Unit 15

According to a NEMA report, 11 percent of the GFCI breakers protecting indoor receptacles failed, and _____ percent protecting outdoor receptacles failed.

20%

The current in a short-circuit type arc is limited by the system impedance and the impedance of the arcing fault itself. Typically, at a receptacle, fault current will be above 75A, but not likely above _____.

450A

Arcing is a luminous discharge of electricity across an insulating medium. Electric arcs operate at temperatures between _____ and expel small particles of very hot molten material.

5,000 and 15,000 degrees Farenheit

If the difference between the current leaving and returning through the current transformer of the GFCI-protection device exceeds _____, the solid-state circuitry de-energizes the circuit.

5mA

As current flows through the element of a fuse, it generates heat. When a sustained overload occurs, the heat melts _____, stopping the flow of current.

A portion of the element

A ground-fault type parallel arc can only occur when a ground path is present. This type of arcing fault can be quickly cleared by a(n) _____ circuit protective device.

AFCI or Arc-Fault-Circuit-Interrupter

_____ breakers permit the thermal trip setting to be adjusted to coordinate the circuit breaker's operation with other protection devices.

Adjustable Trip

To help reduce the hazard of electrical fires from a parallel arcing fault, the NEC requires a listed AFCI-protection device to protect _____ wiring in dwelling unit bedrooms.

Branch-circuit

When equipment does not have a withstand rating sufficient for the available fault current, the equipment can be protected by the use of _____.

Current-Limiting fuse or Fast-clearing fuse

True or False: A GFCI-protection device contains an internal monitor that prevents the device from being turned on if there is a neutral-to-case connection downstream of the device. But this only occurs if there is a load on the circuit.

False

True or False: Inverse time breakers operate on the principle that as the current decreases, the time it takes for the device to open decreases.

False

To remove dangerous touch voltage on metal parts from a(n) _____, the fault-current path must have low impedance to allow the fault current to quickly rise to facilitate the opening of the protection device.

Ground Fault

The purpose of overcurrent protection is to protect conductors and equipment against excessive or dangerous temperatures because of overcurrent. Overcurrent is current in excess of the rated current of equipment or conductors. It may result from a(n) _____.

Ground Fault, Overload, or Short Circuit

_____ breakers operate on the principle of electromagnetism only and are used for very large motors.

Instantaneous Trip

_____ breakers operate on the principle that as the current increases, the time it takes for the device to open decreases.

Inverse Time

A short circuit is a _____ electrical connection between any two conductors of the electrical system.

Line-to-line or line-to-neutral

Factors that impact the available short-circuit current include circuit conductor _____.

Material, size, and length

A fuse consists of an element electrically connected to end blades, which is enclosed in a tube and surrounded by a _____ filler material.

Nonconductive

A(n)_____ is the operation of equipment or conductors in excess of their rated ampacity.

Overload

To protect against electric shock or to prevent a fire, a dangerous _____ must quickly be removed by opening the circuit's overcurrent protection device.

Overload, Short Circuit, and Ground Fault

When a short circuit or ground fault occurs, _____ melt(s), removing the load from the source very quickly.

Several elements

Magnetic time-delay circuit breakers operate on the solenoid principle where a movable core, held with a spring, is moved by the magnetic field of a(n) _____.

Short Circuit or Ground Fault

Equipment must have a(n) _____ current rating that permits the protection device to clear a short circuit or ground fault without extensive damage to the components of the circuit.

Short-Circuit

The _____ sensing element causes the circuit breaker to open when a predetermined calibration temperature is reached.

Thermal

True or False: A series arc can occur when the conductor in series with the load is unintentionally broken. A series arc-fault current is load limited.

True

True or False: An AFCI-protection device provides protection from an arcing fault by recognizing the characteristics unique to a parallel arcing fault and by functioning to de-energize the circuit when an arc fault is detected.

True

True or False: Available short-circuit current is the current in amperes that is available at a given point in the electrical system.

True

True or False: Circuit breakers and fuses are intended to interrupt the circuit, and they must have an ampere interrupting rating (AIR) sufficient for the available short-circuit current.

True

True or False: If the protection device is not rated to interrupt the available fault current at its listed voltage rating, it can explode while attempting to clear the fault.

True

True or False: Severe electric shock or death can occur if a person touches the ungrounded and the neutral conductors at the same time, even if the circuit is GFCI protected.

True

True or False: The opening time for a protection device is inversely proportional to the magnitude of the current. The greater the current value, the less time it takes for the protection device to open.

True

True or False: Typically, when a GFCI-protection device fails, the switching contacts remain closed and the device will continue to provide power without GFCI protection.

True

True or False: Unless marked otherwise, circuit breakers have a 5,000 AIC rating and fuses have a 10,000 AIC rating.

True

True or False: Unsafe arcing faults can occur in one of two ways, as series arcing faults or as parallel arcing faults. The most dangerous is the parallel arcing fault.

True

True or False: Ground-fault protection devices protect equipment from damaging ground-fault currents by opening all ungrounded conductors of the faulted circuit. This device will also protect persons.

True?

A GFCI is designed to protect persons against electric shock. It operates on the principle of monitoring the imbalance current of the circuit's _____ conductor.

Ungrounded and grounded

The available short-circuit current is different at each point of the electrical system; it is highest at the _____.

Utility Transformer

Factors that impact the available short-circuit current include transformer _____.

Voltage, kVA rating, and Impedance

A thermal-magnetic circuit breaker typically clears fault current in less than 3 to 5 cycles when subjected to a(n) _____.

short circuit or ground fault