Type MFVU 21Digital Definite Time, Frequency Relay

2Type MFVU 21Digital Definite Time, Frequency Relay

Features Two under or over frequency

stages

Fully independent or differentialpick-up/drop-off operation

Wide frequency setting range

Built-in timer for each stage

Wide operating voltage range

Positive calibrated settings bymeans of switches

Test facility

Application andDescriptionThe type MFVU 21 digital, definitetime relay consists of two fullyindependent frequency monitoringcircuits which can be used as eitherunder or over frequency protection.In addition, the two operatingcircuits can be used together toprovide pick-up and drop-off atdifferent frequencies.

The relay is suitable for anyapplication in industrial plants andto generators where definite timeunder or over frequency protectionis required.

In addition multi-stage schemesusing several relays can beprovided for load shedding andreconnection applications.

Integral timers are provided for eachoperating circuit and separateeletromagnetic auxiliary relaysensure maximum flexibility ofapplication.

Figures 2 and 3 are block diagramsshowing relays suitable for use withac and dc auxiliary power supplyvoltages respectively.

Inputs, Outputs andIndicationsThree terminals are provided for thevoltage input to the frequencymonitoring circuits of which two areselected depending on themaximum voltage which can appearat the terminals. The voltage inputconnections must be either phase-to-phase or phase-to-neutral and themaximum permissible input voltagefor each pair of terminals is detailed

Figure 1: Type MFVU 21 relaywithdrawn from case

3T1 T T1

T2 T T2

2

3

6

1

5

4

9

13

11

10

14

12

28

27

26

17

18

Test

ResetSet

SetReset

ResetSet

2

1

RL11

RL12

RL21

RL22

Reset

RL22

RL12

PU : DO2

1

+

0V

V

V

VV

V

t1

t2

f2 : f1

f2 : f2

Case earth1 2

3 4

5 6

7

9 10

11 12

13 14

15 16

17 18

19 20

21 22

23 24

25 26

27 28

Module terminalblock viewed from rear

8

L

NVx

< f1

< f2

> f1

> f2

f2

f1

Note 1

(a) CT shorting links makebefore (b) & (c) disconnect

(b) Short terminals break before (c)

(c) Long terminals

in Figure 4. The relay can besupplied for use with either ac or dcauxiliary supply voltage.

For applications in which operationof the relay and subsequent loadshedding is not desired, when thesystem voltage drops to a very lowvalue, it is recommended to drivethe auxiliary voltage from the samesource as the measured voltage.With this method, the relay stopsoperating when the voltage dropsbelow approximately 65%. When adifferent voltage cut-off is specified,it is recommended to use a separateundervoltage relay MVTI with theunderfrequency relay MFVU 21,suitable for dc auxiliary supplyvoltage.

Separate electromagnetic auxiliaryoutput relays are provided for eachfrequency monitoring circuit.Each output relay provided twochangeover contacts.

Front plate mounted LEDs areprovided to indicate the operationof each of the two monitoringcircuits. These can be reset by apush-button which can be operatedwith the front cover of the relay inposition.

Operation of the relay can be testedby means of a test push-buttonwhich energises the output relaysand LEDs after the set time delayswhich the channels set tounderfrequency operation.Access to the test push-buttonrequires removal of the front cover.This test facility should only normallybe used with the relay trip circuitsisolated.

Relay SettingsThe two frequency detector circuitshave set frequencies defined

by f1 = 1T1

and f2 = 1T1

where T1 and T2 are the periods ofthe operation frequencies in secondsand are set by thumb-wheel switcheson the relay frontplate.

In each case, T is selectablebetween 0.09999s and 0.00200 insteps of 0.00001s. This correspondsto a frequency setting range of10.001 to 500Hz.

Switches are provided on the relayfront plate to select and, also, toinhibit the operation of eitherchannel.

Note: The channel on/off switchmust be in the off position beforeattempting to alter the T settingwhile the relay is in service.

A further switch is provided to selecteither independent operation of thetwo channels or configuration of thetwo channels with f2 as pick-up andf1 as drop-off. In this configuration,output auxiliary relay RL2 energisesat pick-up (setting f2) and de-energises at drop-off (setting f1).The output auxiliary relay RL1energises and de-energises at the f1setting.

Definite time delays t1 and t2 for thetwo channels are set by means ofswitches. Each channel is adjustablebetween 0.1 and 21.15s in steps of0.05s.

It should be noted that it is possible,by use of the thumbwheel switches,to set frequencies higher than500Hz, but beyond 500Hz theoperation characteristics of the relaycannot be guaranteed.

Figure 2: Type MFVU 21 relay: Block diagram, ac relay

4T1 T T1

T2 T T2

Note 1

(a) CT shorting links makebefore (b) & (c) disconnect

(b) Short terminals break before (c)

(c) Long terminals

2

3

6

1

5

4

9

13

11

10

14

12

28

27

26

17

18

Test

ResetSet

SetReset

ResetSet

2

1

RL11

RL12

RL21

RL22

Reset

RL22

RL12

PU : DO2

1

+

0V

V

V

VV

V

t1

t2

f2 : f1

f2 : f2

Case earth1 2

3 4

5 6

7

9 10

11 12

13 14

15 16

17 18

19 20

21 22

23 24

25 26

27 28

Module terminalblock viewed from rear

8

L/+

N/

Vx+

A: Auxilliary supply unit required for ac and dc power suppliesfor Vx>125V and is for use with 110V dc relay

A

< f1

< f2

> f1

> f2

f2

f1

Input at terminals 2826

Input at terminals 2827

0 10 20 30 40 50 60 Hz1530

100

200

300

400

V

Figure 4: Maximum permissible input voltage with different terminal connections.

Figure 3: Type MFVU 21 relay: block diagram, dc relay

5Technical Data

AC voltage ratings Phase-to-phase or phase-to-neutralSee Figure 4 for maximumadmissible voltage value

Minimum operating voltage(terminals 28-27): 10V

Minimum operating voltage(terminals 28-26): 20V

Auxiliary voltage rating

Operating rangeVx Vmin Vmax(ac) Vmax(dc) Frequency

(ac version)

24 21.6 26.4 28.8 50-60Hz30 24 33 36 50-60Hz48 38.4 52.8 57.6 50-60Hz110 88 121 132 50-60Hz125 110 137.5 150 50-60Hz

Vx Vmin Vmax Frequency

(Uses 110V dc relay withauxiliary power supply unit) ac 160/220 128 242 50-60Hz

(Uses 110V dc relay with auxiliarypower supply unit) dc 160/250 128 275

Settings

T1 and T2 0.09999s to 0.00200s adjustablein steps of 0.00001s independently

(f1 =1T1

Hz) (f2 =1T2

Hz)

Contacts

2 changeover self reset - trip output f12 changeover self reset - trip output f2

Ratings

Carry continuously 5A

Make and carry for 0.5s 30A at 110V dc

Breaking capacity (105 operations) 0.3A at 110V dc L/R = 40ms

Burdens

Measuring circuits 1VA at 150V and 50Hz

Auxiliary supply:relay de-energised < 30mA (dc)

< 60mA (ac)relay energised As above plus 2W

6Accuracy

Variation in auxiliary supply 3%

Variation in temperature (25C to +55C) 3%

Frequency detector

Measuring time 50ms

Reset time

797

177

Push buttonprojection 10 max.

32 21225 min.

157 max.

11103

99

52

23.54 holes 4.4

168 159

Panel cut-out:Flush mounting fixing details.

All dimensions in mm.

Flush mounting.

Reset

Environmental withstand

TemperatureIEC 6006821/IEC 6006822 Storage and transit 25C to +70C

Operating 25C to +55C

HumidityIEC 60529 56 days (dust protected)

VibrationIEC 60255211 0.5g between 10Hz and 150Hz

Mechanical durability

Loaded contact 10,000 operations minimumUnloaded contact 100,000 operations minimum

Figure 5: Case outline size 4

Cases

MFVU 21 relays are housed in size4 cases (see Figure 5)

Information Requiredwith Order

Auxiliary supply voltage ac or dc

St Leonards Works, Stafford, ST17 4LX EnglandTel: 44 (0) 1785 223251 Fax: 44 (0) 1785 212232 Email: pcs.enquiries@tde.alstom.com Internet: www.alstom.com

2000 ALSTOM T&D Protection & Control Ltd

Our policy is one of continuous development. Accordingly the design of our products may change at any time. Whilst every effort is made to produce up to date literature, this brochure shouldonly be regarded as a guide and is intended for information purposes only. Its contents do not constitute an offer for sale or advice on the application of any product referred to in it.

ALSTOM T&D Protection & Control Ltd cannot be held responsible for any reliance on any decisions taken on its contents without specific advice.

Publication R6061G 010010 CPS Printed in England.

ALSTOM T&D Protection & Control Ltd