DEMA CPM 310 G User Manual page 73

I > Negative Sequence Overcurrent 1
2
Protection Menu
Main Screen » Set » I
Protection
Can be set as "Active" or "Passive", to have the protection into or out of service.
I > (Threshold)
2
Indicates the threshold value for the protection function. For I
where I is the phase nominal current value of the current transformer.
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)
2
TMS (Time Multiplier Setting) or tI
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
2
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
2
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 0.50 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. □
Negative Sequence Overcurrent Protection is
symbolized as I
IEEE/ANSI Standards. I
current value.
I > symbol indicates that the protection function
2
monitors the negative sequence value of the phase
current and intervenes when current values above the
1 st threshold are detected.
I > negative sequence overcurrent function is applied
2
where load unbalances need to be controlled over the
absolute value of the negative sequence.
The picture on the left shows the Negative Sequence
Overcurrent 1
>
comprises 6 parameters, as shown in the picture.
2
Settings and options in the menu are described in the
following paragraphs.
> (definite time delay) determines the character of the protection
2
would trigger the trip timer, however, if the current measurement drops
n
Threshold
st
> in IEC Standards, and coded as 46 in
2
describes negative sequence
2
st Threshold Protection Menu - the menu
>, the set value range is (0.1-40.0) I
2
Protection and Reset Curves
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n
section for available