D20/D200 Technical Overview
GE Grid Solutions
96
PRPI-019-3.00-10
GE Information
Example
:
Assume you are installing three D20A and two D20S modules on an RS-485 D.20 Link using
wire gauge #22 and a peripheral supply of 48 V. Calculate the maximum distance of the D.20
Link as follows:
•
P
Total
= n
A
A + n
S
S
= 3 x A + 2 x S
= 3 x 5 W + 2 x 3 W
= 21 W
•
I
= P
Total
/ V
p
= 21 W / 48 V
= 0.44 A
•
V
d
= I x Rs
= 0.44 A x 0.016 ohms/ft
= 0.00704 V/ft
•
D
max
=
MIN
[(V
p
- V
t
) / (2 x V
d
) or 1000 feet]
=
MIN
[(48 V - 20 V) / (2 x (0.00704 V/ft)) or 1000 feet]
=
MIN
[1989 feet or 1000 feet]
=1000 feet
Therefore, the maximum distance that you can operate the D.20 Link would be 1000 feet.
Note:
If external digital input contact wetting is supplied by station battery, omit the Power
Consumption of each Status Point factor (SP) from the Total Power (PT) equation.
