Schweitzer Engineering Laboratories SEL-2020, Instruction Manual, Page: 459 / 470

Date Code 20010518 Appendix I I-11
SEL-2020 Instruction Manual
Internal Indication Object
Within the Internal Indications (IIN) object, the bits are used as specified within the DNP
standard. When TIME_SRC=DNP within the Global settings, the SEL-2020 requests time
synchronization every 15 minutes. Bit 4 within the IIN object will be set and remain set until the
SEL-2020 receives a time synchronization. If the SEL-2020 receives a time synchronization, it
will clear the bit and then set it again 15 minutes later. The SEL-2020 does not have
local/remote states, so the local/remote bit indicates whether or not SEL
OGIC
is running. If
SEL
OGIC
is not running, the status is indicated as local since the DNP data will not be updated
by SET M while SEL
OGIC
is not running.
T
IMING
Maximum data-link response time (without confirmation): 150 milliseconds.
Maximum class 0 request response time (without confirmation): 300 milliseconds.
Maximum data-link confirm time: 150 milliseconds.
Maximum application confirm time (without data-link confirmation): 150 milliseconds.
T
IME
S
YNCHRONIZATION
When TIME_SRC=DNP within the Global settings, you can perform Time Synchronization via
DNP by executing a write to the Date/Time object (object 50). The DNP protocol assumes that
the time value sent by the master device is the time at which the first bit of the first byte of the
write request is received by the slave (SEL-2020). It is the responsibility of the master to
account for transmission delay between sending the request and the SEL-2020 receipt of the
request. In many systems this transmission delay will be 0. For example, in a simple point-to-
point connection, the moment the first bit is transmitted by the master, it is received by the slave
device. In configurations where the communication link may introduce delays, the master may
perform a Delay Measurement command and then calculate the transmission delay based on the
result of the Delay Measurement. The master can then add this calculated transmission delay
time to the time value that it sends to the SEL-2020 when it writes the time. When time
synchronization is performed, the SEL-2020 will synchronize itself to within 5 milliseconds (+3/-
2) of the given time. When the Delay Measurement command is performed, the value reported
by the SEL-2020 is accurate to 10 milliseconds (+5/-5). So, disregarding errors external to the
SEL-2020, a time synchronization that uses a Delay Measurement calculation is accurate to
within 15 milliseconds (+8/-7).
"J
OB
D
ONE
" E
XAMPLE
This example demonstrates how to configure the SEL-2020 to provide data to a DNP master.
For this example we will have two SEL-121F relays connected to the SEL-2020, on ports 1
and 2. The following procedure explains how to set the SEL-2020 and collect data.
1. Connect the two relays to ports 1 and 2 of the SEL-2020. Establish basic communications
settings to the first relay by auto-configuring it using the SET P 1 command. Use SET A 1 to
enable operate control and to collect meter and target data. Use COPY 1 2 with auto-
configuration to establish settings with the second relay.
2. Determine how you want to operate the DNP connection and configure it using SET P 1. For
this example we will assume polled static operation only.