Open Circuit (46Bc) - Siemens 7SR242 Duobias Technical Manual

2.5

Open Circuit (46BC)

Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
This function uses the ratio of NPS current to PPS current to detect an open circuit . These quantities can be
produced directly from many advanced test sets but with limited equipment the following approach can be
applied.
Apply 3P balanced current with normal phase rotation direction. This current will consist of PPS alone, no NPS or
ZPS.
Increase 1 phase current magnitude in isolation to produce NPS. The single phase unbalance current will contain
equal quantities of ZPS, NPS and PPS. The NPS component will be 1/3 of the unbalance current and the total
PPS component will be value of the original balanced 3P current plus 1/3 of the additional unbalance current. i.e.
as the single phase unbalance current increases, the ratio of NPS to PPS will also increase. The levels of each
sequence component current can be monitored in the Current Meters in Instruments Mode.
Inject 1A of balanced current. Gradually increase imbalance current, operating level should be as follows:
©2015 Siemens Protection Devices Limited
Chapter 6) 7SR242 Duobias Commissioning & Maintenance Guide
Figure 2-7 Open Circuit
n/a
W1-I (I ), W1-I (I ), W1-I
L1 A L2 B
51N, 46IT, 46DT
46BC - Self Reset
(I ), or W2-I (I ), W2-I
L3 C L1 A L2
(I ), W2-I (I ),
B L3 C
Chapter 6 Page 32 of 62