PST: Programmable System Timer
The PST timing system provides commissioning and protection engineers with a simple to use and highly accurate timing system for all types of protective devices. The unit is based on the highly regarded timing systems used in the T&R current injection systems.
The unit has three trigger sources for starting and stopping timing: two contact inputs and one current input. The contact inputs accept either volt-free contacts or a dc voltage, and auto-select for normally open or normally closed contacts.
The timer is started on the first change of state of contact set 1, and stopped on the second change of contact set 1.
The timer starts on the first change of state of contact set 1 and stops on the first change of state of contact set 2.
Three current input ranges are available on the PST: 1A, 2.5A and 5A. The timer will start when the current exceeds 20% of the selected range (e.g. 1A on the 5A range) and stop when the current drops below 20%.