Manual 7SJ45 Construction
C53000-K1174-C001-7 47
The Numerical Overcurrent Protection SIPROTEC
®
easy 7SJ45
offers the following scope of functions:
Overcurrent protection
• 2-stage overcurrent protection. The device has always a
normal stage for phase currents (definite-time or inverse-
time). For the second stage, the user can choose between a
high-current stage for phase currents (definite-time) or a
normal stage for calculated earth currents (definite-time or
inverse-time).
• Inverse-time overcurrent protection with integrating
measurement method (disk emulation), IEC or ANSI
characteristics.
• Insensitivity against DC components, inrush and charging
currents as well as higher-frequency transients.
Monitoring functions
• Increased reliability thanks to monitoring of the hardware and
software. The monitoring function controls the RUN and
ERROR LEDs.
2.6 Construction
The 7SJ45 overcurrent protection is a compact unit that
comprises all components for:
• Measuring and processing
• Alarm and command output
• Operation and indication
• Control of an optional mechanical trip indication
• Auxiliary supply from current transformers
Variants
The user can choose between variants with pulse output and
relay output.
• Versions with pulse output
These devices require a low energy trip actuator in the circuit
breaker (24V/0.1 Ws 20 Ω) and are designed for modern
switchgear (see Figure 2-27 and see also the ordering data
and accessories in section 2.11).
In case a fault occurs the trip circuit is released for 100 ms.
When a switching operation is carried out, the trip command
is repeated until the circuit breaker picks up. Between trips
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