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Table 3: Controls interlocking logic
Fusesaver
Siemens
external
Connect
lever
Down on any
Not relevant
Fusesaver
Up on all
In session
Fusesavers
Up on all
Not running
Fusesavers
Up on all
Not running
Fusesavers
Up on all
Not running
Fusesavers
22
Fusesaver
operator
Remote
control panel
control on/
ignore
off switch
remote
switch
parameter
Not relevant
Not relevant
Not relevant
Not relevant
On
False
On
True
Off
Not relevant
Condition-based controls
The RCU also has the capability to do post
processing of events received from the
Fusesavers to assess whether certain
conditions have occurred from which the
RCU may apply commands to the
Fusesavers.
Excessive cleared faults
This section describes a system whereby the
RCU monitors the number and time frame of
cleared faults of Fusesavers under the RCU's
control. The RCU changes the Fusesavers'
protection mode to "Protection OFF" if the
number of cleared faults is deemed
excessive according to the excessive cleared
fault parameters set in the RCU.
The RCU analyzes cleared fault events from
Fusesavers and keeps a running tally of the
number of cleared faults that occur on the
line within a configurable time frame. An
attempt to match cleared fault events from
different phases is made by using a 30 s
time-match window in order to count
simultaneous multiple phase faults as one
event for the line.
When the configured number of cleared
faults is reached, the RCU will send a remote
protection mode change control to the
Fusesavers, as if it is another control such as
a SCADA operator, setting the protection
mode to "Protection OFF".
Mode control
Mode control
by Fusesaver
by SCADA
control panel
Not allowed
Not allowed
Not allowed
Not allowed
Allowed
Not allowed
Allowed
Allowed
Not allowed
Allowed
The event record of the Fusesaver will show
the source of the control as "RCU". The RCU
will also set the protocol database digital
point for "Excessive Cleared Faults Flag" if
the threshold is exceeded.
If the RCU is unable to control the Fusesaver
remote protection mode, the control is lost,
but will be attempted again if there is
another cleared fault which exceeds the
count/time constraint. Reasons for a control
fail/rejected are:
1. The Fusesaver external lever is down,
2. Siemens Connect is in session,
3. Communications failure, or
4. Another control is in progress.
When the Fusesaver active protection mode
bits change, the RCU will also reset the
timing/counting of cleared fault events. This
means that any change of active protection
mode by the user (e.g., pulling down the
external lever of the Fusesaver or by a
SCADA control) resets the excessive cleared
faults count and timing starts again.
Comment
Mode will be forced to the mode defined in the
Fusesaver policy file for the Fusesavers which
have levers down
When Siemens Connect is in-session (i.e., on
the operate page), all other sources of control
are locked out
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