480V Metal-Enclosed Switchgear
LV Power Circuit Breaker Trip Unit
General
Static Trip® III Trip Unit
Static overcurrent tripping devices have been standard on Siemens circuit break- ers for over thirty years. The Static Trip Ill trip unit features
The time / current characteristics of the Static Trip III trip unit are shown on page 62.
All communicating Static Trip III trip units include a local communication port that supports the
Static Trip® Ill Trip Unit (right) and Breaker Display Unit (left)
4
480V
This data can also be communicated to other devices or computers for control monitoring via Siemens’ ACCESS sys- tem. See Section 1 of this guide for a thorough description of ACCESS.
Siemens RMS sensing samples the entire current wave shape and calculates the effective heating value of the current. Static Trip Ill trip units provide accurate protection and avoid unnecessary trips.
Table 4.2 Static Trip III Settings
T: Long Time
Setting a | Delay |
(X Sensor Rating) | (Seconds @ 6X Setting) |
.5, .55, .6, .65, .7, .75, | 3.5, 6, 10 |
.8, .85, .9, .95, 1.0 | 17, 30 |
S: Short Time |
|
Pickup | Delay |
(X LT Setting) | (Seconds) |
2, 3, 4, 5, | 0.8, .15, .22 |
6, 7, 8, 12 | .30, .40 |
I: Instantaneous |
|
Pickup | Delay |
(X Sensor Rating) | (Seconds) |
2, 4, 6, 8, | No Intentional |
12, 15 | Delay |
G: Ground Fault |
|
Pickup | Delay |
(% Ground Sensor) | (Seconds) |
20, 30, 40, 50, 60 | .10, .25, .40 |
aPickup is fixed at 1.1 times long time setting.
Harmonics distort the current wave shape and can increase its peak value. Normal
56 | Siemens Electrical Products and Systems | CSI Section 16470 | |
Specification Guide | |||
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