Internal Faults - ABB RELION SMU615 Technical Manual

Basic functions
as the relay scheme's ability to refrain from operating when not required. The
dependability is increased by letting the system operators know about the problem,
giving them a chance to take the necessary actions as soon as possible. The security
is increased by preventing the relay from making false decisions, such as issuing
false control commands.
There are two types of fault indications.

• Internal faults

• Warnings
3.2.1 Internal faults
When an internal relay fault is detected, the relay protection operation is disabled,
the green Ready LED begins to flash and the self-supervision output relay is de-
energized, i.e. the change-over contact is released.
An event about the fault is stored as a message on the WHMI. The text Internal
Fault with an additional text message, a code, date and time, is stored to indicate
the fault type.
Different actions are taken depending on the severity of the internal fault. In case of
a temporary fault, the merging unit tries to recover from the situation by restarting.
Restarting varies per fault type. The restart procedure includes two stages; when
the merging unit detects a fault, it restarts itself in a few seconds after the fault
occurrence. If the merging unit did not recover after the first fast self-recovery
attempts (typically 1-2 restarts), or the fault reoccurs during the next 60 minutes,
the next self-recovery attempts (typically 3 restarts) are delayed for 10 minutes. In
case of a permanent fault, the merging unit stays in the internal fault mode. All
output relays are de-energized and contacts are released for the internal fault. The
merging unit continues to perform internal tests during the fault situation. If the
internal fault disappears, the green Ready LED stop flashing and the merging unit
returns to the normal service state.
One possible cause for an internal fault situation is a so-called soft error. The soft
error is a probabilistic phenomenon which is rare in a single device, statistically
not happening more often than once in a relay's lifetime. No hardware failures are
expected and a full recovery from the soft error is possible by a self-supervision
controlled restart of the merging unit.
The self-supervision signal output operates on the closed-circuit principle. Under
normal conditions, the merging unit is energized and the contact gaps 3-5 in slot
X100 is closed. If the auxiliary power supply fails or an internal fault is detected, the
contact gaps 3-5 are opened.
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1MRS758407 C
SMU615
Technical Manual