Ashida ADR241B, Instruction Manual

Page: 103 / 272

ADR241B
Doc ID : ADR241B-DO_IM_01
Ref ID : ADR241B/IM/PLF
Rev No. : 06
Page No. : 103 of 272
4.7.2 C12 – User Define Curve
The ADR241B relay has special feature of C12 - User Define Curve which is design for
phase Overcurrent, ground OC, residual OC and negative phase sequence OC.
The user can set the different definite operating time ( T1 to T5) with respect to settable
multiple trip setting (M1 to M5) as per the requirement. This Operating time settings are
multiply with Set TMS value.
The C12 - User Define curve consist of five stages of multiplier setting with time delay. The
relay operate with set delay of respective stage when fault current exceeds the set current
T
1
T
2
T
3
T
4
T
5
M
1
M
2
M
3
M
4
M
5
Current I
Time
(Sec
)
Figure 14: Graph for User Define Curve Characteristic
4.7.3 Timer Hold Facility / Reset Characteristics
The first stage (stage 1) of phase over current, ground OC (EF), residual OC (3Io) and
negative phase sequence (NPS) OC protection is provided with a timer hold facility "tReset".
It can be programmed as a definite time.
A possible situation arises where the reset timer may be used to reduce the fault clearance
time where intermittent faults occur.
For example, a cable with plastic insulation application, it is possible that the fault energy
melts the cable insulation, which then reseals after clearance, thereby eliminating the cause
for the fault. This process repeats itself to give a succession of fault current pulses, each of
increasing duration with reducing intervals between the pulses, until the fault becomes
permanent.
The range of DT time setting is 0.00 – 100.00 sec in steps of 0.01 sec.
Following diagram explain the function of definite time reset characteristic