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DESCRIPTION
The Current
Measurement and Protection Unit (IMPR-1) has been designed to
measure the line and ground RMS currents and supply RMS
voltages under normal conditions or under disturbances. The
voltage and current signals are sensed throughout potential
transformers (PT) and current transformers (CT) from each
line. This information is internally processed by the
microprocessor, to take the current protection actions defined
under ANSI, IAC or IEC standard. Additionally the operational
conditions of the breaker or disconnector are also signalized.
The different functions provided by the IMPR-1 may be
classified into the following groups:
Applications:
- Primary and backup protection
for power plants, utility and industrial distribution
systems.
- Protection of transformers,
overhead lines, cables and generators.
- Permits the opening of the
switch/disconnector within the limits of its capacity, those
identifying the excess (e.g. straight short-circuits),
leaving the circuit interruption to the back-up fuses.
Protection:
- CT primary ratio selectable in
5 amp steps (10 A to 5000 A).
- Inverse time phase overcurrent
(ANSI 51) and inverse time ground overcurrent (ANSI
51N/51G), with selection of curves according to ANSI, IAC or
IEC/BS142, as follows:
Moderately inverse.
Standard inverse.
Very inverse.
Extremely inverse.
Definite time.
- Instantaneous overcurrent
(ANSI 50).
- Instantaneous ground
overcurrent (ANSI 50N/50G).
- Overload alarm adjustment to
one level.
- Overvoltage (ANSI 59).
- Undervoltage or minimum
voltage (ANSI 27).
- Accumulated kA per phase on
breaker interruption.
- 1 trip relay and 1 alarm
relay.
- 1 breaker close relay
- Loss of control volts relay.
- 4 contact inputs from
external devices (breaker status, breaker earthed,
external reset and input 1).
Digital
Measurement:
- RMS line and ground
currents.
- Maximum instantaneous line
and ground currents.
- RMS line or phase voltages.
Signaling and
Programming:
- LED and LCD display
indication.
- Touchpad programming.
- Indication and storage of
fault conditions and their values.
- Indication of the breaker or
disconnector position (open, close, earthed).
Communication:
- Remote digital communication
to a PC or PLC, via RS422 or RS485.
- Remote adjustment of
protection and relay characteristics.
- Storage of faults and events
for further statistical treatment.
- Capable of remote opening or
closing of the breaker or switch/disconnector.
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