GE MLJ1000 User manual

GGEEKK--105560105560

GE Power Management
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“We bring good things to life”
MLJ
MLJ1000
DIGITAL SYNCHRONISM
CHECK RELAY

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TABLE OF CONTENTS
1. DESCRIPTION ....................................................................................................................4
2. APPLICATION....................................................................................................................5
2.1 DESIGN CHARACTERISTICS ..........................................................................................5
2.2 APPLICATIONS..................................................................................................................7
3. OPERATION PRINCIPLES.............................................................................................11
3.1 CONFIGURATION UNIT.................................................................................................11
3.1.1 GENERAL Settings.......................................................................................................11
3.2 SYNCHRONISM CHECK UNIT......................................................................................11
3.2.1 Mode of Operation.......................................................................................................12
3.2.2 Settings.........................................................................................................................13
3.2.3 Failure of Closure Conditions .....................................................................................13
3.3 UNDERVOLTAGE UNIT.................................................................................................14
3.3.1 Mode of Operation.......................................................................................................14
3.3.2 Settings.........................................................................................................................14
3.4 INPUT UNITS....................................................................................................................15
3.5 SELF-CHECK UNIT..........................................................................................................15
3.5.1 Mode of Operation.......................................................................................................15
3.6 OUTPUT UNITS................................................................................................................16
3.6.1 Mode of Operation.......................................................................................................16
3.6.2 Settings.........................................................................................................................16
3.7 POWER SUPPLY ..............................................................................................................17
4. TECHNICAL CHARACTERISTICS..............................................................................18
4.1 MODEL LIST.....................................................................................................................18
4.2 TECHNICAL CHARACTERISTICS ................................................................................18
4.3 INSULATION ....................................................................................................................19
4.4 TYPE TESTS .....................................................................................................................20
5. DESCRIPTION OF HARDWARE...................................................................................21
5.1 CASE..................................................................................................................................21
5.2 INTERNAL CONNECTIONS ...........................................................................................21
5.3 IDENTIFICATION.............................................................................................................21
5.4 MLJ FRONT DEVICES.....................................................................................................21
6. OPERATION OF MLJ (KEYPAD AND DISPLAY) .....................................................23
6.1 READOUT SEQUENCE...................................................................................................24
6.1.1 F0: State of relay, error codes .....................................................................................25
6.1.2 F1, F2: VL, VB, Voltage in line and buses...................................................................25
6.1.3 F3: ∆ V Voltage difference module................................................................................25

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6.1.4 F4: ∆θ Phase angle......................................................................................................25
6.1.5 F5: ∆ f Frequency Slip ..................................................................................................25
6.1.6 F6, F7, F8, F9, and F10 Magnitudes recorded ...........................................................26
6.1.7 F11: TEST Display and inputs test ..............................................................................26
6.1.8 F12: VL VB State of Line and buses ............................................................................26
6.2 SEQUENCE OF SETTINGS .............................................................................................26
6.3 CALIBRATION SEQUENCE............................................................................................28
6.4 SUMMARY OF SETTINGS..............................................................................................29
7. ACCEPTANCE TESTS.....................................................................................................31
7.1 INTRODUCTION..............................................................................................................31
7.2 VISUAL INSPECTION......................................................................................................31
7.3 INSULATION ....................................................................................................................31
7.4 SYNCHRONISM UNIT.....................................................................................................31
7.4.1 Voltage unit test............................................................................................................32
7.4.2 Angle unit test...............................................................................................................32
7.5 UNDERVOLTAGE UNIT.................................................................................................32
7.6 CONTINUOUS AND MANUAL MODE TESTS.............................................................33
7.7 CALIBRATION .................................................................................................................33
7.8 GROUNDING....................................................................................................................33

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List of Figures
FIGURE 1 LOGICAL DIAGRAM OF OPERATION (226B2202H2)..............................35
FIGURE 2 NAMEPLATE (226B1276H1).................................................................36
FIGURE 3 OUTLINE AND PANEL DRILLING (226B6086H1)....................................37
FIGURE 4 REAR TERMINAL PLATE (226B3205H1)................................................38
FIGURE 5 EXTERNAL CONNECTIONS (226B6265H1)............................................39
FIGURE 6 INTERNAL SETTINGS (301A7408H1) ....................................................40
FIGURE 7 BLOCK DIAGRAM (226B2201H1).........................................................41
The information provided herein does not intend to cover all details of variations of the
described equipment nor does it take into account the circumstances that may be present in
your installation, operating or maintenance activities.
Should you wish to receive additional information, or for any particular problem which cannot
be solved by referring to the information contained herein, please write to:
GENERAL ELECTRIC (USA) POWER MANAGEMENT, S.A.

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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.

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2. APPLICATION
2.1 DESIGN CHARACTERISTICS
Measurement accuracy
The differential angle measurement of the MLJ is high precision and is limited solely by errors in
available voltage transformers .
The measurement of the angle is practically independent of the voltage.
In the MLJ the measurement is obtained via a numerical calculation done on digital voltage samples,
thus achieving high precision. This allows for a rating of 2º, which is clearly better than the possible
rating using other technologies.
Influence of harmonics
The pillar of the MLJ measurement calculation is the discrete Fourier transform, which is in essence a
harmonics filter. For this reason the voltage and line measurements are not affected by frequencies
other than the fundamental.
The rejection of harmonics is added to the independence of measurements, both magnitude and
phase, relative to frequency signal variations, which is very important in a synchronism checking relay
which, by its own nature, works in variable frequencies.
Given that in power systems, synchronization or synchronism checking is carried out in a steady state,
that is with voltage magnitudes near or equal to the rated value, close enable is not emitted for very low
voltages. Therefore, for voltage of less than 9 volts, the relay stops measuring phase and frequency,
not giving permission to close under such conditions.
The MLJ also offers additional insensitivity to frequency measurement concerning harmonics, since
this is done via a hardware circuit, a zero-cross detector, with an intrinsic harmonics filter. Furthermore,
it has a software filter which operates by double-period measurement, both between the rising and
falling edges, averaging them out and allowing for better performance of algorithm frequency
(improving security and response).
Closing time delay
The minimum closing time, set at 100 ms, is actually 160 ms, as it is necessary to add the time
required by the measurement units and the operation of the output relays to the set 100 ms. It should
be kept in mind that during the first cycles, from the time of a closure, the voltage is stabilizing both in
the line as well as in the buses and it is no desirable to allow a closure under these conditions. What is
more, it is necessary to take into consideration the response of both the high voltage transformers and
the internal transformers of the relay.

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There is also a time for sustaining the permission signal, which always has a fixed value of some 130
ms., being the result of a prefixed delay of 100 ms. added to the dropout time of the measurement
units (one cycle = 20 ms. at 50 Hz.) and the deactivation of the output relay (10 ms.).
Minimum settings
Barring any special requirements, it is not recommended to use settings that near the minimum limits
for the relays, (2 V for the voltage difference, 2º for the angle difference), so as to avoid being too
restrictive in close enabling, given the real characteristics of accuracy in the installations, measurement
transformers, etc.
Close enable
Close enable is defined by three conditions in the system:
• The difference in amplitude of the two voltage signals to be synchronized defines a circle shifted
from the axis of abscissa a distance equal to the magnitude of the minimum vector and having a
maximum radius equal to the difference ∆V.
• The angular difference, allowed either in positive or negative, between the two approaching vectors,
forms a cone on which the close enable takes place.
• The frequency slip, ∆f = f1- f2, which has to be less than that specified, configures a third and
basic condition of closure, optimum for carrying out closure procedures in ideal conditions, with
similarity between signals.
∆V
V
1
V
2
θ1θ2
CLOSE ENABLE
∆f =

f1- f2


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2.2 APPLICATIONS
Synchronism
In general, synchronism check is intended primly for application where the two parts of a system to be
joined by the closure of a circuit breaker are interconnected at other points throughout the system.
Usually, performing synchronism check measurements is done with relatively long times in order to
make sure the voltages are synchronized. Nevertheless, this long timer, which can be on the order of
10 to 20 seconds, is not appropriate when both ends of the line are to be reclosed at high speed. If the
measurement time is lower, then the synchronism check can be done faster, although this means that
the reclosing could be done under no-synchronism conditions, with greater frequency slip than for ideal
condition.
It is essential to point out the intrinsic relation that invariably exists between time, frequency slip and
angle of closure, in such a way that, for constant slip, the following expression is carried out:
SDT =**
1000
180
Where: D= angle of closure in degrees
S= Frequency slip in mHz
T= Total time in seconds
For applications where a preferred value for frequency slip does not exist, it is recommended to use
the maximum. This way the behavior of other synchronism relays which do not have this feature can
be reproduced.
If a preferred value for the voltage difference does not exist, it is recommended to use the maximum
rating; in doing so closure is permitted monitoring only conditions of phase, slip and time.
If the time of the circuit breaker closure is known, the maximum angle difference can be estimated by
applying the above expression; it will be obtained during closure of the circuit breaker.
For example, let us take: a setting of 30º for the angle, a setting of 167 ms for the time,
and that the time of operation of the circuit breaker to be 83 ms.
From the above equation we obtain the value of 1 Hz (360º/s) for frequency slip S. If we
had frequency slip greater than 1 Hz, we would not have close enable.
If we adjust the maximum frequency slip to 330 mHz, then:
330 mHz ≅120º/s ⇒120º/s * 167 ms = 20º
and the movement in the difference of the angle during the circuit breaker closure will be:
83 ms * 120º/s = 10º
20º+10º=30º, which is the fixed phase setting, and therefore the closure occurs at the
optimum moment, when the voltages in the line and bus are completely in phase.

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In a large majority of cases, the typical slip can be set at around 20 to 40 mHz. This is the situation for
short lines.
In lines with short “dead times”, that is, immediate reclosing in the remote end, with very similar
operation in case of internal faults in both circuit breakers and channel transmission times less than 25
ms, the slip setting may be set at 200 to 250 mHz.
In any case, the order and operating times of the different elements involved should be observed;
these are the elements with which the synchronism check relay must be coordinated, and whose
typical magnitudes are shown on the following page.

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t1t2t3t4t5t6t7t8t9t10 t11 t12
t1 = Moment of detection of the fault in protections A and B.
t2 = Tripping order of circuit breakers A and B (it may not happen at the same time).
t3 = Opening of circuit breakers A and B (it may not happen at the same time).
t4 = Spark quenching of the arcs in circuit breakers A and B.
t5 = End of safety waiting period, in order to compensate error clear up discrepancies between circuit
breakers A and B, and order reclosing of circuit breaker B.
t6 = Closure of circuit breaker B and initiation of stabilization of relay signals of synchronism relay A.
t7 = Initiation of the set time in synchronism relay A.
t8 = End of synchronism relay time delay and internal output of synchronization enable.
t9 = Reclose order of circuit breaker A.
t10 = Closure of circuit breaker A.
t11 = Resetting of synchronism relay A.
t12 = End of output enable of synchronism relay A.
∆1 = Opening time of circuit breakers = 60 ms.
∆2 = Spark quenching time = 20 ms.
∆3 = Additional waiting time for discrepancies in opening of circuit breakers A and B.
∆4 = Closure time of circuit breaker B = 80 ms.
∆5 = Stabilization time of synchronism relay signals = 30 ms.
∆6 = Time set in the synchronism relay for voltage checking (setting).
∆7 = Time for action of output unit of the synchronism relay = 30 ms.
∆8 = Closure time of circuit breaker A = 80 ms.
∆9 = Reset time of the synchronism relay = 130 ms.
∆10 = Sustained time of synchronism enable = 130 ms.
Λ3
Λ1Λ2Λ4Λ6
Λ5Λ7Λ8Λ9Λ10
AB