I>> Phase Overcurrent - DEMA CPM 310 G User Manual

I>> Phase Overcurrent 2
Main Screen » Set » I>>
Protection
Can be set as "Active" or "Passive", to have the protection into or out of service.
I>> (Threshold)
Indicates the threshold value for the protection function. For I>>, the set value range is (0.50-40.0)
I , where I is the phase nominal current value of the current transformer.
n n
DType (Delay Type)
Indicates the Delay Type for the protection function. DMT (Definite Minimum Time) or IDMT (Inverse
Definite Minimum Time) delay types are available. Delay Type parameter can be set as any curve
described in the Introduction section.
TMS or tI>> (Tripping Delay)
TMS (Time Multiplier Setting) or tI>> (definite time delay) determines the character of the protection
function along with the Delay Type parameter. If the delay type is selected as "DMT", the delay will be
displayed as "tI>>" and will have a range of (0.01 – 150) s. If the delay type is selected as one of
IDMT curves (e.g. IEC SI), the delay will be displayed as "TMS" and will have a range of (0.025 – 3.2).
TMS or tI>> value is calculated through an engineering process that takes many parameters into
account; such as the network characteristics, protected load characteristics and selectivity schemes.
RType and tReset (Reset Type and Reset Delay)
Reset Type and Reset Time configures the curve type and delay parameter to determine the reset
behavior of a function, which takes place when a disturbance (e.g. a current measurement over the
threshold value) does not continue enough time to trip. For the above settings, e.g., a current
measurement above 5.00 I
below the threshold without having the circuit breaker tripped, the trip timer will be reset after 0.04
seconds. DEMA CPM 310 G has DMT (Definite Minimum Time) and IDMT (Inverse Definite Minimum
Time) options as reset characteristics. Please see the
Reset Types for each protection function. □
nd
Phase overcurrent protection functions are symbolized
as I>, I>> and I>>> in IEC Standards, and coded as
50 and 51 in IEEE/ANSI Standards.
Symbol I>> indicates that the protection function
monitors the phase current and intervenes when
current values above the 2
The picture on the left shows the Phase Overcurrent
2 nd Threshold Protection Menu - the menu comprises 6
parameters, as shown in the picture.
Settings and options in the menu are described in the
following paragraphs.
would trigger the trip timer, however, if the current measurement drops
n
Threshold Protection Menu
nd
Protection and Reset Curves
- 68 -
threshold are detected.
section for available