Siemens SIPROTEC 7UM62, Manual

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Differential Protection (ANSI 87G/87M/87T)
89
7UM62 Manual
C53000-G1176-C149-3
2.12.2 Setting Hints
General The differential protection is only effective and accessible if the type of protected
object for this function was set within the framework of the protective function
configuration (Section 2.2, address
0120
,
DIFF. PROT.
=
Generator/Motor
or
Three-phase trans.
). Only the relevant parameters for that object are offered, all
others are hidden.
Disabled
is set if the function is not required. At the address
2001 DIFF. PROT.
the user can switch the function
ON
or
OFF
, or only block the trip
command (
Block Relay
).
The primary rated current I
p, CT
of the used CTs should normally be higher than the
rated current I
N, Object
of the object to be protected. However, at least the following
condition should be observed with regard to the upper limit of the linear zone of the
7UM62, which is 20
⋅ Ι
N
:
2.12.2.1 Differential Protection for Generators and Motors
Precondition A precondition for the functioning of the generator or motor differential protection is
that during configuration at the address
0120 DIFF. PROT.
=
Generator/Motor
has been set.
One important setting is the location of the CT starpoints on both sides of the protected
object (addresses
0201 STRPNT->OBJ S1
for side 1 and
0210 STRPNT->OBJ S2
for side 2, see Section 2.3).
Also, the nominal values (S
N GEN/MOTOR
, U
N GEN/MOTOR
) of the machine to be
protected, and the primary and secondary nominal currents of the main CTs on both
sides must be entered. The settings are referred to these values. They are also used
e.g. for determining the primary measured values.
Information as to the treatment of the starpoint on both sides is required for the
measured value monitoring; it has already been entered during configuration at the
addresses
0241 STARPNT SIDE 1
and
0244 STARPNT SIDE 2
(see Section 2.3.2).
Increase of Pickup
Value on Startup For additional security against overfunctioning when a non-energized protection
object is switched in, an increase of the pickup value on startup can be set at address
2005 INC.CHAR.START
. On delivery of the device, this function is switched
OFF
.
The associated parameters can be found at addresses
2051A
,
2052A
and
2053
.
Address
2051A I-REST. STARTUP
is used to set the pickup value for startup
detection. The function is disabled by setting I/I
nO
= 0. The
START-FACTOR
specifies
the increase factor of the pickup values on startup. For generator and motor
protection, a setting of
2052A START-FACTOR
=
2.0
is recommended.
Note:
When the device is delivered, the differential protection function is switched
OFF
. This
is because this protection function must not be used before at least the vector groups
and matching values have been correctly set. Without these settings the device may
show unpredictable behaviour (e.g. tripping)!
I
p, CT
0.75 I
N, Object
⋅ >