High Current Lockout
High Current Lockout(HCL) is an additional protection feature which operates in conjunction with the protection elements.
It is one of several features that can cause an ACR to go to lockout earlier than it normally would according to the Trips to Lockout settings.
Usage of HCL helps to prevent the ACR from closing back onto a heavy fault. Alternatively it can limit the number of times this can happen. It is important to note that HCL does not affect tripping. It merely determines if an automatic reclose must occur.
HCL Configuration
HCL can be enabled and configured in WSOS on the HCL page in the Protection settings.
Or on the operator interface.
HCL is configured per protection group.
HCL Operation
Apart from the On/Off control, there are two settings that determine how HCL operates:
-
Lockout Current
-
Active Trip No
If HCL is On and a sequence is in progress:
The controller checks the following during each dead time when an automatic reclose is pending:
-
Does the trip current measurement for the most recent protection trip exceed the Lockout Current setting?
-
Is the trip number of the most recent protection trip equal to or greater than the Active Trip No.?
If the answer to both the above is Yes, the ACR records that the High Current setting was exceeded and goes to lockout.
HCL is recorded in the Event Log.
HCL and Single Shot
HCL can occur when an ACR is closed onto a fault. In this case the ACR will perform a Single Shot trip and go directly to lockout even if Auto Reclose is On.
Consequently there are two factors helps preventing an auto reclose in this situation:
-
Single Shot Active
-
HCL
This situation can be identified by events in the Event Log, typically:
-
Phase Protection Trip
-
Single Shot
-
Max Current ≥ 1000 A (where 1000 A is the Lockout Current setting)
Table 42 HCL Settings/Specifications
|
HCL Settings/Specifications |
|
|---|---|
|
Maximum Effective Setting |
12.5 kA |
|
Minimum Effective Setting |
10 A |
|
Current Setting Resolution |
1 A |
|
Accuracy |
± 15% |
High Neutral Current Lockout Summary
High Neutral Current Lockout is an additional protection feature which operates in conjunction with the other protection elements. It detects that an Earth current is above a defined threshold and raises a high current condition. A lockout of the controller will occur when it is tripped. It requires Earth protection to be on to operate. The operation is basically identical to HCL (phase) excepting that it uses Earth (Neutral) current as the measurement.
Figure 146
High Neutral current lockout