Electrical Safety Guidelines

Electrical Safety and Preventive Measures

30 ma used for portable tools (1 Ampere = 1000 MA)
1 ohm required for Diesel Generator or portable diesel engines
25 mili ohms is enough to kill a person
Min 3 mtrs clearance from electric to the person when passing. HV
Low voltage. <250 V
Medium voltage. 250 V – 650 V
High voltage. 650 V – 33 KV
Extra high voltage. Above 33 KV

Precaution:

PTW
Isolation
LOTO
Insulation
RCD (Residual current device) circuit breaker
Bonding & Grounding
Guarding
Electric resistant PPE’s
Safe work practice
ELCB (Earth leakage circuit breaker)
GFCI (Ground fault circuit interrupter)
OCB (oil circuit breaker)
VCB (Vacuum circuit breaker)
Use flameproof apron while putting ON/OFF

Points to Remember:

The equipment itself should be checked to ensure that it is suitable and conforms with recognized standards such as CE marking and European standards,
Vertical clearance above walkways shall not be less than 3 mtrs (10ft) for circuits carrying 600 volts or less.
Current: the flow of electricity through a conductor
Voltage: the potential difference between two points of a conductor
HIPOT TEST: It is the insulation leakage test done for high voltage electrical

Standard Electric Boards Colour Code:

Purple. 24 v dc
Yellow. 110 v ac
Blue. 220 v ac
Red. 440 v ac

Effects of Amount of A/C Current 60 Cycles/Seconds:

More than 3 ma. Painful shock, incident, accident
More than 10 ma. muscle contraction can’t go
25 mA can kill a person
More than 30 ma. Temporary lung paralysis
More than 50 ma. Heart dysfunction, usually fatal
More than 100 ma – 4 a. Heart dysfunction, fatal
Over 4 a. heart paralysis, severe. burn
50 – 100 a. for a person will be fatal.
For earth rod (D.G. or welding gen) required 1 ohm
ARC: Electrical passing through the air
Minimum acceptable value of insulation resistance, 1 megohm for each 1000 V
e.g. one motor 2400 V so you should have a minimum insulence resistance megohms
Clearance a person from live 50 kv lines shall be 10 feet 0.4 inches

Difference Between Grounding & Bonding?

Earthing is the attachment of a bonded metallic system to earth, typically through ground rods or other suitable grounding electrodes. The NEC prohibits earthing via isolated ground rods. As the only means of equipment grounding.

Transformer requires min 4 earthing.
Grounding deep 10.
Ground rods shall not be less than 5/8 inch in diameter by 8 feet in length.
Ground rods shall be driven into the ground so that one end of the ground rod is at a minimum depth of 8 feet below the surface of the ground.
Distance (away) from other grounding is 50.
Rod: copper or galvanized
Transformer requires min 4 earthing standard ground resistance value of 5.0 ohms or less
Bonding: grounding one equipment’s to another to avoid static electricity
The telecommunications industry has often used 5 ohms or less as their value for grounding and bonding while electric utilities construct their ground systems so that the resistance at a large station will be no more than a few tenths of one ohm.
Platform wide enough with guard rails (39 – 43”) and toe boards (4’’ - 6”)