D.21
Date Code 20150130 Instruction Manual SEL-787 Relay
DNP3 Communications
DNP3 Documentation
Binary Outputs
Binary Output status (Object 10, Variation 2) is supported. Static reads of
points RB1–RB32, OC/CC respond with the on-line bit set and the state of the
requested bit. Reads from control-only binary output points respond with the
on-line bit set and a state of 0. The SEL-751 supports Control Relay Output
Block objects (Object 12,Variation 1). The control relays correspond to the
remote bits and other functions as shown previously. Each DNP Control
message contains a Trip/Close code (TRIP, CLOSE, or NUL) and an
Operation type (PULSE ON, LATCH ON, LATCH OFF, or NUL). The Trip/
Close code works with the Operation Type to produce set, clear, and pulse
operations.
Control operations differ slightly for single-point controls compared to paired
outputs. Paired outputs correspond to the complementary two-output model,
and single-point controls follow the complementary latch or activation model.
In the complementary two-output model, paired points only support Trip or
Close operations, which, when issued, will Pulse On the first or second point
in the pair, respectively. Latch commands and Pulse operations without a Trip
code are not supported. You can cancel an operation in progress by issuing a
NUL Trip/Close Code with a NUL Operation Type. Single output points
support both Pulse and Latch operations. See Control Point Operation for
details on control operations.
Use of the Status field is exactly as defined. All other fields are ignored. A
pulse operation is asserted for a single processing interval. You should
exercise caution if sending multiple remote bit pulses in a single message
(i.e., point count > 1), because this can result in some of the pulse commands
being ignored and the return of an already active status message. The SEL-787
will only honor the first ten points in an Object 12, Variation 1 request. Any
additional points in the request will return the DNP3 status code
TOO_MANY_OBJS.
The SEL-787 also supports Pattern Control Blocks (Object 12, Variations 2
and 3) to control multiple binary output points. Variation 2 defines the control
type (Trip/Close, Set/Clear, or Pulse) and the range of points to operate.
Variation 3 provides a pattern mask that indicates which points in that range
should be operated. Object 12, Variations 2 and 3 define the entire control
command: the DNP3 master must send both for a successful control. For
example, the DNP3 master sends an Object 12, Variation 2 message to request
a Trip of the range of indices 0–7. The DNP3 master then sends an Object 12,
Variation 3 message with a hexadecimal value of “BB” as the pattern mask
(converted to binary notation: 10111011). Read right to left in increasing bit
order, the Pattern Block Control command will result in a Trip of indexes 0, 1,
3 to 5, and 7. Multiple binary output point control operations are not
guaranteed to occur during the same processing interval.
To Next Page
Loading...
