MSC High Voltage Safety Flashcards - Volume 2 (Questions 51-100)

A set of vocabulary terms based on MSC High Voltage Safety procedures, covering boundaries, risk assessments, testing protocols, and safety equipment.

Arc Flash Protection Boundary

The distance from an arc source where a person could receive a second-degree burn without proper PPE.

Energized Electrical Work Permit (EEWP)

To authorize justified energized work while documenting hazards and required protections.

Qualified Person

Someone trained to recognize electrical hazards and safely work on energized equipment.

Restricted Approach Boundary

The distance from exposed energized parts where only qualified persons with proper precautions may enter.

Limited Approach Boundary

The distance where an electrical shock hazard exists and access must be controlled.

Incident energy

The thermal energy released during an arc flash at a specified working distance.

ATPV

Arc Thermal Performance Value—the arc rating of protective clothing.

Personal Protective Equipment (PPE)

The last line of defense against electrical hazards.

Leather protectors

Worn over rubber gloves to protect the rubber gloves from physical damage.

Rubber insulating gloves

Must be electrically tested before first issue and at required periodic intervals, typically every $6\,months$ while in service.

Rubber glove pre-use check

Perform a visual inspection and an air test before each use.

Ozone

Deteriorates rubber and causes cracking; rubber gloves should be kept away from it.

Arc-rated clothing

To reduce burn injury from an arc flash.

Contaminated PPE

If contaminated with oil or grease, it must be removed from service until properly cleaned or replaced.

Infrared thermography

The safest way to verify overheating electrical equipment.

Job briefing

A discussion of hazards, work procedures, responsibilities, and emergency actions before work begins.

Shock risk assessment

An evaluation of electrical shock hazards and protective measures.

Arc flash risk assessment

An evaluation used to determine incident energy, boundaries, and PPE requirements.

Safety attendant

To observe work and respond during an emergency.

Situational awareness

Recognizing hazards and anticipating changes in the work environment.

Absence of voltage verification

The first action after isolating equipment.

Live–Dead–Live testing

Used to confirm the voltage tester is operating correctly before and after testing.

Proximity voltage detector

Used to detect the presence of voltage without direct contact.

Exact absence of voltage confirmation

An approved contact voltage tester or phasing tester.

Temporary protective grounds

Installed to protect workers from induced or accidental energization.

Equipotential zone

An area where all grounded objects are at the same electrical potential.

Hot stick

To safely operate or test energized high-voltage equipment.

Shepherd's Hook

Used to rescue a person from energized equipment.

Sanction for Test

A permit allowing controlled energized testing after isolation procedures.

Permit to Work

A document controlling hazardous maintenance activities.

Earthing switch

To connect isolated equipment to ground.

Automatic shutters

Installed on withdrawable breakers to cover energized contacts when the breaker is removed.

HRC fuse

A High Rupturing Capacity fuse used for short-circuit protection.

Megger

An instrument that measures insulation resistance.

Polarization Index formula

$$\frac{10\text{-minute insulation resistance}}{1\text{-minute insulation resistance}}$$

Low Polarization Index

Indicates possible insulation deterioration or contamination.

Insulation resistance factors

Temperature, humidity, contamination, and insulation condition.

Switchgear

Used to control, protect, and isolate electrical systems.

Vacuum circuit breakers

Preferred because they require little maintenance and extinguish arcs efficiently.

Load shedding

Automatic removal of nonessential electrical loads to protect the power system.

Emergency generator

Required to automatically restore essential power after loss of the main supply.

Grounding

Reduces shock hazards and provides a path for fault current.

Touch potential

The voltage difference between an energized object and the ground where a person is standing.

Step potential

The voltage difference between a person's feet during a ground fault.

Ventricular fibrillation

The heart condition that is most dangerous from electric shock.

Electrical burns cause

Heat generated by electrical current or an arc.

Arc blast

The pressure wave produced by an electrical arc.

Arc flash

Intense heat and light produced by an electrical arc.

De-energized electrical work

Should be performed whenever it is feasible to do so.

Primary goal of electrical safety

Protect personnel from shock, arc flash, and other electrical hazards.