PN 769 Inc Involving Electricty

Question 1

Electricity company premises include

Answer 1

Power stations(powered by fossil fuels such as coal,oil,wood chip)
Substations(indoor outdoor maybe present in a office block or factory)
Fenced enclosures (contains transformers maybe staffed or remotely monitored)
Distribution cables/equipment (cables on poles; towers and pylons underground including pavement level electrical ducting)

Question 2

At premises where a sub station is present with in the building
Where would you expect to be sited?

Answer 2

It will sited against a outer wall with 4 hours fire separation from the rest of the building

Question 3

Do Incidents involving smoke issuing from pavements or explosions in pavements hazard to crews ?

Answer 3

Crews have been injured whilst removing inspection or accessing ducting, short circuiting & violent arching can cause a explosion and lift inspection covers scattering debris over a freak distance
even when arcing is not present fires in cable insulation can create sufficient over pressure to dislodge covers

Question 4

What are the hazards related to electricity?

Answer 4

Electric shock
Fire 
Explosion
Fires in cable insulation
Hazardous gases 
Trip hazard

Question 5

How could a FF receive a electric shock at an inc ?

Answer 5

Touching live or damaged apparatus
Illegal activity and overloading electrical supply
Application of water foam
Standing in water,oil,fluids or wearing wet PPE which is exposed to live electricity
High voltage overhead transmission lines (when in contact with heat/smoke, ionisation of the air may occur possible causing arching to ground via equipment).
switching off current does not necessarily render it safe (as a residule charge may still be present which maybe sufficiently powerful to cause electrocution)
Theft of electric components may render parts of the site live

Question 6

In a fire situation what hazards should be considered ?

Answer 6

Large quantities of fuel may be present also hazardous substances such as methano,propane,hydrogen,methane, chlorine and oxygen
Oil filled transformers and switchgear can unexpectedly fail and pose risk of explosion
Insulation materials, paper,oil or plastic may create large amounts of toxic irritant smoke containing hazardous gases

Question 7

Why would you expect to find Hazardous gases or liquid at a electrical inc?

Answer 7

Some transformers and switch gear are protected by fixed installations which when operated will fill the compartment that might be a asphyxiation
Also PVC insulation materials when involved I a fire will produce large volumes of smoke containing hydrogen-chloride gas

Question 8

What are the trip hazards associated with electrical incidents?

Answer 8

Un even/broken concrete covers over cable ducting
open excavations
Rubber mats in enclosed substations
Sumps and wells

Question 9

What are the operational considerations of the IC?

Answer 9

Risk assess and identify whether electricity Involved, type, how will it affect Firefighting and rescue operations,restricted zone or HZ.
In the case of pavement level ducting the HZ should take into account debris can be thrown significant distance and other inspection covers may become involved and present a hazard to surrounding area for example glass fronted buildings
Crews MUST NOT PASS warning signs or gain access until responsible or authorised person in attendance.

Question 10

What must be included in any message sent requesting attendance of represenitive of national grid or other energy organisations ?

Answer 10

information form unique identification plates

Pylons and other infrastructure will have unique markings/identification plates

Question 11

IC’s must consider the effect of isolating power supplies in premises where?

Answer 11

There are machine processes
The absence of electrical supplies will affect occupants safety/welfare
There may be an adverse impact on business continuity

Question 12

when the Authorised person can not confirm all electrical supplies isolated, without entering the compartment, what should the IC consider?

Answer 12

The risk against benefit of any possible action
If the possibility of high voltage supplies present no entry into the risk are should be made
If confirmed the residule electric supply is low voltage, actions can be taken provided appropriate control measures put in place

Question 13

What are the fire fighting considerations ?

Answer 13

• Whilst waiting for the responsible person crews should focus attention on protecting surrounding risks
• Substations in buildings have 4hours fire protection
• ladders and aerials should not be used at external substations without assurance from the authorised person (AP)
• Carbon dioxide or vaporising liquids do not damage electrical components (important factor when dealing with incidents involving delicate /complex apparatus e.g. Computers, switchboards)
• Ground and aerial monitors should not be used with in 30m of live conductor

Question 14

What are the operational considerations with overhead power lines ?

Answer 14

No structure or pole should ever be climbed without authorisation of AP (They will also be able to give guide on safe working distance for line opps)
If it’s nec to use ladders or aerials they must be at 10m (20m for training) From them
Crews should avoid positioning themselves or equip within a 10m corridor either side of the power cable (measured along the ground)
Safety officers appointed to inform crews of their proximity to them

Question 15

Witch regard wind turbines and solar panels what should the IC ensure

Answer 15

That they have been isolated from the area of opps the risk of low voltage electric discharge still remains and LFB electrical glove should be worn

Question 16

With regard uninterruptible power supplies (UPS) what are the considerations?

Answer 16

These may be generators powered by fossil fuels and/or battery banks
Battery banks will remain live until such time they have been drained. Isolation is only in relation to circuits it provides, unless otherwise marked they low voltage and electrical gloves provide adequate protection .
Be mindful that batteries are predominately variants of lead/acid the contents are likely to pose a hazardous materials Risk if damaged

Question 17

When attempting a rescue and the casualty is lying on top of a transformer, switch, or anywhere above ground. Then what?

Answer 17

They should NOT be touched until word is received from the AP of the electrical authority that it’s safe for rescue work to be carried out.

Question 18

Where would you expect to find high voltage cables ?

Answer 18

High voltage cables are seldom less than 2.5m above the ground. Protective screens are used where such apparatus cannot be placed 2.5m above ground

Question 19

What does the the LFB consider high voltage and low voltage?

Answer 19

High voltage 1000v ac / 1500v dc or greater

Low voltage less than 1000v ac / 1500v dc

Question 20

Who is the Authorised Person?

Answer 20

A represenitve from the electrical authority who is competent to isolate ,divert, make safe and / or de-energise their own equipment or instalation
Do not confuse with Responsible Person - the person who has control of the premises or their representative

Question 21

What are the minimum safe approach distances? For overhead cables.

Answer 21

For rescues: 5m
for other operational inc then: 
(Not using hose) 
Ladders/ aerials 10m (20m in training)
Dense smoke 10m corridor 
(When using hose)
Hand held jets 20m corridor
Monitors (ground or aerial) 30m

Question 22

With regard insulating materials what is PCB’s?

Answer 22

Polychlorinated Biphenyls (PCB’s): which are used in some transformers and other electrical equipment as a insulating liquid which highly toxic and have harmful environmental effects if released

Question 23

With regard insulating materials what is (SF6)

Answer 23

Sulphur Hexafluoride (SF6): gas used as a insulating and interrupting medium in many types of electrical apparatus heavier than air and will not disperse easily can act as asphyxiate. Advise of HMEPO or SA should be sought as hazardous breakdown products may present in the form of gas or powder.