Hioki - Grounding Measurement
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Transcript of Hioki - Grounding Measurement
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Peninsula Hotel Jakarta, 19 June 2014
By Diyah Handayani KHIOKI SINGAPORE PTE. LTD
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What is Grounding ?
A grounding is a conducting connection by which anelectrical circuit or equipment is connected to theearth or some conducting body.
Source: IEEE Standard 81
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What is Grounding ?
A conducting connection, between an electricalcircuit or equipment and the earth, or to someconducting body that serves in place of the earth.
Source: NFPA 70-1981; National Electrical Code
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PURPOSE OF GROUNDING
The purpose of a ground besides the protection
of people, plants and equipment is to provide asafe path for the dissipation of fault currents,
lightning strikes, static discharges, EMI and RFI
signals and interference.
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2 TYPE GROUNDING SYSTEM
Earth grounding
is an intentional connection from a circuit conductor,
usually the neutral, to a ground electrode placed in the
earth.
Equipment grounding
ensures that operating equipment within a structure is
properly grounded
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EXAMPLE OF GROUNDING
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Why we must test Ground ?
Poor grounding not only contributes to unnecessary downtime,but a lack of good grounding is also dangerous and increasesthe risk of equipment failure.
Without an effective grounding system,we could be exposed tothe risk of electric shock, not to mention instrumentationerrors,harmonic distortion issues, power factor problems and ahost of possible intermittent dilemmas.
If fault currents have no path to the ground through a properlydesigned and maintained grounding system, they will findunintended paths that could include people.
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GROUND STANDARDS
NFPA and IEEE have recommended a ground resistancevalue of 5.0 ohms or less.
The NEC has stated to "Make sure that system
impedance to ground is less than 25 ohms specified in
NEC 250.56.
The Telecommunications industry has often used 5.0
ohms or less as their value for grounding and bonding.
Communication requires lower signal level with higher
frequency characteristics than 60 Hz Utility requirements
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GROUND RESISTANCE TARGET
Typical values for a power company:
- Generating station: 1 maximum
- Large sub-station: 1 maximum
- Small sub-station: 5
maximum
Water pipe ground should be less than 3 and
frequently less than 1 .
The Telecomunication industry has often used 5or
less as their value for grounding and bonding.
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COMPONENT OF GROUND ELECTRODE
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WHAT AFFECTS THE
GROUNDING RESISTANCE?
First, the NEC code (1987, 250-83-3) requires a minimum ground
electrode length of 2.5 meters (8.0 feet) to be in contact with soil.
But, there are variables that affect the ground resistance of a
ground system:
1. Length/depth of the ground electrode2. Diameter of the ground electrode
3. Number of ground electrodes
4 . Ground system design
5. Soil
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Length/depth of the ground electrode
The dept of the electrode can lower the resistance valueeffectively, Normally doubling the length of the earthelectrode can reduce the resistance by an additionally40%.
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Diameter of the ground electrode
Increasing the diameter of the ground electrode has
very little effect in lowering the resistance. Forexample, you could double the diameter of a groundelectrode and your resistance would only decrease by10 %.
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Number of ground electrodes
Another way to lower ground resistance is to use multipleground electrodes. In this design, more than oneelectrode is driven into the ground and connected inparallel to lower the resistance. For additional electrodes
to be effective, the spacing of additional rods need to beat least equal to the depth of the driven rod.
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GROUND SYSTEM DESIGN
Single ground electrode Multiple ground electrode
Mesh Network Ground Plate
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SOIL
Soil resistance values depend on soil composition,moisture & temperature
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TESTING METHODS
Normally single electrode earthing is used for domestic
applications, but for power generating substations and industrieswe use a grid network with multiple electrodes.
The "3-pole fall of potential" testing method can be used for a
complex earth system. In this technique, the earth grid is
disconnected from the earth electrode. Two auxiliary electrodes
(one current electrode and a second potential electrode) areplaced beside the electrode to be tested at an equal distance in a
straight line. The current passed through the auxiliary current
electrode is to be noted and recorded. In this way, the potential
difference generated between the auxiliary potential electrode and
the current electrode can be measured.
Measurement of earth resistance and leakage current without
disconnecting the circuit can be done using portable
instruments. The clamp-on type of earth resistance tester can
measure earth resistance and leakage current.
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WHATS A CLAMP ON EARTH TESTER?
Measure Closed Loop Resistance
1
Closed Loop
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Ground Resistance Measurement
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Clamp Earth TesterFT6380 / FT6381
Allows you to hold the displayvalue.
With the bright back light, you can easily
read the measurement value even in dark
locations.
You can store up to 2,000 measurement
values in the field and recall them in your
office later.
No wait time after powering on.
Start measuring instantly without
zero-calibration.
Resistance mode filter: Digital filter gives you
steadier readings.
Current mode filter: Low-pass filter
eliminates harmonics current over 180Hz.
Set the alarm to audible and visually
notify you that the resistance or
current value exceeds the threshold.
Switch between resistance
measurement mode or current
measurement mode.
32mm
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For multiple grounding systems
RnRRRR
RxI
V
1.....
4
1
3
1
2
1
1
1
1
RxI
Vn =
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HIOKI
26mm 20mm
53mm
38mm45%Smaller
How Compact?
Comparison of cross-sectional area of the Jaw
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Access to tight spots
Why Compact?
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Pole
Grounding Electrode
Large Jaw Ground
Clamps: Strugglewith dirt
HIOKI: Easy access to tight spots
At your field, what happens?
Feel the difference
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ACCURACY OF FLAT CORE
View of Core Sensor of Flat Jaw
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ACCURACY OF INTERLOCKING CORE
View of Core Sensor of Interlocking Jaw
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INTERLOCKING CORE
-50%
-40%
-30%
-20%
-10%
0%
10%
20%
30%
40%
50%
0 200 400 600 800 1000 1200 1400 1600
HIOKI
+3
-3
Spec
Spec
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RELIABILITY
R
Voltage
Injection
Current
Detection
I = V/R
R =V/I
Designed to last!
Prevents leakage current
Interlocking Shield Design
R
I = V/R
R =V/ (I+Iflux)
Leakage FluxLeakage Flux
With micro-meter gap
Accurate Reading!!
CT Magnetic Core
Magnetic Shield
VT Magnetic Core
Cross-section view of jaw
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Magnetic Cores
Air Gap
EFFECT OF AIR GAP
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AC CURRENT MEASUREMENT (LEAKAGE
CURRENT)
Wide range: From 1mA to 60Awith Filter ON/OFF
Function
Safe: EN61010 CAT IV 600V
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ENERGY EFFICIENT
Uses only 2 x LR6 Alkaline Batteries
Continuous Usage of up to 35 hours (Backlight &
Bluetooth OFF)
ReducedBy more
than 50%
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SAFETY
CAT IV 600V
Withstand Voltage: AC 7400 Vrms for one minute
Between clamp sensor and casing
Max. Input current: AC 100A continuous, AC 200A for 2
minute (50 / 60Hz)
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Auto Report
Generation
Via email
DOWNLOAD APPS FROM GOOGLE PLAY STORE
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REPORT FUNCTION
Get
Time Stamp
Measuring Data with screen
imageLocation information with map
image
Reports are
Sent via e-mailSynchronized using Cloud servers
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APPLICATIONS
All overhead transmission conductor lines that may be exposed to
lightning should be protected by a means for diverting any electricsurge to earth.
The grounding cables of transmission towers should be tested
frequently.
Transformer earthing terminal measurements should be
conducted to ensure proper contact between the soil and theearth point.
Low earthing wire resistance is most important for motors, power
distribution panels, and control panels.
The earthing of a telecommunication control cabin or signal relay
board is important to reduce stray electrodynamic stress andnoise.
Separate earthing should be provided for PLC and SCADA
instruments in a control panel.
Good earthing is required for petrochemicals pipelines and oilstorage tanks.
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