ADR141A /
Ref ID : ADR241A/IM/PLF
Rev No. : 02
fault current has not been interrupted following a set time delay from circuit breaker trip
initiation, breaker failure protection (CBF) will operate. CBF operation can be use to operate
back-trip, upstream circuit breakers to ensure that the fault is isolated correctly.
4.4 Phase Over current Element (50/51)
Phase Over-current function operates for a set value of current with time delay (IDMT/DT).
This function provided with two stages, Where Stage 1 (IP>) can be programmed as IDMT or
Definite Time (DT) provided with the Range of 5% to 250% in step of 1%. The Stage 2 (IP>>)
can be programmed as Instantaneous or Definite Time (DT) provided with the Range of 50%
to 3000% in step of 1%.
4.5 Ground Over current Element (50N/51N)
Ground Over-current (EF) function operates for a set value of current with time delay
(IDMT/DT). This function provided with two stages, Where Stage 1 (IE>) can be programmed
as IDMT or Definite Time (DT) provided with the Range of 5% to 250% in step of 1%. The
Stage 2 (IE>>) can be programmed as Instantaneous or Definite Time (DT) provided with the
Range of 50% to 3000% in step of 1%.
4.6 IDMT Characteristics
ADR141A/ ADR241A relay provides inverse time over current characteristic for phase over
current and ground over current elements. The phase and ground over current elements are
independently settable with inverse time or definite time characteristic. The following tripping
characteristics curves are available
• Normal Inverse 1 Curve (C1)
• Normal Inverse 2 Curve (C2)
• Very Inverse Curve (C3)
• Extremely Inverse Curve (C4)
• Extremely Inverse Curve (C4A) as per EE relays
• Long time Inverse Curve (C5)
• Definite time Over current (C6)
The phase over current and earth fault function are programmable as per IDMT
characteristic based on IEC standards. The inverse time delay is calculated with the
following mathematical formula:
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