Broken Conductor (46Bc); Figure 3-4 Broken Conductor - Siemens 7SR21 Manual

3.4

Broken Conductor (46BC)

Voltage Inputs:
Current Inputs:
Disable:
Map Pickup LED:
Broken Conductor uses the ratio of NPS current to PPS current to detect an open circuit conductor. 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:
©2010 Siemens Protection Devices Limited
7SR21 & 7SR22 Argus Commissioning and Maintenance

Figure 3-4 Broken Conductor

n/a
I (I ), I (I ), I (I ),
L1 A L2 B L3 C
51N, 46IT, 46DT
46BC - Self Reset
Chapter 6 Page 63 of 69