700
8000
9000
10000
7000
6000
5000
4000
3000
2000
800
900
1000
700
500
400
600
1000
900
800
200T
8 9
300
7
200
6
80
90
100
5
70
4
60
3
50
2
40
.7 .8 .9 1
30
.6
20
.5
140T
1000
900
800
10
CURRENT IN AMPERES
700
600
600
6T, 10T, 15T, 25T, 40T, 65T,
100T, 140T, AND 200T ARE
PREFERRED RATINGS; 8T,
12T, 20T, 30T, 50T, AND
80T ARE INTERMEDIATE
RATINGS.
80T
100T
65T
50T
40T
30T
25T
20T
15T
12T
8T
6T
400
10T
500
400
300
200
200
100
90
80
100
90
80
70
70
60
60
50
50
40
40
30
30
20
20
10
9
8
10
9
8
7
7
6
6
5
5
4
4
3
3
2
2
1
.9
.8
1
.9
.8
.7
.7
.6
.6
.5
.5
.4
.4
.3
.3
.2
.2
.1
.09
.08
.1
.09
.08
.07
.07
.06
.06
.05
.05
.04
.04
.03
.03
.02
.02
8000
9000
10000
7000
6000
5000
4000
3000
2000
800
900
1000
700
600
500
400
8 9
300
7
200
6
80
90
100
5
70
4
60
3
50
2
40
.7 .8 .9 1
30
.6
20
.01
.5
10
.01
CURRENT IN AMPERES
MINIMUM MELTING TIME-CURRENT CHARACTERISTIC CURVES
POSITROL® FUSE LINKS—S&C “T” SPEED
BASIS—These fuse links are tested in accordance with the procedures described in ANSI Standard C37.41-1981, to comply with
ANSI Standard C37.42-1981. As required by these standards, the
minimum melting current is not less than 200% of fuse-link ampere
rating, and the minimum melting curves are based on tests starting
with the fuse link at an ambient temperature of 25°C and no initial
load.
CONSTRUCTION—Fusible elements for fuse links rated 6T through
100T amperes are silver-copper eutectic, helically coiled; fusible
elements for fuse links rated 140T and 200T amperes are cast tin.
All are of solderless construction.
TOLERANCES—Curves are plotted to maximum test points. Maximum variations within the coordinating range (melting times less
than 10 seconds) expressed in current values are:
Plus 10% for fuse links rated 6T through 100T amperes;
Plus 20% for fuse links rated 140T and 200T amperes.
APPLICATION—Like all high-voltage fuses, these fuse links are
intended to accommodate overloads, not to interrupt them. Accordingly, they feature fusible elements which are designed with a minimum melting current of 200% of the fuse-link ampere rating (for
fuse links rated 100T amperes or less) or 220% of the fuse-link
ampere rating (for fuse links rated over 100T amperes). As a result,
these fuse links have considerable peak-load capabilities; however,
they should never be exposed to loading in excess of the peak-load
capabilities listed in S&C Data Bulletin 350-190.
Since fuse links having silver-copper eutectic element construction are not subject to damage by aging or transient overcurrents, it
is unnecessary to replace unblown fuse links of such construction in
single-phase or three-phase installations when one or more fuse
Supersedes TCC No. 170-6 dated 7-11-83 and 8-29-83
links have blown. However, it is advisable to replace unblown casttin element fuse links under the same conditions, since they may be
damaged by transient overcurrents.
COORDINATION—Any preloading reduces melting time. While this
phenomenon is especially pronounced in fuse linkss having minimum melting currents appreciably less than 200% of rating, the
effect of preloading (as described in S&C Data Bulletin 350-195)
must nonetheless be determined for the fuse links represented by
these curves and adjustments to these curves must be made:
1. When close coordination is required;
2. When automatic circuit reclosers or three-shot cutouts are
involved;
3. When, regardless of the preciseness of coordination, the fuse
link is subjected to temporary overloads.
If close coordination is to be achieved, overloading must be
avoided since it causes a significant shift in time-current characteristics.
Because of the damageability of cast-tin element fuse links
(rated 140T and 200T amperes), setback allowances must be used
in coordinating these fuse links as “protected” devices. These are
applied by reducing the current value in the above curves by 10%.
On the other hand, silver-copper eutectic element fuse links (rated
6T through 100T amperes) are nondamageable, and no such setback allowances are necessary.
The exclusive use of S&C Positrol Fuse Links—because of their
inherently narrower tolerance band and because of their nondamageability—will expand the scope of coordination as follows:
1.
Coordination of preferred with adjacent intermediate ratings,
2.
3.
4.
giving twice as many sectionalizing points. This is true for the
sequence operation of fuse links alone, or for the sequence
operation of fuse links coordinated with automatic circuit
reclosers.
Coordination of a larger number of fuse-link ratings with a
given automatic circuit recloser between the fast and retarded
curves.
Coordination through a greater range, and to higher levels of
fault current, with respect to automatic circuit reclosers.
Coordination to higher levels of fault current with respect to
sequence operation of fuse links.
The breadth of coordination described above can be obtained
only by the use of S&C Positrol Fuse Links. No fuse link of low-temperature element construction (tin, lap-joint) can provide similar
performance.
NOTE—A coordination scheme designed to take full advantage of
the nondamageability and the superior coordination capabilities of
S&C Positrol Fuse Links may not function satisfactorily if fuse links
of the same speed but of other makes are substituted. However,
S&C “T” Speed Positrol Fuse Links can replace, on a one-for-one
basis, other manufacturers’ “T” speed fuse links in existing coordination schemes. Such replacements, unlike tin-element fuse links,
are not subject to nuisance fuse operations (“sneakouts”) due to
damage from surge currents, load cycling, vibration, and aging.
FUSE LINKS AVAILABLE—
Style
Ampere Ratings
Universal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6T through 200T
Extra-Performance . . . . . . . . . . . . . . . . . . . . . . . . . 6T through 200T
c1984
TCC NUMBER
s
S&C ELECTRIC COMPANY • Chicago
S&C ELECTRIC CANADA LTD. • Toronto
Reprinted with permission of S&C Electric
170-6
Page 1 of 1
December 17, 1984
TIME IN SECONDS
TIME IN SECONDS
300
500