VCG202/EN M/H11
Technical
The power factor is calculated by rotating the load current by –90° to make it relative to
Vbc. The calculated power pf is converted into a ‘numeric quantity (in the form of
‘Mantissa, Sign, Exponent, Units’) to allow it to be used by the measurement display. The
power factor is stored in cell location 0205.
pf = [real power]/[apparent power]
6.1.5 Tap position
The relay provides an indication of the actual tap position (1 to 30). The tap position is
determined by applying Vbc to a potential divider and determining the tap position from
the output voltage which is measured by the relay. The tap position is rounded to the
nearest integer.
The voltage of each step is given by Vbc/Number of taps selected on the relay.
The value of the tap position is stored in cell location 0207.
The highest and lowest tap positions since last reset are also recorded and the values
are stored in cell locations 0208 and 0209 respectively. The values can be reset to zero
by pressing the [0] key.
6.1.6 Tap changer operations counter
The “Tap Change Operations Counter” is incremented by 1 each time the tap position is
changed. The tap change may be initiated by the internal tap change control fuctions,
manual tap change, local control sequences or remote tap change sequences. Logic
ensures that register is only incremented by 1 in any one tap changing operation. The
value of the counter is stored in cell location 020A which can be reset to zero by pressing
the [0] key.
6.1.7 Frequent operations monitor
The frequent operations counter is incremented every time a tap change operation is
initiated over a preset time (tP), after which an event is raised and the value of the
number of operations is recorded. The delay timer and the counter for the tap change
operation are reset to zero after the event is logged. The counter can be reset to zero at
any time by pressing the [0] key. The value of the counter is stored in cell location 020B.
6.1.8 Time remaining to next tap
The value of location 020C (tREMAIN) is measured and displayed as time remaining to
change next tap. When a tap change is initiated (Raise or Lower volts) the value of the
initial time delay setting is first stored into this location. When the initial time has elapsed
(i.e. decremented to zero) this location is then stored with the value of the inter-tap delay
setting. When the inter-tap has elapsed (decremented to zero), a tap change is initiated
and the location is re-stored with inter-tap delay value. This process continous until the
regulated voltage is within the deadband.
6.2 Event records
Fifty time tagged event records can be stored, after which the oldest record is overwritten.
They are stored in non volatile memory and will be lost if the relay is powered down. The
event records can only be accessed via the serial communication port and PC software is
available to support the automatic extraction and storing of these records.
The following items are recorded with a time tag by the event recorder:
- Changes to settings made locally.
- Alarm status.
- Frequent Operations Monitor.
Events for change in state of an logic input and/or an output relay can be recorded by
setting the system data link [SD7]. These two particular forms of events will occur
frequently and so by setting [SD7]=0, the recording of these events can be inhibited.
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