Identify the effects that heat has on electrical insulation.

Insulation materials break down when exposed to excessive temperature.

Identify the reasons for excessive load current interruption.

Protective devices interrupt the current path before load current becomes excessive.

Identify effects an open has upon total circuit current, total resistance, and equipment in the circuit.

An open circuit interrupts current flow in a conductor, causing infinite resistance.  With an infinite resistance, current flow would be zero.

An open circuit may or may not damage circuit equipment but

Total circuit current will always decrease.

Total circuit resistance will always increase.

Identify the indications, which identify an electrical open.

Equipment is de-energized.

An open circuit may or may not damage circuit equipment but

Total circuit current will always decrease.

Total circuit resistance will always increase

Identify effects of a short upon total circuit current

A short always:

Raises circuit current.

and increases total current flow. 

Identify effects of a short upon total resistance.

A short always:

Lowers circuit resistance.

Effects of a Short Circuit

(1) High temperatures breakdown insulation.

(2) If an exposed conductor contacts another portion of a circuit, a short

circuit develops.

(3) A short increases total current flow. Heat produced in a conductor increases.

(4) Fire, damage to equipment, or personnel may occur.

(5) Protective devices are needed to open circuit, removing excessive load.

(6) Common indications of short are:

(a) Burned or discolored insulation.

(b) Acrid odor of burning insulation.

(c) Visible smoke near electrical equipment.

(d) Burned or discolored surrounding

surfaces.

(e) Melting or melted conductors.

(f) Abnormal current meter indications.

(g) Activated protective devices.

Identify the indications, which identify an electrical short.

Burned or discolored insulation.

Acrid odor of burning insulation.

Visible smoke near electrical equipment.

Burned or discolored surrounding surfaces.

Melting or melted conductors.

Abnormal current meter indications.

Activated protective devices (open fuses, open circuit breakers…).

Identify the reasons for grounding.

Prevent damage to equipment and injury to personnel in the event of an internal short.

Reduce operating and maintenance expense.

Keep transient overvoltages at a minimum.

Improve lightning protection.

Better overcurrent protection.

Limit neutral displacement.

Readily locate and isolate grounded circuits.

Improve reliability.

Identify four (4) steps, which should be taken upon the discovery of an electrical fire.

Report the fire to the control room.

Ask to de-energize the circuit.

Call the fire department.

Control or extinguish the fire using the correct type of fire extinguisher.

Identify the best extinguishing agents for an electrical fire.

The two (2) best agents are carbon dioxide (CO₂) and halon.

Carbon dioxide deprives the fire of oxygen and can cool the fire. 

If released close to burning material CO₂ displaces oxygen in the room from ground up.

Halon breaks into small chemical units called ions.  They migrate toward the hottest part of the fire and rob heat from the flame.  Acts as a cooling agent without cooling surrounding components.

Describe electrical shock potentials when working on electrical equipment.

Identify the methods for proper electrical equipment isolations.

Grounded

Lighting panel breaker tagged open

Fuses pulled

Larger breakers racked out

Identify basic safety rules used when working on electrical equipment.

1) Use common sense

2) Remove all loose articles of clothing.
3) Remove all extraneous metal.
4) Use protective clothing.
5) Use rubber mats or an insulated tool when appropriate.
6) De-energize as much equipment in area as possible.
7) All equipment should be dry.
8) Treat all electrical equipment as if it were energized.

9) Use insulated tools whenever possible.
10) Minimum distance for working on various voltage ranges. 
11) Do not service equipment alone.
12) Do not tamper with interlocks nor depend on interlocks for protection.

Identify the methods of verifying breaker position.

The following are the guidelines to be utilized for

verifying breaker position:

1) 4160 Vac breakers

a) These breakers should be visually checked by:

(1) Verify the breaker is racked IN or OUT by checking its physical position.

(2) Check that the rectangular OPEN/CLOSED indication flag, on the bottom front of the breaker is in the desired position.

(3) Check the indicating window for proper position.

(4) Verify that the “NR” fuse block is:

(a) Installed for a racked in breaker.

(b) Removed for a racked out breaker.

(5) Check the light indication on the front panel for desired position.

(a) Breaker Open-Green and White

(b) Breaker Closed-Red and White

(6) Local meter reading SHALL be “0” amps with the breaker open.

(7) Check the control room light indication if applicable.

2) 480 Vac breakers

a) These breakers should be visually checked by:

(1) Observing position-indicating flag for desired position.

(a) CONN – Racked in position

(b) DISC – Racked out position

(2) Observing the OPEN/CLOSE flag on the breaker front.

(3) For breakers controlled from the Control Room, observe indicating lights for desired position.

3) 480 Vac MCC breakers

a) Visually check by doing the following:

(1) Breaker switch position

(a) Vertical – pointed end up for closed position.

(b) Horizontal – pointed end towards 9 o’clock position for open.

(2) Checking power available light indications for the equipment supplied.