Siemens 7UT51

5
Motor or Generator Differential Protection (87M/G)
7UT51 v3
68 PRIM-2330C
5.2.1 Type of Protected Object
The relay uses different settings and algorithms for
different types of protected objects. Address 7801
specifies what type of device or equipment is being
protected.
Model 7UT513 is required (instead of a 7UT512) only
if the application includes measurement of a ground
(or neutral) current. A 7UT513 can also be used to
protect simultaneously both a motor/generator and an
additional protected device.
5.2.2 Normal Operational Status
The 87M/G differential function can be set either to
exist (ENABLED) or not exist. The choice is made in
Address 7816.
Once the 87M/G function is set to exist, it can be
configured. Its normal status is set in Address 1701.
5.2.3 System Frequency
The rated nominal frequency of the protected
equipment is specified in Address 7899.
Note:
The choice of frequency affects the availability
the auxiliary protection functions. With rated
frequency 60Hz, the backup overcurrent time
protection or the restricted earth fault
protection/tank leakage protection (dependent
on the ordered model) can be used besides the
differential protection for the motor/generator.
With rated frequency 50Hz, the backup overcurrent
time protection or the restricted earth fault protection/
tank leakage protection (dependent on the ordered
model) can be used besides the differential protection
for the motor/generator.
With rated frequency 16 2/3 Hz, no restriction
concerning the additional functions are present.
5.2.4 Motor/Generator
Information
The phase-to-phase voltage and rated apparent
power of the protected motor/generator is specified in
Addresses 1202 and 1203. The relay automatically
calculates the primary measured values based on this
information.
7801 PROT.OBJ
Type of object the relay is protecting.
Option Description
2
-
WIND
-
TRANSF two
-
winding transformer (default)
(see Chapter 4)
3
-
WIND
-
TRANSF three
-
winding transformer
(see Chapter 4)
MOTOR/
GENERATOR
motor or generator
2 ENDED TIE PT. two
-
branch bus (see Chapter 6)
3 ENDEDTIE PT. three
-
branch bus (see Chapter 6)
1Ph.
-
TRANSF single
-
phase transformer
(see Chapter 4)
7816 87 STATUS
Choice of whether motor/generator differential
protection function (87M/G) exists.
Option Description
EXISTENT 87M/G function exists (default).
NONEXISTENT 87M/G function does not exist.
1701 87 STATUS
Operational status of differential protection (87M/G)
when the protected object is a motor or generator.
Option Description
OFF 87M/G function is inactive (default).
ON 87M/G function is active.
BLOCK
TRIPPING
87M/G function is active except that trip
contacts and signal contacts will not
respond to 87M/G events.
7899 FREQUENCY
Rated nominal frequency of the protected motor/
generator.
Option Description
FREQ 50 Hz 50 Hertz
FREQ 60 Hz 60 Hertz (default)
FREQ 16 2/3 Hz 16
-
2/3 Hertz
1202 Vn M/G
Rated phase
-
to
-
phase voltage of the motor or
generator
Range: 0.4
–
800.0 kV
Default: 21.0
1701 87 STATUS
Operational status of differential protection (87M/G)
when the protected object is a motor or generator.