ABB REG316 4 Series - Page 274

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-236
Important note:
The tripping and alarm outputs are disabled as long as one of
the two binary Inputs ‘AdjMTRInp’ or ‘AdjREsInp’ is enabled,
i.e. the protection will not trip if the stator circuit is grounded.
The two signals ‘InterruptInt’ and ‘InterruptExt’, however, are
not disabled.
REs and MTR in the case of primary injection at the
generator star-point
An injection transformer block Type REX 011 is needed for this
circuit.
Fig. 3.5.24.1 shows the wiring diagram for primary injection
(peak value of U
is
110 or 96 V DC) at the generator star-point.
The star-point is grounded via the resistor R
Es
and the parallel
resistor R
Ps
. The current at the star-point must not exceed 20 A.
It is recommended, however, to select the resistors such that the
star-point current is
£ 5 A to protect as much of the winding as
possible.
The total resistance is thus:
Condition 1:
RR
U
3I
Es Ps
Gen
Emax
+³
´
where: U
Gen
phase-to-phase voltage at the generator
terminals
I
Emax
max. star-point current = 20 A
The following conditions must also be fulfilled:
Condition 2: R 130
Ps
³W and R 500
Ps
£W
Condition 3: R 4.5 R
Es Ps
³´
Condition 4: R 0.7 k
Es
³W and R 5 k
Es
£W
The v.t. must be designed such that for a solid ground fault at
the generator terminals, the rated frequency component voltage
Us = 100 ±20 %, i.e. the ratio MTR = N
12
/ N
11
must lie within the
following range:
Condition 5:
1. 2 n
N
N
0.8 n
12
11
´³ ³ ´, where n
U
3100V
R
RR
Gen Es
Es Ps
=
´
´
+
A v.t.
N
N
=
U
3100V
12
11
Gen
´
will fulfil condition 5 in most cases.