Seg HighTECH Line MRI1IU User manual

MRI1-IU -Voltage controlled time overcurrent relay

2 TB MRI1-IU 10.98 E
Contents
1 Introduction and application
2 Features and characteristics
3 Design
3.1 Connections
3.1.1 Analog input circuits
3.1.2 Output relays
3.1.3 Blocking input
3.1.4 External reset input
3.2 LEDs
4 Working principle
4.1 Analog circuits
4.2 Digital circuits
4.3 Voltage controlled tripping
characteristic
4.4 Demand imposed on the main current
transformers
5 Operation and setting
5.1 Display
5.2 Setting procedure
5.2.1 Current setting values for overcurrent
relay (ISN und ISL)
5.2.2 Time current characteristics for phase
overcurrent element (CHAR I>)
5.2.3 Trip delay or time multiplier for phase
overcurrent element (tI>)
5.2.4 Reset setting for inverse time tripping
characteristics in the phase current path
5.2.5 Current setting for high set element
(I>>N und I>>L)
5.2.6 Trip delay for high set element (tI>>)
5.2.7 Undervoltage set reference value
5.2.8 Nominal frequency
5.2.9 Adjustment of the slave address
5.2.10 Blocking the protection functions and
assignment of the output relays
5.3 Indication of measuring values and fault
data
5.3.1 Indication of measuring values
5.3.2 Indication of fault data
5.4 Reset
6 Relay testing and commissioning
6.1 Power-On
6.2 Testing the output relays and LEDs
6.3 Checking the set values
6.4 Secondary injection test
6.4.1 Test equipment
6.4.2 Example of test circuit
6.4.3 Checking the input circuits and
measured values
6.4.4 Checking the operating and resetting
values of the relay under normal and
low voltage
6.4.5 Checking the relay operating time
6.4.6 Checking the high set element
6.4.7 Checking the external blocking and
reset functions
6.5 Primary injection test
6.6 Maintenance
7 Technical data
7.1 Measuring input circuits
7.2 Common data
7.3 Setting ranges and steps
7.3.1 Definite time overcurrent protection
relay
7.3.2 Inverse time overcurrent protection relay
7.4 Inverse time characteristics
7.5 Output contacts
8 Order form
Important:
For additional common data of all MR-relays please
refer to manual "MR - Digital Multifunctional relays".
This technical manual is valid for software version
D08-6.00.

TB MRI1-IU 10.98 E 3
1 Introduction and application
The digital multifunctional relay MRI1-IU is an universal
protection device for alternators and other equipment.
It provides the following functions:
• Independent (definite) time overcurrent protection
(DMT)
• Inverse time overcurrent protection (IDMT) with the
following selectable characteristics:
Normal Inverse
Very Inverse
Extremely Inverse
Automatic change over characteristic by
undervoltage
2 Features and characteristics
• Digital filtering of the measured values by using
discrete Fourier analysis to suppress the high
frequence harmonics and DC components induced
by faults or system operations
• Selectable protective functions between:
definite time overcurrent relay and
inverse time overcurrent relay
• Selectable inverse time characteristics according to
BS 142 and IEC 255-4:
Normal Inverse
Very Inverse
Extremely Inverse
• Reset setting for inverse time characteristics
selectable
• High set overcurrent unit with instantaneous or de-
finite time function.
• Two-element (low and high set) overcurrent relay.
• Voltage controlled characteristic
• Measuring of phase currents in operation without
short-circuit storage of tripping values
• Numerical display of setting values and actual mea-
sured values.
• Withdrawable modules with automatic short circuitof
C.T. inputs when modules are withdrawn.

4 TB MRI1-IU 10.98 E
3 Design
3.1 Connections
Figure 3.1: Connection diagram
3.1.1 Analog input circuits
The protection unit receives the analog input signals of
the phase currents IL1 (B3-B4), IL2 (B5-B6), IL3 B7-
B8)), as well as the phase voltages via isolated input
transformers in V-connection.
The constantly detected current measuring values are
galvanically decoupled, filtered and finally fed to the
analog/digital converter.
3.1.2 Output relays
The MRI1-IU has five output relays. Two output relays
with two change-over contacts and two with one
change-over contacts can be assigned as required.
All relays are working current relays, only the relay for
self supervision is an idle current relay. To prevent that
the C.B. trip coil circuit is interrupted by the MRI1-IU
first, i.e. before interruption by the C.B. auxiliary
contact, a dwell time is fixed.
This setting ensures that the MRI1-IU remains in self
holding for 200ms after the fault current is interrupted.
3.1.3 Blocking input
The blocking functions adjusted before will be blocked
if an auxiliary voltage is connected to (terminals)
D8/E8. (Refer to chapter 5.2.10)
3.1.4 External reset input
Please refer to chapter 5.4.

TB MRI1-IU 10.98 E 5
3.2 LEDs
The LEDs left from the display are partially bi-colored,
the green indicating measuring, and the red fault
indication.
The LED marked with letters RS lights up during setting
of the slave address of the device for serial data
communication.
The 5 LEDs arranged at the characteristic points on the
setting curves support the comfortable setting menu
selection.
Figure 3.2: Front panel
4 Working principle
4.1 Analog circuits
The incoming currents from the main current
transformers on the protected object are converted to
voltage signals in proportion to the currents via the
input transformers and burden. The noise signals
caused by inductive and capacitive coupling are
supressed by an analog R-C filter circuit.
The analog voltage signals are fed to the A/D-
converter of the microprocessor and transformed to
digital signals through Sample- and Hold-circuits. The
analog signals are sampled at 50 Hz (60 Hz) with a
sampling frequency of 800 Hz (960 Hz), namely, a
sampling rate of 1.25 ms (1.04 ms) for every
measuring quantity. (16 scans per periode).
The incoming voltages from the main voltage
transformers are led to operational amplifiers through
the input transformers and R-C filters.
Figure 4.1: Block diagram

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4.2 Digital circuits
The essential part of the MRI1-IU relay is a powerful
microcontroller. All of the operations, from the analog
digital conversion to the relay trip decision, are carried
out by the microcontroller digitally. The relay program
is located in an EPROM (Electrically-Programmable-
Read-Only-Memory). With this program the CPU of the
microcontroller calculates the three phase currents in
order to detect a possible fault situation in the
protected object.
For the calculation of the current value an efficient
digital filter based on the Fourier Transformation (DFFT -
Discrete Fast Fourier Transformation) is applied to
suppress high frequency harmonics and DC
components caused by fault-induced transients or other
system disturbances.
The calculated actual current values are compared
with the relay settings. If a phase current exceeds the
pickup value, an alarm is given and after the set trip
delay has elapsed, the corresponding trip relay is
activated.
The relay setting values for all parameters are stored in
a parameter memory (EEPROM - Electrically Erasable
Programmable Read-only Memory), so that the actual
relay settings cannot be lost, even if the power supply
is interrupted.
The microprocessor is supervised by a built-in
"watchdog" timer. In case of a failure the watchdog
timer resets the microprocessor and gives an alarm
signal, via the output relay "self supervision".
selection of current transformers. It implies that, if an
electromechanical relay is replaced by MRI1, a high
accuracy limit factor is automatically obtained by using
the same current transformer.
4.3 Voltage controlled tripping
characteristic
The voltage controlled time overcurrent relay MRI1-IU
is the combination of a time overcurrent relay (basic
unit MRI1) and an additional undervoltage supervision
unit.
The undervoltage supervision unit has an influence on
the tripping delay of the overcurrent and short-circuit
steps by switching two setting points. In normal
operation (at nominal voltage) the MRI1-IU operates
like a normal time overcurrent relay with preselected
tripping characteristic (IDMT, DMT) and adjusted pick
up value IS.
The following diagram explains the switching-over to
another IS value. ISN is the pickup value during
normal operation and ISL at undervoltage (low
voltage).
Switching-over at undervoltage (Example ISL = 0.5)
0.4 0.6 0.8 11 2 4 6 8 1010 20
I/I
N
1
1010
100100
t[s]
1.0
1.0
t
I>
=
I
SL
=0.5
I
SN
=1.0
In case of failure (short-circuit of the alternator) the
alternator voltage decreases. The MRI1-IU will
recognize this and then switch over without delay to a
lower pickup value IS. The value ISL can be adjusted.
As a result, shorter tripping periods of the overcurrent
and short-circuit step can be achieved. The adjusted
tripping characteristics (normal inverse, very inverse,
extremely inverse or DMT is maintained). Setting
ranges see in 7.3.
4.4 Demand imposed on the main
current transformers
The current transformers have to be rated in such a
way, that a saturation should not occur within the
following operating current ranges:
Independent time overcurrent function: K1 = 2
Inverse time overcurrent function: K1 = 20
High-set function: K1 = 1.2 - 1.5
K1 = Current factor related to set value
Moreover, the current transformers have to be rated
according to the maximum expected short circuit
current in the network or in the protected objects.
The low power consumption in the current circuit of
MRI1, namely <0,2 VA, has a positive effect on the
selection of current transformers. It implies that, if an
electromechanical relay is replaced by MRI1, a high
accuracy limit factor is automatically obtained by using
the same current transformer.

TB MRI1-IU 10.98 E 7
5 Operation and setting
5.1 Display
Function Display shows Pressed push button Corresponding LED
Normal operation SEG
Measured operating values: Actual measured values,
(IL1, IL2, IL3, U12, U23, U31)
<SELECT/RESET>
one time for each
L1, L2, L3, U
Measuring range overflow max. <SELECT/RESET> L1, L2, L3, U
Setting values:
phase (I>; CHAR I>; tI>; I>>; tI>>)
Current settings
Trip delay characteristics
<SELECT/RESET>
one time for each
parameter
I >; CHAR I>; tI>;
I>>; tI>>; LED →←
voltage Voltage switch value <SELECT/RESET><+><-> U
Reset setting (only available at
inverse time characteristics)
0s / 60s <SELECT/RESET>
<+><->
I>; CHAR I>; tI>
Nominal frequency f=50 / f=60 <SELECT/RESET><+><->
Blocking of function EXIT <+> until max. setting
value
LED of blocked
parameter
Slave address of serial interface 1 - 32 <SELECT/RESET><+><-> RS
Recorded fault data: Tripping currents and
other fault data
<SELECT/RESET>
one time for each phase
L1, L2, L3, U
I>, I>>
Save parameter? SAV? <ENTER>
Save parameter! SAV! <ENTER> for about 3 s
Software version First part (e.g. D01-)
Sec. part (e.g. 8.00)
<TRIP>
one time for each part
Manual trip TRI? <TRIP> three times
Inquire password PSW? <TRIP><ENTER>
Relay tripped TRIP <TRIP>or after fault tripping
Secret password input XXXX <SELECT/RESET>
<+><-><ENTER>
System reset SEG <SELECT/RESET>
for about 3 s
Table 5.1: possible indication messages on the display
The table below shows how the display and LED´s indicate the set values of MRI1-IU
Set parameter LED alight Colour Displays shows
Low set current at nominal voltage I>; U I> yellow, U green x In
Low set current at low voltage I>; U I> yellow, U red x In
Tripping characteristics CHAR I> Yellow DEFT/NINV/
VINV/EINV
Time delay tI> tI> Yellow seconds
Time multiplier at inverse time characteristics tI> Yellow time multiplier
High set current at nominal voltage I>>; U I>> Yellow, U green x In
High set current at low voltage I>>; U I>> yellow, U red x In
Time delay tI>> Yellow seconds
Undervoltage setting U red volt
Rated frequency f = 50 / f = 60
Slave address RS yellow 1 -32
Table 5.2: Indicated set values

8 TB MRI1-IU 10.98 E
5.2 Setting procedure
After push button <SELECT/RESET> has been pressed,
always the next measuring value is indicated. Firstly
the operating measuring values are indicated and then
the setting parameters. By pressing the <ENTER> push
button the setting values can directly be called up and
changed.
5.2.1 Current setting values for
overcurrent relay (ISN und ISL)
When adjusting the setting values ISN (during normal
operation) and ISL (during undervoltage) the values
shown on the display are related to the nominal
current IN.
This means:
Pickup current (ISN) = displayed value x rated current
(IN)
e.g. if displayed value = 1.25, then Is = 1.25 x IN.
The pickup of the relay is indicated by the flashing LED
I>. LED U flashes red.
The pickup value ISL is also indicated by the flashing
LED I>. LED U however flashes red.
5.2.2 Time current characteristics for
phase overcurrent element
(CHAR I>)
By setting this parameter, one of the following
4 messages appears on the display:
DEFT - Definite Time
NINV - Normal Inverse
VINV - Very Inverse
EINV - Extremely Inverse
Anyone of these four characteristics can be chosen by
using <+> <->-push buttons, and can be stored by
using <ENTER>-push button.
5.2.3 Trip delay or time multiplier for
phase overcurrent element (tI>)
Usually, after the characteristic is changed, the time
delay or the time multiplier should be changed
accordingly. In order to avoid an unsuitable
arrangement of relay modes due to carelessness of the
operator, the following precautions are taken:
After the characteristic setting, the setting process turns
to the time delay setting automatically. The LED tI> is
going to flash yellow to remind the operator to change
the time delay setting accordingly. After pressing the
<SELECT>-push button, the present time delay setting
value is shown on the display. The new setting value
can then be changed by using <+> <-> -push buttons.
If, through a new setting, another relay characteristic
other than the old one has been chosen (e.g. from
DEFT to NINV), but the time delay setting has not been
changed despite the warning from the flashing LED,
the relay will be set to the most sensitive time setting
value of the selected characteristics after five minutes
warning of flashing LED tI>. The most sensitive time
setting value means the fastest tripping for the selected
relay characteristic.

TB MRI1-IU 10.98 E 9
5.2.4 Reset setting for inverse time
tripping characteristics in the
phase current path
To ensure tripping, even with recurring fault pulses
shorter than the set trip delay, the reset mode for
inverse time tripping characteristics can be switched
over. If the adjustment tRST is set at 60s, the tripping
time is only reset after 60s faultless condition. This
function is not available if tRST is set to 0. With fault
current cease the trip delay is reset immediately and
started again at recurring fault current.
5.2.5 Current setting for high set
element (I>>N und I>>L)
The current setting value of this parameter appearing
on the display is related to the nominal current of the
relay
This means: I>> = displayed value x IN.
The response value I>>N is indicated by flashing the
LED I>>. LED U flashes green.
The response value I>>L is also indicated by flashing
the LED I>>. LED U however flashes red.
When the current setting for high set element is set out
of range (on display appears "EXIT"), the high set
element of the overcurrent relay is blocked.
The high set element can be blocked via terminals
E8/D8 if the corresponding blocking parameter is set
to bloc.
5.2.6 Trip delay for high set element (tI>>)
Independent from the chosen tripping characteristic for
I>, the high set element I>> has always a definite-time
tripping characteristic. An indication value in seconds
appears on the display.
5.2.7 Undervoltage set reference value
When adjusting the undervoltage switching point a
value in volt is shown on the display.
The LED U flashes red during the setting.
5.2.8 Nominal frequency
The adapted FFT-algorithm requires the nominal
frequency as a parameter for correct digital sampling
and filtering of the input currents.
By pressing <SELECT> the display shows "f=50" or
"f=60". The desired nominal frequency can be
adjusted by <+> or <-> and then stored with
<ENTER>.
5.2.9 Adjustment of the slave address
Pressing push buttons <+> and <-> the slave address
can be set in range of 1-32.

10 TB MRI1-IU 10.98 E
5.2.10 Blocking the protection functions
and assignment of the output
relays
Blocking the protection functions:
The blocking function of the MRI1-IU can be set
according to requirement. By applying the aux.
voltage to D8/E8, the functions chosen by the user
are blocked. Setting of the parameter should be done
as follows:
• When pressing push buttons <ENTER> and <TRIP>
at the same time, message "BLOC" is displayed (i.e.
the respective function is blocked) or "NO_B"
(i.e. the respective function is not blocked). The LED
allocated to the first protection function I> lights red.
• By pressing push buttons <+> <-> the value
displayed can be changed.
• The changed value is stored by pressing <ENTER>
and entering the password.
• By pressing the <SELECT/RESET> push button, any
further protection function which can be blocked is
displayed.
• Thereafter the blocking menu is left by pressing
<SELECT/RESET> again.
Function Display LED/Colour
I> Overcurrent
(Low set)
NO_B I> yellow
I>> Overcurrent
(High set)
BLOC I>> yellow
Table 5.3: Default settings of blocking functions
Assignment of the output relays:
The relay has five output relays. The fifth output relay is
provided as permanent alarm relay for self supervision
is normally on. Output relays 1 - 4 are normally off
and can be assigned as alarm or tripping relays to the
current functions which can either be done by using
the push buttons on the front plate or via serial
interface RS485. The assignment of the output relays is
similar to the setting of parameters, however, only in
the assignment mode. The assignment mode can be
reached only via the blocking mode.
By pressing push button <SELECT/RESET> in blocking
mode again, the assignment mode is selected.
The relays are assigned as follows: LEDs I>, I>>, are
two-coloured and light up green when the output
relays are assigned as alarm relays and red as
tripping relays.
Definition:
Alarm relays are activated at pickup.
Tripping relays are only activated after elapse of the
tripping delay.
After the assignment mode has been activated, first
LED I> lights up green. Now one or several of the four
output relays can be assigned to current element I> as
alarm relays. At the same time the selected alarm
relays for frequency element 1 are indicated on the
display. Indication "1_ _ _" means that output relay 1
is assigned to this current element. When the display
shows "_ _ _ _", no alarm relay is assigned to this
current element. The assignment of output relays 1 - 4
to the current elements can be changed by pressing
<+> and <-> push buttons. The selected assignment
can be stored by pressing push button <ENTER> and
subsequent input of the password. By pressing push
button <SELECT/RESET>, LED I> lights up red. The
output relays can now be assigned to this current
element as tripping relays.
Relays 1 - 4 are selected in the same way as
described before. By repeatedly pressing of the
<SELECT/RESET> push button and assignment of the
relays all elements can be assigned separately to the
relays. The assignment mode can be terminated at any
time by pressing the <SELECT/RESET> push button for
some time (abt. 3 s).
Note:
• The function of jumper J2 described in general
description "MR Digital Multifunctional Relays" has
no function. For relays without assignment mode
this jumper is used for parameter setting of alarm
relays (activation at pickup or tripping).
• A form is attached to this description where the
setting requested by the customer can be filled-in.
This form is prepared for telefax transmission and
can be used for your own reference as well as for
telephone queries.
Relay function Output relays Display- Lighted LED
1234
indication
I> alarm X _ 2 _ _ I>: green
tripping X 1 _ _ _ tI>: red
I>> alarm X _ _ 3 _ I>>: green
tripping X 1 _ _ _ tI>>: red
Table 5.4: Example of assignment matrix of the output relay (default settings).

TB MRI1-IU 10.98 E 11
5.3 Indication of measuring values
and fault data
5.3.1 Indication of measuring values
The following measuring quantities can be indicated
on the display during normal service:
• Apparent current in phase 1 (LED L1 green)
• Apparent current in phase 2 (LED L2 green)
• Apparent current in phase 3 (LED L3 green)
• Phase to phase voltage U12 (LED L1, L2, U green)
• Phase to phase voltage U23 (LED L1, L3, U green)
• Phase to phase voltage U31 (LED L1, L3, U green)
5.3.2 Indication of fault data
All of the faults detected by the relay are indicated on
the front panel optically. The three phase LEDs L1, L2,
L3, the undervoltage LED U and the two function LEDs
I>, I>> are used to indicate the fault events.
At the time when a certain relay function is energized
by a fault, the corresponding function LED lights up
yellow. At the same time, the phase LED(s) is (are)
flashing red to indicate the faulty phase(s).
After the time delay is expired, the relay tripps, the
LED(s) for faulty phase(s) indication turn(s) to a steady
red light.
5.4 Reset
Unit MRI1-IU has the following three possibilities to
reset thedisplay of the unit as well as the output relay
at jumper position J3=ON.
Manual Reset
• Pressing the push button <SELECT/RESET> for some
time (about 3 s)
Electrical Reset
• Through applying auxiliary voltage to C8/D8
Software Reset
• The software reset has the same effect as the
<SELECT/RESET> push button (see also
communication protocol of RS485 interface).
The display can only be reset when the pickup is not
present anymore (otherwise "TRIP" remains in display).
During resetting of the display the parameters are not
affected.

12 TB MRI1-IU 10.98 E
6 Relay testing and
commissioning
The test instructions following below help to verify the
protection relay performance before or during
commissioning of the protection system. To avoid a
relay damage and to ensure a correct relay operation,
be sure that:
• the auxiliary power supply rating corresponds to the
auxiliary voltage on site.
• the rated current and rated voltage of the relay
correspond to the plant data on site.
• the current transformer circuits and voltage
transformer circuits are connected to the relay
correctly.
• all signal circuits and output relay circuits are
connected correctly.
6.1 Power-On
NOTE!
Prior to switch on the auxiliary power supply, be sure
that the auxiliary supply voltage corresponds with the
rated data on the type plate.
Switch on the auxiliary power supply to the relay and
check that the message "ISEG" appears on the display
and the self supervision alarm relay (watchdog) is
energized (Contact terminals D7 and E7 closed).
6.2 Testing the output relays and LEDs
NOTE!
Prior to commencing this test, interrupt the trip circuit to
the circuit breaker if tripping is not desired.
By pressing the push button <TRIP> once, the display
shows the first part of the software version of the relay
(e.g. D08-). By pressing the push button <TRIP>
twice, the display shows the second part of the
software version of the relay (e.g. 4.01). The
software version should be quoted in all
correspondence. Pressing the <TRIP> button once
more, the display shows "PSW?". Please enter the
correct password to proceed with the test. The
message "TRI?" will follow. Confirm this message by
pressing the push button <TRIP> again. All output
relays and LEDs should then be activated and the self
supervision alarm relay (watchdog) be deactivated
one after another with a time interval of
3 second. Thereafter, reset all output relays back to their
normal positions by pressing the push button
<SELECT/RESET> (about 3 s).
6.3 Checking the set values
By repeatedly pressing the push button <SELECT>, all
relay set values may be checked. Set value
modification can be done with the push button <+><-
> and <ENTER>. For detailed information about that,
please refer to chapter 5.
For a correct relay operation, be sure that the
frequency set value (f=50/60) has been selected
according to your system frequency (50 or 60 Hz).
6.4 Secondary injection test
6.4.1 Test equipment
• Voltmeter, Ammeter with class 1 or better
• Auxiliary power supply with the voltage
corresponding to the rated data on the type plate
• Single-phase current supply unit (adjustable from
0 to ≥4 x In)
• Three-phase voltage supply unit (adjustable from 0 to
≥1.2 x Un)
• Timer to measure the operating time
(Accuracy class ≤±10 ms)
• Switching device
• Test leads and tools

TB MRI1-IU 10.98 E 13
6.4.2 Example of test circuit for MRI1-IU
relays without directional feature
For testing MRI1-IU relays current and voltage input
signals are required. Figure 6.1 shows an example of
a test circuit connected to the MRI1-IU relay under test.
For testing relays with voltage controlled feature, three
phase voltages from a variable voltage source should
be applied to the relay with a V-connection as shown
in the diagram.
The three phase voltage should be adjustable within
the effective operating range of the undervoltage
element and have a phase relationship apart from
120°. The current inputs could be single or three
phase.
Figure 6.1: Test curcuit
6.4.3 Checking the input circuits and
measured values
Apply three phase rated voltage (e.g. 100 V phase to
phase) to the voltage input circuits (terminals A3, A5,
A7) and inject a current, which is less than the relay
pickup current set values, in phase 1 (terminals B3-B4),
and check the measured current on the display by
pressing the push button <SELECT/RESET>. For a
relay with rated current In = 5A, for example, a
secondary current injection of 1A should be indicated
on the display with about 0.2 (0.2 x In). The voltage
will be indicated on the display in volts. The current
can be also injected into the other current input circuits
(Phase 2: terminals B5-B6, Phase 3: terminals B7-B8).
Compare the displayed current and voltage value with
the reading of the ammeter and voltmeter. The
deviation must not exceed 3%. By using an RMS-
metering instrument, a greater deviation may be
observed if the test current contains harmonics.
Because the MRI1-IU relay measures only the
fundamental component of the input signals, the
harmonics will be rejected by the internal DFFT-digital
filter. Whereas the RMS-metering instrument measures
the RMS-value of the input signals.

14 TB MRI1-IU 10.98 E
6.4.4 Checking the operating and
resetting values of the relay under
normal and low voltage
Apply three phase voltages 5% above the
undervoltage set value and inject a current which is
less than the relay low set current at low voltage
condition in phase 1 of the relay. Gradually increase
the current until the relay starts, i.e. at the moment
when the LED I> and L1 light up or the alarm output
relay I> is activated. Read the operating current
indicated by the ammeter. The deviation must not
exceed 5% of the pickup current at nominal voltage
condition.
Furthermore, gradually decrease the current until the
relay resets, i.e. the alarm output relay I> is
disengaged. Check that the resetting current is smaller
than 0.97 times the operating current.
Apply three phase voltages 5% below the
undervoltage set value. Do the same test as above
mentioned and check the relay operating current value
and resetting value at low voltage condition.
Repeat the test on phase 2, phase 3 in the same
manner.
6.4.5 Checking the relay operating time
To check the relay operating time, a timer must be
connected to the trip output relay contact. The timer
should be started simultaneously with the current
injection in the current input circuit and stopped by the
trip relay contact. Set the current to a value
corresponding to twice the operating value and inject
the current instantaneously. The operating time
measured by the timer should have a deviation of less
than 3% of the set value or ±10 ms (DEFT). Accuracy
for inverse time characteristics refer to IEC 255-3.
Repeat the test on the other phases or with the inverse
time characteristics in the similar manner.
In case of inverse time characteristics the injected
current should be selected according to the
characteristic curve, e.g. two times IS. The tripping time
may be red from the characteristic curve diagram or
calculated with the equations given under "technical
data".
Please observe that during the secondary injection test
the test current must be very stable, not deviating more
than 1%. Otherwise the test results may be wrong.
6.4.6 Checking the high set element
of the relay
Set a current above the set operating value of I>>.
Inject the current instantaneously and check that the
alarm output relay I>> (contact terminals D5/E5)
operates. Check the tripping time of the high set
element according chapter 6.4.5.
Check the accuracy of the operating current setting by
gradually increasing the injected current until the I>>
element picks up. Read the current value form the
ammeter and compare with the desired setting.
Repeat the entire test on other phases in the same
manner.
Note !
Where test currents >4 x INare used, the thermal
withstand capability of the current paths has to be
considered (see technical data, chapter 7.1).
6.4.7 Checking the external blocking and
reset functions
The external blocking input inhibits e. g. the function of
the high set element of the phase current. To test the
blocking function apply auxiliary supply voltage to the
external blocking input of the relay (terminals E8/D8).
The time delay tI> should be set to EXIT for this test.
Inject a test current which could cause a high set (I>>)
tripping. Observe that there is no trip and alarm for the
high set element.
Remove the auxiliary supply voltage from the blocking
input. Inject a test current to trip the relay (message
TRIP on the display). Interrupt the test current and
apply auxiliary supply voltage to the external reset
input of the relay (terminals C8/D8). The display and
LED indications should be reset immediately.

TB MRI1-IU 10.98 E 15
6.5 Primary injection test
Generally, a primary injection test could be carried out
in the similar manner as the secondary injection test
described above. With the difference that the
protected power system should be, in this case,
connected to the installed relays under test on line,
and the test currents and voltages should be injected to
the relay through the current and voltage transformers
with the primary side energized. Since the cost and
potential hazards are very high for such a test, primary
injection tests are usually limited to very important
protective relays in the power system.
Because of its powerful combined indicating and
measuring functions, the MRI1-IU relay may be tested
in the manner of a primary injection test without extra
expenditure and time consumption.
In actual service, for example, the measured current
values on the MRI1-IU relay display may be compared
phase by phase with the current indications of the
ammeter of the switchboard to verify that the relay
works and measures correctly.
6.6 Maintenance
Maintenance testing is generally done on site at
regular intervals. These intervals vary among users
depending on many factors: e.g. the type of protective
relays employed; the importance of the primary
equipment being protected; the user's past experience
with the relay, etc.
For electromechanical or static relays, maintenance
testing will be performed at least once a year
according to the experiences. For digital relays like
MRI1, this interval can be substantially longer. This is
because:
• the MRI1-IU relays are equipped with very wide self-
supervision functions, so that many faults in the relay
can be detected and signalized during service.
Important: The self-supervision output relay must be
connected to a central alarm panel!
• the combined measuring functions of MRI1-IU relays
enable supervision the relay functions during service.
• the combined TRIP test function of the MRI1-IU relay
allows to test the relay output circuits.
A testing interval of two years for maintenance will,
therefore, be recommended.
During a maintenance test, the relay functions
including the operating values and relay tripping
characteristics as well as the operating times should be
tested.

16 TB MRI1-IU 10.98 E
7 Technical data
7.1 Measuring input circuits
Rated data: Nominal current IN1A or 5A
Nominal voltage UN100 V, 230 V, 400 V
Nominal frequency fN50 Hz; 60 Hz adjustable
Power consumption in
current circuit: at IN= 1 A 0.2 VA
at IN= 5 A 0.1 VA
Power consumption in
voltage circuit: < 1 VA
Thermal withstand capability
in current circuit: dynamic current withstand
(half-wave) 250 x IN
for 1 s 100 x IN
for 10 s 30 x IN
continuously 4 x IN
Thermal withstand in
voltage circuit: continuously 1.5 x UN
7.2 Common data
Dropout to pickup ratio: > 97 %
Returning time : 30 ms
Time lag error class index E: ±10 ms
Minimum operating time: 30 ms
Transient overreach at
instantaneous operation: ≤5 %

TB MRI1-IU 10.98 E 17
7.3 Setting ranges and steps
7.3.1 Definite time overcurrent protection relay
Setting range Step Tolerance
ISN;ISL
tI>
0.2...4.0 x IN
0.03 - 260 s
0.05; 0.1 x IN
0.01; 0.02; 0.05; 0.1; 0.2; 0.5; 1.0;
2.0; 5.0 s
±3 % from set value or
min. ±1 % In
±3 % or ±10 ms
I>>N
I>>L
tI>>
1...40 x IN
0.03...2 s
0.1; 0.2; 0.5; 1.0 x IN
0.01 s; 0.02 s; 0.05 s
±3 % from set value or
min. ±1 % In
±3 % or ±10 ms
UU
N
= 100 V: 10 - 110 V
UN= 230 V: 20 - 250 V
UN= 100 V: 40 - 440 V
5 V
10 V
20 V
±5 % from set value
7.3.2 Inverse time overcurrent protection relay
According to IEC 255-4 or BS 142
Normal Inverse
[]
t
I
Is
tIs
=



−
>
014
002
1
,
,
Very Inverse
[]
tI
Is
tIs
=



−>
135
1
,
Extremely Inverse
[]
t
I
Is
tIs
=



−
>
80
2
1
Where: t = tripping time
tI> = time multiplier
I = fault current
Is = Starting current
Setting range Step Tolerance
ISN;ISL
tI>
0.2...4.0 x IN
0.05 - 10
0.05; 0.1 x IN
0.01; 0.02
±3 % from set value or
min. ±1 % In
±5 % for NINV
and VINV
±7.5 % for NINV
and EINV
I>>N
I>>L
tI>>
1...40 x IN
0.03...2 s
0.1; 0.2; 0.5; 1.0 x IN
0.01 s; 0.02 s; 0.05 s
±3 % from set value or
min. ±1 % In
±3 % or ±10 ms
UU
N
= 100 V: 10 - 110 V
UN= 230 V: 20 - 250 V
UN= 100 V: 40 - 440 V
5 V
10 V
20 V
±5 % from set value

18 TB MRI1-IU 10.98 E
7.4 Inverse time characteristics
1 2 3 4 5 6 7 8 910 20
I/I
S
0.1
1
10
100
1000
t[s]
t
I>
=
3.0
10.0
8.0
6.0
4.0
2.0
0.05
0.1
0.2
0.3
0.4
0.5
0.6
0.8
1.0
1.4
Figure 7.1: Normal Inverse
1 2 3 4 5 6 7 8 910 20
I/I
S
0.01
0.1
1
10
100
1000
t[s]
t
I>
=
10.0
8.0
6.0
4.0
3.0
2.0
0.05 0.1 0.2
0.3
0.4
0.5
0.6
0.8
1.0
1.4
Figure 7.2: Extremely Inverse
1 2 3 4 5 6 7 8 910 20
I/I
S
0.1
1
10
100
1000
t[s] t
I>
=
10.0
8.0
6.0
4.0
3.0
2.0
0.05
0.1
0.2
0.3
0.4
0.5
0.6
0.8
1.0
1.4
Figure 7.3: Very Inverse
1 10
I/I
N
0.01
0.1
1
10
100
t[s]
t
I
>
I>>
t
I
>>
260
0.03
1.0 40 2.0
0.03
I>
0.02 4.0
Figure 7.4 Definite time overcurrent relay
7.5 Output contacts
Number of relays: dependent on relay type
Contacts: 2 change-over contacts for trip relay
1 change-over contact for alarm relays
Technical data subject to change without notice!

TB MRI1-IU 10.98 E 19
8 Order form
MRI1- IU
3-phase measuring I>, I>>
Rated current 1 A
5 A
1
5
Voltage dependent tripping characteristic
Rated voltage 100 V
230 V
400 V
1
2
4
Housing (12TE) 19-rack
Flush mounting
A
D
Setting of code jumpers
Code jumper J1 J2 J3
Default setting Actual setting Default setting Actual setting Default setting Actual setting
Plugged no function
Not plugged X X
Assignment of the output relays:
Function Relay 1 Relay 2 Relay 3 Relay 4
Default
setting
Actual
setting
Default
setting
Actual
setting
Default
setting
Actual
setting
Default
setting
Actual
setting
I> alarm X
I> tripping X
I>> alarm X
I>> tripping X
Assignment of the blocking function:
Default setting Actual setting
Function Blocking Not blocking Blocking Not blocking
I> X
I>> X

20 TB MRI1-IU 10.98 E
Setting list MRI1
Note !
All settings must be checked at site and should the occasion arise, adjusted to the object / item to be protected.
Project: SEG job.-no.:
Function group: = Location: + Relay code: -
Relay functions: Password:
Date:
Setting of the parameters
Default Actual
Function Unit settings settings
I>SNormal Low set current at nominal voltage x In 0.2
I>SLow Low set current at low voltage x In 0.2
CHAR I> Tripping characteristics DEFT
tI> Time delay at independent time s 0.03
tI> Time multiflier at dependent time characteristics
tI> Reset Reset Modus for dependent time characteristics
I>>SNormal High set current at nominal voltage x In 1.0
I>>SLow High set current at low voltage x In 1.0
tI>> Time delay s 0.03
U Threshold value for undervoltage setting V 10V / 20V /
40V *
Rated frequency Hz 50
RS Slave adress 1
All settings must be checked at site and should the occarision arise, adjusted to the object/item to be protected.
* thresholds dependent on rated voltage 100 V / 230 V / 400 V