Technical Manual
KVCG202/EN M/H11
KVGC202
6.2.1
Triggering event records
Event records are triggered automatically in response to the functions listed in
Chapter 6.2.
6.2.2
Time tagging of event records
The KVGC202 relay does not have a real time clock. Instead, it has a free-running 32-bit
counter that increments every 1 millisecond. When an event occurs, the value of this
millisecond counter is recorded (Ta) and stored in the event buffer. When the event is
extracted, the present value of the millisecond counter is also sent in the message (Tb).
The master station must record the actual time at which it received the event message
(Tc). This is equivalent to Tb if we consider the transmission time of the event over the
communication network to be negligible. It then calculates how long ago the event
occurred by:
How long ago
= (Tb – Ta) milliseconds ago
Real time
= (time message was received) – (how long ago it occurred)
= (Tc) – (Tb – Ta)
Time tagging is to a resolution of 1 millisecond, the incrementation rate of the counter and
remain valid for approximately 49 days. However, the crystal to control the timing has a
nominal accuracy of ±50 ppm, is not externally synchronised and has no temperature
compensation. It can therefore introduce an error of ±1 second in every 5.5 hours.
The event recording was originally designed for use with automatic extraction programs
running on a personal computer (PC) when these timing errors would be insignificant.
6.2.3
Accessing and resetting event records
Event records cannot be viewed on the relay and can only be accessed via the serial
communication port of the relay. A PC with suitable software, such as PAS&T, can
automatically extract the records, display them on a screen, print them, or store them to
either a floppy disc or to the hard disc of the computer.
When a new record is generated the oldest event record is automatically overridden and
the event flag set. The PAS&T software responds to this flag and extracts the record.
When all records have been read, the event flag resets.
6.2.4
Recorded times
The times recorded for the opto-isolated inputs is the time at which the relay
accepted them as valid and responded to their selected control function. This will be 12.5
±2.5ms at 50 Hz (10.4 ±2.1ms at 60 Hz) after the opto-input was energised. The time
recorded for the output relays is the time at which the coil of the relay was energised and
the contacts will close approximately 5ms later. Otherwise, the time tags are generally to
a resolution of 1ms for events and to a resolution of 1µs for the samples values.
6.3
Alarm records
6.3.1
Watchdog
The watchdog relay will pick-up when the relay is operational to indicate a healthy state,
with its “make” contact closed. When an alarm condition is detected that requires some
action to be taken, the watchdog relay will reset and its “break” contact will close to give
an alarm.
The green LED will usually follow the operation of the watchdog. It will be lit when the
relay is powered-up, operational and no abnormal conditions have been detected for
healthy conditions.
The watchdog can be tested by setting alarm flag 6 to “1” in menu cell 0022 in the
SYSTEM DATA column of the menu.
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