ERL F-PRO 116, Руководство пользователя

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D05125R01.20 F-PRO 116 User Manual 5-15
46BC Broken Conductor
The Broken Conductor (46BC) function can detect unbalanced series or open circuit faults
(referred to as series faults from here on). Series faults can arise from broken conductors or
jumpers, maloperation of single phase switchgear or the operation of series fuses. Series faults
do not cause an increase in phase currents in the system and thus are not easily detectable by
standard overcurrent relays. However, series faults produce an unbalance and a detectable level
of negative sequence current.
A negative sequence overcurrent relay (46-50/46-51) could possibly be used to detect series fault
conditions. However, on a lightly loaded line, the negative sequence current resulting from a
series fault may be very close to, or less than, the full load steady state unbalance in the system.
A negative sequence element therefore would not operate at low load levels. For this reason, the
46BC function based on I2/I1 principle is used to detect series faults.
The function incorporates an element which measures the ratio of negative sequence to positive
sequence current (I2/I1). This ratio is affected less severely than the measurement of negative
sequence current alone, since the ratio remains approximately constant with variations in load
current. This ratio allows for a more sensitive setting to be achieved.
An adequate time delay should be used to coordinate with other protective devices and to ensure
that the device does not trip during the normal operation of single phase switchgear or during re-
close sequences.
46BC – Broken conductor Logic diagram
Figure 5.13: Logic Diagram of 46BC Functions
Table 5.14 46BC Broken Conductor
Setting Description Range
Function Activation Enable/Disable
Pickup I2/I1 20.0% to 100.0 %
Pickup Delay 0.02 to 999.99 seconds