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Mounting and Commissioning
3.1 Mounting and Connections
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
500
If the calculation results that R
max
< R
min
, then the calculation must be repeated, with the next lowest switching
threshold U
BI min
, and this threshold must be implemented in the relay using plug-in jumpers (see Section „Hard-
ware Modifications“).
For the power consumption of the resistance the following applies:
Example:
The closest standard value of 39 k
Ω
is selected; the power is:
Pilot Wire Comparison
If the distance protection is supplemented with the transmission scheme
Teleprot. Dist.
=
Pilot wire
comp
(address
121
), it has to be secured that the quiescent state loop is supplied with enough auxiliary voltage.
The function itself is described in section 2.7.
Please note that both binary inputs are interconnected and connected in series with the resistor of the pilot
wires. Therefore, the loop voltage must not be too low and the pickup voltage of the binary inputs must not be
too high. In general, the lowest threshold (17 V) must be selected for the auxiliary voltages of 24 V to 60 V, the
threshold of 73 V for 110 V to 125 V and the threshold of 154 V for 220 V to 250 V.
Due to the low current consumption of the binary inputs it may be necessary to additionally burden the pilot wire
loop with an external shunt connected resistor so that the binary inputs are not blocked by the wire capacitance
after an interruption of the loop. Alternatively, auxiliary relay combinations can be connected.
Pilot wires used as cable connections between stations must always be checked for their high-voltage capabil-
ity. The pilot wires of the pilot cables must stand external strains.
The worst electrical fault that may occur to the pilot cables is generated in the pilot wire system by an earth
fault. The short-circuit current induces a longitudinal voltage into the pilot wires lying parallel to the high voltage
line. The induced voltage can be reduced by well-conductive cable jackets and by armouring (low reduction
factor, for both high voltage cable and pilot cables).
I
BI (HIGH)
1.8 mA (SIPROTEC 4 7SD5)
U
BI min
17 V for delivery setting for nominal voltages of 24/48/60 V
(from the device 7SD5);
73 V for delivery setting for nominal voltages110/125/220/250 V
(from the device 7SD5);
154 V for delivery setting for nominal voltages 220/250 V
(from the device 7SD5)
U
ST
110 V (system / trip circuit)
R
CBTC
500
Ω
(system / trip circuit)
U
CBTC (LOW)
2 V (system / trip circuit)