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1. DESCRIPTION
The main applications of the MLJ are:
• Connecting a generator to the system.
• Reestablishing 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.
The equipment with communications added to the RS-485, through RS-232 and plastic or glass fiber
optics, models MLJ1006 MLJ1007, come with an additional 2-inch wide card, and is mounted in a 4-
inch module (also compatible with MID systems), or on a 1/4 rack as an individual relay.
GEK - 105560
4
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