Functions
2.2 Overcurrent Protection 50, 51, 50N, 51N
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
86
The corresponding time multiplier for an IEC characteristic is set at address
1208
51 TIME DIAL
and in
address
1209
51 TIME DIAL
for an ANSI characteristic. It must be coordinated with the grading coordination
chart of the system.
The time multiplier can also be set to
∞
. In this case, the element will not trip after pickup. However, pickup, will
be signaled. If the 51 element is not required at all, address
112
Charac. Phase
should be set to
Definite
Time
during protective function configuration (see Section 2.1.1.2).
If highly sensitive settings close to the load current are required in weak power systems or transformers, the
element can be stabilized via the undervoltage as an additional criterion for the power system fault. The oper-
ating modes can be set in address
1223
VOLT. INFLUENCE
. In a voltage-controlled operation, the voltage
threshold is defined via parameter
1224
51V V<
below which the current element is released.
51N Element (ground) with IEC or ANSI Characteristics
Having set address
113
Charac. Ground
=
TOC IEC
when configuring the protection functions (Section
2.1.1), the parameters for the inverse characteristics will also be available. Specify in address
1311
51N IEC
CURVE
the desired IEC characteristic (
Normal Inverse
,
Very Inverse
,
Extremely Inv.
or
Long
Inverse
). If address
113
Charac. Ground
was set to
TOC ANSI
, you can select the desired ANSI
characteristic (
Very Inverse
,
Inverse
,
Short Inverse
,
Long Inverse
,
Moderately Inv.
,
Extremely Inv.
or
Definite Inv.
) at address
1312
51N ANSI CURVE
.
If the inverse time trip characteristic is selected, it must be noted that a safety factor of about 1.1 has already
been included between the pickup value and the setting value. This means that a pickup will only occur if a
current of about 1.1 times the setting value is present. If
Disk Emulation
was selected at address
1310
51
Drop-out
, reset will occur in accordance with the reset curve as described before.
The current value is set in address
1307
51N PICKUP
. The setting is mainly determined by the minimum an-
ticipated ground fault current.
The corresponding time multiplier for an IEC characteristic is set at address
1308
51N TIME DIAL
and in
address
1309
51N TIME DIAL
for an ANSI characteristic. This has to be coordinated with the grading coor-
dination chart of the network. For ground currents with grounded network, you can often set up a separate
grading coordination chart with shorter delay times.
The time multiplier can also be set to
∞
. In this case, the element will not trip after pickup. However, pickup, will
be signaled. If the
51N-TOC
element is not required at all, address
113
Charac. Ground
should be set to
Definite Time
during configuration of the protection functions (see Section 2.1.1).
User-defined Characteristics (phases and ground)
Having set address
112
Charac. Phase
or
113
=
Charac. Ground
=
User Defined PU
or
User def.
Reset
when configuring the protective functions (Section 2.1.1.2), the user-defined curves will also be avail-
able. A maximum of 20 value pairs (current and time) may be entered at address
1230
51/51N
or
1330
50N/51N
in this case. This option allows point-by-point entry of any desired curve. When setting address
112
=
User def. Reset
or
113
=
User def. Reset
additional value pairs (current and reset time) may be
entered in address
1231
MofPU Res T/Tp
or
1331
MofPU Res T/TEp
to represent the dropout curve.
Since current values are rounded in a specific pattern before they are processed in the device (see Table 2-4),
we recommend to use exactly the same preferred current values you can find in this table.
The current and time value pairs are entered as multiples of addresses
1207
51 PICKUP
and
1208
51 TIME
DIAL
for the phase currents and
1307
and
1308
for the ground system. Therefore, it is recommended that
these addresses are initially set to 1.00 for simplicity. Once the curve is entered, the values at addresses
1207
or
1307
or/and
1208
or
1308
can be modified later to allow moving the curve in a different direction.
The default setting of current values is
∞
. They are, therefore, disabled and no pickup or tripping of these pro-
tection functions will occur.
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