Basics
Types of Grounding Systems
  • ground rod group
  • typically for lightning protection on larger
    structures or protection around potential
    hotspots such as substations.

Ground rod group
11
Earth / Ground Basics
Types of Grounding Systems
  • For areas where there is rock (or other poor
    conducting material) fairly close to the surface
    ground plates are preferred as they are more
    effective

Ground plate
12
Earth / Ground Basics
Types of Grounding Systems
  • A ground mesh consists of network of bars
    connected together, this system is often used at
    larger sites such as electrical substations.

Ground mesh
13
Earth / Ground Basics
Types of Grounding Systems
For the purposes of this presentation the
grounding system will referred to as ground
electrode.
14
Ground Testing Methods
What are the available techniques?
  • Resistivity
  • Fall of Potential Three and Four Pole Testing
  • Selective Testing
  • Stakeless Testing
  • Two pole method

15
Ground Testing Methods (1)
Resistivity Measurement
The purpose of resistivity measurements is to
quantify the effectiveness of the earth where a
grounding system will be installed. Differing
earth materials will affect the effectiveness of
the grounding system. The capability of
different earth materials to conduct current can
be quantified by the value ?E (resistivity in
W.m). Resistivity measurements should be made
prior to installing a grounding system, the
values measured will have an effect on the design
of the grounding system.
16
Ground Testing Methods (1)
Resistivity values for different earth materials
17
Ground Testing Methods (1)
Resistivity Measurement ( Wenner method)
Resistivity measurements are performed by using a
four wire method. Used to determine
which KIND of

earthing should be
used, so BEFORE
placing earth
stakes
18
Ground Testing Methods (1)
Resistivity Measurement
From the indicated resistance value RE, the soil
resistivity is calculated according to the
equation ?E 2 ? . a . RE   ?E ......
mean value of soil resistivity (W.m) RE ......
measured resistance (W) a ...... probe distance
(m)
19
Ground Testing Methods (1)
Resistivity Measurement
Curve 1 As ?E decreases only deeper down, a deep
earth electrode is advisable Curve 2 As ?E
decreases only down to point A, an increase in
the depth deeper than A does not improve the
values. Curve 3 With increasing depth ?E is not
decreasing a strip conductor electrode is
advisable.
20
Ground Testing Methods (2)
Fall of Potential - Testing
  • The Fall of Potential method is the most commonly
    used method of testing.
  • Three or four pole method, this refers to the
    number of connections made to the ground tester.
  • The forth pole of the connection is made if the
    wire to connect to the system under test is
    particularly long
  • gt 4 meters. The additional wire cancels out an
    error due to the extended length of wire used.

21
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential 3 / 4 Pole Testing
The E terminal of the instrument is connected to
the electrode under test
22
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential 3 / 4 Pole Testing
If the length of this wire is greater than 4
meter it is recommended that an extra wire is
connected between the electrode under test and
the ES terminal to eliminate any error introduced
due to the length of the lead, this is then known
as the 4 pole test
23
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential 3 / 4 Pole Testing
The test spike C2 is placed in the ground some
distance from electrode under test (typically 50
meter)
24
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential 3 / 4 Pole Testing
During the test the instrument drives a current
through the test spike, through the surrounding
earth and returns through the electrode under
test, the potential caused by this current is
measured using the P2 spike.
The voltage spike P2 is placed in the ground some
distance from electrode under test (typically 80
feet) . Once the stakes are in place the test
can proceed.
From the current and voltage measurements made it
is possible to calculate a value of ground
resistance.
25
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential 3 / 4 Pole Testing
A number of readings should be taken with the the
P2 spike at different distances, say from 20 to
35 meters at 3 meter intervals.
26
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential 3 / 4 Pole Testing
The distance of the P2 spike is varied to ensure
that it is positioned outside of the sphere
influence of the electrode under test. When the
P2 spike is close to the electrode under test the
measured value appears to be lower and as it
becomes influenced by the C2 spike the measured
value rises. The optimal point of measurement is
outside of the influence of the electrode and the
C2 spike. Taking a series of measurements and
plotting these against distance produces the
curve shown.
27
Earth Testing Methods (1)
Ground Testing Methods (2)
Fall of Potential Creating the S Curve
The optimum value is that indicated on the flat
part of the curve
28
Earth Testing Methods (1)
Ground Testing Methods (2)
The 62 Rule
The 62 rule is a guide to how far away the P2
and C2 stakes should be placed from the electrode
under test. The distances are nominally based on
the depth of the electrode.
29
Earth Testing Methods (1)
Ground Testing Methods (2)
Distances for Electrode Arrays
The 62 rule is a guide to how far away the P2
and C2 stakes should be placed from the electrode
under test. The distances are nominally based on
the depth of the electrode.
30
Selective Measurement Method
Ground Testing Methods (3)
  • The selective method is based on the fall of
    potential test
  • But without the need to disconnect the ground
    electrode under test.

A current clamp is used to isolate the test
current injected in to the electrodes under test.
31
Selective Measurement Method
Ground Testing Methods (3)
This application example shows the benefit of the
selective test in a typical installation
Firstly the ground spikes are positioned
according to the requirements of the system under
test.
32
Selective Measurement Method
Ground Testing Methods (3)
Then individual elements of the system can be
measured by placing the currentclamp around the
different connections to ground without the need
of any disconnection.
33
Selective Measurement Method - Advantages
Ground Testing Methods (3)
  • Ground electrodes can be tested without powering
    down the system they are protecting saving time
    and money
  • Testing can be carried out without disconnecting
    saves time, money and improves safety
  • Multiple electrodes can be tested quickly simply
    by moving the current clamp to individual
    electrodes

34
Ground Testing Methods (4)
  • The stakeless method eliminates the need for
    temporary ground stakes. This is useful in a
    wide range of situations. Examples include
  • Inside buildings
  • Airports
  • Urban locations
  • Chemical and industrial plants
  • The stakeless method is not available on all
    ground testers. However, it comes standard on
    the Fluke 1623 and 1625 earth ground testers.
  • The temporary ground stakes are replaced by two
    current clamps. The first clamp generates a
    voltage on the ground condutor, the second clamp
    measures the current flowing due to the generated
    voltage.

35
Ground Testing Methods (4)
  • The Fluke 1623 and 1625 testers are able to
    measure earth ground loop resistances for multi
    grounded systems using only current clamps.
  • With this test method, two clamps are placed
    around the earth ground rod or connecting cable
    and each connected to the tester. Earth ground
    stakes arent used at all.

36
Ground Testing Methods (4)
The clamps are placed around the ground conductor
37
Stakeless Measurement Equivalent Circuit
Ground Testing Methods (4)
38
Ground Testing Methods (4)
  • If there is only one path to ground, like at some
    residential applications, the stakeless method
    will not provide an acceptable value and the Fall
    of Potential test method must be used.
  • An abnormally high reading or an open circuit
    indication on the instrument points to a poor
    connection between two or more of the
    aforementioned critical components.
  • An abnormally low reading could indicate the
    instrument is measuring a loop of bonding
    conductors.

39
Ground Testing Methods (5)
Two Pole Method
Used where other methods are not available. Uses
nearby metal structures as a temporary
spike. Metal water pipes are typically used
40
Ground Testing Methods (5)
Two Pole Method
Drawbacks The resistance of the metal pipe
should be significantly less than the electrode
under test. Metal pipes are being replaced with
plastic. Some metal pipes use plastic couplings.
41
Selecting a test method
Summary of Ground Electrode Test Methods
Advantages Drawbacks
Fall-of-Potential Widely accepted When you see the characteristic curve you know youve got a good measurement. You have to disconnect ground The stakes may not be to drive There may not be space around the ground electrode to drive the stakes
Selective Method Dont have to disconnect electrode Widely accepted When you see the characteristic curve you know youve got a good measurement. The stakes may not be easy to drive There may not be space around the ground
Stakeless Method Convenience Assumes a low-impedance parallel path Possible to get very low readings by mistakenly measuring on a hard-wired loop
Two-pole Method Convenience Impossible to judge the integrity of the auxiliary electrode. Cant be sure you are outside the area of influence
42
Ground Testing Applications
When and why ground test?
Prior to designing an grounding system the
ground material should be evaluated by
resistivity measurement before designing a ground
system Initial test on new ground systems the
real effectiveness of new ground systems should
be measured before connection fall of potential
test Periodic tests on ground systems ground
systems should be checked periodically to ensure
they are not affected by changes in the ground or
corrosion selective or stakeless test
43
Ground Testing Applications
When and why ground test?
Testing prior to addition of major loads prior
to installation of sensitive equipment such as
servers, CT scanners, control systems, etc.
fall of potential, selective or stakeless Safety
tests on major equipment and plant e.g. ground
tests on machines, elevators, conveyor belts,
transformers, substations, boards, motors
stakeless and selective testing
especially useful
44
Ground Testing Applications
When and why ground test?
All other tests for relevant ground connections
e.g. lightning protection, pipelines, tanks, gas
stations, antenna systems, telecommunication
lines, faraday cages fall of potential,
selective or stakeless PQ troubleshooting,
quantify the effectiveness of grounding by
measurement fall of potential, selective or
stakeless
45
Choosing the right instrument
Introducing the Fluke 1623 and 1625 Ground
Testers
46
Fluke 1623
  • Feature Summary
  • Conventional 3 - and 4 - pole earth/ground
    testing
  • Selective method
  • Stakeless method
  • Two pole AC resistance measurement
  • One button measurement press once to measure
    with simple GO/NOGO indicators
  • Large easy to read display
  • Rugged housing rated to IP56
  • 2-Year Warranty
  • Customer
  • Electrical Consultants, Industrial
  • Application
  • Verification of earth resistance of electrical
    communication systems.

47
Fluke 1625 - the expert instrument
  • Feature summary
  • 3- and 4-pole measurement of earth resistance
  • Selective and Stakeless method
  • Monitoring and display of probe and auxiliary
    earth resistance
  • Automatic display of external voltage and
    frequency
  • Selection of optimal measuring frequency (AFC)
  • measurements down to deep ground layers possible
    (high testsignal power gt250mA, 48V)
  • Earth impedance R of high tension towers - for
    calculation of genuine short circuit current

48
Fluke 1625 - the expert instrument
  • Additional features of Fluke 1625
  • 2 pole AC resistance measurement - Resolution
    0.001 Ohm - Measuring signal 20V / 250mA
  • 2 pole, 4 pole DC resistance measurement - Range
    3 kOhm, resolution 0.001 Ohm - automatic
    polarity reversal, adaptation of test period -
    short circuit current gt200mA as per IEC/EN
    61557-5 , UM gt4V
  • User defined limit settings - adjustable limits
    for any individual applications
  • Interface and software available as option - data
    transfer to PC or printer - comfortable data
    evaluation with WinGEO software

49
Unique R - Earth impedance
Fluke 1625 - the expert instrument
  • Measurement of complex earth-impedance at 55Hz
    which determines the real short circuit current

50
Fluke 1625 - the expert instrument
Unique R - Earth impedance
Measurement of complex earth-impedance at 55Hz
which determines the real short circuit current
51
Chosing the right instrument
Introducing the Fluke 1623 and 1625 Ground
Testers
52
Clamp-On Earth Loop Tester GEO 30
  • Feature Summary
  • Ground loop resistance clamp measurement
  • Low level measurement of ground leakage current
  • Wide AC current measurement range up to 30A with
    one instrument
  • Rapid evaluation of continuity loop resistance by
    audible HI/LO alarm
  • Easy to use, convenient, Display-HOLD function
  • Time saving memory function for saving measured
    values and automatic recording
  • Automatic self calibration ensures correct
    measurement every time
  • Customer
  • Residential, Commercial, Industrial Electricians
  • Application
  • Earth loop resistance testing for houses,
    commercial and industrial buildings

53
Clamp-On Earth Loop Tester GEO 30
Stakeless Ground Resistance Measurement
The voltage U developed by the clamp is injected
into the circuit. This causes a current I which
flows in this measuring circuit. The second clamp
measures this current I and the earth clamp
displays the ground loop resistance RxRn.
54
Clamp-On Earth Loop Tester GEO 30
High quality, rugged carrying case
High Quality measuring instrument
Calibration loop for instrument check
Includes five language operators manual
E/D/F/ES/IT
55
Fluke 1653
  • Target Customer Professional Electrician /
    Testing Specialist
  • Top Line Model with Unmatched performance
  • Features
  • Volts Frequency to 500V
  • Insulation Resistance
  • Continuity Measurement
  • Loop /PSC Measurement
  • RCD Testing
  • Earth resistance Tests
  • Phase Sequence Indication
  • On-Board Memory
  • Interface for Downloading data

56
Summary
  • Resistivity measurement provides important data
    regarding the earth material prior to system
    design
  • Fall of Potential Test is the most widely
    accepted
  • Four pole measurement compensates for voltage
    drop in measuring cable
  • The 62 rule provides some guidance to the
    required distance for the temporary test spikes
  • Selective testing allows testing without
    disconnection

57
Summary
  • Selective test is based on fall of potential
    test that speeds measurement and provides
    additional safety
  • Stakeless Testing is a fast method for multiple
    electrode systems
  • Two pole ground testing provides minimal
    information and should be used very cautiously
  • The Fluke 1623 provides the majority of the
    required functions for industrial users
  • The Fluke 1625 is the advanced ground tester for
    utilities

58
Why should I invest on Earth Ground?
  • The WW market for Earth Ground is estimated to be
    25 Million
  • With only two major US competitors (AEMC,
    Megger), with inferior product lines, there is no
    reason why Fluke shouldnt have 40 market share
    in 3 years.
  • Fluke 1623 and 1625 are the most complete Earth
    Ground testers available anywhere
  • In the US, Megger AEMC do not have the best
    products, they only have inroads into Utilities.
    Perfect value selling opportunity.
  • Your customers have been asking for it
  • It is core to our strategy (along with PQ,
    Insulation and Thermography)
  • Another opportunity to educate our customers
    about a product category. Take the high road,
    educate, convert to the best products. Repeat
    what youve done again and again.

59
Who to target?
60
Which product for which user?
Fluke 1653
61
1625 worth the money?
  • Why would anyone pay 650,- more for the Fluke
    1625?
  • Utility customers will pay because they see value
    in the following advanced features
  • Automatic Frequency Control (AFC) identifies
    existing interference and chooses a measurement
    frequency to minimize its effect, providing more
    accurate earth ground values
  • R Measurement calculates earth ground
    impedance with 55 Hz to more accurately reflect
    the earth ground resistance that a fault-to-earth
    ground would see. Impedance is a frequency
    dependent measurement.
  • Adjustable Limits for quicker testing.
  • Power utility technicians are interested in two
    things
  • The ground resistance in case of lightning strike
  • The impedance of the entire system in case of a
    short circuit on a specific point in the line.

62
Product line-up
  • Delivery content
  • Fluke-1623 Basic GEO Earth Ground Tester
  • Contains Fluke-1623 tester, test leads,
    batteries, manual (GB, FR, IT, DE, ES, PT)
  • Fluke-1625 Advanced GEO Earth Ground Tester
  • Contains Fluke-1625 tester, test leads,
    batteries, manual (GB, FR, IT, DE, ES, PT)
  • Fluke-1623/1625 Kit Advanced GEO Earth Ground
    Tester Kit
  • Contains (1) Fluke-1623 or 1625 tester, (4)
    stakes, (2) 25m cable reels, (1) 50m cable reel,
    (1) Sensing clamp, (1) Inducing clamp, all
    necessary connectors, test leads, batteries,
    manual, rugged carrying case

63
Accessories
  • EI-1623 Selective/Stakeless Clamp Set for
    Fluke-1623.
  • Contains both the Inducing and Sensing clamp all
    necessary adapters
  • Already in the Fluke-1623 Kit.
  • EI-1625 Selective/Stakeless Clamp Set for
    Fluke-1625.
  • Contains both the Inducing and Sensing clamp all
    necessary adapters
  • Already in the Fluke-1625 Kit.
  • ES-162P3 3-Pole Stake Kit. (used for both the
    Fluke-1623 and Fluke-1625)
  • Contains (3) Stakes, (1) 50m cable reel of wire,
    (1) 25m cable reel of wire
  • Already in the Fluke-1623 Kit/Fluke-1625 Kit.
  • ES-162P4 4-Pole Stake Kit. (used for both the
    Fluke-1623 and Fluke-1625)
  • Contains (4) Stakes, (1) 50m cable reel of wire,
    (2) 25m cable reel of wire
  • Already in the Fluke-1623 Kit/Fluke-1625 Kit.
  • EI-162BN 320mm Diameter Split Core Transformer
  • Used as a Selective clamp for ground loop
    resistance measurement around power pylons
  • Contains the split core transformer and all
    necessary adapters/connections

64
Marcom material
  • Distributor product announcement
  • Sales PPT
  • Value selling tool

65
Questions
  • and answers
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