GE MLJ Digital Synchromism Check

Synchronism check relay for interconnection of AC system parts.

Features and Benefits

• RS485. RS232 or fiber comm. available

• Configurable auxiliary outputs

• V  f  Hz line and bus metering

• Continuous or manual modes

• Part of a modular system

• Independent 2" or 4" modules

• 1/4 or 1/8 standard 19" rack case available

• 3 digit display

Applications

• Generator and network synchronism

• Bus or line synchronism check

• Manual closing of breakers

Protection and Control

• Synchronism check operation

• Undervoltage supervision

• DLDB, DLLB and LLDB indication

Description

The MLJ is a digital synchronism check relay that measures bus

and line voltages, checking:

• voltage differences

• frequency slip

• phase angle between both voltages

The main applications of the MLJ are:

• connection of a generator to the network

• reestablishing the connection between two parts of the

network

• manual closing of breakers

The relay sends a closing output to the breaker when all of the

values fall within the set limits and maintain these values for a

period of time which has been set by the user. If any of the

condi tions are not met, the relay will provide a close condition

fault signal.

The relay has two operational modes:

• a continuous mode in which itconstantly checks the synchro

nism

• the manual mode is activated when voltage is applied to a

manual digital input, initiating the synchronism supervision

when voltage is applied by another check starting digital

input

The synchronism function (with the presence of line and bar volt

age) can be supervised by two undervoltage units that permit

the synchronism function when both voltages are above the set

value.

Additionally, the relay contains dead line-dead bus (DLDB), dead

line-live bus (DLLB) and live line dead bus (LLDB) units, with the

ability to select any combination of them through independent

settings.

The basic relay, MLJ1000. and the RS-485 communications

model, MLJ1005. are mounted in a 2" module that is compatible

with the MID industrial systems.

They can also be provided in an individual 1/8 rack. The relays

with additional communications via RS232 and plastic or glass

fiber optics, models MLJ1006 and MLJ1007. come with an addition

al 2" card. The set can be mounted in either a 4" module for

MID compatibility or a 1/4 rack case to be used as a stand alone

relay.

Functions

• programmable synchronism verification (voltage, phase and

frequency)

• two operating modes: continuous and manual

• dead line-dead bus (DLDB), dead line-live bus (DLLB) and live line

dead bus (LLDB) units

• real time measuring of line and bus voltages, voltage difference,

phase difference and slip

• registering of the last close permitted

• visual indication of the line and bus status (live/dead)

• configurable auxiliary outputs

• local interface with push buttons and display

• RS485. RS232 and fiber optics communications

• self test functions

• compatible with MID industrial systems

Man Machine Interface

Keypad

Composed of three buttons with the symbols +, -, and ENTER.

Permits performing the following functions:

• view measurements

• view relay status

• view or change settings

• indicators and inputs testing