Technical data
Siemens SIP · 2008
12 Motor Protection / 7SK80
12
12/17
Chatter disable
The chatter disable feature evaluates
whether, in a set period of time, the num-
ber of status changes of indication input
exceeds a specified number. If exceeded,
the indication input is blocked for a certain
period, so that the event list will not record
excessive operations.
Indication filtering and delay
Binary indications can be filtered or de
-
layed.
Filtering serves to suppress brief changes in
potential at the indication input. The indi
-
cation is passed on only if the indication
voltage is still present after a set period of
time. In the event of an indication delay,
there is a delay for a preset time. The infor
-
mation is passed on only if the indication
voltage is still present after this time.
Indication derivation
User-definable indications can be derived
from individual or a group of indications.
These grouped indications are of great
value to the user that need to minimize the
number of indications sent to the system
or SCADA interface.
Fig. 12/12 CB switching cycle diagram
Measured values
The r.m.s. values are calculated from the
acquired current and voltage along with
the power factor, frequency, active and
reactive power. The following functions
are available for measured value process
-
ing:
•
Currents I
L1
, I
L2
, I
L3
, I
E
, I
EE
(67Ns)
•
Voltages V
L1
, V
L2
, V
L3
, V
L1L2
, V
L2L3
, V
L3L1
•
Symmetrical components
I
1
, I
2
,3I
0
; V
1
, V
2
, V
0
•
Power Watts, Vars, VA/P, Q, S
(P, Q: total and phase selective)
•
Power factor (cos ϕ),
(total and phase selective)
•
Frequency
•
Energy ± kWh, ± kVarh, forward and
reverse power flow
• Mean as well as minimum and maximum
current and voltage values
• Operating hours counter
• Mean operating temperature of the over-
load function
• Limit value monitoring
Limit values can be monitored using pro-
grammablelogicintheCFC.Commands
can be derived from this limit value indi-
cation.
•
Zero suppression
In a certain range of very low measured
values, the value is set to zero to suppress
interference.
Metered values
For internal metering, the unit can calcu
-
late an energy metered value from the
measured current and voltage values. If an
external meter with a metering pulse out
-
put is available, the 7SK80 can obtain and
process metering pulses through an indica
-
tion input.
The metered values can be displayed and
passed on to a control center as an accu
-
mulated value with reset. A distinction is
made between forward, reverse, active and
reactive energy.
Circuit-breaker wear monitoring
Methods for determining circuit-breaker
contact wear or the remaining service life
of a circuit-breaker (CB) allow CB mainte
-
nance intervals to be aligned to their actual
degree of wear. The benefit lies in reduced
maintenance costs.
There is no exact mathematical method to
calculate the wear or the remaining service
life of a circuit-breaker that takes arc-
chamber’s physical conditions into account
when the CB opens. This is why various
methods of determining CB wear have
evolved which reflect the different operator
philosophies. To do justice to these, the
relay offers several methods:
•
I
•
Σ I
x
, with x = 1... 3
•
Σ i
2
t
The devices also offer a new method for
determining the remaining service life:
•
Two-point method
The CB manufacturers double-logarithmic
switching cycle diagram (see Fig. 12/12) and
the breaking current at the time of contact
opening serve as the basis for this method.
After CB opening, the two-point method
calculates the remaining number of possible
switching cycles. Two points P1 and P2 only
have to be set on the device. These are speci-
fied in the CB’s technical data.
All of these methods are phase-selective
and a limit value can be set in order to ob-
tain an alarm if the actual value falls below
or exceeds the limit value during determi-
nation of the remaining service life.
Commissioning
Commissioning could not be easier and
is supported by DIGSI 4. The status of
the binary inputs can be read individually
and the state of the binary outputs can be
set individually. The operation of switch
-
ing elements (circuit-breakers, disconnect
devices) can be checked using the switch
-
ing functions of the relay. The analog
measured values are represented as wide-
ranging operational measured values. To
prevent transmission of information to
the control center during maintenance,
the communications can be disabled to
prevent unnecessary data from being trans
-
mitted. During commissioning, all indica
-
tions with test tag for test purposes can be
connected to a control and protection
system.
Test operation
During commissioning, all indications can
be passed to a control system for test pur
-
poses.
Further functions