36
36
SME2-IS - Manual - 06 - 2021
FUNCTIONAL CHARACTERISTICS
Operating logic
and regulations
The polarising parameter used as a reference for the residual current phase shift measurement is
the value of the calculated residual voltage, so that the protection uses the residual voltage phasor
U
E
, the modulus and argument of which are calculated as the fundamental component and phase
respectively of the sum of the instantaneous values of the three phase voltages measured at the
voltmetric inputs.
It follows that the protection measures the phase shift of the residual current phasor I
E
relative to
the residual voltage phasor U
E
, which is positive with the current delayed relative to the voltage
(Φ
E
=(∠U
E
- ∠I
E
, where ∠ indicates the argument operator).
For each of the four thresholds I
ED
>, I
ED
>>, I
ED
>>> and I
ED
>>>>, the characteristic angle can be
regulated relative to the polarising parameter, conventionally positive in the clockwise direction.
The characteristic angle can be regulated in the range 0…359°. The regulation of the characteristic
angle identies the angular position of the characteristic half-axis, which represents the bisector of
the angular tripping sector. For each of the four thresholds, the angular tripping half-sector can be
adjusted relative to the characteristic semi-axis over the range 1…180°.
I
ED
I
ED
>> I
ED
>>>
t
ED
>
t
ED
>>
t
ED
>>>
t
ED
>>>>
I
ED
>
t
Tripping characteristic of the four thresholds of the ground directional function - 67N
I
ED
>>>>
INTERVENTION
Vectorial diagram of the directional ground function - 67N
I
E
Non-actuation sector
UE
Characteristic semi-axis
Φ
E
ορ Φ
EX
Tripping threshold
(I
ED
>, I
ED
>>, I
ED
>>>, I
ED
>>>>)
Characteristic angle
(ϑ
E>
, ϑ
E>>
, ϑ
E>>>
, ϑ
E>>>>
)
Actuation sector
Angular tripping sector
semi-amplitude
(β
E>
, β
E>>
, β
E>>>
, β
E>>>>
)
Angular tripping sector
semi-amplitude
(β
E>
, β
E>>
, β
E>>>
, β
E>>>>
)
I
E
SME2-IS
67N
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