115
relay first waits until the link becomes idle. After this, a backoff time starts. When
the backoff time elapses, the relay checks the link again. If the link is not busy, the
relay starts the transmission. The backoff time is calculated as follows:
backoff time = silent interval + random delay
The silent interval is set with SPA parameter 503V232 and the maximum random
delay with SPA parameters 503V233 (the width of a single time slot in
milliseconds) and 503V234 (the maximum number of time slots). By setting the
time-slot width to 10 milliseconds and the maximum number of time slots to 10, for
instance, the maximum random delay is 100 milliseconds.
In a network consisting of several slaves, the priority between the
devices are defined with SPA parameters 503V233 and 503V234.A
device with shorter silent interval and maximum random delay has
higher sending priority than a device with longer silent interval and
maximum random delay.
Collision detection is always active during transmission (provided that it has been
enabled). While sending a message, the relay supervises collisions on the link. If a
collision is detected, the transmission is immediately cancelled. After this, the relay
tries to transmit the message again, using collision avoidance before sending the
message.
Scaling DNP analog values
The DNP analog values can be scaled using either an internal (fixed) or a user-
defined scaling factor. If the scaling factor index for a certain analog value is set to
0, the internal scaling factor is used. If set to 1...5, the user-defined scaling factor of
the corresponding scaling factor parameter, SPA parameter 503V (100+index), is
used:
503V101 Scaling factor 1
503V102 Scaling factor 2
503V103 Scaling factor 3
503V104 Scaling factor 4
503V105 Scaling factor 5
Example:
Phase current l
a
0.00...50.0 × I
n
(CT)
Internal scaling factor 100
Default DNP range 0...5000
Feeder Protection Relay
Technical Reference Manual - ANSI Version
REF610REF610
1MRS755535
To Next Page
Loading...
