NSI Dangers

Question 1

NSI 12

Answer 1

The System Danger(s) to Personnel working On or Near exposed Live LV Equipment are electrocution, burns and effects on eyes arising from:

• Personnel mistaking Equipment on which it is safe to work
• Equipment being worked on accidentally or inadvertently being made Live
• Inadequate precautions being taken under Live conditions
• Dangerous Potential on open-circuited current transformer secondary windings and associated wiring arising from open circuits or disconnection from earth
• Short Circuit of Live LV system
• Induced voltages or currents arising from fault or load currents in other HV and LV circuits.

Question 2

NSI 2

Answer 2

The System Danger(s) to Personnel applying or removing Earthing Device(s) to HV Equipment are electrocution, burns and effects on eyes arising from:-
 Inadvertent infringement of Safety Distance
 The application of Earthing Device(s) to Live HV Equipment
 Badly connected or insecure Earthing Device(s)
 The incorrect sequence or method of application or removal of Earthing Device(s)
 Charged Equipment and the voltage difference across a break in electrical conductors
 Incorrect management of circulating currents
 The electrical arc drawn by the application or removal of an Earthing Device
 The application of Earthing Device(s) to an inadequate or defective earth system
 Incorrect identification of Earthing Device(s)
 Inadequate

Question 3

NSI 6

Answer 3

The System Danger(s) to Personnel arising out of inadequate demarcation in substations
are electrocution, burns, impact from release of pressure and effects on eyes arising from:-
 The possibility of mistaking Equipment on which it is unsafe to work, from that which it is safe to work
 Inadvertently infringing Safety Distance
 Inadequate planning leading to a failure in the co-ordination of all work activities
 Failure to adequately control risks associated with Hazard Areas and Testing activities

Question 4

NSI 8

Answer 4

The System Danger(s) to personnel during the movement and use of mobile elevated work platforms, lorry loaders, vehicles, cranes and Objects, in substations containing exposed Live HV conductors and Equipment operating above atmospheric pressure are electrocution, burns and effects on eyes arising from:-
 Inadvertent infringement of Safety Distance
 Badly connected or insecure Field Equipment Earth
 Incorrectly identified Field Equipment Earth
 The application of Field Equipment Earth to an inadequate or defective earth system
 Induced voltages
 Uncontrolled release of stored pressure

Question 5

NSI 9

Answer 5

The Danger(s) to personnel during the course of testing are electrocution, burns and effects
on eyes arising from:-
• Contact with electrical test supplies at dangerous voltages / energy levels
• Contact with the unearthed System
• Contact with Charged HV Equipment
• Incorrect management of circulating currents

Question 6

NSI 14

Answer 6

The System Danger(s) to personnel working on Equipment which has automatic and/or
remote control systems, may arise from the inadvertent operation of the Equipment, if these
systems have not been Isolated from the Equipment. These are:
• Electric shock due to inadvertent re-energisation
• Inadvertent operation of moving parts
• Sudden release of high pressure and noise due to inadvertent operation

Question 7

NSI 17

Answer 7

The main Danger(s) from Pressure System(s) arise from
• Mistaking Equipment that is in service from Equipment which has been made safe from
the System
• Accidental release of stored energy
• Accidental release or injection into the body of compressed hydraulic fluids or gas
• Impact from parts of equipment that fail
• Noise
• Trapped compressed fluid or gas that cannot be released by normal means of venting

Question 8

NSI 1

Answer 8

Electrocution, burns and effects on the eyes?

And…