Safety
procedure in
electrical work
(Standards and best
practices)
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Prevent direct contacts
 Remoteness
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Prevent direct contacts
 Obstacles
 Insulation
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Prevent Indirect Contact

By automatic
disconnection of
supply

 Without
This principle consist
in connected to the
earth all metallic
part of equipment
and appliances. The
disconnection can
be done by MCB or
RCCD depending
on the earthing
system.
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automatic
disconnection of
the supply

This can be done
by three ways:
 Class
II equipment
 Isolated circuits
 Very low voltage
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Voltage range from IEC & Risks
IEC voltage range
High voltage
(supply system)
Low voltage (supply
system)
Extra-low voltage
(supply system)
AC
DC
Defining risk
> 1000 Vrms
> 1500 V
electrical arcing
50–1000 Vrms
120–1500 V
Electrical shock
< 50 Vrms
< 120 V
Low risk
Protection by class II equipment
A class II equipment in addition of the main insulation has a double
insulation.
Protection by Isolated circuits
The principle of this protection is by using transformer to isolate
circuits. The second circuit is completely isolated from the earth and
from the power supply.
Protection by using Extra-low voltage
The protection is ensured by the use of a voltage under 50 V in AC,
voltage under this there is no danger for people.
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Equipment classification

Class 0


These appliances have no
protective-earth
connection and feature
only a single level of
insulation and were
intended for use in dry
areas.

Class 2

Class 1

These appliances must
have their chassis
connected to electrical
earth . The earth
connection is achieved
with a 3-conductor mains
cable.

Class 3

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A Class II or double
insulated electrical
appliance is one which
has been designed in
such a way that it does
not require a safety
connection to electrical
earth (ground).
A Class III appliance is
designed to be supplied
from a separated/safety
extra-low voltage (SELV)
power source.
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IP Code (is.iec.60529.2001)
The IP Code, International Protection Marking (IEC 60529),
classifies and rates the degree of protection provided against
the intrusion (including body parts such as hands and fingers),
dust, accidental contact, and water by mechanical casings
and electrical enclosures.
The standard aims to provide users more detailed information
than vague marketing terms such as waterproof. The digits
(characteristic numerals) indicate conformity with the
conditions summarized in the tables below. Where there is no
protection rating with regard to one of the criteria, the digit is
replaced with the letter X.
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Additionalletters
The standard defines additional letters that can be appended to classify only the level of protection against access to hazardous parts by persons:
Level
A
B
C
D
Protected against access to hazardous parts with
Back of hand
Finger
Tool
Wire
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IK Code definition

Standard IEC 62262 defines an IK code that characterises the aptitude
of equipment to resist mechanical impacts on all sides.
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Overvoltage categories
Overvoltage categories classification of live electric circuits is used
in measurement and testing of installations and equipment, usually
in the relation within a building (residential or industrial)
There are four categories designated by a mark such as “CAT III,
150 V" or "CAT IV, 1000 V".
• CAT I is applicable to instruments and equipment, which are not
intended to be connected to the mains supply
• CAT II defines circuits which are intended for direct connection
into mains sockets or similar points.
• CAT III is for circuits which can be connected to the mains
installation of a building
• CAT IV includes circuits which are connected directly to the
source of power for a given building.
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In addition to the label “CAT”, the maximum voltage must be marked. This voltage is the maximum voltage between live and ground of the circuit or the same overvoltage range.
Rated Voltage
150V
300V
600V
1,000V
Resistance
IEC 61010-1 2nd Edition
CAT IV CAT III
CAT II
4,000V
2,500V
1,500V
6,000V
4,000V
2,500V
8,000V
6,000V
4,000V
12,000V 8,000V
6,000V
2 ohms
2 ohms 12 ohms
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Security equipment
 Personal







protective equipment (PPE)
safety glasses
face shields
hard insulated hats
safety isolated shoes
insulating (rubber) gloves with leather
protectors
insulating sleeves
flame-resistant (FR) clothing
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 Insulating







Protective Equipment (IPE)
Insulating mat
Insulating tools
Insulating ladder
Insulating pole
Insulating tools
voltage detector
temporary-grounding and temporary-shortcircuit set
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 Collective



protective equipment
Protective screen
Poles, chains
Warning board and sign
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Measuring devices
 The




measuring device should:
Have an insulating case
Be Class II
Have an IP2X
Have the right measurement
category.
 Accessories
should have the
same characteristics
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Permit-to-work system
(IS.5216.1.1982)



The permit is to be prepared in duplicate by the
person-in-charge of operation on the basis of
message, duly logged, from the person-m-charge
of the work.
The original permit will be issued to the person-incharge of work and the duplicate will be retained
in the permit book. For further allocation of work
by the permit receiving officer, tokens may be
issued to the workers authorizing them individually
to carry out the prescribed work.
On completion of the work, the original shall be
returned to the issuing officer duly discharged for
cancellation.
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Work zone and vicinity


The vicinity zone has been defined when a
live part of an equipment is close to people.
The distance between them depends of the
voltage. In lower voltage (50 – 1000 V AC) this
distance is 30 cm (11 in). It has also to be
taken in account the possible movement of
the worker, movement of live part (aerial
wire), tools…
It has been defined that the accessible live
part are equipment with:



In LV the IP is lower than IP2X
In LV the IP is lower than IP3X
Work in a vicinity area requires the use of PPE
and PEI
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



Zone 1: Non vicinity
Zone 4: Vicinity area in LV (less than 30 cm from
live parts). All equipment with IP < IP2X is
considered as live part.
Zone 2: Vicinity area in HV (up to red line)
 2 m (79 in) if U < 50 000 V (3 m -118 In – for aerial
wire)
 3 m (118 in) if U < 250 000 V (5 m -197 In – for
aerial wire)
 4 m (157 in) if U < 400 000 V (5 m -197 In – for
aerial wire)
 5 m (197 in) if U < 750 000 V (5 m -197 In – for
aerial wire)
Zone 3 : This is the distance between the live part
and the Minimum Distance Approach (MDA). In
this area there a risk of electric arc. The MDA
distance is 60 cm (24 in) up to 50 000 V. From
50 000 V the MDA is given by the following
formula: MDA(m) = 0,005 x U(kV) + 0,5
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THANK YOU
Standards :





IS.5216.1.1982_Recommendations on Safety Procedures and Practices in Electrical Work.
IEC 61140: Protection against electric shock – Common aspects for installation and
equipment
IEC 60950-1: Information technology equipment – Safety
IEC 60529: Degrees of protection provided by enclosures (IP Code) (is.iec.60529.2001)
IEC 61010: Safety requirements for electrical equipment for measurement, control, and
laboratory use
Doc:

TOT-M1-B-LE_00_00_002-RES-Model form of work permit
Schneider Electric “Cahier Techniques”

CT 166 – Enclosure and Degree of Protection
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