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1. Leakage Current
How Testing & Measuring Done
What Is

2. Leakage Current is almost everywhere the electrical system is used. When
you are blindfolded, it is a subject current leakage that causes work accidents,
loss of life and property. Observation and precautions taking are also
mandatory by law. Firstly, Understand; What is the leakage current,
it is necessary to describe it. If the vectored sum of the phase currents and the
neutral return current is zero, then there is no leakage current.
But in this cycle, if the current from the neutral
is less than the total current from the excess,
then the electric current has found a shorter
path to itself. This path can be a person directly,
a point to be isolated, or any other
hardware. This problem can be experienced in
electrical devices which are generally
insufficient insulation, manufacturing defects
or outdated electrical devices.

3. Leakage current is the current that streams from either DC or
AC circuit in an equipment to the ground or framework and
can be from the output or input.
If the equipment is not properly grounded, the current flows
through other paths such as
the human body.
This mighty also occur
if the ground is incompetent
or is disrupted unintentionally
or intentionally.

4. The leakage current in an equipment flows when an
unintentional electrical connection occurs between the
ground and an energized part or conductor.
The ground may be the reference
point of zero voltage, or the earth
ground. Ideally, the current leaking
from the power supply unit should
flow through the ground connection
and into the installations earth
ground.

5. When these problematic devices are used in systems such as electric
panels, they will cause problems in the surrounding equipment. It is
necessary to measure and detect before taking precautions. It is
important to stop when it happen immediately.
This measurement and cutting operation
can be performed with direct connected
devices at low current levels.
Directly connected devices without
setting feature set 30mA for people
and 300mA for fire prevention.
We can see almost everywhere these
devices are used as we work.

6. There are situations where direct connection cannot be made in high current
measurements. The current transformers that we use when installing the energy
meters or analyzers are used here.
Especially toroidal current transformers
are the most used equipment.
The current transformer usage logic is
based on passing each current through
the current transformer in each line to
be measured and taking measurements
by the secondary in accordance with the
winding ratio.

7. In the case of leakage current measurement, the situation changes slightly.
Leakage current measurement is done to protect the systems. In order to be
able to measure the current difference we have explained at the beginning of
the article, the vectored measurement of the sum of the total input currents
and the neutrally rotating currents is required.
For this reason, all phase and neutral cables
are passed through these toroidal current
transformers specifically together.
Passed through the toroidal current
transformer of course vary according to
the size of the cable thickness.
Openable types provides easiness at
system maintenance and transformer
malfunctions. The secondary side of
the transformer is now ready for
measurement.
According to the IEC 60479-1 standard, the critical
current threshold for human life is determined as 30mA.

8. The leakage current must be measured and checked after the current value is
measured by the transformer. Leakage current relays are used for this task. These
relays are usually manufactured as adjustable time to failure.
The level of the leakage current which cannot be prevented according to the
usage place of the system to be
protected can be higher than the
levels I just mentioned
(30mA and 300mA).
It is an ideal
solution for users to adjust the
leakage current level in such
situations. This limit can be increased
up to 250A current levels.

9. The inadequacies in the materials that build up the elements like the
capacitors and semiconductors are the main cause of leakage current. These
results in to small current leaking or flowing through the through the dielectric, in
the case of a capacitor.
This measurement is done during the electrical safety test of a device. The
currents flowing through the protective conductor or metallic parts of the earth
are measured.
Why is Leakage Current Measurement Important ?
Electrical system usually consists of a grounding technique that offers shield
against a shock hazard if an insulation fault occurs. The grounding system
comprises of a grounding rod that connects the instrument to the earth.
If ever a disastrous failure of insulation between power line and conductive parts
occur, the voltage will be pushed to ground. The current that is created because
of this event will flow, causing a circuit breaker to open or a fuse to blow thus
avoiding a shock hazard.

10. Why is Leakage Current Measurement Important ?
Clearly, a shock hazard prevails if the earth or ground connection is intruded,
either accidentally or intentionally. The possibility for a shock might be larger than
assumed if there is case of leakage currents. Even in the scenario of no
insulation failure, intrusion of leakage currents streaming through the grounding
rod still pose a threat of electric shock to somebody meeting the ungrounded
system and ground at the same time.
This is a huge concern when it comes to the field of medical applications, where
a patient might be the receiver of the electric shock. A shock can be even fatal if
the patient is weak or unconscious, or if the current flows to internal organs.
The two-layered insulation offered in non-grounded equipment ensures
protection. The security in this scenario is made sure because both coats of
insulation are not likely to collapse together. Nevertheless, the situations that
leads to leakage currents still exists and must be considered.

11. Hence, how can you eradicate or reduce the outcomes of leakage current ?
Measure the leakage current and then recognize the cause. Purpose of the Test
is to measure the amount of current that passes through a person when that
person touches an electrical product.
What is Done During Leakage Current Measurement ?
•Meter particularly designed for determining leakage currents is utilised.
•The current streaming through the ground rod is quantified by attaching the
meter in series with the earthing connection.
•The ground connection is unsealed and the current streaming to the neutral
side of the power line is measured, for data processing equipment.
•The meter may also be connected between the outputs of the power supply
and ground.
•Test conditions consists of exchanging the neutral connections and ac line
and turning power switches on and off while monitoring the current.
•The test is done once the system has warmed to typical functioning
temperature.

12. • The intention is to identify and measure the worst-case leakage current.
• For very small leakage currents, the meter is substituted with a network
comprising of either a resistor or a resistor and capacitor grouping.
• The voltage drop throughout the network is then quantified using an ac
voltmeter.
• Double-insulated equipment or ungrounded is verified by attaching the meter
amid any touchable conductive part and earth.
• A copper foil of a specific dimension is placed on the
housing, for a nonconductive housings, and the current flowing from it to ground
is determined.
Type of Equipment Maximum Leakage Current
Class I 0.75mA for hand held devices
3.5mA for other devices
Class II 0.25mA
Class III No hazardous voltages

13. How is Leakage Current Measurement Performed ?
Direct Measurement
Direct measurement has precision and a meter especially designed
for determining leakage currents is used. The current flowing in the ground
conductor is measured by connecting the meter in series with the grounding
connection of the device concerned.
Leakage current clamp meter is the most popular
device used to measure leakage current. They
are like the clamp meters utilized for finding load currents
but gives considerably better results when quantifying
Currents less than 5mA. Generally, clamp meters wouldn’t
Register such small currents. After we position the jaws of a clamp meter around
a conducting rod or wire, the current reading is taken, and the value depends upon the
intensity of the alternating electromagnetic field around the conductor. The clamp meter
will identify the magnetic field around conductors like a wire armor cable, single core
cable, a water pipe etc. The paired neutral and phase conductors of a single-phase
circuit, or all live conductors of a three-phase circuit.

14. Testing Different Kinds of Conductors:
•When testing the grouped live conductors of a circuit, the magnetic fields produced by the
load currents cancel each other out. Any uneven current coming from the conductors to
ground is measured with a leakage clamp meter and must have a reading less than 0.1
mA.
•If you performed an insulation test on a circuit that was powered down, the result would be
in the range of 50MΩ or further, because the insulation tester utilizes s a dc voltage for
checking, which do not consider the capacitive effect.
•If you measured the same circuit loaded with office equipment, the result would be
significantly different due to the capacitance of the input filters on these devices.
•When a lot of parts of equipment are functioning on a circuit, the result will be collective,
that is, the leakage current will be greater and could well be in the range of milliamps.
Adding new pieces of equipment to a circuit protected by a GFCI could trip the GFCI. And
as the value of leakage current differs based on how the equipment is functioning, the
GFCI may trip unintentionally.
•When telecommunications equipment is present, the value of leakage indicated by a
clamp meter may be considerably more than that resulting from insulation impedance at 60
Hz because, telecommunications system usually consists of filters that generate functional
grounding currents and other gears that generates harmonics, etc.

15. Measurement of Leakage Current to Ground
•When the load is switched on, the leakage current measured includes leakage
in load equipment. If the leakage is adequately small with the load attached,
•then circuit wiring leakage is even smaller. If circuit wiring leakage alone is
required, disconnect the load.
•If you test single-phase circuits by clamping the phase and neutral conductor,
the obtained amount will be any current streaming to ground.
•Test 3 phase circuits by fastening a clamp around all 3 phase conductors. If a
neutral is present, it must be clamped along with the phase conductors and the
measured amount will be any current flowing to ground.

16. Measuring Leakage Current through the Ground Conductor
•To quantity the sum of leakage streaming to the proposed earth connection,
position the clamp around the ground rod.
Measuring Leakage Current to Ground via unintentional paths to ground.
•Clamping neutral/phase/ground all together recognizes uneven current that
means leakage at a passage or electrical panel via unintended pathways to
ground.
•If a connection to a water pipe or other electrical connections
occur, similar inequality might happen.
Tracing the source of Leakage Current
•This series of measurements identifies the overall leakage and the source. The
first measurement can be made on the main conductor to the panel.
•Measurements 2 to 5 are made consequently to find out circuits carrying
the bigger amounts of leakage current.

17. Leakage Current Measurement in Medical Devices
The objective of the Leakage Current test is to verify that the electrical insulation used to protect
the user from a Risk of Shock is suitable for the application. Leakage Current testing is used to
verify that the product does not leak excessive current when contacted by the user. For medical
equipment, the current flowing to ground is measured.
•Excessive leakage current can cause the heart to go into ventricular fibrillation resulting in
cardiac arrest which can lead to death.
•Leakage current measurement levels depend on the amount of capacitance in the products’
solid insulating materials. Different types and number of layers of an electrical insulation results
in varying amounts of inherent capacitance through the insulation. This capacitance causes low
amounts of current to “leak” through the insulation.
•Leakage current levels can be significantly elevated in products that are subject to EMI
requirements (FCC, CE-EMC). These products must incorporate EMI filters on their incoming
mains power to provide clean power to sensitive electronics while also protecting from radiating
emissions back onto the power line. These filters incorporate capacitors to ground, these
capacitors can cause high leakage current when operating normally. If the product is for
professional use only, the standard may permit high leakage current with warning markings for
the user to insure the product is reliably grounded (so the user isn’t subjected to the high
leakage current). Otherwise, an isolation transformer must be added to power the product
thereby isolating the product from ground – which will almost eliminate leakage current to
ground.

18. Hipot Leakage Current Testers
•The HIPOT test also called Dielectric Withstand Test is a routine test that is performed in
electrical production industry. This is a high voltage test that stresses the insulation of an
electrical product far 80 M.
•If the insulation of product can withstand a much higher voltage for a given time, then it can
withstand normal voltage for its whole life.
•The basic function of HIPOT tester is to monitor excessive leakage current to ground.
•Hipot tester applies a high voltage across the insulation of device that is tested. This
is generally higher 1400 Volts to test a device that is planned to be operated on 220 Volts.
•Terminals A and B are connected to supply voltage of 220 or 110, terminal C is grounded, return
lead is floating as shown here.
•The device to be tested should be separated electrically
from ground.
•One lead from winding is connected to HV out probe and
return lead to motor body. This applies high voltage across
winding and case.
•If winding is short or weak at any point a current will stream to return lead and meter
will display that current.
•All HIPOT testers have an over-current trip to secure the tester itself. This is vital in case if
device is completely shorted to its body and extreme current flows upon application of high
voltage from HIPOT tester.

19. Benefits of Leakage Current Measurement
Advantages of leakage current measurement are:
•The device under test is not placed into service, and its polarity need not be
reversed
•No stressing due to high switching current
Leakage current can be a sign of the inefficiency of insulation on conductors. It
is achievable to trace the cause of leakage current with the help of a low current
leakage current clamp to interpret orderly measurements as needed. If
required, this allows you to re-allocate loads all around the installation in a
better unbiased manner.

20. How electricity affects your body
Electric shock occurs when your body becomes part of a closed circuit and electric current
flows into one part of your body and out another, like into your hands and out of your feet
for instance.
Direct current (DC) is generally less dangerous than alternating current (AC).
The effects of AC on the body depend largely on the frequency. Low frequency currents of
50 to 60 Hz are usually more dangerous than high frequency currents.
How bad you are injured by electrical shock is determined by the pathway of the current
through your body. Current traveling from arm to foot is likely to go through the heart,
making it more dangerous than current traveling between a leg and ground.
Let-Go current is the maximum amount of current that can cause your arm muscles to
contract while maintaining the ability to release your hand from the current source. The let-
go current varies depending on muscle mass. For DC, the let-go current is about 75 mA for
a 70-kg body; for AC, it is about 15 mA.
Ventricular fibrillation occurs with currents as low as 60-100 mA in AC systems. For DC,
about 300 to 500 mA.

21. Effects of electrical current on the human body
•Current flowing through the heart causes fibrillation of the heart.
•Current flowing through muscles causes contraction of the muscles.
•Current flowing through the brain causes a loss of consciousness and
seizers.
In many cases, electric shock causes death. The threshold of perception for
current entering the hand is about 5-10 mA for direct-current and about 1-5
mA for alternating-current at 60 hertz.
How to calculate current flow through the body
The human body is a good conductor of electric current simply because it is 70% water.
Human tissue is very sensitive to the flow of electric current and is more susceptible to
electric shock when wet.
How much current flows through a person’s body can be estimated using ohms law (I =
E/R). The average resistance of a dry human body can be as high as 100,000 ohms, of
course this varies from person to person depending on their body structure. When wet,
the resistance may drop as low as 500 ohms depending on the voltage level.

22. Electrical Burns
Heating due to the resistance of the body is the cause of electrical burns. If skin resistance
is low, few, if any burns will occur. If skin resistance is high, energy may be dissipated at the
surface resulting in large surface burns.
Internal tissues are burned depending on their resistance; nerves, blood vessels, and
muscles conduct electricity better than denser tissues like fat, tendon, and bone. Arc-
flash temperatures can reach or exceed 35,000 °F (19,400 °C) at the source of the arc,
which can result in severe burning of the skin.
Neurological Effects
Electric current can interfere with the central nervous system, especially over the heart and
lungs. Severe or repeated non-leathal shocks can damage nerves, which may impair
sensation, movement, and gland or organ function.
Prevention
Education about the respect for electricity and safe work practices is critical in preventing
injuries from electrical shock. Any electrical device that may be touched by the body could
be life threatening and should be properly grounded and protected.