Siemens 3AD8 Instruction Manual page 19

Protection mode bits
A Fusesaver can be in one of five protection
modes. Refer Fusesaver operations manual
(IC1000-F320-X170-X-XXXX).
Controlling the protection in the Fusesaver
are three bits, which are available in the
database as digital points in Table 13.
Protection is operating normally when all
the bits are clear.
When there is a change of protection mode
(e.g., the mode is changed from Normal to
Fast Single), the protection bits are changed
as shown in Table 14.
In the database and controls available to the
SCADA system, the RCU provides indication
and control of both protection modes and
protection bits.
In other words, when setting up the SCADA
system the engineer can choose to control
the protection bits directly (CPID 15, 16, 17)
or by control of modes (CPID 9, 10, 11, 12,
14).
The choice between these two methods is
wholly up to the user. Both methods give
equivalent control of the Fusesaver
protection; however, each may have its own
advantages to the utility.
Control of protection modes is simple to
implement and allows the user to easily
restrict the choice for the operator to the
two or three modes that are going to be
used operationally (it is unlikely that a utility
will want to use all the five available
modes). Also, to change between modes,
such as protection normal and protection
fast single, requires only one command in
mode control, but two commands in bit
control (to change the auto-reclose bit and
the instantaneous bit). Consequently, there
is more room for operator error in
controlling bits.
On the other hand, if the SCADA and other
operators in the utility are familiar with
changing protection on a bit-by-bit basis,
then control of bits may be a better fit with
existing practices compared to control of
modes.
Bit DPID
Protection OFF 119, 120, 121
Auto-reclose OFF 125, 126, 127
Instantaneous trip 122, 123, 124
Table 13: Protection mode bits
Protection mode/protection control bit relationship
New mode
Name Indication DPID
Protection OFF 80, 81, 82
Normal 74, 75, 76
Normal single 98, 99, 100
Fast 116, 117, 118
Fast single 77, 78, 79
Table 14: Protection mode/protection control bit relationship
Finally, there is a further set of bits in the
database, which show the remote set status
of all the protection mode and protection
bits. These are the points that are kept by
the Fusesaver when the external lever is
pulled down and will be re-instated when
the external lever is returned up. These
points may be of little interest to the SCADA
operator for operational purposes, but they
do indicate the protection that will be in
force when the Fusesaver external lever is
returned to the up position. The remote
protection mode bits are DPID 65 to 73, 95
to 97, 113 to 115. It is recommended that
these bits are not mapped unless they are of
specific interest.
Protection mode bits
State Functionality in Fusesaver
Set Protection tripping inhibited
Clear Will trip on protection
Set Auto-reclose inhibited
Clear Will auto-reclose
Protection will trip at as soon as the
Set
pick-up current is exceeded
Clear Protection will trip as configured
Protection OFF Auto-reclose
bit OFF bit
Set Not changed
Clear Clear
Clear Set
Clear Clear
Clear Set
Instantaneous
bit
Not changed
Clear
Clear
Set
Set
19