Siemens 7UT51

7UT51 v3
Tank Leakage Protection (64T)
10
PRIM-2330C 113
10 Tank Leakage Protection (64T)
A 7UT513 relay can ordered with a tank-leakage
protection element (64T). The element can either
measure the tank-leakage current in milliamperes, or
as a fraction (or multiple) of the nominal rated current
of the protected object.
Note:
When protecting a 60Hz object, the relay can
provide tank leakage protection if the protected
object has one or two windings (or sides), but
not three.
If desired, the tank leakage protection element can
protect a separate, additional object instead of the
main protected object.
10.1 Method of Operation
“ Tank leakage ” is current flowing from a
phase-conductor (winding or bus bar) of the protected
object to the frame of the protected object (or to a
conducting tank surrounding the protected object). A
fault causing tank leakage may be highly resistive.
The tank leakage current is measured by a CT
attached to a conductor connecting the frame or tank
to an earth ground (as shown in Figure 10.1). The
frame or tank must otherwise be electrically isolated.
Figure 10.1
Tank Leakage Protection
Tank leakage protection (64T) operates like an
overcurrent element using one of the following two
method: If the element uses the less sensitive
ground-current input (I
Ga
), the pickup level is specified
as a fraction (or multiple) of the rated nominal current
of the protected object. If instead the element uses the
relay’s highly sensitive ground-current input (I
Gb
), the
pickup level is specified in milliamperes.
Address 2705 setting specifies whether the measured
current includes only the fundamental component or
the true rms current. The dropout level is specified in
Address 2709 as a fraction of the pickup level. If
desired, time delays can be set.
10.2 Normal Operational
Status
The tank leakage element (64T) can be either
NON-EXISTENT/DISABLED or the element can
monitor the tank leakage current either as an absolute
current or as a multiple of the rated nominal current of
the protected object. The choice is made in
Address 7827.
7827 TANK PROT.
Existence and type of tank leakage protection. The relay
must be a 7UT513 that was ordered with the tank leakage
option.
Option Description
NON
-
EXISTENT/
DISABLED
Tank leakage element exists (default).
SENSITIVE CT B Tank leakage element exists and
monitors the absolute tank
-
leakage
current. (Connect the tank
-
leakage
CT to the I
Gb
current input.)
INSENSITIVE CT
A
Tank leakage element exists and
compares the tank
-
leakage current to
the rated nominal current of the
protected object. (Connect the
tank-leakage CT to the I
Ga
current
input.)