Siemens SIPROTEC 7UT613 series Manual page 148

2 Functions
Additional Restrict-
ed Earth Fault Pro-
tection Functions
148
Note
When delivered from factory, the restricted earth fault protection is switched OFF. The
reason is that the protection must not be in operation unless at least the assigned side
and CT polarity have been properly set before. Without proper settings, the device
may show unexpected reactions (incl. tripping)!
The sensitivity of the protection is determined by I-REF> setting (address 1311). This
is the earth fault current which flows through the starpoint lead of the protected object
(transformer, generator, motor, shunt reactor). A further earth current which may be
supplied from the network does not influence the sensitivity. The setting value refers
to the rated current of the protected side of the main protected object or, in case of a
further protected object, to the rated operation current of the corresponding measuring
location.
Note
In case of large mismatching, the indication 199.2494
(EarthDiff.Fault: MatchFac I-CT. too lar/sml.) appears. The setting value should then
be increased.
The set value can be increased in the tripping quadrant depending on the arithmetic
sum of the currents (restraint by the sum of all current magnitudes) which is set at ad-
dress1313 SLOPE. This parameter can only be set with DIGSI at Additional Settings.
The preset value 0 is normally adequate.
In special cases it may be advantageous to delay the trip signal of the protection. This
can be done by setting an additional delay time (address 1312 T I-REF>). This pa-
rameter can only be set with DIGSI at Additional Settings. This additional time delay
is usually set to 0. This setting is a pure additional delay time which does not include
the inherent operating time of the protection.
In the aforementioned description, the first restricted earth fault protection is described
respectively. The differences in the parameter addresses and message numbers of
the first and second restricted earth fault protection are illustrated in the following
table. The positions marked by x are identical.
1. Restricted earth fault protection
2. Restricted earth fault protection
Note
In the following parameter overview the current values I/I
of the side to be protected of the main protected object. If the restricted earth fault pro-
tection is not referred to the main protected object, the rated current of the 3-phase
measuring location is the applicable reference value.
Parameter addresses
13xx
14xx
refer to the rated current
NS
C53000-G1176-C160-2
Message no.
199.xxxx(.01)
205.xxxx(.01)
7UT613/63x Manual