MRI3 - Digital multifunctional relay for overcurrent protection
2 TD_MRI3_11.07_GB
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 Relay output contacts
3.2.1 Fault recorder
3.2.2 Parameter settings ( see chapter 5)
3.3 LEDs
4 Working principle
4.1 Analog circuits
4.2 Digital circuits
4.3 Directional feature
4.3.1 Reversal in direction during the activation
phase
4.4 Earth fault protection
4.4.1 Generator stator earth fault protection
4.4.2 System earth fault protection
4.5 Earth-fault directional feature
( ER/ XR-relay type)
4.6 Determining earth short-circuit fault
direction
4.6.1 Directly ï ¿ ½ earthed system
4.6.2 Resistance ï ¿ ½ earthed system
4.6.3 Connection possibilities of the voltage
transformers for SR relay types
4.7 Demand imposed on the main curren
transformers
5 Operation and settings
5.1 Display
5.2 Setting procedure
5.3 System parameter
5.3.1 Display of measuring values as primary
quantities ( Iprim phase)
5.3.2 Display of earth current as primary quantity
( Iprim earth)
5.3.3 Display of residual voltage UE as primary
quantity ( Uprim/ Usec)
5.3.4 Voltage transformer connection for residual
voltage measuring ( 3pha/ e-n/ 1: 1)
5.3.5 Nominal frequency
5.3.6 Display of the activation storage
( FLSH/ NOFL)
5.3.7 Parameter switch/ external triggering of the
fault recorder
5.4 Parameter protection
5.4.1 Pickup current for phase overcurrent
element ( I> )
5.4.2 Time current characteristics for phase
overcurrent element ( CHAR I> )
5.4.3 Trip delay or time factor for phase
overcurrent element ( tI> )
5.4.4 Reset setting for all tripping characteristics
in the phase current path
5.4.5 Current setting for high set element ( I> > )
5.4.6 Trip delay for high set element ( tI> > )
5.4.7 Relay characteristic angle RCA
5.4.8 Pickup value for residual voltage UE
( ER/ XR-relay type)
5.4.9 Pickup current for earth fault element ( IE> )
5.4.10 WARN/ TRIP changeover
( E/ X and ER/ XR-relay type)
5.4.11 Time current characteristics for earth fault
element ( CHAR IE) ( not for ER/ XR-relay
type)
5.4.12 Trip delay or time multiplier for earth fault
element ( tIE> > )
5.4.13 Reset mode for inverse time tripping in
earth current path
5.4.14 Current setting for high set element of
earth fault supervision ( IE> > )
5.4.15 Trip delay for high set element of earth
fault supervision ( tIE> > )
5.4.16 COS/ SIN Measurement
( ER/ XR-relay type)
5.4.17 SOLI/ RESI changeover ( SR-relay type)
5.4.18 Block/ Trip ï ¿ ½ time
5.4.19 Circuit breaker failure protection tCBFP
5.4.20 Adjustment of the slave address
5.4.21 Setting of Baud-rate ( applies for Modbus
Protocol only)
5.4.22 Setting of parity ( applies for Modbus
Protocol only)
5.5 Fault recorder
5.5.1 Adjustment of the fault recorder
5.5.2 Number of the fault recordings
5.5.3 Adjustment of trigger occurrences
5.5.4 Pre-trigger time ( Tpre)
5.6 Adjustment of the clock
5.7 Additional functions
5.7.1 Blocking the protection functions and
assignment of the output relays
5.8 Setting value calculation
5.8.1 Definite time overcurrent element
5.8.2 Inverse time overcurrent element
5.9 Indication of measuring and fault values
5.9.1 Indication of measuring values
5.9.2 Units of the measuring values displayed
5.9.3 Indication of fault data
5.9.4 Fault memory
5.10 Reset
5.10.1 Erasure of fault storage
TD_MRI3_11.07_GB 3
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 for MRI3 relays
without directional feature
6.4.3 Checking the input circuits and measured
values
6.4.4 Checking the operating and resetting
values of the relay
6.4.5 Checking the relay operating time
6.4.6 Checking the high set element of the relay
6.4.7 Example of a test circuit for MRI3 relay
with directional feature
6.4.8 Test circuit earth fault directional feature
6.4.9 Checking the external blocking and reset
functions
6.4.10 Testing the external blocking with
Block/ Trip function
6.4.11 Test of the CB failure protection
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 Time overcurrent protection ( I-Type)
7.3.2 Earth fault protection ( SR-Type)
7.3.3 Earth fault protection ( E/ X-Type)
7.3.4 Earth fault protection ( ER/ XR-Type)
7.3.5 Block/ Trip ï ¿ ½ time
7.3.6 Switch failure protection
7.3.7 Interface parameter
7.3.8 Parameter for the fault recorder
7.3.9 Inverse time overcurrent protection relay
7.3.10 Direction unit for phase overcurrent relay
7.3.11 Determination of earth fault direction
( MRl3-ER/ XR)
7.3.12 Determination of earth fault direction
( MRl3-SR)
7.4 Inverse time characteristics
7.5 Output contacts
8 Order form
4 TD_MRI3_11.07_GB
1 Introduction and application
The MRl3 digital multifunctional relay is a universal
time overcurrent and earth fault protection device intended
for use in medium-voltage systems, either with
an isolated/ compensated neutral point or for networks
with a solidly earthed/ resistance-earthed neutral point.
The protective functions of MRI3 which are implemented
in only one device are summarized as follows:
ï ¿ ½ Independent ( Definite) time overcurrent relay,
ï ¿ ½ inverse time overcurrent relay with selectable characteristics,
ï ¿ ½ integrated determination of fault direction for application
to doubly infeeded lines or meshed systems,
ï ¿ ½ two-element ( low and high set) earth fault protection
with definite or inverse time characteristics,
ï ¿ ½ integrated determination of earth fault direction for
application to power system networks with isolated
or arc suppressing coil ( Peterson coil) neutral
earthing. ( ER/ XR-relay type) ,
ï ¿ ½ integrated determination of earth short-circuit fault direction
in systems with solidly-earthed neutral point or
in resistance-earthed systems ( SR-relay type) .
Furthermore, the relay MRI3 can be employed as a
back-up protection for distance and differential protective
relays.
A similar, but simplified version of overcurrent relay
IRI1 with reduced functions without display and serial
interface is also available.
Important:
For additional common data of all MR-relays please
refer to manual " MR - Digital Multifunctional relays" .
On page 51 of this manual you can find the valid
software versions.
2 Features and characteristics
ï ¿ ½ 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,
ï ¿ ½ two parameter sets,
ï ¿ ½ selectable protective functions between:
definite time overcurrent relay and
inverse time overcurrent relay,
ï ¿ ½ selectable inverse time characteristics according to
IEC 255-4:
Normal Inverse ( Type A)
Very Inverse ( Type B)
Extremely Inverse ( Type C)
Special characteristics,
ï ¿ ½ reset setting for inverse time characteristics selectable,
ï ¿ ½ high set overcurrent unit with instantaneous or definite
time function,
ï ¿ ½ two-element ( low and high set) overcurrent relay both
for phase and earth faults,
ï ¿ ½ directional feature for application to the doubly infeeded
lines or meshed systems,
ï ¿ ½ earth fault directional feature selectable for either isolated
or compensated networks,
ï ¿ ½ sensitive earth fault current measuring with or without
directional feature ( X and XR-relay type) ,
ï ¿ ½ determination of earth short-circuit fault direction for
systems with solidly-earthed or resistance-earthed
neutral point,
ï ¿ ½ numerical display of setting values, actual measured
values and their active, reactive components, memorized
fault data, etc.,
ï ¿ ½ display of measuring values as primary quantities,
ï ¿ ½ withdrawable modules with automatic short circuiters
of C.T. inputs when modules are withdrawn,
ï ¿ ½ blocking e.g. of high set element ( e.g. for selective
fault detection through minor overcurrent protection
units after unsuccessful AR) ,
ï ¿ ½ relay characteristic angle for phase current directional
feature selectable,
ï ¿ ½ circuit breaker failure protection,
ï ¿ ½ storage of trip values and switching-off time ( tCBFP) of
5 fault occurences ( fail-safe of voltage) ,
ï ¿ ½ recording of up to eight fault occurences with time
stamp,
ï ¿ ½ free assignment of output relays
ï ¿ ½ serial data exchange via RS485 interface possible;
alternatively with SEG RS485 Pro-Open Data Protocol
or Modbus Protocol,
ï ¿ ½ suppression of indication after an activation
( LED flash) ,
ï ¿ ½ display of date and time
TD_MRI3_11.07_GB 5
3 Design
3.1 Connections
Phase and earth current measuring:
Figure 3.1: Measuring of the phase currents for over-current- and
short-circuit protection ( I> , I> > )
Figure 3.2: Earth-fault measuring by means of ring-core C.T. ( IE)
When phase-- and earth-fault current measuring are
combined, the connection has to be realized as per
Figure 3.1and Figure 3.2 or Figure 3.3.
Figure 3.3: Phase current measuring and earth-current detection
by means of Holmgreen-circuit.
This connection can be used with three existing phase
current transformers when combined phase and earthcurrent
measuring is required.
Disadvantage of holmgreen-circuit:
At saturation of one or more C.Ts the relay detects
seeming an earth current.
* This arrow shows the current flow in forward direction, for this LED ï ¿ ½ ï ¿ ½ lights up green
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Voltage measuring for the directional detection:
Figure 3.4: Measuring of the phase voltages for the directional
detection at overcurrent, short-circuit or earth-fault
protection ( I> , I> > , IE> and IE> > ) .
For details on the connection of ER/ XR-unit type c.t.s,
see para 4.5.
I>
I>
I>
A3 L1
U1
U2
A5 L2
A7 L3
A2 N
U3
L1
L2
L3
a
b
c
Figure 3.5: Voltage transformer in V-connection for the
directional detection at overcurrent and short-circuit
protection.
The V-connection can not be applied at earth fault directional
feature.
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)
and the current IE ( B1-B2) , phase voltages U1 ( A3) ,
U2 ( A5) , U3 ( A7) with A2 as star point, each via
separate input transformers.
The constantly detected current measuring values are
galvanically decoupled, filtered and finally fed to the
analog/ digital converter.
For the unit type with earthfault directional features
( ER/ XR-relay type) the residual voltage UE in the secondary
circuit of the voltage transformers is internally
formed.
In case no directional feature for the phase current
path is necessary the residual voltage from the open
delta winding can directly be connected to A3 and
A2.
See Chapter 4.5 for voltage transformer connections
on isolated/ compensated systems.
3.1.2 Output relays
The MRI3 is equipped with 5 output relays. Apart from
the relay for self-supervision, all protective functions
can be optionally assigned:
ï ¿ ½ Relay 1: C1, D1, E1 and C2, D2, E2
ï ¿ ½ Relay 2: C3, D3, E3 and C4, D4, E4
ï ¿ ½ Relay 3: C5, D5, E5
ï ¿ ½ Relay 4: C6, D6, E6
ï ¿ ½ Relay 5: Self-supervision C7, D7, E7
All trip and alarm relays are working current relays,
the relay for self supervision is an idle current relay.
3.1.3 Blocking input
The blocking functions adjusted before will be blocked
if an auxiliary voltage is connected to ( terminals)
D8/ E8. ( See chapter 5.7.1)
3.1.4 External reset input
Please refer to chapter 5.10.
TD_MRI3_11.07_GB 7
3.2 Relay output contacts
Figure 3.6
3.2.1 Fault recorder
The MRI3 is equipped with a disturbance value recorder
which records the measured analogue values
as momentary values. The momentary values
iL1, iL2, iL3, iE,
are scanned within a grid 1.25 ms ( with 50 Hz) or
1.041 ms ( with 60 Hz) and filed in a circulating storage.
The max. storage capacity amounts to 16 s ( with
50 Hz) or 13.33 s ( with 60 Hz) .
Storage division
Independent of the recording time, the entire storage
capacity can be divided into several cases of disturbance
with a shorter recording time each. In addition,
the deletion behaviour of the fault recorder can be influenced.
No writing over
If 2, 4 or 8 recordings are chosen, the complete
memory is divided into the relevant number of partial
segments. If this max. number of fault event has been
exceeded, the fault recorder block any further recordings
in order to prevent that the stored data are
written over. After the data have been read and deleted,
the recorder to ready again for further action.
Writing over
If 1, 3 or 7 recordings are chosen, the relevant number
of partial segments is reserved in the complete
memory. If the memory is full, a new recording will
always write over the oldest one.
The memory part of the fault recorder is designed as
circulating storage. In this example 7 fault records can
be stored ( written over) .
Memory space 6 to 4 is occupied.
Memory space 5 is currently being written in
Figure 3.7: Division of the memory into 8 segments, for example
Since memory spaces 6, 7 and 8 are occupied, this
example shows that the memory has been assigned
more than eight recordings. This means that No. 6 is
the oldest fault recording and No. 4 the most recent
one.
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trigger occurence
recording duration
Tpre
[ s]
Figure 3.8: Recording scheme of the fault recorder with
pre-trigger time
Each memory segment has a specified storage time
which permits setting of a time prior to the trigger
event.
Via the interface RS485 the data can be read and
processed by means of a PC with HTL/ PL-Soft4. The
data is graphically edited and displayed. Binary
tracks are recorded as well, e.g. activation and trip.
TD_MRI3_11.07_GB 9
3.2.2 Parameter settings ( see chapter 5)
System parameter
Relay type MRI3- I IE
IX
IRE
IRX
IR IER
IXR
IRER
IRXR
ER
XR
E
X
ISR IRSR SR
Display of measuring values as primary
quantities ( Iprim phase)
X X X X X X X X
Display of earth current as primary
quantities ( Iprim earth)
X X X X X X X X X
Display of residual voltage UE as primary
quantity ( Uprim/ Usec)
X X X
3pha/ e-n/ 1: 1 X X X
50/ 60 Hz X X X X X X X X X X X
LED-Flash X X X X X X X X X X X
RS 485/ Slaveaddress X X X X X X X X X X X
Baud-Rate 1) X X X X X X X X X X X
Parity-Check 1) X X X X X X X X X X X
Adjustment of the clock:
Y = year; M = month; D = day;
h = hour; m = minute; s = sec.
X X X X X X X X X X X
Table 3.1: System parameters of the different relay types
Protection parameter
Relay type MRI3- I IE
IX
IRE
IRX
IR IER
IXR
IRER
IRXR
ER
XR
E
X
ISR IRSR SR
2 parameter sets X X X X X X X X X X X
I> X X X X X X X X
CHAR I> X X X X X X X X
tI> X X X X X X X X
0 s/ 60 s 2) X X X X X X X X
I> > X X X X X X X X
tI> > X X X X X X X X
RCA X X X X
UE X X X
IE> X X X X X X X X X
warn/ trip X X X X X X
CHAR IE X X X X X X
tIE X X X X X X X X X
0s / 60 s 3) X X X X X X
IE> > X X X X X X X X X
tIE> > X X X X X X X X X
sin/ cos X X X
soli/ resi X X X
tCBFP X X X X X X X X X X X
Block/ Trip X X X X X X X X X X X
Table 3.2: Protection parameters of the different relay types.
1) Only devices with Modbus-Protocol
2) Reset setting for inverse time characteristics in phase current path
3) Reset setting for inverse time characteristics in earth current path
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Parameter for the fault recorder
Relay type MRI3- I IE
IX
IRE
IRX
IR IER
IXR
IRER
IRXR
ER
XR
E
X
ISR IRSR SR
Number of fault events X X X X X X X X X X X
Trigger events X X X X X X X X X X X
Pre-trigger time ( Tpre) X X X X X X X X X X X
Table 3.3: Parameters for the fault recorder of the different relay types
Additional parameters
Relay-type MRI3- I IE
IX
IRE
IRX
IR IER
IXR
IRER
IRXR
ER
XR
E
X
ISR IRSR SR
Blocking mode 1) X X X X X X X X X X X
Relay parameterizing X X X X X X X X X X X
Fault recorder X X X X X X X X
Table 3.4: Additional parameters of the different relay types
1) For 2 parameter sets ( separately for each parameter set)
TD_MRI3_11.07_GB 11
Figure 3.9: Front plate MRI3-I
Figure 3.10: Front plate MRI3-E/ X
Figure 3.11: Front plate MRI3-IR
Figure 3.12: Front plate MRI3-ER/ XR
12 TD_MRI3_11.07_GB
Figure 3.13: Front plate MRI3-SR
Figure 3.14: Front plate MRI3-IRER/ IRXR and MRI3-IER/ IXR
3.3 LEDs
The LEDs left from the display are partially bi-coloured,
the green indicating measuring, and the red fault indication.
MRI3 with directional feature have a LED ( green- and
red arrow) for the directional display. At pickup/ trip
and parameter setting the green LED lights up to indicate
the forward direction, the red LED indicates the
backward direction.
The LED marked with letters RS lights up during setting
of the slave address of the device for serial data communication.
The LEDs arranged at the characteristic points on the
setting curves support the comfortable setting menu selection.
In accordance with the display 5 LEDs for
phase fault overcurrent relay and 5 LEDs for earth-fault
relay indicate the corresponding menu point selected.
The LED labelled with the letters LR is alight while the
fault recorder is being adjusted.
Figure 3.15: Front plate MRI3-IRSR; MRI3-IRE/ IRX and MRI3-ISR
TD_MRI3_11.07_GB 13
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/ Dconverter
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) .
Figure 4.1: Block diagram
4.2 Digital circuits
The essential part of the MRI3 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 and
ground current 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" .
4.3 Directional feature
A built-in directional element in MRI3 is available for
application to doubly infeeded lines or to ring networks.
The measuring principle for determining the direction is
based on phase angle measurement and therefore
also on coincidence time measurement between current
and voltage. Since the necessary phase voltage
for determining the direction is frequently not available
in the event of a fault, whichever line-to-line voltage follows
the faulty phase by 90ï ¿ ½ is used as the reference
voltage for the phase current. The characteristic angle
at which the greatest measuring sensitivity is achieved
can be set to precede the reference voltage in the
range from 15ï ¿ ½ to 83ï ¿ ½ .
Figure 4.2: Relay characteristic angle
The TRIP region of the directional element is determined
by rotating the phasor on the maximum sensitivity
angle for ï ¿ ½ 90ï ¿ ½ , so that a reliable direction decision
can be achieved in all faulty cases.
14 TD_MRI3_11.07_GB
4.3.1 Reversal in direction during the
activation phase
Reversal of the current direction during the activation
phase can lead to hyperfunctions. This mainly applies
to installations where parallel connected lines are
monitored by current relays with directional feature.
For this reason the directional determination for the
phase current is shown in a time window; this applies
to all SR versions. In case of activation due to a fault,
a timer is started and measures the time in the determined
direction for max. 1 s. This timer runs backwards
at half speed if, during the activation phase, a
fault causes reversal of the direction. Only when the
timer is at zero again, the MRI3 recognizes the reversal
in direction. The switch-over time is max. 2 s. The
activation delays tl> and tl> > are not affected by the
delayed recognition of direction.
1.5 1.0 0.5 0.5 1.0 1.5 [ s]
Trip delay at direction reversal
max. time
Recognition of direction reversal
Recognition of
backward direction
is alight
Recognition of
forward direction
is alight
Timer runs at
half speed
actual
direction reversal
t= 1/ 2
Figure 4.3: Recording scheme of the fault recorder with lead
time
MRI3
MRI3 MRI3
MRI3
G
IK = 0, 3 kA
IK = 3, 61 kA
IK = 0, 9 kA
IK = 3, 31 kA
IK = 1, 2 kA
l = 3 km
l = 0, 5 km
l = 3 km
No. 2 No. 4
No. 1 No. 3
Figure 4.4
Example:
Figures 4.4 and 4.5 illustrate a possible fault situation
with a reversal in direction in the fault-free line.
The current transformers used have a primary current of
250 A. The switch point for the I> stage is 0.25 kA
and for the I> > stage 1 kA. All devices have the same
setting and will, if set to ï ¿ ½ Forwardï ¿ ½ , recognize the direction
in relation to the forward direction of the line.
The critical point here is the MRI3 No. 1. Using delay
action in directional recognition, it is possible to prevent
shut-down of the fault-free line.
The following relay setting applies:
I> 1.00 x In
CHAR I> DEFT ( inverse)
trip delay
tI> ( V) 10s
Trip delay in forward
direction
tI> ( R) EXIT ( no trip) Delay in
backward direction
I> > 4.00 x In
tI> > ( V) 0.1 s
tI> > ( R) EXIT
MRI3
MRI3 MRI3
MRI3
G
IK = 1, 2 kA
IK = 2, 0 kA
IK = 1, 2 kA
IK = 0, 8 kA
l = 0, 5 km
l = 3 km
l = 3 km
No. 1 No. 3
No. 2 No. 4
Figure 4.5
TD_MRI3_11.07_GB 15
If line impedance and internal resistance of the generator
is only ohmic:
If line impedance and internal resistance of the generator
is only inductive:
The maximum sensitivity angle corresponds to the R/ L
component.
The TRIP region of the directional element is determined
by rotating the phasor on the maximum sensitivity
angle for ï ¿ ½ 90ï ¿ ½ , so that a reliable direction decision
can be achieved in all faulty cases.
Figure 4.6: TRIP/ NO-TRIP region for directional element in MRI3.
In this case the foreward direction is defined as TRIP
region and the backward direction as NO-TRIP region.
By means of accurate hardware design and by using
an efficient directional algorithm a high sensitivity for
the voltage sensing circuit and a high accuracy for
phase angle measurement are achieved so that a correct
directional decision can be made even by close
three-phase faults.
As an addition, to avoid maloperations due to disturbances,
at least 2 periods ( 40 ms at 50 Hz) are
evaluated.
For the MRI3-overcurrent relays with directional feature
different time delays or time multipliers can be set for
forward and backward faults ( ref. to chapter 5.4.3) .
If the trip delay for backward faults is set longer than
the one for forward faults, the protective relay works
as a " backup" -relay for the other lines on the same
busbar. This means that the relay can clear a fault in
the backward direction with a longer time delay in
case of refusal of the relay or the circuit breaker on the
faulted line.
If the trip delay for backward faults is set out of range
( on the display " EXIT" ) , the relay will not trip in case of
backward faults.
The assignment of the output relays can be used to select
in which direction the failure is to be indicated ( refer
also to Chapter 5.7.1) . It is possible to indicate the
activation and/ or the tripping for each tripping direction
via the output relays.
16 TD_MRI3_11.07_GB
4.4 Earth fault protection
4.4.1 Generator stator earth fault
protection
With the generator neutral point earthed earthed as
shown in Figure 4.7 the MRI3 picks up only to phase
earth faults between the generator and the location of
the current transformers supplying the relay.
Earth faults beyond the current transformers, i.e. on the
consumer or line side, will not be detected.
Figure 4.7: Generator stator earth fault protection
4.4.2 System earth fault protection
With the generator neutral point earthed as shown in
Figure 4.8, the MRI3 picks up only to earth faults in
the power system connected to the generator. It does
not pick up to earth faults on the generator terminals or
in generator stator.
Figure 4.8: System earth fault protection
TD_MRI3_11.07_GB 17
4.5 Earth-fault directional feature
( ER/ XR-relay type)
A built-in earth-fault directional element is available for
applications to power networks with isolated or with
arc suppressing coil compensated neutral point.
For earth-fault direction detection it is mainly the question
to evaluate the power flow direction in zero sequence
system. Both the residual voltage and neutral
( residual) current on the protected line are evaluated to
ensure a correct direction decision.
In isolated or compensated systems, measurement of
reactive or active power is decisive for earth-fault detection.
It is therefore necessary to set the ER/ XR-relay
type to measure according to sin ï ¿ ½ or cos ï ¿ ½ methods,
depending on the neutral-point connection method.
The residual voltage UE required for determining earth
fault direction can be measured in three different
ways, depending on the voltage transformer connections.
( refer to Table 4.1) . Total current can be measured by
connecting the unit either to a ring core C.T. or to current
transformers in a Holmgreen circuit. However,
maximum sensitivity is achieved if the MRl1 protective
device is connected to a ring core C. T. ( see Figure
3.2) .
The pick-up values IE> and IE> > ( active or reactive current
component for cos ï ¿ ½ or sin ï ¿ ½ method) for ER-relay
types can be adjusted from 0.01 to 0.45 x IN. For relay
type MRI3-XR these pick-up values can be adjusted
from 0.1 to 4.5% IN.
Adjustment
possibility
Application Voltage transformer
connections
Measurd
voltage at
earth fault
Correction factor
for residual
voltage
ï ¿ ½ 3phaï ¿ ½
3-phase voltage
transformer connected
to terminals A3, A5,
A7, A2
( MRI3-IRER;
MRI3-IER;
MRI3-ER/ XR)
3 x UN = 3 x U1N K = 1 / 3
ï ¿ ½ e-nï ¿ ½
e-n winding
connected to
terminals A3, A2
( MRI3-IER;
MRI3-ER/ XR)
UN = 3 x U1N K = 1 / 3
ï ¿ ½ 1: 1ï ¿ ½
Neutral-point voltage
( = residual voltage)
terminals A3, A2
( MRI3-IER;
MRI3-ER/ XR)
U1N = UNE K = 1
Table 4.1: Connection of the voltage transformers
18 TD_MRI3_11.07_GB
Figure 4.9: Phase position between the residual voltage and zero sequence current for faulted and non-faulted lines in case of isolated
systems ( sin ï ¿ ½ )
UE - residual voltage
IE - zero sequence current
IC - capacitive component of zero sequence current
IW - resistive component of zero sequence current
By calculating the reactive current component ( sin ï ¿ ½
adjustment) and then comparing the phase angle in
relation to the residual voltage UE, the ER/ XR-relay
type determines whether the line to be protected is
earth-faulted.
On non-earth-faulted lines, the capacitive component
Ic( a) of the total current precedes the residual
voltage by an angle of 90ï ¿ ½ . In case of a faulty line
the capacity current IC( b) lags behind the residual
voltage at 90ï ¿ ½ .
Figure 4.10: Phase position between the residual voltage and zero sequence current for faulted and non-faulted lines in case of
compensated systems ( cos ï ¿ ½ )
UE - residual voltage
IE - zero sequence current
IL - inductive component of zero sequence current
( caused by Petersen coil)
IC - capacitive component of zero sequence current
IW - resistive component of zero sequence current
In compensated mains the earthfault direction cannot
be determined from the reactive current components
because the reactive part of the earth current depends
upon the compensation level of the mains. The ohmic
component of the total current ( calculated by cos ï ¿ ½ adjustment)
is used in order to determine the direction.
The resistive component in the non-faulted line is in
phase with the residual voltage, while the resistive
component in the faulted line is opposite in phase with
the residual voltage.
By means of an efficient digital filter harmonics and
fault transients in the fault current are suppressed. Thus,
the uneven harmonics which, for instance, are caused
an electric arc fault, do not impair the protective function.
19 TB MRI1 09.98 E
4.6 Determining earth short-circuit
fault direction
The SR-relay type is used in solidly-earthed or resistance-
earthed systems for determining earth short-circuit
fault direction. The measuring principle for determining
the direction is based on phase angle measurement
and therefore also on the coincidence-time measurement
between earth current and zero sequence voltage.
The zero sequence voltage U0 required for determining
the earth short-circuit fault direction is generated internally
in the secondary circuit of the voltage transformers.
With SR/ ISR-relay types the zero sequence voltage U0
can be measured directly at the open delta winding
( e-n) . Connection A3/ A2.
4.6.1 Directly ï ¿ ½ earthed system
Most faults in a characteristic angle are predominantly
inductive in character. The characteristic angle between
current and voltage at which the greatest measuring
sensitivity is achieved has therefore been selected
to precede zero sequence voltage U0 by 110ï ¿ ½ .
Figure 4.11: Characteristic angle in solidly earthed-systems ( SOLI)
4.6.2 Resistance ï ¿ ½ earthed system
Most faults in a resistance-earthed system are predominantly
ohmic in character, with a small inductive
part. The characteristic angle for these types of system
has therefore been set at + 170ï ¿ ½ in relation to the zero
sequence voltage U0 ( see Figure 4.12) .
Figure 4.12: Characteristic angle in resistance-earthed systems
( RESI)
The pickup range of the directional element is set by
turning the current indicator at the characteristic angle
through + 90ï ¿ ½ , to ensure reliable determination of the
direction.
Figure 4.13: Adjustable characteristical angle of 45ï ¿ ½ to 309ï ¿ ½
For all other applications the characteristical angle between
45ï ¿ ½ and 309ï ¿ ½ is free selectable
20 TD_MRI3_11.07_GB
4.6.3 Connection possibilities of the voltage
transformers for SR relay types
Application Voltage transformer
connections
3-phase voltage
transformer connected
to terminals
A3, A5, A7, A2
( MRI3-IRSR;
MRI3-ISR;
MRI3-SR)
e-n winding
connected to
terminals A3, A2
( MRI3-ISR;
MRI3-SR)
Neutral-point voltage
( = residual voltage)
terminals A3, A2
( MRI3-ISR;
MRI3-SR)
4.7 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
MRI3, namely , IE>
Measuring range overflow max. L1, L2, L3, E
Setting values:
phase ( I> ; CHAR I> ; tI> ; I> > ; tI> > )
earth ( IE> ; CHAR IE; tIE> ; IE> > ; tIE> > ; UE> )
Current settings
Trip delay
Characteristics
one time for each
parameter
I > ; CHAR I> ; tI> ; I> > ;
tI> > ; LED ï ¿ ½ ï ¿ ½
IE> ; CHAR IE; tIE> ; IE> > ;
tIE> > ; UE>
Current display as second rated repetition
current Iprim ( phase) / Iprim ( earth)
SEC ( 0.001-50.0 kA prim) L1, L2, L3, E
Parameter switch/ external triggering of
the fault recorder
SET1, SET2, B_S2, R_S2,
B_FR, R_FR, S2_FR
P2
LED blinking after activation FLSH, NOFL
Characteristics DEFT, NINV, VINV, EINV,
LINV, RINV
CHAR I>
Characteristics DEFT, NINV, VINV, EINV,
LINV, RINV, RXIDG
CHAR IE>
Reset setting ( only available at inverse
time characteristics)
0s / 60s
I> ; CHAR I> ; tI>
IE> ; CHAR IE> ; tIE>
Relay characteristic angle for pase current
directional feature
RCA in degree ( ï ¿ ½ )
LED ï ¿ ½ ï ¿ ½ ( green)
Warning or Trip at earth fault
measuring ( E- and ER/ XR-types)
TRIP
WARN
IE>
Measured method of the residual
voltage UE 1)
3 PHA ; E-N ; 1: 1
UE>
residual voltage setting voltage in volts UE>
changeover of isolated ( sin ï ¿ ½ )
or compensated ( cos ï ¿ ½ )
networks ( for ER/ XR-type)
SIN
COS
Change over of solidly/ resistance
earthed networks ( SR-type)
SOLI
RESI
Switch failure protection tCBFP
Tripping protection
switch failure protection
CBFP After fault tripping
Nominal frequency f= 50 / f= 60
Blocking of function EXIT until max. setting value LED of blocked
parameter
Slave address of serial interface 1 - 32
RS
Baud-Rate 2) 1200-9600 RS
Parity-Check 2) even odd no RS
Recorded fault data Tripping currents and other
fault data
one time for each phase
L1, L2, L3, E
I> , I> > , IE> , IE> > , UE>
Save parameter? SAV?
Delete failure memory wait
Enquiry failure memory FLT1; FLT2..... L1, L2, L3, E
I> , I> > , IE> , IE> > ,
Trigger signal for the fault recorder TEST, P_UP, A_PI, TRIP FR
Number of fault occurences S = 2, S = 4, S = 8 FR
Display of date and time Y = 99, M = 10, D = 1,
h = 12, m = 2, s = 12
ï ¿ ½
Change over the blocking function PR_B, TR_B und ;
I> , I> > , IE> , IE> > oder
tI> , tI> > , tIE> , tIE> >
1) refer to 4.4
2) only Modbus
22 TD_MRI3_11.07_GB
Function Display shows Pressed push button Corresponding LED
Blocking of the protection function BLOC, NO_B I> , I> > , IE> , IE> >
Save parameter! SAV! for about 3 s
Software version First part ( e.g. D01-)
Sec. part ( e.g. 8.00)
one time for each part
Manual trip TRI? three times
Inquire password PSW?
Relay tripped TRIP
or after fault tripping
Secret password input XXXX
System reset SEG
for about 3 s
Table 5.1: possible indication messages on the display
1) refer to 4.4
2) only Modbus
TD_MRI3_11.07_GB 23
5.2 Setting procedure
After push button 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 push
button the setting values can directly be called up and
changed. Before parameter setting can be started the
relevant password must be entered ( refer to chapter
4.4 of the " MR Digital Multifunctional Relay" description) .
5.3 System parameter
5.3.1 Display of measuring values as
primary quantities ( Iprim phase)
With this parameter it is possible to show the indication
as primary measuring value. For this purpose the
parameter must be set to be equal with the rated primary
CT current. If the parameter is set to " SEK" , the
measuring value is shown as a multiple of the rated
secondary CT current.
Example:
The current transformer used is of 1500/ 5 A. The
flowing current is 1380 A. The parameter is set to
1500 A and on the display " 1380 A" are shown. If
the parameter is set to " SEK" , the value shown on the
display is " 0.92" x In.
Note:
The pick-up value is set to a multiple of the rated secondary
CT current.
5.3.2 Display of earth current as primary
quantity ( Iprim earth)
The parameter of this function is to be set in the same
way as that described under 5.3.1. If the parameter is
not set to " SEK" , to relay types MRI3-X and MRI3-XR it
applies too, that the measuring value is shown as primary
current in ampere. Apart from that the indication
refers to % of IN.
5.3.3 Display of residual voltage UE
as primary quantity ( Uprim/ Usec)
The residual voltage can be shown as primary measuring
value. For this parameter the transformation ratio of
the VT has to be set accordingly. If the parameter is
set to " SEK" , the measuring value is shown as rated
secondary voltage.
Example:
The voltage transformer used is of 10 kV/ 100 V. The
transformation ratio is 100 and this value has to be set
accordingly. If still the rated secondary voltage should
be shown, the parameter is to be set to 1.
5.3.4 Voltage transformer connection for
residual voltage measuring
( 3pha/ e-n/ 1: 1)
Depending on the connection of the voltage transformer
of ER/ XR-relay types three possibilities of the
residual voltage measurement can be chosen
( see chapter 4.5) .
5.3.5 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 the display shows " f= 50" or
" f= 60" . The desired nominal frequency can be adjusted
by or and then stored with .
5.3.6 Display of the activation storage
( FLSH/ NOFL)
If after an activation the existing current drops again
below the pickup value, e.g. I> , without a trip has
been initiated, LED I> signals that an activation has
occurred by flashing fast. The LED keeps flashing until
it is reset again ( push button ) . Flashing can
be suppressed when the parameter is set to NOFL.
24 TD_MRI3_11.07_GB
5.3.7 Parameter switch/ external
triggering of the fault recorder
By means of the parameter-change-over switches it is
possible to activate two different parameter sets.
Switching over of the parameter sets can either be
done by means of software or via the external inputs
RESET or blocking input. Alternatively, the external inputs
can be used for Reset or blocking of the triggering
of the fault recorder.
Softwareparameter
Blocking input
used as
RESET Input
use as
SET1 Blocking input RESET Input
SET2 Blocking input RESET Input
B_S2 Parameter switch RESET Input
R_S2 Blocking input Parameter
switch
B_FR Ext. triggering of
the FR
Reset input
R_FR Blocking input Ext. Trigger for
FR
S2_FR Parameter switch Ext. Trigger for
FR
With the settings SET1 or SET2 the parameter set is
activated by software. Terminals C8/ D8 and D8/ E8
are then available as external reset input or blocking
input.
With the setting B_S2 the blocking input ( D8, E8) is
used as parameter-set change-over switch. With the
setting R_S2 the reset input ( D8, E8) is used as parameter-
set change-over switch. With the setting B_FR
the fault recorder is activated immediately by using the
blocking input. On the front plate the LED FR will then
light up for the duration of the recording. With the setting
R_FR the fault recorder is activated via the reset
input. With the setting S2_FR parameter set 2 can be
activated via the blocking input and/ or the fault recorder
via the reset input.
The relevant function is then activated by applying the
auxiliary voltage to one of the external inputs.
Important note:
When functioning as parameter change over facility,
the external input RESET is not available for resetting.
When using the external input BLOCKING the protection
functions must be deactivated by software blocking
separately ( refer to chapter 5.7.1) .
5.4 Parameter protection
5.4.1 Pickup current for phase
overcurrent element ( I> )
The setting value for this parameter that appears on
the display is related to the nominal current ( IN) of the
relay. This means: pickup current ( Is) = displayed value
x nominal current ( IN) e.g. displayed value = 1.25
then, Is = 1.25 x IN.
5.4.2 Time current characteristics for
phase overcurrent element
( CHAR I> )
By setting this parameter, one of the following 6 messages
appears on the display:
DEFT - Definite Time
NINV - Normal Inverse
VINV - Very Inverse
EINV - Extremely Inverse
RINV - RI-Inverse
LINV - Long Time Inverse
Anyone of these four characteristics can be changed
by using -push buttons, and can be stored by
using -push button.
5.4.3 Trip delay or time factor 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:
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. If a definite time characteristic has
been selected, the display shows the trip delay in seconds.
When selecting an inverse time characteristic,
the time multiplier appears on the display. Both settings
can be charges by push-buttons . When the
time delay or the time multiplier is set out of range
( Text " EXIT" appears on the display) , the low set element
of the overcurrent relay is blocked. The " WARN" -
relay will not be blocked.
TD_MRI3_11.07_GB 25
For the MRI3-version with directional feature, the different
trip time delays or the time multipliers can be
chosen for forward and backward faults.
By setting the trip delay, the actual set value for forward
faults appears on the display first and the LED
under the arrows is alight green. It can be changed
with push button and then stored with push
button . After that, the actual trip delay ( or
time factor) for backward faults appears on the display
by pressing push button and the LED under
the arrows is alight red.
Usually this set value should be set longer than the one
for forward faults, so that the relay obtains its selectivity
during forward faults. If the time delays are set
equally for both forward and backward faults, the relay
trips in both cases with the same time delay,
namely without directional feature.
Note:
When selecting dependent tripping characteristics at
relays with directional phase current detection, attention
must be paid that a clear directional detection will
be assured only after expiry of 40 ms.
5.4.4 Reset setting for all 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 60 s, the tripping
time is only reset after 60 s 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.
5.4.5 Current setting for high set element
( I> > )
The current setting value of this parameter appearing
on the display is related to the rated current of the relay.
This means: I> > = displayed value x IN.
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 ( refer to chapter 5.7.1) .
5.4.6 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.
The setting procedure for forward- or backward faults,
described in chapter 5.4.3, is also valid for the tripping
time of the high set element.
5.4.7 Relay characteristic angle RCA
The characteristic angle for directional feature in the
phase current path can be set by parameter RCA to
15ï ¿ ½ , 27ï ¿ ½ , 38ï ¿ ½ , 49ï ¿ ½ , 61ï ¿ ½ , 72ï ¿ ½ or 83ï ¿ ½ , leading to the
respective reference voltage ( see chapter 4.3) .
5.4.8 Pickup value for residual voltage
UE ( ER/ XR-relay type)
Regardless of the preset earth current, an earth fault is
only identified if the residual voltage exceeds the set
reference value. This value is indicated in volt.
5.4.9 Pickup current for earth fault
element ( IE> )
( Similar to chapter 5.4.1)
The pickup value of X and XR-relay type relates to %
IN.
5.4.10 WARN/ TRIP changeover
( E/ X and ER/ XR-relay type)
A detected earth fault can be parameterized as follows.
After delay time.
a) " warn" only the alarm relay trips
b) " trip" the trip relay trips and tripping values are
stored.
26 TD_MRI3_11.07_GB
5.4.11 Time current characteristics for
earth fault element ( CHAR IE)
( not for ER/ XR-relay type)
By setting this parameter, one of the following 7 messages
appears on the display:
DEFT - Definite Time ( independent overcurrent
time protection)
NINV - Normal inverse ( Type A)
VINV - Very inverse ( Type B)
EINV - Extremely inverse ( Type C)
RINV RI-Inverse
LINV Long Time Inverse
RXID Special characteristic
Anyone of these four characteristics can be chosen by
using -pushbuttons, and can be stored by using
-pushbutton.
5.4.12 Trip delay or time multiplier for
earth fault element ( tIE> > )
( Similar to chapter 5.4.3)
5.4.13 Reset mode for inverse time
tripping in earth current path
( Similar to chapter 5.4.4)
5.4.14 Current setting for high set element
of earth fault supervision ( IE> > )
( Similar to chapter 5.4.5)
The pickup value of X and XR-relay type relates to % IN.
5.4.15 Trip delay for high set element
of earth fault supervision ( tIE> > )
( Similar to chapter 5.4.6)
5.4.16 COS/ SIN Measurement
( ER/ XR-relay type)
Depending on the neutral earthing connection of the
protected system the directional element of the earth
fault relay must be preset to cos ï ¿ ½ or sin ï ¿ ½ measurement.
By pressing the display shows " COS" resp.
" SIN" . The desired measuring principle can be selected
by or and must be entered with password.
5.4.17 SOLI/ RESI changeover
( SR-relay type)
Depending on the method of neutral-point connection
of the system to be protected, the directional element
for the earth-current circuit must be set to " SOLI" ( = solidly
earthed) or " RESI" = ( resistance earthed) .
5.4.18 Block/ Trip ï ¿ ½ time
The block/ trip time serves for detection of a c.b. failure
protection by rear interlocking. It is activated by
setting the blocking input D8/ E8 and by setting the
parameter to TR_B. After the set block/ trip time has
expired, the relay can be tripped if the excitation of a
protective function has been applied the delay time of
which has expired and the blocking function is still active.
If the parameter PR_B is set, the individual protection
stages are blocked ( refer to Chapter 5.7.1) .
5.4.19 Circuit breaker failure protection
tCBFP
The CB failure protection is based on supervision of
phase currents during tripping events. Only after tripping
this protective function becomes active. The test
criterion is whether all phase currents are dropped to
; IE> ; IE> > are simultaneously alight in case of
protective blocking " PR_B" and LEDs tI> ; tI> > ; tIE> ,
tIE> > simultaneously emit light in case of trip
blocking " TR_B" .
ï ¿ ½ Actuation of the key with a one-time entry
of the password will store the set function.
ï ¿ ½ After this actuate the key to call
up the first blockable protection function.
ï ¿ ½ The display will show the text " BLOC" ( the respective
function is blocked) or " NO_B" ( the respective
function is not blocked.
ï ¿ ½ Actuation of the key will store the set
function.
ï ¿ ½ By pressing the pushbutton, all
further protective function that can be blocked are
called one after the other.
After selection of the last blocking function renewed
pressing of the pushbutton switches
to the assignment mode of the output relays.
Function Display LED/ Colour
Blocking of the protection
stage
PR_B I> ; I> > ; IE> ;
IE> >
Blocking of the trip function TR_B tI> ; tI> > ; tIE> ;
tIE> >
I> Overcurrent NO_B I> red
I> > Short circuit BLOC I> > red
IE> Earth current
1st element
NO_B IE> red
IE> > Earth current
2nd element
NO_B IE> > red
tCBFP Circuit breaker
failure protection
NO_B CB green
Table 5.2: Default settings of both parameter sets
Assignment of the output relays:
Unit MRI3 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 in blocking
mode again, the assignment mode is selected.
The relays are assigned as follows: LEDs I> , I> > , IE> ,
IE> > are two-coloured and light up green when the output
relays are assigned as alarm relays and red as
tripping relays.
In addition, the LED ï ¿ ½ ï ¿ ½ also lights up with each adjustment.
Green means forward and red backward direction.
Definition:
Alarm relays are activated at pickup.
Tripping relays are only activated after elapse of the
tripping delay.
TD_MRI3_11.07_GB 29
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 and subsequent
input of the password. By pressing push button
, 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
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 push button for
some time ( abt. 3 s) .
Note:
ï ¿ ½ 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) .
ï ¿ ½ A form is attached to this description where the setting
requested by the customer can be filled-in. This
form is prepared for fax transmission and can be
used for your own reference as well as for telephone
queries.
Relay function Output relays Display- Lighted LED
2 3 4 indication
I> ( V) alarm X _2 __I> ; ï ¿ ½ ï ¿ ½ green
tI> ( V) tripping X 1 ___tI> ; ï ¿ ½ ï ¿ ½ green
I> ( R) alarm X _2 __I> ; ï ¿ ½ ï ¿ ½ red
tI> ( R) tripping X 1 ___tI> ; ï ¿ ½ ï ¿ ½ red
I> > ( V) alarm X __3 _I> > ; ï ¿ ½ ï ¿ ½ green
tI> > ( V) tripping X 1 ___tI> > ; ï ¿ ½ ï ¿ ½ green
I> > ( R) alarm X __3 _I> > ; ï ¿ ½ ï ¿ ½ red
tI> > ( R) tripping X 1 ___tI> > ; ï ¿ ½ ï ¿ ½ red
IE> ( V) alarm X ___4 IE> ; ï ¿ ½ ï ¿ ½ green
tIE> ( V) tripping X 1 ___tIE> ; ï ¿ ½ ï ¿ ½ green
IE> ( R) alarm X ___4 IE> > ; ï ¿ ½ ï ¿ ½ red
tIE> ( R) tripping X 1 ___tIE> > ; ï ¿ ½ ï ¿ ½ red
IE> > ( V) alarm X ___4 IE> > ; ï ¿ ½ ï ¿ ½ green
tIE> > ( V) tripping X 1 ___tIE> > ; ï ¿ ½ ï ¿ ½ green
IE> > ( R) alarm X ___4 IE> > ; ï ¿ ½ ï ¿ ½ red
tIE> > ( R) tripping X 1 ___tIE> > ; ï ¿ ½ ï ¿ ½ red
tCBFP tripping ____C.B.; red
( V) = forward direction;
( R) = backward direction
This way, a tripping relay can be set for
each activation and tripping direction.
Table 5.4: Example of assignment matrix of the output relays ( default settings) .
30 TD_MRI3_11.07_GB
5.8 Setting value calculation
5.8.1 Definite time overcurrent element
Low set element ( I> )
The pickup current setting is determined by the load
capacity of the protected object and by the smallest
fault current within the operating range. The pickup
current is usually selected about 20% for power lines,
about 50% for transformers and motors above the
maximum expected load currents.
The delay of the trip signal is selected with consideration
to the demand on the selectivity according to system
time grading and overload capacity of the protected
object.
High set element ( I> > )
The high set element is normally set to act for near-by
faults. A very good protective reach can be achieved
if the impedance of the protected object results in a
well-defined fault current. In case of a line-transformer
combination the setting values of the high set element
can even be set for the fault inside the transformer.
The time delay for high set element is always independent
to the fault current.
5.8.2 Inverse time overcurrent element
Beside the selection of the time current characteristic
one set value each for the phase current path and
earth current path is adjusted.
Low set element I>
The pickup current is determined according to the
maximum expected load current. For example:
Current transformer ratio: 400/ 5 A
Maximum expected load current: 300 A
Overload coefficient: 1.2 ( assumed)
Starting current setting:
Is = ( 300/ 400) x 1.2 = 0.9 x IN
Time multiplier setting
The time multiplier setting for inverse time overcurrent is
a scale factor for the selected characteristics. The
characteristics for two adjacent relays should have a
time interval of about 0.3 - 0.4 s.
High set element I> >
The high set current setting is set as a multiplier of the
nominal current. The time delay tI> > is always independent
to the fault current.
5.9 Indication of measuring and fault
values
5.9.1 Indication of measuring values
The following measuring quantities can be indicated
on the display during normal service:
ï ¿ ½ Apparent current in phase 1 ( LED L1 green) ,
ï ¿ ½ active current in Phase 1 ( LED L1 and IP green) , *
ï ¿ ½ reactive current in Phase 1 ( LED L1 and IQ green) , *
ï ¿ ½ apparent current in phase 2 ( LED L2 green) ,
ï ¿ ½ active current in Phase 2 ( LED L2 and IP green) , *
ï ¿ ½ reactive current in Phase 2 ( LED L2 and IQ green) , *
ï ¿ ½ apparent current in phase 3 ( LED L3 green) ,
ï ¿ ½ active current in Phase 3 ( LED L3 and IP green) , *
ï ¿ ½ reactive current in Phase 3 ( LED L3 and IQ green) , *
ï ¿ ½ apparent earth current ( LED E green) ,
ï ¿ ½ active earth current ( LED E and IP green) , *
ï ¿ ½ reactive earth current ( LED E and IQ green) , *
ï ¿ ½ residual voltage UR ( LED UE) only at ER/ XR-relay
type,
ï ¿ ½ angle between IE and UE ( only ER/ XR)
( LED E green, LED IE> yellow and LED UE> yellow) .
* only in case that the directional option is built in.
The indicated current measuring values refer to rated
current. ( For MRI3-XR/ X relays the indicated measuring
values refer to % of IN)
TD_MRI3_11.07_GB 31
5.9.2 Units of the measuring values
displayed
The measuring values can optionally be shown in the
display as a multiple of the " sec" rated value ( xln) or as
primary current ( A) . According to this the units of the
display change as follows:
Phase current:
Indication as Range Unit
Secondary current
Active portion IP
Reactive portion IQ
0.00 ï ¿ ½ 40.0
ï ¿ ½ .00 ï ¿ ½ 40
ï ¿ ½ .00 ï ¿ ½ 40.
x In
x In
x In
Primary current .000 ï ¿ ½ 999.
k000 ï ¿ ½ k999
1k00 ï ¿ ½ 9k99
10k0 ï ¿ ½ 99k0
100k ï ¿ ½ 999k
1M00 ï ¿ ½ 2M00
A
kA*
kA
kA
kA
MA
active portion IP ï ¿ ½ .00 ï ¿ ½ ï ¿ ½ 999
ï ¿ ½ k00 ï ¿ ½ ï ¿ ½ k99
ï ¿ ½ 1k0 ï ¿ ½ ï ¿ ½ 9k9
ï ¿ ½ 10k ï ¿ ½ ï ¿ ½ 99k
ï ¿ ½ M10 ï ¿ ½ ï ¿ ½ M99
ï ¿ ½ 1M0 ï ¿ ½ ï ¿ ½ 2M0
A
kA*
kA
kA
MA
MA
Reactive portion IQ ï ¿ ½ .00 ï ¿ ½ ï ¿ ½ 999
ï ¿ ½ k00 ï ¿ ½ ï ¿ ½ k99
ï ¿ ½ 1k0 ï ¿ ½ ï ¿ ½ 9k9
ï ¿ ½ 10k ï ¿ ½ ï ¿ ½ 99k
ï ¿ ½ M10 ï ¿ ½ ï ¿ ½ M99
ï ¿ ½ 1M0 ï ¿ ½ ï ¿ ½ 2M0
A
kA*
kA
kA
MA
MA
* rated current transformer > 2kA
Earth current ( sensitive) :
Indication as Range Unit
Secondary current
Active portion IP
Reactive portion IQ
( X/ XR types)
.000 ï ¿ ½ 15.0
ï ¿ ½ .00 ï ¿ ½ 15
ï ¿ ½ .00 ï ¿ ½ 15
x In
x In
x In
Primary earth
current
00m0 ï ¿ ½ 99m9
100m ï ¿ ½ 999m
.000 ï ¿ ½ 999.
k000 ï ¿ ½ k999
1k00 ï ¿ ½ 9k99
mA*
mA*
A
kA*
kA
Active portion IP ï ¿ ½ 00m - ï ¿ ½ 99m
ï ¿ ½ .10 ï ¿ ½ ï ¿ ½ 999
ï ¿ ½ k00 ï ¿ ½ ï ¿ ½ k99
ï ¿ ½ 1k0 ï ¿ ½ ï ¿ ½ 9k9
mA*
A
kA* *
kA
Reactive portion IQ ï ¿ ½ 00m - ï ¿ ½ 99m
ï ¿ ½ .00 ï ¿ ½ ï ¿ ½ 999
ï ¿ ½ k00 ï ¿ ½ ï ¿ ½ k99
ï ¿ ½ 1k0 ï ¿ ½ ï ¿ ½ 9k9
mA*
A
kA* *
kA
* rated current transformer 0.019kA
* * rated current transformer 20kA
Earth current ( normal) :
Indication as Range Unit
Secondary current
Active portion IP
Reactive portion IQ
( E/ SR/ ER types)
.000 ï ¿ ½ 15.0
ï ¿ ½ .00 ï ¿ ½ 15
ï ¿ ½ .00 ï ¿ ½ 15.
x In
x In
x In
Primary earth
current
.000 ï ¿ ½ 999.
k000 ï ¿ ½ k999
1k00 ï ¿ ½ 9k99
10k0 ï ¿ ½ 99k0
100k ï ¿ ½ 999k
1M00 ï ¿ ½ 2M00
A
kA*
kA
kA
kA
MA
Active portion IP ï ¿ ½ .00 ï ¿ ½ ï ¿ ½ 999
ï ¿ ½ k00 ï ¿ ½ ï ¿ ½ k99
ï ¿ ½ 1k0 ï ¿ ½ ï ¿ ½ 9k9
ï ¿ ½ 10k ï ¿ ½ ï ¿ ½ 99k
ï ¿ ½ M10 ï ¿ ½ ï ¿ ½ M99
ï ¿ ½ 1M0 ï ¿ ½ ï ¿ ½ 2M0
A
kA*
kA
kA
MA
MA
Reactive portion IQ ï ¿ ½ .00 ï ¿ ½ ï ¿ ½ 999
ï ¿ ½ k00 ï ¿ ½ ï ¿ ½ k99
ï ¿ ½ 1k0 ï ¿ ½ ï ¿ ½ 9k9
ï ¿ ½ 10k ï ¿ ½ ï ¿ ½ 99k
ï ¿ ½ M10 ï ¿ ½ ï ¿ ½ M99
ï ¿ ½ 1M0 ï ¿ ½ ï ¿ ½ 2M0
A
kA*
kA
kA
MA
MA
* rated current transformer > 2kA
Earth voltage:
Indication as Range Unit
sec. Voltage 000V ï ¿ ½ 999V V
primary voltage .000 ï ¿ ½ 999V
1K00 ï ¿ ½ 9K99
10K0 ï ¿ ½ 99K9
100K ï ¿ ½ 999K
1M00 ï ¿ ½ 3M00
KV
KV
KV
KV
MV
5.9.3 Indication of fault data
All faults detected by the relay are indicated on the
front plate optically. For this purpose, the four LEDs ( L1,
L2, L3, E) and the four function LEDs ( I> , I> > , IE> ,
IE> > und ï ¿ ½ ï ¿ ½ ) are equipped at MRI3. Not only fault
messages are transmitted, the display also indicates
the tripped protection function. If, for example an
overcurrent occurs, first the corresponding LEDs will
light up. LED I> lights up at the same time. After tripping
the LEDs are lit permanently.
32 TD_MRI3_11.07_GB
5.9.4 Fault memory
When the relay is energized or trips, all fault data and
times are stored in a non-volatile memory manner. The
MRI3 is provided with a fault value recorder for max.
five fault occurrences. In the event of additional trippings
always the oldest data set is written over.
For fault indication not only the trip values are recorded
but also the status of LEDs. Fault values are indicated
when push buttons or are pressed
during normal measuring value indication.
ï ¿ ½ Normal measuring values are selected by pressing
the button.
ï ¿ ½ When then the button is pressed, the latest fault
data set is shown. By repeated pressing the
button the last but one fault data set is shown etc.
For indication of fault data sets abbreviations FLT1,
FLT2, FLT3, ... are displayed ( FLT1 means the latest
fault data set recorded) . At the same time the parameter
set active at the occurrence is shown.
ï ¿ ½ By pressing the fault measuring
values can be scrolled.
ï ¿ ½ By pressing it can be scrolled back to a more
recent fault data set. At first FLT8, FLT7, ... are always
displayed. When fault recording is indicated
( FLT1 etc) , the LEDs flash in compliance with the
stored trip information, i.e. those LEDs which
showed a continuous light when the fault occurred
are now blinking blinking to indicate that it is not a
current fault. LEDs which were blinking blinking during
trip conditions, ( element had picked up) just
briefly flash.
ï ¿ ½ If the relay is still in trip condition and not yet reset
( TRIP is still displayed) , no measuring values can be
shown.
ï ¿ ½ To delete the trip store, the push button combination
and has to be pressed
for about 3s. The display shows ï ¿ ½ waitï ¿ ½ .
Recorded fault values:
Value displayed Relevant LED
Phase currents L1, L2, L3 in I/ In L1, L2, L3
Earth current IE in I/ IEn E
C.B. switching time in s 1) C.B.
Expired tripping time of I>
in % of tI> 2)
I>
Expired tripping time of IE>
in % of tIE> 2)
IE>
Time stamp
Date: Y = 99
M = 04
D = 20
ï ¿ ½
ï ¿ ½
ï ¿ ½
time: h = 11
m = 59
s = 13
ï ¿ ½
ï ¿ ½
ï ¿ ½
Table 5.3
1) C.B. tripping time:
Time between energizing of the trip output relay
and switching of the C.B. ( current and IE> .
5.10 Reset
Unit MRI3 has the following three possibilities to reset
thedisplay of the unit as well as the output relay at
jumper position J3= ON.
Manual Reset
ï ¿ ½ Pressing the push button for some
time ( about 3 s)
Electrical Reset
ï ¿ ½ Through applying auxiliary voltage to C8/ D8
Software Reset
ï ¿ ½ The software reset has the same effect as the
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.
5.10.1 Erasure of fault storage
The fault storage is erased by pressing the key combination
and for about 3 s. At the
display " Wait" appears.
TD_MRI3_11.07_GB 33
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:
ï ¿ ½ The auxiliary power supply rating corresponds to the
auxiliary voltage on site.
ï ¿ ½ The rated current and rated voltage of the relay correspond
to the plant data on site.
ï ¿ ½ The current transformer circuits and voltage transformer
circuits are connected to the relay correctly.
ï ¿ ½ 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 once, the display
shows the first part of the software version of the relay
( e.g. ï ¿ ½ D08-ï ¿ ½ ) . By pressing the push button
twice, the display shows the second part of the software
version of the relay ( e.g. ï ¿ ½ 4.01ï ¿ ½ ) . The software
version should be quoted in all correspondence. Pressing
the 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
again. All output relays should then be activated and
the self supervision alarm relay ( watchdog) be deactivated
one after another with a time interval of
3 second and all LEDs with a delay of 0.5 seconds,
with the self-supervision relay dropping. Thereafter, reset
all output relays back to their normal positions by
pressing the push button ( about 3 s) .
6.3 Checking the set |
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