Ashida ADR241B, Instruction Manual

Page: 108 / 272

ADR241B
Doc ID : ADR241B-DO_IM_01
Ref ID : ADR241B/IM/PLF
Rev No. : 06
Page No. : 108 of 272
4.12 Broken Conductor (46BC)
+Ve seq -Ve seq
Figure 18: Circuit Diagram for Broken conductor application
ADR241B equipped with broken conductor detection protection. Broken conductor condition
can be detected by the ratio of Negative sequence current to Positive sequence current
(I2/I1). Protection provides higher sensitivity on High resistive fault.
Most of the faults that affect a power system are phase to phase and the phase to earth fault.
These faults are shunt faults, such faults lead the current to increase appreciably and
therefore they can easily be detected in most applications.
Open circuit faults (or Series faults) are a different type of faults that can happen in electrical
networks. These faults can be caused by broken conductors, blown fuses or maloperation of
a pole of a circuit-breaker. Open circuit faults will not lead to an increase in phase current
and therefore they cannot be easily detected by common over current relays. However, this
type of faults produces an unbalance that creates negative phase sequence current, which
can be detected.
The ADR241B relays incorporated a Brocken conductor (46BC) protection element with two
stages, stage 1 is for BC Alarm and stage 2 is for BC Trip. The Brocken conductor Figure 15
explains the Brocken conductor 46BC on “ON” Selection. Which checks the ratio of negative
to positive phase sequence current (I2/I1) exceeds the set value if this condition is satisfied,
After elapsed set delay, then relay will generate I2/I1 Trip or BC Alarm as per the associated
settings.
Timer
&
I2/I 1 ratio
I2/I 1 >n
+
-
Trip I2/I1>n
I2/I1>nP
I2/I1=ON
Figure 19: Logic Diagram for Brocken conductor 46BC