C&s Mrn3 User manual

High-Tech Range

MRN3- Mains decoupling Relay

C&S Protection & Control Ltd.

TRIP

ENTER

SELECT/RESET

U<<

1/3

U>>

MRN3-1

D/Y

max

min

U>>

U<<

Contents

1. Introduction and application

2. Features and characteristics

3. Design

3.1 Connections

3.1.1 Analog input circuits

3.1.2 Blocking input

3.1.3 Reset input

3.1.4 Output relays

3.1.5 Fault recorder

3.2 Parameter settings

3.3 LEDs

3.4 Front plate

4. Working principle

4.1 Analog circuits

4.2 Digital circuits

4.3 Voltage supervision

4.3.1 Selection of star or delta connection

4.4 Principle of frequency supervision

4.5 Measuring of frequency gradient (MRN3-2)(MRN3-2)

(MRN3-2)(MRN3-2)

(MRN3-2)

4.6 Vector surge supervision (MRN3-1)(MRN3-1)

(MRN3-1)(MRN3-1)

(MRN3-1)

4.6.1 Measuring principle of vector surge

supervision

4.7 Voltage threshold value for frequency

measuring

4.8 Blocking function

5. Operation and settings

5.1 Display

5.2 Setting procedure

5.3 Systemparameter

5.3.1 Display of residual voltage UEas primary

quantity (Uprim/Usec)

5.3.2 Δ/Y - Switch over

5.3.3 Setting of nominal frequency

5.3.4 Display of the activation storage (FLSH/

NOFL)

5.3.5 Parameterswitch / external trigger for the

fault recorder

5.4 Protection parameters

5.4.1 Parameter setting of over and under-

voltage supervision

5.4.2 Number of measuring repetitions (T) for

frequency functions

5.4.3 Threshold of frequency supervision

5.4.4 Tripping delays for the frequency elements

5.4.5 Parameter setting of vector surge

supervision (MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1)

5.4.6 Parameter setting of frequency gradient

(MRN3-3MRN3-3

MRN3-3MRN3-3

MRN3-3)

5.4.7 Voltage threshold value for frequency and

vector surge measuring (df/dt at MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2)

5.4.8 Adjustment of the slave address

5.4.9 Setting of Baud-rate (applies for Modbus

Protocol only)

5.4.10 Setting of parity (applies for Modbus

Protocol only)

5.5 Adjustment of the fault recorder

5.5.1 Number of the fault recordings

5.5.2 Adjustment of trigger occurences

5.5.3 Pre-trigger time (Tpre)

5.6 Adjustment of the clock

5.7 Additional functions

5.7.1 Setting procedure for blocking the

protection functions

5.8 Indication of measuring values

5.8.1 Measuring indication

5.8.2 Min./Max. values

5.8.3 Unit of the measuring values displayed

5.8.4 Indication of fault data

5.9 Fault memory

5.9.1 Reset

5.9.2 Erasure of fault storage

6. Relay testing and commissioning

6.1 Power-On

6.2 Testing the output relays

6.3 Checking the set values

6.4 Secondary injection test

6.4.1 Test equipment

6.5 Example of test circuit

6.5.1 Checking the input circuits and measuring

functions

6.5.2 Checking the operating and resetting values

of the over/undervoltage functions

6.5.3 Checking the relay operating time of the

over/undervoltage functions

6.5.4 Checking the operating and resetting values

of the over/underfrequency functions

6.5.5 Checking the relay operating time of the

over/underfrequency functions

6.5.6 Checking the vector surge function

6.5.7 Checking the external blocking and reset

functions

6.6 Primary injection test

6.7 Maintenance

7. Technical data

7.1 Measuring input circuits

7.2 Common data

7.3 Setting ranges and steps

7.3.1 Interface parameter

7.3.2 Parameters for the fault recorder

7.4 Output relays

8 Order form

1. Introduction and application

The MRN3MRN3

MRN3MRN3

MRN3 is a universal mains decoupling device and

covers the protection requirements from VDEW and most

other utilities for the mains parallel operation of power

stations.

zOver/ and undervoltage protection

zOver/ and underfrequency protection

zExtremely fast decoupling of generator in case of

mains failure ((

((

(MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1))

))

) or

zRate of change of frequency df/dt ((

((

(MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2))

))

)

Because of combination of three protectional functions in

one device the MRN3MRN3

MRN3MRN3

MRN3 is a very compact mains de-

coupling device. Compared to the standardly used single

devices it has a very good price/performance ratio.

For applications where the single protection functions are

required CSPCCSPC

CSPCCSPC

CSPC can offer the single MRMR

MRMR

MR-relays as follows:

zMRU3-1MRU3-1

MRU3-1MRU3-1

MRU3-1 four step independent over-/ and

undervoltage protection (also used for

generator earth fault protection)

zMRU3-2MRU3-2

MRU3-2MRU3-2

MRU3-2 two step independent over-/ and

undervoltage protection with

evaluation of the symmetrical voltage

components

zMRF3MRF3

MRF3MRF3

MRF3 four step independent over/ and

underfrequency protection and two

step frequency gradient supervision

df/dt

zMRG2MRG2

MRG2MRG2

MRG2 generator mains monitor / vector

surge detection

2. Features and characteristics

zMicroprocessor technology with watchdog,

zeffective analog low pass filter for suppressing

harmonics when measuring frequency and vector

surge,

zdigital filtering of the measured values by using

discrete Fourier analysis to suppress higher

harmonics and d.c. components induced by faults or

system operations

zintegrated functions for voltage, frequency and vector

surge in one device as well as single voltage,

frequency and vector surge devices,

ztwo parameter sets,

zvoltage supervision each with two step under-/ and

overvoltage detection

zFrequency supervision with three step under-/ or

overfrequency (user setting)

zCompletely independent time settings for voltage and

frequency supervision

zadjustable voltage threshold value for blocking

frequency and vector surge measuring.

zdisplay of all measuring values and setting

parameters for normal operation as well as tripping

via a alphanumerical display and LEDs

zdisplay of measuring values as primary quantities

zStorage of trip values and switching-off time (tCBFP) of

5 fault occurences (fail-safe of voltage),

zrecording of up to eight fault occurences with time

stamp

zfor blocking the individual functions by the external

blocking input, parameters can be set according to

requirement,

zuser configurable vector surge measurement 1-of-3

or 3-of-3,

zreliable vector surge measuring by exact calculation

algorithm

zsuppression of indication after an activation (LED

flash),

zfree assignment for output relays,

zdisplay of date and time,

zin complience with VDE 0435, part 303 and IEC

255,

zserial data exchange via RS485 interface possible;

alternatively with CSPC RS485 Pro-Open Protocol or

Modbus Protocol.

3.1.1 Analog input circuits

The analog input voltages are galvanically decoupled by

the input transformers of the device, then filtered and

finally fed to the analog digital converter. The measuring

circuits can be applied in star or delta connection (refer

to chapter 4.3.1).

3.1.2 Blocking input

The blocking function can be set according to

requirement. By applying the auxiliary voltage to D8/E8,

the previously set relay functions are blocked (refer to

4.8 and 5.7.1).

3.1.3 Reset input

Please refer to chapter 5.9.1

3.1.4 Output relays

The MRN3MRN3

MRN3MRN3

MRN3 is equipped with 5 output relays. Apart from

the relay for self-supervision, all protective functions can

be optionally assigned :

zRelay 1 : C1, D1, E1 and C2, D2, E2

zRelay 2 : C3, D3, E3 and C4, D4, E4

zRelay 3 : C5, D5, E5

zRelay 4 : C6, D6, E6

zRelay 5 : Signal self supervision (internal fault of the

unit) C7, D7, E7

All trip and alarm relays are working current relays, the

relay for self supervision is an idle current relay.

3.1.4 Output relays

The MRN3MRN3

MRN3MRN3

MRN3 has a fault value recorder which records the

measured analog values as instantaneous values.

The instantaneous values

UL1; UL2; UL3; for star connection

or U12; U23; U21 for delta connection

are scanned at a raster of 1.25 ms (at 50 Hz) and

possible to store 1-8 fault occurences with a total

recording time of 16 s (with 50 Hz) and 13.33 s (with 60

Hz) per channel.

Fig. 3.1 : Connection diagram MRN3-1 and MRN3-2Fig. 3.1 : Connection diagram MRN3-1 and MRN3-2

Fig. 3.1 : Connection diagram MRN3-1 and MRN3-2

Storage division

Independent of the recording time, the entire storage

capacity can be divided int0 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).

Fig. 3.2 : Division of the memory into 8 segments,Fig. 3.2 : Division of the memory into 8 segments,

Fig. 3.2 : Division of the memory into 8 segments,

for examplefor example

for example

Memory space 6 to 4 is occupied.

Memory space 5 is currently being written in

tdt

tf</tf>

f<</f>>

f</f>

tf<</tf>>

tu<</tu>>

E8D8CB

Blocking

input

External

Reset

L3L2L1

Serial Interface

selfsupervision

Alarm

Relay 1

L-/N

L+/L

U</U>

U<</U>>

TRIP

ENTER

SLECT/

REST

tu</tu>

Power

supply

Relay 2

Relay 3

Relay 4

3. Design

3.1 Connections

Blocking function

Parameter Settingarameter Setting

arameter Settingarameter Setting

arameter Setting MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2

U< X X

U<< X X

U> X X

U>> X X

f1 X X

f2 X X

f3 X X

ΔΘ X

df/dt X

Table 3.3 : Blocking functionable 3.3 : Blocking function

able 3.3 : Blocking functionable 3.3 : Blocking function

able 3.3 : Blocking function

Parameters for the fault recorder

Parameter Settingarameter Setting

arameter Settingarameter Setting

arameter Setting MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2

Number of fault X X

events

Trigger events X X

Pre-Triggerzeit Tpre XX

Table 3.4 : Parameters for the fault recorderable 3.4 : Parameters for the fault recorder

able 3.4 : Parameters for the fault recorderable 3.4 : Parameters for the fault recorder

able 3.4 : Parameters for the fault recorder

Additional functions

Parameter Settingarameter Setting

arameter Settingarameter Setting

arameter Setting MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2

Relay assignment X X

Fault recorder X X

Table 3.5 : Additional functionsable 3.5 : Additional functions

able 3.5 : Additional functionsable 3.5 : Additional functions

able 3.5 : Additional functions

Date and time

Parameter Settingarameter Setting

arameter Settingarameter Setting

arameter Setting MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2

Year Y = 99 X X

Month M = 03 X X

Day D = 16 X X

hour h = 07 X X

minute m = 29 X X

second s = 56 X X

Table 3.6 : Date and timeable 3.6 : Date and time

able 3.6 : Date and timeable 3.6 : Date and time

able 3.6 : Date and time

The window for parameter setting is located behind the

measured value display. The parameter window can be

accessed via the <SELECT/RESET> key.

3.2 Parameter settings

System parameter

Parameter Settingarameter Setting

arameter Settingarameter Setting

arameter Setting MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2

Uprim/Usek XX

Δ/Y X X

fN X X

P2/FR X X

LED-Flash X X

Table 3.1 : System parametersable 3.1 : System parameters

able 3.1 : System parametersable 3.1 : System parameters

able 3.1 : System parameters

Protection parameters

Setting parameterSetting parameter

Setting parameter MRMR

MRMR

MRN3-1N3-1

N3-1N3-1

N3-1 MRN3-2MRN3-2

MRN3-2MRN3-2

MRN3-2

U< X X

tU< XX

U<< X X

tU<< XX

U> X X

tU> XX

U>> X X

tU>> XX

TXX

f1XX

tf1 XX

f2XX

tf2 XX

f3XX

tf3 XX

df X

dt X

1/3 X

ΔΘ X

UB<XX

RS485/Slave X X

Baud-Rate* X X

Parity-Check* X X

Table 3.2: Protection parametersable 3.2: Protection parameters

able 3.2: Protection parametersable 3.2: Protection parameters

able 3.2: Protection parameters

* only Modbus

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.

trigger occurrence

recording duration

pre

[s]

Fig. 3.3 : Basic set-up of the fault recorderFig. 3.3 : Basic set-up of the fault recorder

Fig. 3.3 : Basic set-up of the fault recorder

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 (HTL/PL-Soft4). The data is

graphically edited and displayed. Binary tracks are

recorded as well, e.g. activation and trip.

4. Working principle

4.1 Analog circuits

The input voltages are galvanically insulated by the input

transformers. 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 with a sampling frequency of 16 x fN,

namely, a sampling rate of 1.25 ms for every measuring

quantity, at 50 Hz.

4.2 Digital circuits

The essential part of the MRN3MRN3

MRN3MRN3

MRN3 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 voltage in

order to detect a possible fault situation in the protected

object.

For the calculation of the voltage value an efficient digital

filter based on the Fourier Transformation (DFFT-Discrete

Fast Fourier Transformation) is applied to suppress high

frequency harmonics and d.c. components caused by

fault-induced transients or other system disturbances. The

microprocessor continuously compares the measured

values with the preset thresholds stored in the parameter

memory (EEPROM). If a fault occures an alarm is given

and after the set tripping 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 Voltage supervision

The voltage element of MRN3MRN3

MRN3MRN3

MRN3 has the application in

protection of generators, consumers and other electrical

equipment against over/and undervoltage. The relay is

equipped with a two step independent three-phase

overvoltage (U>, U>>) and undervoltage (U<, U<<)

function with completely separate time and voltage

settings.

In delta connection the phase-to-phase voltages and in

star connection the phase-to-neutral voltages are

continuously compared with the preset thresholds.

For the overvoltage supervision the highest, for the

undervoltage supervision the lowest voltage of the three

phases are decisive for energizing.

3.3 LEDs

All LEDs (except LED RS, min. and max.) are two-

coloured. The LEDs on the left side, next to the alpha-

numerical display light up green during measuring and

red after tripping.

The LEDs below the push button <SELECT/RESET> are lit

green during setting and inquiry procedure of the setting

values which are printed on the left side next to the LEDs.

The LEDs will light up red after parametrizing of the

setting values next to their right side.

The LED marked with letters RS lights up during setting of

the slave address of the device for serial data

communication.

The LED marked with the letters FR is alight while the fault

recorder is being adjusted.

3.4 Front plate

TRIP

ENTER

SELECT/RESET

U<<

1/3

U>>

MRN3-1

D/Y

max

min

f1tf1

tf2

tf3

tU>>

tU<<

tU<

tU>

TRIP

ENTER

SELECT/RESET

U<<

U>>

MRN3-2

D/Y

max

min

U>>

U<<

Fig. 3.5 : Front plate MRN3-2Fig. 3.5 : Front plate MRN3-2

Fig. 3.5 : Front plate MRN3-2

Fig. 3.4 : Front plate MRN3-1Fig. 3.4 : Front plate MRN3-1

Fig. 3.4 : Front plate MRN3-1

4.3.1 Selection of star or delta connection

All connections of the input voltage transformers are led

to screw terminals. The nominal voltage of the device is

equal to the nominal voltage of the input transformers.

Dependent on the application the input transformers can

be connected in either delta or star. The connection for

the phase-to-phase voltage is the delta connection. In star

connection the measuring voltage is reduced by 1/√3.

During parameter setting the connection configuration

either Y or Δhas to be adjusted.

Fig. 4.1: Input v.t.s in delta connectionFig. 4.1: Input v.t.s in delta connection

Fig. 4.1: Input v.t.s in delta connection ((

((

(ΔΔ

ΔΔ

Δ))

))

)

Fig. 4.2: Input v.t.s in star connection (Y)Fig. 4.2: Input v.t.s in star connection (Y)

Fig. 4.2: Input v.t.s in star connection (Y)

4.4 Principle of frequency supervision

The frequency element of MRN3 protects electrical

generators, consumers or electrical operating equipment

in general against over- or underfrequency. The relay

has independent three frequency elements f1- f3with a

free choice of parameters, with separate adjustable

pickup values and delay times.

The measuring principle of the frequency supervision is

based on the time measurement of complete cycles,

whereby a new measurement is started at each voltage

zero passage. The influence of harmonics on the

measuring result is thus minimized.

Fig. 4.3: Determination of cycle duration byFig. 4.3: Determination of cycle duration by

Fig. 4.3: Determination of cycle duration by

means of zero passagesmeans of zero passages

means of zero passages.

In order to avoid false tripping during occurence of

interference voltages and phase shifts the relay works with

an adjustable measuring repetition (see chapter 5.4.2)

Frequency tripping is sometimes not desired by low

measured voltages which for instance occur during

alternator acceleration. All frequency supervision

functions can be blocked with the aid of an adjustable

voltage threshold UBin case the measured voltage value

is below this value.

4.5 Measuring of frequency gradient

(MRN3-2)

Electrical generators running in parallel with the mains,

e.g. industrial internal power supply plants, should be

separated from the mains when failure in the intrasystem

occurs for the following reasons:

zIt must be prevented that the electrical generators are

damaged when mains voltage recovering

asynchrone, e.g. after a short interruption.

zThe industrial internal power supply must be

maintained.

A reliable criterion of detecting mains failure is the

measurement of the rate of change of frequency df/dt.

Precondition for this is a load flow via the mains coupling

point. At mains failure the load flow changing then

spontaneously leads to an increasing or decreasing

frequency. At active power deficit of the internal power

station a linear drop of the frequency occurs and a linear

increase occurs at power excess. Typical frequency

gradients during application of “mains decoupling” are in

the range of 0.5 Hz/s up to over 2 Hz/s. The MRN3

detects the instantaneous frequency gradient df/dt of each

mains voltage period in an interval of one half period

each. Through multiple evaluation of the frequency

gradient in sequence the continuity of the directional

change (sign of the frequency gradient) is determined.

Because of this special measuring procedure a high safety

in tripping and thus a high stabilty against transient

processes, e.g. switching procedure are reached. The

total switching off time at mains failure is between 60 ms

and 80 ms depending on the setting.

Sec. Winding of

mains V.T.

U31

U23

U12

CA7

Sec. Winding of

mains V.T.

u(t) T

The rotor displacement angle ϑbetween stator and rotor

is depending of the mechanical moving torque of the

generator shaft. The mechanical shaft power is balanced

with the electrical feeded mains power, and therefore the

synchronous speed keeps constant (Fig. 4.5).

Fig. 4.5: Voltage vectors at mains parallelFig. 4.5: Voltage vectors at mains parallel

Fig. 4.5: Voltage vectors at mains parallel

operationoperation

operation

4.6 Vector surge supervision (MRN3-1)

The vector surge supervision protects synchronous

generators in mains parallel operation due to very fast

decoupling in case of mains failure. Very dangerous are

mains auto reclosings for synchronous generators. The

mains voltage returning after 300 ms can hit the

generator in asynchronous position. A very fast

decoupling is also necessary in case of long time mains

failures. Generally there are two different applications:

a) Only mains parallel operation no singleOnly mains parallel operation no single

Only mains parallel operation no singleOnly mains parallel operation no single

Only mains parallel operation no single

operation:operation:

operation:

In this application the vector surge supervision

protects the generator by tripping the generator

circuit breaker in case of mains failure.

b) Mains parallel operation and singleMains parallel operation and single

Mains parallel operation and singleMains parallel operation and single

Mains parallel operation and single

operation:operation:

operation:

For this application the vector surge supervision trips

the mains circuit breaker. Here it is insured that the

gen.-set is not blocked when it is required as the

emergency set.

A very fast decoupling in case of mains failures for

synchronous generators is known as very difficult. Voltage

supervision units cannot be used because the synchronous

alternator as well as the consumer impedance support the

decreasing voltage.

For this the mains voltage drops only after some 100 ms

below the pickup threshold of voltage supervision relays

and therefore a safe detection of mains auto reclosings is

not possible with this kind of relay.

Frequency relays are partial unsuitable because only a

highly loaded generator decreases its speed within 100

ms. Current relays detect a fault only when shortcircuit

type currents exist, but cannot avoid their development.

Power relays are able to pickup within 200 ms, but they

cannot prevent power to rise to short-circuit values too.

Since power changes are also caused by sudden loaded

alternators, the use of power relays can be problematic.

Whereas the MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 detects mains failures within 60

ms without the restrictions described above because they

are specially designed for applications where very fast

decoupling from the mains is required.

Adding the operating time of a circuit breaker or contactor,

the total disconnection time remains below 150 ms. Basic

requirement for tripping of the generator/mains monitor

is a change in load of more than 15 - 20 % of the rated

load. Slow changes of the system frequency, for instance

at regulating processes (adjustment of speed regulator) do

not cause the relay to trip.

Trippings can also be caused by short-circuits within the

grid, because a voltage vector surge higher than the

preset value can occur. The magnitude of the voltage

vector surge depends on the distance between the short-

circuit and the generator. This function is also of

advantage to the Power Utility Company because the

mains short-circuit capacity and consequently the energy

feeding the short-circuit is limited.

To prevent a possible false tripping the vector surge

measuring can be blocked at a set low input voltage (refer

to 5.4.7). The undervoltage lockout acts faster then the

vector surge measurement.

Vector surge tripping is blocked by a phase loss so that a

VT fault (e.g. faulty VTs fuse) does not cause false tripping.

When switching on the aux. voltage or measuring voltage,

the vector surge supervision is blocked for 5 s (refer to

chapter 4.8).

Note:Note:

Note:

In order to avoid any adverse interference voltage effects,

for instance from contactors or relays, which may cause

overfunctions, MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 should be connected separately

to the busbar.

4.6.1 Measuring principle of vector surge

supervision

When a synchronous generator is loaded, a rotor

displacment angle is build between the terminal voltage

(mains voltage U1) and the synchronous internal voltage

(Up). Therefore a voltage difference ΔU is built between

Up and U1 (Fig. 4.4).

Fig. 4.4: Equivalent circuit at synchronousFig. 4.4: Equivalent circuit at synchronous

Fig. 4.4: Equivalent circuit at synchronous

generator in parallel with the mainsgenerator in parallel with the mains

generator in parallel with the mains

ΔU= .jX

U1Z

Mains

ΔU= l

.jX

Generator Mains / Load

Fig. 4.6: Equivalent circuit at mains failureFig. 4.6: Equivalent circuit at mains failure

Fig. 4.6: Equivalent circuit at mains failure

Fig. 4.7: Voltage vectors at mains failureFig. 4.7: Voltage vectors at mains failure

Fig. 4.7: Voltage vectors at mains failure

In case of mains failure or auto reclosing the generator

suddenly feeds a very high consumer load. The rotor

displacement angle is decreased repeatedly and the

voltage vector U1changes its direction (U1‘) (Fig. 4.6 and

4.7).

Fig. 4.8: Voltage vector surgeFig. 4.8: Voltage vector surge

Fig. 4.8: Voltage vector surge

As shown in the voltage/time diagram the instantaneous

value of the voltage jumps to another value and the phase

position changes. This is named phase or vector surge.

The MRN3-1MRN3-1

MRN3-1MRN3-1

MRN3-1 measures the cycle duration. A new

measuring is started at each voltage zero passage. The

measured cycle duration is internally compared with a

quartz stable reference time and from this the deviation

of the cycle duration of the voltage signal is ascertained.

In case of a vector surge as shown in fig. 4.8, the zero

Application hint

Although the vector surge relay guarantees very fast and

reliable detection of mains failures under nearly all

operational conditions of mains parallel running

alternators, the following borderline cases have to be

considered accordingly:

a) None or only insignificant change of power flow at the

utility connection point during mains failures.

This can occur during peak lopping operation or in CHP

stations (Combined Heat and Power) where the power

flow between power station and the public grid may be

very low. For detection of a vector surge at parallel

running alternators, the load change must be at least 15

- 20 % of the rated power. If the active load at the utility

connection point is regulated to a minimal value and a

high resistance mains failure occurs, then there are no

vector surge nor power and frequency changes and the

mains failure is not detected.

This can only happen if the public grid is disconnected

near the power station and so the alternators are not

additionally loaded by any consumers. At distant mains

failures the synchronous alternators are abruptly loaded

by remaining consumers which leads directly to a vector

surge and so mains failure detection is guaranteed.

If such a situation occurs the following has to be taken into

account:

In case of an undetected mains failure, i.e. with the mains

coupling C.B. closed, the vector surge relay reacts upon

the first load change causing a vector surge and trips the

mains C.B.

For detecting high resistance mains failures a minimum

current relay with an adjustable trip delay can be used. A

trip delay is needed to allow regulating actions where the

current may reach “zero” at the utility connection point.

At high resistance mains failures, the mains coupling C.B.

is tripped by the minimum current relay after the time

delay.

To prevent asynchronous switching on, an automatic

reclosing of the public grid should be not possible during

this time delay.

passage occurs either earlier or later. The established

deviation of the cycle duration is in compliance with the

vector surge angle.

If the vector surge angle exceeds the set value, the relay

trips immediately.

Tripping of the vector surge is blocked in case of loss of

one or more phases of the measuring voltage.

Tripping logic for vector surge measurement:ripping logic for vector surge measurement:

ripping logic for vector surge measurement:ripping logic for vector surge measurement:

ripping logic for vector surge measurement:

The vector surge function of the MRN3-1 supervises vector

surges in all three phases at the same time. Tripping of the

relay can be adjusted for one phase vector surge (more

sensitive measurement). For this the parameter 1/3 has

to be set to “1Ph”. When the parameter 1/3 is set to

“3Ph”, tripping of the vector surge element occurs only if

the vector surge angle exceeds the set value in all three

phases at the same time.

UP~

ΔU’= l’

1.jXdl’1

U’

Mains

Load

Generator

U’1

ΔU’= l’

.jXd

U(t)

Voltage vector surge

(t) u ’(t)

Trip

Dt~ DQ

4.7 Voltage threshold value for frequency

measuring

At low measuring voltages, e.g. during generator start-

up, frequency and vector surge or df/dt-measuring is

perhaps not desired.

By means of the adjustable voltage threshold value UB<,

functions f1- f3, df/dt or ΔΘ are blocked if the measured

voltage falls below the set value.

Blocking function set in compliance with require-

ments :

The MRN3MRN3

MRN3MRN3

MRN3 has an external blocking input. By applying

the auxiliary voltage to input D8/E8, the requested

protection functions of the relay are blocked (refer to

5.7.1).

A further measure could be, that the load regulation at

the utility connection point guarantees a minimum power

flow of 15 - 20 % of rated power.

b) Short circuit type loading of the alternators at distant

mains failures

At any distant mains failure, the remaining consumers

cause sudden short circuit type loading of the power

station generators. The vector surge relay detects the

mains failure in about 60 ms and switches off the mains

coupling C.B. The total switch off time is about 100 - 150

ms. If the generators are provided with an extremely fast

1010

4.8 Blocking function

No.No.

No. DynamicDynamic

DynamicDynamic

Dynamic BehaviourBehaviour

BehaviourBehaviour

Behaviour U</<<U</<<

U</<<U</<<

U</<< U>/>>U>/>>

U>/>>U>/>>

U>/>> ff

f11

1, f, f

, f, f

, f22

2, f, f

, f, f

, f33

3ΔΔ

ΔΔ

ΔΘΘ

ΘΘ

Θdf/dtdf/dt

df/dtdf/dt

df/dt

1 voltage to external free program- free program- free program- free program- free program-

blocking input is mable mable mable mable mable

applied

2 blocking input is released released released after released after released after

released instantaneously instantaneously 1 s 5 s 5 s

3 supply voltage is blocked for blocked for blocked for 1 s blocked for 1 s blocked for 1 s

switched on 200 ms 200 ms

4 3ph measuring volt. released released blocked for 1 s blocked for 5 s blocked for 5 s

is suddenly applied

5 one or several released released blocked blocked blocked

measuring voltages

are switched off

suddenly (phase

failure)

6 measuring voltage released released blocked blocked blocked

smaller UB< (adjust-

able voltage thresh-

old value)

Table 4.1: Dynamic behaviour of MRN3 functionsable 4.1: Dynamic behaviour of MRN3 functions

able 4.1: Dynamic behaviour of MRN3 functionsable 4.1: Dynamic behaviour of MRN3 functions

able 4.1: Dynamic behaviour of MRN3 functions

short circuit protection e.g. able to detect di/dt, the

alternators might be switched off unselectively by the

generator C.B., which is not desireable because the power

supply for the station is endangered and later on

synchronized changeover to the mains is only possible

after manual reset of the overcurrent protection.

To avoid such a situation, the alternator C.B.s must have

a delayed short circuit protection. The time delay must be

long enough so that mains decoupling by the vector surge

relay is guaranteed.

1111

5.1 Display

Function Display shows Pressed pushbutton Corresponding Type of relay

LED

Normal operation CSPC all types

Measured operating values Actual measured value <SELECT/RESET> one time L1, L2, L3,

Min. and max. values of for each value f, min, max

voltage, frequency and

ΔΘ

MRN3-1

vector surge df MRN3-2

Transformer ratio of the CT’s (SEK) 1.01-6500=prim <SELECT/RESET><+><-> L1, L2, L3

Setting values: Y/DELT <SELECT/RESET><+><->

star/delta connection

Parameter switch/ext. Trigger for FR SET1, SET2, B_S2, R_S2, <SELECT/RESET><+><-> P2

B_FR, R_FR, S2_FR

Switch-over LED flash FLSH <SELECT/RESET><+><->

No LED flash NOFL

undervoltage (low set) setting value in volt <SELECT/RESET><+><-> U<

tripping delay of low set element setting value in seconds one time for each value t

undervoltage (high set) setting value in volt <SELECT/RESET><+><-> U<<

tripping delay of high set element setting value in seconds one time for each value t

U<<

overvoltage (low set) setting value in volt <SELECT/RESET><+><-> U>

tripping delay of low set element setting value in seconds one time for each value t

overvoltage (high set) setting value in volt <SELECT/RESET><+><-> U>>

tripping delay of high set element setting value in seconds one time for each value t

U>>

rated frequency setting value in Hz <SELECT/RESET><+><-> f

frequency measuring repitition setting value <SELECT/RESET><+><-> T

frequency element f1 setting value in Hz <SELECT/RESET><+><-> f

tripping delay of frequency element f1 setting value in seconds one time for each value t

frequency element f2 setting value in Hz <SELECT/RESET><+><-> f

tripping delay of frequency element f2 setting value in seconds one time for each value t

frequency element f3 setting value in Hz <SELECT/RESET><+><-> f

tripping delay of frequency element f3 setting value in seconds one time for each value t

1-of-3/3-of-3 measurement 1Ph/3Ph <SELECT/RESET><+><-> 1/3 MRN3-1

threshold for vector surge setting value in degree <SELECT/RESET><+><->

ΔΘ

MRN3-1

setting value df/dt setting value in Hz/s <SELECT/RESET><+><-> df MRN3-2

measuring repitition df/dt setting value in periods one time for each value dt

Blocking EXIT <+> until max. setting value LED of blocked

parameter

Undervoltage blocking of setting value in Volt <SELECT/RESET><+><-> f,

ΔΘ

, df

frequency and vector surge meas-

uring (df/dt for MRN3-2)

Slave address of serial interface 1 - 32 <SELECT/RESET><+><-> RS

Baud-Rate

1200-9600 <SELECT/RESET><+><-> RS

Parity-Check

even odd no <SELECT/RESET><+><-> RS

Recorded fault data: tripping values in Volt <SELECT/RESET><+><-> L1, L2, L3,

star—connection: one time for each phase U<, U<<,

U1, U2, U3 U>, U>>

delta-connection: tripping values in Volt <SELECT/RESET><+><-> L1, L2, L3

U12, U23, U31 one time for each phase U<, U<<,

U>, U>>

frequency tripping values in Hz <SELECT/RESET><+><-> f, f1, f2, f3

one time for each phase

rate of change of frequency tripping value in Hz/s <SELECT/RESET><+><-> df MRN3-2

vector surge tripping value in degree <SELECT/RESET><+><->

ΔΘ

+L1,L2 or L3 MRN3-1

one time for each phase

Delet failure memory wait <-><SELECT/RESET>

Enquiry failure memory FLT1; FLT2.... <+><-> L1, L2, L3, U<

U<<, U>, U>>

f, Ddf/dt,

ΔΘ

Save parameter? SAV? <ENTER>

Save parameter! SAV! <ENTER> for about 3 s

5. Operation and settings

only Modbus

1212

Function Display shows Pressed pushbutton Corresponding Type of relay

LED

Trigger signal for the fault recorder TEST, P_UP, A_PI, TRIP <SELECT/RESET><+><-> FR

Number of fault occurences S=2, S=4, S=8 <SELECT/RESET><+><-> FR

Display of date and time Y=99, M=10, D=1, <SELECT/RESET><+><->



h=12, m=2, s=12

Software version First part (e.g. D02-) <TRIP>

Sec. part (e.g. 6.01) one time for each part

Manual trip TRI? <TRIP>

three times

Inquire password PSW? <SELECT/RESET>/

<+>/<->/<ENTER>

Relay tripped TRIP <TRIP> or fault tripping

Secret password input XXXX <SELECT/RESET>/

<+>/<->/<ENTER>

System reset CSPC <SELECT/RESET>

for about 3 s

Table 5.1: possible indication messages on the displayable 5.1: possible indication messages on the display

able 5.1: possible indication messages on the displayable 5.1: possible indication messages on the display

able 5.1: possible indication messages on the display

5.2 Setting procedure

In this paragraph the settings for all relay parameters are

described in detail. For parameter setting a password has

to be entered first (please refer to 4.4 of description “MR-

Digital Multifunctional Relays”).

5.3 Systemparameter

5.3.1 Display of residual voltage UEas

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/100V. 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.

5.3.2 ΔΔ

ΔΔ

Δ/Y - Switch over

Depending on the mains voltage conditions, the input

voltage transformers can be operated in delta or Y

connection. Change-overs are effected via the <+> and

the <-> keys and stored with <ENTER>.

5.3.3 Setting of nominal frequency

For proper functioning it is necessary to first adjust the

rated frequency (50 oder 60 Hz).

For this a distinction has to be made between the settings

v = 50 Hz / f = 50 Hz or v = 60 Hz / f = 60 Hz

The difference lies in the method of voltage measuring.

With the setting “v” = 50/60 Hz voltage measuring is

independent of the existing frequency. This means, the

voltage value can be correctly measured between 30 Hz

and 80 Hz without adverse effects from the frequency.

With the setting “f” = 50/60 Hz the measured voltage

value is influenced by the frequency. (see Table 5.2)

This difference in settings is required for the fault

recorder. If the fault recorder is to be used, the setting

must be f = 50 Hz or f = 60 Hz.

The different designations “f” or “v” have no influence on

any of the other functions.

All frequency functions are determined by setting the

nominal frequency, i.e. whether the set frequency

thresholds are evaluated as over or under frequency (see

also chapter 5.4.4). Also the cycle duration (20 ms at 50

Hz and 16.67 ms at 60 Hz) derives from this setting which

determines the minimum tripping delay for frequenc y

elements f1- f3with an adjustable multiplier (see also

chapter 5.4.5).

During setting of the nominal frequency a value in Hz is

shown on the display.

Declination of measuring value at 50Hz

Declination of measuring value at 60Hz

[%]

100.5

100.0

44 46 48 50 52 54 56

[Hz]

99.5

99.0

98.5

98.0

97.5

54 56 58 60 62 64 66

[Hz]

[%]

100.5

100.0

99.5

99.0

98.5

98.0

97.5

1313

SettingSetting

Setting v = 50v = 50

v = 50v = 50

v = 50 f = 50f = 50

f = 50f = 50

f = 50 v = 60v = 60

v = 60v = 60

v = 60 f = 60f = 60

f = 60f = 60

f = 60

Rated frequency 50 Hz 50 Hz 60 Hz 60 Hz

Influence on voltage none 0.5..1%/Hz (see none 0.5..1%/Hz (see

measurement table 5.2) table 5.2)

Fault recorder Recording Recording Recording Recording

distorted** distorted*** distorted** distorted***

Influence on all other functions none none none none

Table 5.2 : Deviation of measured value at 50 or 60 Hzable 5.2 : Deviation of measured value at 50 or 60 Hz

able 5.2 : Deviation of measured value at 50 or 60 Hzable 5.2 : Deviation of measured value at 50 or 60 Hz

able 5.2 : Deviation of measured value at 50 or 60 Hz

* Setting is important for differentiation between over-and underfrequency.

** Sample rate is variably adjusted to the momentarily measured frequency. 16 samples are always measured in one period.

*** Sample rate setting is fixed to 50 Hz or 60 Hz. 16 samples per 20 ms or 16.67 ms are always measured.

5.3.4 Display of the activation storage

(FLSH/NOFLE)

If after an activation the existing current drops again

below the pickup value, e.g. U<, without a trip has been

initiated, LED U< signals that an activation has occured by

flashing fast. The LED keeps flashing until it is reset again

(push button <RESET>. Flashing can be suppressed

when the parameter is set to NOFL.

5.3.5 Parameterswitch / external trigger

for 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 and for the triggering of the fault

recorder.

SoftwareSoftware

Software Blocking inputBlocking input

Blocking inputBlocking input

Blocking input RESET inputRESET input

RESET inputRESET input

RESET input

parameterparameter

parameter used asused as

used asused as

used as used asused as

used asused as

used 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 External trigger- RESET input

ing of the fault

recorder

R_FR Blocking input External trigg-

ering of the

fault recorder

R_FR Parameter switch External trigg-

ering of the

fault recorder

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 immediatelay 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. 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 Protection parameters

5.4.1 Parameter setting of over-and

undervoltage supervision

The setting procedure is guided by two coloured LEDs.

During setting of the voltage thresholds the LEDs U<,

U<<, U> and U>> are lit green. During setting of the

trip delays tU>, tU>>, tU< and tU<< the according LEDs light

up red.

Thresholds of the voltage supervisionThresholds of the voltage supervision

Thresholds of the voltage supervision

During setting of the threshold U>, U>>, U< and U<<

the displays shows the voltages directly in volt. The

thresholds can be changed by the <+><-> push buttons

and stored with <ENTER>.

The undervoltage supervision (U< and U<<) as well as

the overvoltage supervision (U> and U>>) can be

deactivated by setting the threshold to “EXIT”.

1414

Tripping delay of voltage supervisionripping delay of voltage supervision

ripping delay of voltage supervisionripping delay of voltage supervision

ripping delay of voltage supervision

During setting of the tripping delays tU<, tU<<, tU> and tU>>

the display shows the value directly in seconds. The

tripping delay is changed via the push button <+> and

<-> in the range of 0.04 s to 50 s and can be stored with

the push button <ENTER>.

When setting the tripping delay to “EXIT” the value is infinit

meaning only warning, no tripping.

5.4.2 Number of measuring repetitions (T)

for frequency functions

In order to avoid false tripping of the unit at short voltage

drops of the system voltage or interference voltages,

MRN3 works with an adjustable measuring repetition.

When the instantaneous frequency measuring value

exceeds (at overfrequency) or falls below (at

uncremented, otherwise the counter is decremented

down to the minimum value of 0. Only when the counter

exceeds th value adjusted at T, alarm is given and after the

tripping delay of the frequency element has elapsed the

tripping command is given.

The setting range for T is between 2-99.

Recommendation for setting :Recommendation for setting :

Recommendation for setting :

For short tripping times, e.g. for machine prptection or for

mains decoupling T should be set in the range from 2-5.

At precision measurements, e.g. exact measurement of

the system frequency a setting of T in the range from 5-

10 is recommended.

5.4.3 Threshold of frequency supervision

The frequency supervision of MRN3MRN3

MRN3MRN3

MRN3 has three frequency

elements independent from each other. Acc. to settin the

pickup value above or below the nominal frequency,

these elements can be used for over- or underfrequency

supervision.

Dependent on the preset nominal frequency fNthe pickup

values from 30 Hz up to 70 Hz at fN= 50 Hz and from

40 Hz to 80 Hz at fN= 60 Hz can be set. During settin

of the pickup values f1-f3the display shows the values in

Hz. A value of for instance 49.8 Hz is indicated with

“4980”.

The function of the individual frequency elements can be

deactivated by settin the pickup values to “EXIT”. The

setting value “EXIT” corresponds to the rated frequency.

5.4.4 Tripping delays for the frequency

elements

Tripping delays tf1-tf3 of the four frequency elements can

be set independently from tf1min-50 s. The minimum

tripping delay tf1min of the relay depends upon the number

of set measuring repetitions T (periods) and amounts to :

f,min

2....49 (T+1).20 ms

50...69 (T-49).50 ms + 1 s

70...99 (T-69).100 ms + 2 s

When setting the tripping delay to “EXIT” by pressing push

button <+> up to the maximum setting value, the

corresponding tripping relay is blocked. Pickup of the

frequency element is however displayed on the front plate

by the corresponding LED, an assigned alarm relay is also

activated. This setting applies to 50 Hz and 60 Hz.

5.4.5 Parameter setting of vector surge

supervision MRN3-1)

Both the vector surge angle ΔΘ as well as the tripping

logic concerning the vector surge have to be adjusted for

a vector surge supervision.

If the tripping logic is set to 1-of-3 (=”1Ph” on the

display), the relay trips as soon as the measured vector

surge angle has exceeded the set value ΔΘ in one of the

three phases. This is the more sensitive adjustment when

compared with the three phase tripping logic 3-of-3

(=”3Ph” on the display), where tripping occurs only if the

vector surge angle exceeds the set value in all three

phases.

We recommend to choose the one phase tripping logic

“1Ph”. Only if this adjustment is too sensitive, adjustment

“3Ph” should be used.

The recommended setting of the vector surge angle ΔΘ

in a low impedance mains is 4-6 degrees. This setting is

sufficient in most cases, because low impedace mains do

not have a vector surge greater than this value. In case of

an auto reclosing, this value is exceeded. In high

impedance mains the setting should be 100to 120to

avoid failure tripping when switching on or switching off

big consumer loads.

The vector surge function of this device can be checked

as follows :

a) Generator in isolated operation: Switching off and on

of loads (approx. 20% of the nominal generator

capacity) must trip the relay. Later in normal isolated

operation the tripping of the relay is inhibited.

b) In mains parallel operation switching on and

switching off of consumer loads and controlling the

governor of the prime mover should not trip the

relay.

If possible the test described under a) and b) should be

double checked by a real auto reclosing.

Threshold for the vector surge supervisionThreshold for the vector surge supervision

Threshold for the vector surge supervision

When the pickup value of the vector surge supervision is

set, a value in angular degree is indicated at athe display.

The pickup value requested can be adjusted by

pushbuttons <+> and <-> in the range of 20to 220.

LED ΔΘ lights up red during this procedure.

1515

5.4.6 Parameter setting of frequency

gradient (MRN3-2)

The pickup value of frequency gradient (parameter df)

can be set between 0.2 to 10 Hz/s. The number of

measuring repetitions (parameter dt) can be set between

2-64 cycles. This parameter defines the number of df/dt

measurements, which have to exceed the set value, before

tripping.

Setting information :

The power difference after mains failure causes a change

in frequency, which can approximately be calculated as

follows :

df fN

= . ΔP

dt TA

with

fN = rated frequency in Hz

TA = starting time at rated torque

ΔP = per unit power deficit with reference to the

rated active power of the generator

If the inertia time constant is known and a power

difference given, the frequency gradient can be estimated

by the a.m. equation. At a supposed power difference of

20% and an inertia time constant of 10 s, the frequency

gradient is 1 Hz/s.

To prevent false trippings at loading, deloading or failure

signals, we would recommend a setting value for dt of

minimum 4 cycles.

5.4.7 Voltage threshold value for

frequency and vector surge

measuring (df/dt at MRN3-2)

Correct frequency measuring or vector surge measuring

cannot be obtained if the system voltage is very low, for

instance during generator start up or voltage failure. False

tripping of the MRN3MRN3

MRN3MRN3

MRN3 in such cases is prevented by an

adjustable voltage threshold UB. If the system voltage is

below this threshold, these functions of the relay are

blocked.

During adjustment of UB< LEDs f and ΔΘ or df light up in

the upper display part.

5.4.8 Adjustment of the slave address

By pressing push buttons <+> and <-> the slave address

can be set in the range of 1-32. During this adjustment

the LED RS lights up.

5.4.9 Setting of Baud-rate (applies for

Modbus Protocol only)

Different transmission rates (Baud rate) can be set for data

transmission via Modbus Protocol.

The rate can be changed by push buttons <+> and <-

> and saved by pressing <ENTER>.

5.4.10 Setting of parity (applies for

Modbus Protocol only)

The following three parity settings are possible :

z“even” = even

z“odd” = odd

z“no” = no parity check

The setting can be changed by push buttons <+> and <-

> and saved by pressing <ENTER>.

5.5 Adjustment of the fault recorder

The MRI3 is equipped with a fault recorder (see chapter

3.7). Three parameters can be determined.

5.5.1 Number of the fault recordings

The max. recording time is 16 s at 50 Hz or 13.33 s at

60 Hz.

The number of max. recordings requested has to be

determined in advance. There is a choice of (1)* 2, (3)*

4 or (7)* 8 recordings and dependent on this the duration

of the individual fault recordings is defined, i.e.

(1)* 2 recordings for a duration of 8 s (with 50 Hz)

(6.66 s with 60 Hz)

(3)* 4 recordings for a duration of 4 s (with 50 Ha)

(3.33 s with 60 Hz)

(7)* 8 recordings for a duration of 2 s (with 50 Hz)

(1.66 s with 60 Hz)

* is written over when a new trigger signal arrives

Caution :

If the fault recorder is used, the frequency should be set

to f = 50 Hz or f = 60 Hz (see chapter 5.3.3).

5.5.2 Adjustment of trigger occurences

There is a choice between four different occurences :

P_UP (PickUP) Storage is initiated after recognition

of a general activation.

TRIP Storage is initiated after a trip has

occured.

A_PI (After Pickup) Storage is initiated after the last

activation threshold was fallen short

of.

TEST Storing is activated by simultaneous

actuation of the keys <+> and <->.

During the recording time the display

shows “Test”.

5.5.3 Pre-trigger time (Tpre)

By the time Tpre it is determined which period of time prior

to the trigger occurence should be stored as well. It is

possible to adjust a time between 0.05s and the max.

recording interval (2, 4 and 8s). With keys <+> and <-

> the values can be changed and with <ENTER> be

saved.

1616

5.6 Adjustment of the clock

When adjusting the date and time, LED l light up. The

adjustment method is as follows:

Date : Year Y = 00

Month M = 00

Day D = 00

Time : Hour h = 00

Minute m = 00

Second s = 00

The clock starts with the set date and time as soon as the

supply voltage is switched on. The time is safeguarded

against short-term voltage failures (min. 6 minutes).

Note :

The window for parameter setting is located behind the

measured value display. The parameter window can be

accessed via the <SELECT/RESET> key.

5.7 Additional functions

5.7.1 Setting procedure for blocking the

protection functions

The blocking function of the MRN3MRN3

MRN3MRN3

MRN3 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:

zWhen 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 U< lights red.

zBy pressing push buttons <+> <-> the value

displayed can be changed.

zThe changed value is stored by pressing <ENTER>

and entering the password.

zBy pressing the <SELECT/RESET> push button, any

further protection function which can be blocked is

displayed.

zThereafter the menu is left by pressing <SELECT/

RESET> again.

zIf the <SELECT/RESET> key is actuated again, the

blocking menu is left and the assignment mode is

accessed∧.

FunctionFunction

Function DescriptionDescription

DescriptionDescription

Description DisplayDisplay

DisplayDisplay

Display LEDLED

LEDLED

LED

U< Undervoltage step 1 BLOC red

U<< Undervoltage step 2 BLOCK red

U> Overvoltage step 1 NO_B red

U>> Overvoltage step 2 NO_B red

f1 Frequency step 1 BLOC red

f2 Frequency step 2 BLOC red

f3 Frequenzstufe 3 NO_B red

DQ Vector surge BLOC red

df/dt Frequency changing rate BLOC red

Table 5.3 : Blockadefunktion fur twei parametersatzeable 5.3 : Blockadefunktion fur twei parametersatze

able 5.3 : Blockadefunktion fur twei parametersatzeable 5.3 : Blockadefunktion fur twei parametersatze

able 5.3 : Blockadefunktion fur twei parametersatze

Assignment of the output relays :

Unit MRN3MRN3

MRN3MRN3

MRN3 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 voltage

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 U<, U<<, U>, and U>>,

f1, f2, f3 are two-coloured and light up green when the

output relays are assigned as alarm relays and tU<, tU<<,

tU>, tU>>, tf1, tf2, tf3 df/dt and ΔΘ red as tripping relays.

Definition :Definition :

Definition :

Alarm relaysAlarm relays

Alarm relays are activated at pickup.

Tripping relaysripping relays

ripping relaysripping relays

ripping relays are only activated after elapse of the

tripping delay.

After the assignment mode has been activated, first LED

U< lights up green. Now one or several of the four output

relays can be assigned to under voltage element U< as

alarm relays. At the same time the selected alarm relays

for under voltage element 1 are indicated on the display.

Indication “1_ _ _” means that output relay 1 is assigned

to this under voltage element. When the display shows

“_ _ _”, no alarm relay is assigned to this under voltage

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 U< light up red. The output relays can now

be assigned to this voltage 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 :

zThe function of jumper J2 described in general

description “MR Digital Multifunctional Relays” does

not apply for MRN3MRN3

MRN3MRN3

MRN3. 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.

1717

Relay functionRelay function

Relay function Output relayOutput relay

Output relayOutput relay

Output relay Display IndicationDisplay Indication

Display IndicationDisplay Indication

Display Indication Corresponding LEDCorresponding LED

Corresponding LEDCorresponding LED

Corresponding LED

122

233

344

U< alarm X _2_ _ U<; green

tU< tripping X 1_ _ _ tU< red

U<< alarm X _2_ _ U<< green

tU<< tripping X 1_ _ _ tU<< red

U> alarm X _2_ _ U> green

tU> tripping X 1_ _ _ tU> red

U>> alarm X _2_ _ U>> green

tU>> tripping X 1_ _ _ tU>> red

f1 alarm X _ _3_ f1 green

tf1 tripping X 1_ _ _ tf1 red

f2 alarm X _ _3_ f2 green

tf2 tripping X 1_ _ _ tf2 red

f3 alarm X _ _3_ f3 green

tf3 tripping X 1_ _ _ tf3 red

ΔΘ tripping X _ _ _4 ΔΘ red

df/dt tripping X _ _ _4 df/dt red

Table 5.4 :able 5.4 :

able 5.4 :able 5.4 :

able 5.4 : Example of assignment matrix of the output relay (default settings).Example of assignment matrix of the output relay (default settings).

Example of assignment matrix of the output relay (default settings).Example of assignment matrix of the output relay (default settings).

Example of assignment matrix of the output relay (default settings).

5.8 Indication of measuring values

5.8.1 Measuring indication

In normal operation the following measuring values can

be displayed.

Voltages (LED L1, L2, L3 green)

zIn star connection all phase-to-neutral voltages

zIn delta connection all phase-to-phase voltages

Frequency (LED f green MRN3-1)

Vector surge (LED ΔΘ green)

Frequency gradient df/dt (LED df green;

MRN3-2MRN3-2

MRN3-2)

Min. and max. values prior to the last reset :

zFrequency (LED f + min or f + max)

zVector surge (LED ΔΘ + min or ΔΘ + max)

zFrequency gradient (LED df + min or df + max)

5.8.2 Min./Max.- values

The MRN3MRN3

MRN3MRN3

MRN3 offers a minimum/maximum storage each for

the measuring values of the vector surge as well as the

frequency gradient. These min./max. values are mainly

used to appraise the system quality. Always the highest

and lowest values of each cycleeach cycle

each cycleeach cycle

each cycle are measured and

stored until the next reset.

Min./max. frequency measuring :

The MRN3MRN3

MRN3MRN3

MRN3 ascertains the actual frequency from each

cycle of the system voltage. These measuring values are

entered into the min./max. storage. The latest entered

min./max. values replace the previously stored values.

Dependent on the adjustment of dt and tripping delay, it

is possible that the stored min./max. values are higher

than the tripping threshold without causing a trip. The

reason for this is storage of instantaneous values.

Min./Max. measuring of the frequency gradient:

The procedure described above applies also to storage of

min./max. values of df/dt measurement. Since each

instantaneous df/dt value is stored, high values can occur

which, however, do not cause any tripping.

This can for instance happen during switching procedures

where high positive and negative df/dt values occur, but

they do not cause any tripping due to the special

measuring method.

Min./max. vector surge measuring :

The procedure described above applies also to storage of

min./max. values of vector surge measuring. Since each

instantaneous ΔΘ value is stored, also here high values

are possible which, however, do not cause any tripping.

These min./max. measurements are of great advantage

for long-time analysis of the grid quality.

As to operation :

After each reset (ref. 5.9.1) the min./max. storages are

cleared. As from this instant there is no time limit for the

min./max. storage until the next reset.

By repeatedly pressing the <SELECT/RESET> push

button, the measuring values of the min./max. storage

can be queried. The respective LEDs light up at the same

time; e.g. during minimum frequency is displayed, LEDs

“f” and “min” light up.

1818

5.8.3 Unit of the measuring values

displayed

The measuring values can optionally be shown in the

display as a multiple of the “sec” rated value (x In) or as

primary current (A). According to this the units of the

display change as follows :

Indication asIndication as

Indication as RangeRange

RangeRange

Range UnitUnit

UnitUnit

Unit

sec. voltage 000V - 999V V

primary voltage .000 - 999V V

1K00 - 9K99 KV

10K0 - 99K9 KV

100K - 999K KV

1M00 - 3M00 MV

Table 5.5 : Units of the displayable 5.5 : Units of the display

able 5.5 : Units of the displayable 5.5 : Units of the display

able 5.5 : Units of the display

5.8.4 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,

f) and the four function LEDs (U<, U<<, U>, U>>, f1,

f2, f3, ΔΘ and df/dt) are equipped at MRN3. Not only

fault messages are transmitted, the display also indicates

the tripped protection function. If, for example an

overcurrent occurs, first the respective phase LED will

light up. LED I> lights up at the same time. After trippiung

the LEDs are lit permanently.

5.9 Fault memory

When the relay is energized or is energized or trips, all

fault data and times are stored in a non-volatile memory

manner, The MRN3 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.

zNormal measuring values are selected by pressing

the <SELECT/RESET> button.

zWhen 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 occurence is shown.

zBy pressing <SELECT/RESET> the fault measuring

values can be scrolled.

zBy 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 occured 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.

zIf the relay is still in trip condition and not yet reset

(TRIP is still displayed), no measuring values can be

shown.

zTo delete the trip store, the push button combination

<SWLWCT/RESET> and <->, has to be pressed for

about 3s. The display shows “wait.

Recorded fault data :

MeasuringMeasuring

Measuring Displayed valueDisplayed value

Displayed valueDisplayed value

Displayed value Correspon-Correspon-

Correspon-Correspon-

Correspon-

ding LEDding LED

ding LED

Voltage L1; L2; L3; L1/L2; L1; L2; L3

L2/L3; L3/L1

Frequency f; f min f max f; min; max

Frequency df df

changing rate

Vector surge DQ DQ

Time stamp

Date : Y = 99 

M = 03 

D = 10 

Time : h = 17 

m = 21 

s = 14 

5.9.1 Reset

All relays have the following three possibilities to reset the

display of the unit as well as the output relay at jumper

position J3=ON.

Manual Reset

zPressing the push button <SELECT/RESET> for some

time (about 3 s)

Electrical Reset

zThrough applying auxiliary voltage to C8/D8

Software Reset

zThe 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.

5.9.2 Erasure of fault storage

To delete the trip store, the push button combination

<SELEC/RESET> and <-> has to be pressed for about

3s. The display shows “wait”.

1919

6. Relay testing and commissioning

The following test instructions should 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:

zthe auxiliary power supply rating corresponds to the

auxiliary voltage on site.

zthe rated frequency and rated voltage of the relay

correspond to the plant data on site.

zthe voltage transformer circuits are connected to the

relay correctly.

zall 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 to the rated data

on the type plate.

Switch on the auxiliary power supply to the relay and

check that the message “CSPC” appears on the display

and the self supervision alarm relay (watchdog) is

energized (Contact terminals D7 and E7 closed). It may

happen that the relay is tripped because of under- voltage

condition after power-on. (The message “TRIP” on the

display and LED L1, L2, L3 and U< light up red). An

undervoltage condition has been detected after power-

on, because no input voltages are applied to the relay. In

this case:

zPress the push button <ENTER>, thus entering into

the setting mode. Now set the parameters U< and

U<< to “EXIT” to block the undervoltage functions.

After that, press the <SELECT/RESET> for app. 3 s

to reset the LEDs and “TRIP” message.

zThe undervoltage tripping after power on can also be

eliminated by applying three phase rated voltages

after power-on and reset the LED and “TRIP”

message.

zApply auxiliary voltage to the external blocking input

(Terminals E8/D8) to inhibit the undervoltage

functions (refer to 6.5) and press the <SELECT/

RESET> for app. 3 s to reset the LEDs and “TRIP”

message.

6.2 Testing the output relays

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 should then

be activated and the self supervision alarm relay

(watchdog) be deenergized one after another with a time

interval of 1 second. Thereafter, reset all output relays

back to their normal positions by pressing the push button

<SELECT/RESET>.

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 4.3 of the description “MR - Digital

Multifunctional relays”.

As relay input energizing quantities, three phase voltage

should be applied to MRN3 relay input circuits. Depending

on the system conditions and the voltage transformer

used, three voltages can be connected to the relay input

circuits with either star or delta connection. In case of a

star connection the phase-to-neutral voltage will be

applied to the voltage input circuits, while the phase-to-

phase voltageswill be connected to the voltage input

circuits in case of a delta connection. The voltage input

connection must be set as a parameter, and should

correspond with the actual voltage input connection:

Star connection : Phase-to-neutral voltages will be

measured and evaluated.

Delta connection : Phase-to-phase voltages will be

measured and evaluated.

6.4 Secondary injection test

6.4.1 Test equipment

zVoltmeter and frequency meter with class 1 or better,

zauxiliary power supply with the voltage corresponding

to the rated data on the type plate,

zthree-phase voltage supply unit with frequency

regulation (Voltage : adjustable from 0 to 2 x UN;

Frequency : adjustabe from 40 - 70 Hz),

ztimer to measure the operating time (Accuracy class

±10ms),

zswitching device and

zTest leads and tools

2020

6.5 Example of test circuit

For testing of the MRN3MRN3

MRN3MRN3

MRN3 relay, a three phase voltage

source with adjustable voltage and frequency is required

Figure 6.1 shows an example of a three-phase test circuit

energizing the MRN3MRN3

MRN3MRN3

MRN3 relay during test. The three phase

voltages are applied to the relay in Y-connection.

For testing the vector surge function of the relay, a test

circuit which can produce phase angle change (vector

surge) is required to simulate mains failures (please refer

to chapter 6.5.6).

For testing the df/dt function of the relay, a special test

equipment is required, which produces a constant rate of

change of frequency.

6.5.1 Checking the input circuits and

measuring functions

Apply three voltages of rated value to the voltage input

circuits (terminals A3 - A8) of the relay. Check the

measured voltages, frequency and vector surge on the

display by pressing the push button <SELECT/RESET>

repeatedly. The displayed measuring voltages (shown in

Volt) are dependent on the wiring of the input voltage

converters and the set transformation ratio.

The voltages are indicated on the display in volts

At YAt Y

At Y--

-connection:connection:

connection:connection:

connection:

zPhase-to-neutral voltages: LED L1, L2, L3

At Delta-connection:At Delta-connection:

At Delta-connection:

zPhase-to-phase voltages: LED L1+L2, L2+L3,

L3+L1

The frequency is indicated on the display in Hz: LED f

(system frequency = 50.01Hz, Indication = 5001) The

vector surge is indicated on the display in degrees (for

MRN3-1MRN3-1

MRN3-1): LED ΔΘ (Indication ΔΘ in °)

The rate of change of frequency (LED df) is indicated on

the display in Hz/s (for MRN3-2)

Change the voltages around the rated value and check

the measured voltages on the display. Change the system

frequency around the rated frequency and check the

measured frequency on the display.

Compare the voltage and frequency on display with the

signal on voltmeter and frequency meter. The deviation

for the voltage must not exceed 1% and for frequency <

<0.01 Hz.

By using an RMS-RMS-

RMS-RMS-

RMS-metering instrument, a greater

deviation may be observed if the test voltage contains

harmonics. Because the MRN3MRN3

MRN3MRN3

MRN3 relay measures only the

fundamental component of the input signals, the

Blocking

input

External

Reset

L-/N

L+/L

L+/L L-/N L+/L

MRN1

U3E

U2E

U1E

Warning

Alarm

DQ df/dt

Trip Signal

selfsupervision

Serial Interface

Start

Timer

Voltage Supply

Stop

1. Variable voltage source

with frequency regulation

2. Switching device

3. Voltmeter

4. Timer

5. Relay under test

Fig. 6.1 : TFig. 6.1 : T

Fig. 6.1 : Test circuitest circuit

est circuitest circuit

est circuit

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