ABB Distribution Protection Unit 1500R/2000R
13-4
Applications Notes
9/99
website:www.abb.com/papd
Com 3
55 56 57 58 59 60 61 62 63 64
RS 485 Isolated Port
IRIG B Positive
IRIG B Negative
Each of these units uses the AUX COM port located at the rear of the relay to accept the TTL IRIG B signal. The DPU/
TPU/GPU 2000R and DPU1500R use Pins 63 and 64 to accept the IRIG B negative polarity and IRIG B positive
polarity signals respectively, as illustrated in Figure 3. The DPU/TPU 2000 use pins 65 and 66 as illustrated in Figure
4.
Figure 3. DPU/TPU/GPU 2000R and DPU1500R IRIG B Connector Placement
CO
M PO
RT
AU
X
PO
RT
74 73 72 71 70 69 68 67 66 65
RS 485 Isolated Port
IRIG B Positive
IRIG B Negative
Figure 4. DPU/TPU 2000 IRIG B Connector
Placement
ABB’s implementation of IRIB B requires that the signal be daisy-chained to each device. Each device in the IRIG B
network presents a load to the IRIG B receiver/converter. Daisy-chained inputs are simple parallel circuits. A sample
calculation is shown for the example illustrated in Figure 5.
If the input impedance of each DPU/TPU/GPU 2000/R and DPU1500R is measured at its IRIG B connection, the
impedance would be 1000 ohms. Each IRIG B input requires less than one mA to drive it.
Calculating the load impedance presented to the IRIG B source generator is illustrated in Figure 5. Each IED load on
the IRIG B link presents a parallel impedance to the source. The general equation for parallel impedance is:
1 = 1 + 1 + 1 + . . .
Z
Total
Z
1
Z
2
Z
3
I
Total
= I
1
+ I
2
+ I
3
+ . . .
