West Yangon Technological University
Department of Electrical Power Engineering
Testing The Electrical Safety
EP-61014
Presentation-4
8.3.2024
Supervisor by; Presented by;
Dr.Win Kyaw Myint Hnin Hnin Phyu
VI.EP-1
1
Outlines of presentation
Introduction
Soil resistivity measurement
Earth resistance measurement
Earth resistance measurement in industrial facilities
Earth resistance measurement in TT system
Measurement of the fault-loop impedance in TN systems
Touch voltage measurement in TN systems
Fundamental measurement in IT Systems
Productive conductor continuity test
Insulation resistance test
Conclusion
2
Introduction
The parameter that ensure electrical safety in installation can , and must , be tested to
positively assure that the electric shock is below the limit deemed acceptable by the
electrical design
Electrical safety obtained due to the proper deployment of protective measures against
direct and indirect contact tends to decrease in time due to aging of the electrical system
Electrical safety testing required in health care institutions
Some types of electrical safety tests include
(1)Dielectric withstand test
(2)Insulation resistance test
(3)Earth continuity test
(4)Leakage current test
3
Soil resistivity measurement
The resistivity of soils play a crucial role in determining the performance of ground
electrodes , as it is a major factor in influencing their resistance to earth
The Wenner method is probably the most widely used technique to create soil models
Soil resistivity is another name for the specific resistance of the soil
It is measured in ohm-meters or ohm-centimeters
An ohm-meter is that resistivity of the soil when if has a resistance of 1 ohm between
opposite faces of a cube with one meter sides
4
Earth resistive measurement
The earth potential V depends , among
other parameters , on the total ground
resistance R of the electrode system
The method of the fall of potential ,
which is based on ohm’s la
The precision of this test depends on the
mutual position of potential and current
rods with respect to the electrode under
test
An alternating current I is passed through
the outer electrode C and the voltage is
measured , by means of an inner
electrode P , at some intermediary point
Between them
5
Earth resistive measurement in industrial facilities
In industrial facilities generally characterized by grounding grids ,the earth
resistance measured can be facilitated in the presence of metal bodies embedded in
the earth
Grounding grids in industrial facilities may have a very large extension
The grounding grid of the power station feeding the facility might conveniently
constitute the current electrode
The test current is injected through a de-energized power conductor running between
the station and the facility
\In overhead distribution lines , an overhead ground wire is usually present as a
protection against lighting strikes 6
Earth resistance measurement in TT
system
The fault loop in TT systems includes
both the ground resistance R(G) of the
consumer’ electrode and the utility’s
electrode earth resistance R(N) , which
are independent of each other
7
Measurement of the fault loop impedance in TN system
In TN systems , under low-voltage ground-fault condition , Z(loop) is constituted by
the series of the following impedance: phase conductor , protective conductor(PE) ,
and secondary winding of the transformer
The numerator represents the much simpler algebraic difference between the
magnitudes of the two-voltages
The fault-loop impedance is directly given by the ratio of the reading of voltage and
current
A major drawback of this method is the necessity to put the substation out of service
8
Fundamental measurements in IT system
When the rheostat is fully disengaged , the clap-on current meter reads the first-fault
current
The presence of the rheostat is advisable in order to prevent the inception of the
circuit
Under the first-fault condition , the IT system ” evolves ” into TT or into a TN
For the duration of the test , a temporary connection between the neutral point and the
earth must be carefully realized in order to close the fault-loop otherwise open by
definition
9
Protective conductor continuity test
The ground continuity test checks whether the protective earth conductor is
connected continuously to all metallic enclosure pars that can be touched by the user
The test can be carried out with low currents and voltages
The purpose of this test is to verify that the CPC forms a continuous path around the
circuit under test
The continuity test is not aimed at measuring the resistance of the PE , but only its
electrical integrity
A low value for the PE’s resistance will indicate its electrical continuity
10
Insulation resistance test
High insulation levels between circuits are of paramount importance in preventing
faults
An insulation resistance test measures the total resistance between any two points
separated by electrical insulation
The test determines how effective the dielectric is in resisting the flow of electrical
current
11
Conclusion
Electrical safety at the workplace is of paramount importance to protect employees
and maintain a productive work environment
By understanding potential hazards , implementing safety measures , and fostering a
safety culture ,, business can significantly reduce the risk of electrical accidents
Make sure electrical equipment is properly connected , grounded and in good
working order
Extension cords may not be used as permanent wiring and should be removed after
temporary use for an activity or event
12
Thanks For Your Attentions
13
