Basler Electric BE1-87T - Manual (Page 66)

4-24 BE1-87T Installation 9171300990 Rev V
Figure 4-27. Single-Phase Connections, Delta-Wye Configuration With Two Load Busses
Three-Phase Input Sensing Connections
Three-phase units must be connected in a way that will negate any phase shift introduced by the
protected power transformer. This is accomplished by one of two methods:
Phase Shift Compensation
1. By connecting the system CTs to complement the power transformer connections (i.e., a
wye/delta CT may negate the phase shift of a delta/wye power transformer, and vice versa).
2. By utilizing the internal 30° Phase Shift Compensation that is a feature of three-phase BE1-87T
relays.
Three-phase units provide for internal phase angle compensation. Among the advantages of this method
is the ability to connect all the CTs in wye. This not only simplifies the connections but also facilitates
sharing the CTs with other devices. Furthermore, the wye connection reduces the burden on the CTs.
Advantages of Internal Phase Compensation
A set of movable jumpers (Figure 4-27) determines the direction of the compensating internal phase shift
for each input. Because each jumper can be shifted +30°, –30°, or 0°; a total of 60° is achievable between
two inputs for special applications. In this way, the appropriate direction of phase shift can be matched to
the shift in the protected transformer. This alleviates the need for an extra set of external CTs in most
applications.
Figures 4-28 through 4-34 illustrate the use of internal phase shift in lieu of matching by external CT
connections. These are typical of the many combinations that can occur.
03-12-98
D1186-04
C
B
A
H
3
H
2
H
1
X
3
X
2
X
1
X
0
C
B
A
C
B
A
BE1-87T-1
13
11
12 (2)
(1) (3) 14
C
BE1-87T-1
13
11
12 (2)
(1) (3) 14
C
BE1-87T-1
13
11
12 (2)
(1) (3) 14
C
BE1-87T B TYPE SENSING
SWITCH BOARD
TERMINAL BOARDS
B
C A
H
3
H
2
H 1
X
1
X
2
X
3