GE Multilin MLJ Synchronism Check Relay DESCRIPTION

The MLJ is a digital synchronism check relay that measures bus and line voltages, checking: voltage differences, frequency slip, and phase angle between both voltages

Applications

Generator and network synchronism

Bus or line synchronism check

Protection and Control

Synchronism check operation

Undervoltage supervision

DESCRIPTION

The main applications of the MLJ are:
• Connecting a generator to the system.
• Re-establishing the connection between two parts of the system.
• Manual closing of circuit breakers
• Automatic reclosing of a breaker after a relay trip.
The MLJ is a digital synchronism-checking relay that measures bus and line voltages.

It tests:
• Voltage difference
• Frequency slip
• The phase angle between both voltages
The equipment provides an output to enable to close the circuit breaker when all of the values fall within the
set limits and remain there for the duration of time chosen for the setting. In the event that all the conditions
have not been met, after one minute the equipment gives off a signal showing a failure of closing conditions.
The relay functions in two modes:
• Continuous mode: In this mode synchronism is checked continuously.
• Manual mode: This is activated when voltage is applied through a manually activated input, thus
beginning synchronism control when voltage applied through another digital input for initial checking.
The function of synchronism (with voltage in the line and bus) can be controlled by two undervoltage units,
which allow the synchronism operation when both voltages are higher than the set value.
Additionally, it is equipped with DLDB dead line-dead bus, DLLB dead line-live bus, and LLDB live line-dead
bus, making it possible to select any combination thereof through independent settings.
The basic MLJ1000 equipment and the equipment linkable via RS-485 is mounted in a 2-inch module,
compatible with industrial MID systems, or in a 1/8 rack as an individual relay.