Red Seal Powerline Technician flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Arc flash boundary

The distance from exposed live parts where incident energy equals 1.2 cal/cm², the level that causes second-degree burns; used to set barricades and PPE requirements.

Minimum approach distance

The closest a qualified worker may bring any part of the body or uninsulated tool to an exposed energized part; it depends on voltage, altitude, and the work method used.

Equipotential grounding

A worker protection method that bonds all conductive parts the worker may contact to the same potential, so no hazardous voltage appears across the body during a fault.

Three-phase power formula

P equals the square root of three times line-to-line voltage times line current times power factor; used to compute feeder loading and transformer capacity.

Per-unit impedance conversion

New per-unit impedance equals old per-unit impedance times the ratio of new to old kVA base times the square of the ratio of old to new kV base.

Skin effect

At AC, current crowds toward the conductor surface, raising effective resistance above the DC value; it grows with frequency and conductor size.

Pole setting depth

A common rule sets burial depth at ten percent of pole length plus about 0.6 m (2 ft), adjusted for soil conditions and the loads the pole carries.

NESC Grade B

The higher-strength construction grade required at railroad and highway crossings, using greater safety factors on poles, guys, and conductors than Grade C.

Guy lead angle

The angle between the guy wire and the pole; about 45 degrees balances load, and leads flatter than 2:1 horizontal-to-vertical put excessive strain on the anchor.

Pin versus suspension insulator

Pin insulators are typically used up to about 33 kV; suspension strings are used at higher voltages, and each bell adds roughly 10 kV of wet flashover.

Primary cable burial depth

Typical minimum cover is about 1.05 m (3.5 ft) under roadways and 0.75 m (2.5 ft) in private rights-of-way, with greater depth at crossings.

Stress cone

A termination or splice component that shapes the electric field at the point where the cable shield is cut, preventing concentrated stress and insulation breakdown.

Time-domain reflectometry

A fault-locating method that sends a pulse down a cable and times the reflection; distance equals half the travel time times the propagation velocity.

Cable pulling tension limit

Manufacturer limits, often around 2,700 N (600 lbf) for jacketed primary cable, protect the insulation and shield from damage during installation.

Transformer turns ratio

The ratio of primary to secondary voltage equals the ratio of primary to secondary current; a 14.4 kV to 240 V unit has a 60:1 ratio.

Open-delta bank capacity

Two single-phase transformers in open delta deliver three-phase power at about 58 percent of the sum of their two nameplate ratings.

Recloser versus sectionalizer

A recloser interrupts fault current and recloses on a set sequence; a sectionalizer counts fault-current interruptions and opens only during a dead time.

Voltage regulator step

A step voltage regulator changes voltage in increments, commonly 0.625 percent per step over 32 steps, giving about plus or minus 10 percent control range.

Fuse coordination

The downstream fuse's minimum melting curve must lie below the upstream protective device's trip curve across the full range of fault currents.

Class 2 rubber gloves

Gloves rated for proof testing at 17 kV AC; they are used on circuits up to that voltage class with insulating cover installed and leather protectors worn.

Leather protectors

Worn over rubber insulating gloves to resist cuts, abrasion, and punctures; they add mechanical protection but no electrical insulation.

Glove cover-up sequence

Install insulating cover on conductors and insulators before contact, working from the nearest live part outward, so no exposed energized surface remains within reach.

Hot stick distance

Live-line tool work requires a minimum tool length between the worker and the energized part, commonly about 0.3 m per 100 kV plus a base distance.

One-shot reclosing

Setting the recloser to a single trip and reclose during energized work so a fault cannot repeatedly re-energize the line while workers are in contact.

Faulted circuit indicator

A device that senses and latches on fault current, letting crews narrow an outage to a section without patrolling the entire feeder.

Cold-load pickup

The inrush current when a feeder is re-energized and motors, heaters, and transformers draw above normal current; it can trip instantaneous protection.

Blown fuse on three-phase bank

A single blown fuse in a three-phase transformer bank causes voltage imbalance on the secondary and can overheat three-phase motors on the service.

Voltage complaint isolation

Measure voltage at the meter and at the transformer; low at the transformer means a supply problem, normal there means a service or customer-side fault.

Bridle sling tension

For two legs at angle theta from vertical, each leg tension equals half the load divided by the cosine of theta; flatter legs carry more tension.

Insulating boom test

The insulating section of an aerial device is dielectric-tested at intervals, commonly annually, and must pass before the device is used on energized lines.

Load chart radius

Lifting capacity is read at the actual boom radius and angle; capacity falls sharply as radius increases, so the chart must be consulted at the working position.

Knot efficiency

A knot reduces rope strength; a bowline retains roughly 60 to 70 percent of the rope's rated strength, so knots are avoided in critical lifts.