GE Industrial Solutions Entellisys 5.0 User Manual - Manual (Page 61)

Overcurrent protection 61
5
5.1.2.2 Accuracy
Pickup accuracy is ± 10% over the entire protection range
5.1.2.3 Setup
The setup required for ST protection is done in the HMI and at the Messenger. There are three
options configured at each Messenger that control the operation of Short Time and
Instantaneous overcurrent protection:
•
Short Time option
•
Instantaneous option
•
Switchable Short Time/Instantaneous option
If the Short Time option or the Instantaneous option (or both) is enabled, the state of the
Switchable ST/IOC option is ignored. The Messenger and Entellisys CPU perform the protection
functions specified by the Short Time and Instantaneous options.
If the Short Time and Instantaneous options are disabled and the Switchable ST/IOC option is
enabled, the Messenger defaults to performing Short Time and digital Instantaneous functions
until instructed otherwise by the Entellisys CPU. In this case, the Messenger does not perform
the analog Instantaneous function. The Entellisys CPU instructs the Messenger to turn on or off
Short Time.
Entellisys limits the maximum Instantaneous Overcurrent Pickup Setting (P
IOC
) Multiplier based
on frame type and whether or not Short Time protection is enabled. This relationship is shown
for EntelliGuard circuit breakers in Table 5-2 below:
Parameters such as IOC pickup, ST pickup, curve type and delay bands for Short Time protection
are set in the HMI, as shown in Figure 5-2.
Table 5-2 Maximum P
IOC
Breaker Frame
Size Maximum P
IOC
with
Short Time
Maximum P
IOC
without
Short Time
800 15 10
1600 15 10
2000 15 10
3200 13 10
4000 9 9
5000 7 7