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DISTRIBUTED DIGITAL FAULT RECORDER – INSTRUCTION MANUAL
CONFIGURING THE EXTERNAL WATCHDOG CHAPTER 4: THE DDFR AND RELAY INFORMATION
4.2.1
Types of WatchDog
As indicated in Chapter 3, The DDFR contains three different types of WatchDog, or "health
monitor":
Internal (DDFR) WatchDog
Takes corrective action to ensure that the DDFR application is continually running. If the
DDFR application is NOT running for some reason, the Internal Watchdog will attempt to
fix the situation, by, for example, restarting the application.
The Internal Watchdog is not a configurable WatchDog.
DriveSpace WatchDog
Active when the DDFR’s used storage space is nearing maximum capacity. Once the used
storage space meets a certain threshold, automated maintenance occurs and the oldest
records deleted.
Note
The DriveSpace WatchDog is discussed in detail in section 3.4.3.
External WatchDog
Notifies a UR relay that the DDFR is running.
For UR relays, the External Watchdog causes an action to be performed to notify
management of a "DDFR-not-running" situation. In the UR relay, the Internal Watchdog,
discussed above, thus complements the External Watchdog by initially trying to correct the
problem.
4.2.2
The DDFR External WatchDog
The DDFR External WatchDog indicates that the DDFR is capable of communicating with
UR protection relays located in the station. This External WatchDog operates by regularly
sending a Modbus Force Coil command to a number of user-selected protection relays
connected on the network to the DDFR in question. In this respect the principle is similar to
that of a heart monitoring machine in a hospital; the Modbus Force Coil commands are the
heartbeat pulses. For this reason, we use (see below) the term "heartbeat" to describe the
operation of this Watchdog.
The Force Coil command can send the ON state command and is selectable by you. The
Virtual Input within each relay is also selectable by you. Appropriate logic within the
individual protection (UR) relays detects a loss of communications, and must be set by you
within the UR relay, using FlexLogic (
see section 4.2.3.2 below
).
4.2.2.1 The External WatchDog Heartbeat
As explained above, the External WatchDog allows a number of user-selected UR relays to
monitor the DDFR to ensure it is running, by sending a regular signal (the "heartbeat") to
the receiving relay at regular intervals as set up in the External WatchDog setup page (see
below). If the DDFR fails to signal the relay - that is, if the heartbeat stops - the relay will
generate an alarm which is sent to SCADA. This alarm requires settings to be configured in
the relay.
Summary of Contents for Multilin DDFR
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