Current And Voltage Measuring - GE MLP1000 Manual

CC-5: Reclosing block (to the recloser /MLP2000 and MLP3000)
CC-6: Carrier reception (to the protection /MLP3000)
CC-7: Extended Zone I pull back (to the protection)
CC-8: Reclosing disable (to the recloser /MLP2000 and MLP3000)
Initiate reclosing and block reclosing signals may also reach the recloser from the
protection system.
The extended zone 1 pull back signal may also reach the protection from the
recloser.
If any input is damaged and the MLP reads that this input is changing more than 15
times per second, the MLP decides that this input has to be disabled, leaving it in a
determined state. In this case an event is generated for disabling the input. The disabled
inputs remain in the following states:
CC-1: Breaker........................................... Closed.
CC-2: External trip block............................ Inactive
CC-3: Line pick up..................................... Inactive
CC-4: Reclosing initiation........................... Inactive
CC-5: Reclosing block................................ Blocked
CC-6: Carrier reception............................... No reception
CC-7: Extended Zone 1 pull back unit........ Zone pulled back
CC-8: Reclosing inhibition........................... Inhibited
Analog current and voltage inputs
The voltage transformers of the protected line supply a secondary phase-ground
voltage which is applied to the relay input and reduced by internal voltage transformers
whose secondary voltages provide input voltage to the protection system.
The current transformers of the protected circuit supply a secondary current of up to
160 A which is applied to the relay input and reduced by the internal power transformers.
The secondary currents of the relay's internal transformers are connected to input
resistance which supply voltage that represents the current of the protection .
The relay input voltages as well as the voltages that represent the input current to
the relay pass through lowpass filters (with a 250 Hz break frequency to eliminate high
frequencies that can produce "aliasing" on the software filters of 50 Hz or 60 Hz before
reaching a multiplexer and a variable amplification stage.
The amplified output reaches an analog/digital converter in which the power and
voltage are instantly measured.

4.2 CURRENT AND VOLTAGE MEASURING

The internal microprocessor timer generates an interrupt every 1.25 ms (50 Hz) or
every 1 ms (60 Hz) so there are 16 interrupts per network cycle. In each interrupt a
multiplexer is used to obtain the instantaneous samples of the three phase currents and the
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