Areva MiCOM P441, Техническое руководство

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P44x/EN AD/E44 Update Documentation
Page 52/82
MiCOM P441, P442 & P444
9.8.2 Optos : Dual hysteresis and filter removed or not
The MiCOM P44x is fitted with universal opto isolated logic inputs that can be programmed
for the nominal battery voltage of the circuit of which they are a part i.e. thereby allowing
different voltages for different circuits e.g. signalling, tripping. They can also be programmed
as Standard 60% - 80% or 50% - 70% to satisfy different operating constraints (Dual Opto).
Threshold levels are as follows:
Standard 60% - 80% 50% - 70%
Nominal
Battery Voltage
(Vdc)
No Operation (logic 0)
Vdc Operation (logic 1) Vdc No Operation (logic 0)
Vdc
Operation (logic 1) Vdc
24 / 27 <16.2 >19.2 <12.0 >16.8
30 / 34 <20.4 >24.0 <15.0 >21.0
48 / 54 <32.4 >38.4 <24.0 >33.6
110 / 125 <75.0 >88.0 <55.0 >77.0
220 / 250 <150.0 >176.0 <110 >154
TABLE 1
This lower value eliminates fleeting pickups that may occur during a battery earth fault, when
stray capacitance may present up to 50% of battery voltage across an input.
Each input also has selectable filtering which can be utilised. This allows use of a pre-set
filter of ½ cycle which renders the input immune to induced noise on the wiring: although this
method is secure it can be slow, particularly for intertripping. This can be improved by
switching off the ½ cycle filter in which case one of the following methods to reduce ac noise
should be considered. The first method is to use double pole switching on the input, the
second is to use screened twisted cable on the input circuit.