1MRS 752137-MUM
Combined Overcurrent and Earth-Fault Relay
Operator’s Manual
REJ 525
5
1. Introduction
1.1. About this manual
This manual provides the user with basic information on the combined overcurrent
and earth-fault relay REJ 525 and presents detailed instructions on how to use the
Human-Machine Interface (HMI) of the relay, also known as the Man-Machine
Interface (MMI). In addition to the instructive part, a short chapter on the service of
the relay has been included.
1.2. The use of the relay
The REJ 525 is intended for three-phase overcurrent protection and non-directional
earth-fault protection in medium voltage distribution networks but can also be used
for protection of generators, motors and transformers.
The REJ 525 can also be used in applications requiring single- or two-phase
overcurrent protection.
The REJ 525 is based on a microprocessor environment. A self-supervision system
continuously monitors the operation of the electronics and the software.
The HMI includes a Liquid Crystal Display (LCD) which makes the local use of the
relay safe and easy.
Local control of the relay can be carried out using a portable computer connected to
the front connector and remote control via the rear connector connected to the
distribution automation system through the serial interface and the fibre-optic bus.
1.3. Features
• Three-phase low-set overcurrent stage with definite-time or inverse definite
minimum time (IDMT) characteristic
• Three-phase high-set overcurrent stage with instantaneous or definite-time
characteristic
• Phase discontinuity protection
• Low-set non-directional earth-fault stage with definite-time or IDMT
characteristic
• High-set non-directional earth-fault stage with instantaneous or definite-time
characteristic
• Circuit-breaker failure protection unit (CBFP)
• Disturbance recorder
• recording time up to 10 seconds
• triggering by a start or a trip signal from any protection stage and/or by a binary
input signal
• records four analogue channels and up to eight user-selectable digital channels
• adjustable sampling rate
• Non-volatile memory for
• up to 60 event codes
• setting values
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