3-5-1 Primary Fusing/Fuse Principles Flashcards
An open-link cutout cannot interrupt large value faults.
True
A fuse cutout using an arc confining tube with a de-ionizing fiber liner and a fuse link is an example of the __?__ principle.
Expulsion
The size of the fuse link used depends on the __?__.
backup protection
The definition of the term fuse-coordination means that only fused disconnects is coordinated.
False
The chief aim of fuse-coordination is to provide power to the __?__ when a fault exists on a distribution circuit.
maximum number of customers
The amount of current a fuse is able to interrupt is based on its ability to __?__.
extinguish an arc
The melting and clearing time of a fuse should coordinate with both upstream and downstream protective devices.
True
The heat from an arc inside a fuse chamber acts on a special coating on the inside walls of the chamber.
True
An ordinary expulsion fuse will limit the duration of an arc but not the __?__.
magnitude
A current-limiting fuse used on a transformer will reduce the risk of the transformer __?__.
failing explosively
The current-limiting fuse which is not used in series with another fuse is the __?__ or general-purpose fuse.
full-range
An under-oil expulsion fuse is also called a(n) __?__ fuse.
bayonet style
There are __?__ types of under-oil type fuses in this lesson.
2
The __?__ type fuse has the fastest clearing time.
K
An NX current-limiting fuse is of the __?__ type.
non-expulsion
There are __?__ types of fuses commonly used in electrical utility work.
5
Per NEMA, a 75-ampere fuse would require a __?__ -inch size fuse holder.
7/17
The two most common types of fuses used in overhead distribution are the universal fuse link and the __?__ fuse.
open-link
Fuses were used as early as __?__ to protect telegraph cables.
1864
Fuse links should not be overstressed by pulling on them when installing them in cutout doors because you may exceed the __?__ pull the manufacturer allows.
10-pound
The open-link fuse is the most commonly used fuse in electrical distribution construction.
False
A seven-ampere fuse will blow at 14 A of current in __?__ minutes.
5
All fuses must meet the ANSI-C__?__ standard.
37.42
The formula to find the primary current that a transformer will draw is __?__.
I = P / E
A(n) __?__fuse would normally be used to protect a 50-kilovolt-ampere transformer connected to a 14.4-kilvolt line. (round up to nearest whole number)
7-ampere
When two transformers are connected open-delta on a delta primary, all cutouts are fused with the same size fuse.
False
