18
1.3.5
Timing System
The PCU1 systems are fitted with an integrated timing system linked to the output and the two
sets of contact inputs. The system is highly flexible, and allows for the timing of all common
protection devices and trips. The timer may also be used to time external events not linked to
the output of the set. The timer is auto-ranging.
Full details of operating the timer are given in section 2.
Timer mode
Range
Resolution
Accuracy
Pulse 2s
0-2.000s
1ms
0.01% rdg
2d
Pulse 1s
0-1.000s
1ms
0.01% rdg
2d
Pulse 0.5s
0-0.500s
1ms
0.01% rdg
2d
Pulse 0.2s
0-0.200s
1ms
0.01% rdg
2d
Off
-
-
-
Internal start
0-999.999s/
0-9999.99s/
0-99999.9s
1ms/
10ms/
100ms
0.01% rdg
2d
Single contact
0.01% rdg
2d
Dual contact
0.01% rdg
2d
Current operated
0.01% rdg
4d
In current operated mode timing results obtained with test currents below 20% of the selected
ammeter range are of doubtful accuracy and should be ignored.
The PCU1 systems have two contact inputs which are used to start and stop the timer
depending on the mode selected. Each input has a connection for volt-free contacts and for
triggering by a DC voltage. In each case, the input auto-selects for normally open or normally
closed contacts. The contact state is shown by an LED (off when the contact is closed, on
when the contact is open).
The maximum open circuit voltage across the contact input is 24V, and the short circuit
current through the contacts is limited to 20mA.
The contact inputs are fully isolated.
