ABB Modures LZ92-1 - PT CONNECTIONS; COMMISSIONING PROCEDURES

28
K
L k
5
(11) K
k(U)
+_c-e
-
-
( v) L
I ( V)
Fig. 5.1 - Instrument transformer terminals and polarity check
(U, u, V and v apply to p.t's)
If the star-point of the c.t. windings is not on the busbar end of the windings
as shown in the wiring diagram, provision is made on the relay for reversing
the direction of measurement with the switch I~ (switch 8b respectively
frontplate switch) . The position of this switch has no influence on the star-
ting units (see Section 3.6).
It is particularly important for the connections and c. t. circuit shorting
links of the input transformer unit EW91 with part number HESG 438 454 (see
Section 3 .12) to be carefully checked. 'I'he terminals must be connected in
accordance with the rated current as follows:
I = 1 A
IN = 5 A
N
common
Al(R), A4(S), A7(T)
A2 (R) , A5 (S) , A8 (T)
A3(R), A6(S), A9{T)
Input transformer units with the part number HESG 440 754 resp. HESG 441 721 only
have terminals for the rated current as ordered.
5.4 P.t. connections
Should there be doubt as to the sense of the p.t. windings, then their polarity
can be ascertained in the same manner as for c.t's. In this case, however, the
battery is connected to the secondaries (see terminal references in brackets in
Fig. 5.1). Caution! First switch the voltmeter to a high voltage range. All the
phases of three-phase p.t's must be tested. For each relay the p.t's must be
fused at a rating of 10 A.
The secondary circuits of both c.t's and p.t's should be grounded at only one
point.