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Woodward

Manual MRI3 GB

18

DOK-TD-MRI3 Rev.A

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 sig-
nals caused by inductive and capacitive coupling are supressed by an analog R-C filter circuit.
The analog voltage signals are fed to the A/D-converter of the microprocessor and transformed to
digital signals through Sample- and Hold-circuits. The analog signals are sampled at 50 Hz (60 Hz)
with a sampling frequency of 800 Hz (960 Hz), namely, a sampling rate of 1.25 ms (1.04 ms) for
every measuring quantity. (16 scans per period).

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 sup-press 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 ex-
ceeds the pickup value, an alarm is given and after the set trip delay has elapsed, the correspond-
ing trip relay is activated.
The relay setting values for all parameters are stored in a parameter memory (EEPROM - Electri-
cally 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 "watch-dog" timer. In case of a failure the watchdog
timer re-sets the microprocessor and gives an alarm signal, via the output relay "self supervision".

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Содержание MRI3

Страница 1: ...MRI3 Digital multifunctional relay for overcurrent protection Manual MRI3 Revision A...

Страница 2: ...the right to update any portion of this publication at any time Information provided by Woodward Governor Company is believed to be correct and reliable However no responsibility is as sumed by Woodw...

Страница 3: ...y of residual voltage UE as primary quantity Uprim Usec 31 5 3 4 Voltage transformer connection for residual voltage measuring 3pha e n 1 1 31 5 3 5 Nominal frequency 31 5 3 6 Display of the activatio...

Страница 4: ...ple of test circuit for MRI3 relays without directional feature 47 6 4 3 Checking the input circuits and measured values 48 6 4 4 Checking the operating and resetting values of the relay 48 6 4 5 Chec...

Страница 5: ...o element low and high set earth fault protection with definite or inverse time characteristics integrated determination of earth fault direction for application to power system networks with isolated...

Страница 6: ...nsitive earth fault current measuring with or without directional feature X and XR relay type determination of earth short circuit fault direction for systems with solidly earthed or resistance earthe...

Страница 7: ...ring 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 measu...

Страница 8: ...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 lights up g...

Страница 9: ...erter For the unit type with earth fault 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...

Страница 10: ...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 chapte...

Страница 11: ...of par tial 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 b...

Страница 12: ...IX IRE IRX IR IER IXR IRER IRXR ER XR EX ISR IRSR SR Display of measuring val ues 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...

Страница 13: ...ifferent relay types 2 Reset setting for inverse time characteristics in phase current path 3 Reset setting for inverse time characteristics in earth current path Parameter for the fault recorder Rela...

Страница 14: ...Woodward Manual MRI3 GB 14 DOK TD MRI3 Rev A Front plates Figure 3 9 Front plate MRI3 I Figure 3 10 Front plate MRI3 E X...

Страница 15: ...Manual MRI3 GB Woodward DOK TD MRI3 Rev A 15 Figure 3 11 Front plate MRI3 IR Figure 3 12 Front plate MRI3 ER XR...

Страница 16: ...Woodward Manual MRI3 GB 16 DOK TD MRI3 Rev A Figure 3 13 Front plate MRI3 SR Figure 3 14 Front plate MRI3 IRER IRXR and MRI3 IER IXR...

Страница 17: ...n 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 dat...

Страница 18: ...ram 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 possi...

Страница 19: ...ses 4 3 1 Reversal in direction during the activation phase Reversal of the current direction during the activation phase can lead to hyper functions This main ly applies to installations where parall...

Страница 20: ...elation 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 follo...

Страница 21: ...D MRI3 Rev A 21 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 corr...

Страница 22: ...sturbances 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...

Страница 23: ...mers 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...

Страница 24: ...nt ways depending on the voltage transformer connections refer to Table 4 1 Connection of the voltage transformers Total current can be measured by connecting the unit either to a ring core C T or to...

Страница 25: ...current IC b lags behind the residual voltage at 90 Figure 4 10 Phase position between the residual voltage and zero sequence current for faulted and non faulted lines in case of compensated systems...

Страница 26: ...and therefore also on the coincidence time measurement between earth cur rent and zero sequence voltage The zero sequence voltage U0 required for determining the earth short circuit fault direction is...

Страница 27: ...at 170 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 th...

Страница 28: ...uch 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...

Страница 29: ...eature RCA in Grad SELECT RESET LED green Warning or trip at earth fault measuring E and ER XR types TRIP WARN SELECT RESET IE Measured method of the residual voltage UE 1 3 PHA E N 1 1 SELECT RESET U...

Страница 30: ...ESET System reset WW SELECT RESET for about 3 s Table 5 1 possible indication messages on the display 1 refer to 4 4 2 only Modbus 5 2 Setting procedure After push button SELECT RESET has been pressed...

Страница 31: ...o 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...

Страница 32: ..._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 Term...

Страница 33: ...f 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 se lected the display shows the trip...

Страница 34: ...d 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 ch...

Страница 35: ...characteristics can be chosen by using pushbuttons and can be stored by using ENTER pushbutton 5 4 12 Trip delay or time multiplier for earth fault element tIE Similar to chapter 5 4 3 5 4 13 Reset mo...

Страница 36: ...d on supervision of phase currents during tripping events Only af ter tripping this protective function becomes active The test criterion is whether all phase currents are dropped to 1 x IN within tCB...

Страница 37: ...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 at new trigger signal 5 5 3 5 5 3 Adjustment of trigger occurrences There is a choice between four diffe...

Страница 38: ...s are excited and the set tripping time expires Tripping only takes place when a the voltage at the blocking input D8 E8 is reduced b the voltage at the blocking input D8 E8 is applied the tripping ti...

Страница 39: ...only activated after elapse of the tripping delay After the assignment mode has been activated first LED I lights up green Now one or several of the four output relays can be assigned to current elem...

Страница 40: ...ut relays default settings 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...

Страница 41: ...ependent 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...

Страница 42: ...k0 100k 999k 1M00 2M00 A kA kA kA kA MA Active portion IP 00 999 k00 k99 1k0 9k9 10k 99k M10 M99 1M0 2M0 A kA kA kA MA MA Reactive portion IQ 00 999 k00 k99 1k0 9k9 10k 99k M10 M99 1M0 2M0 A kA kA kA...

Страница 43: ...ent 000 999 k000 k999 1k00 9k99 10k0 99k0 100k 999k 1M00 2M00 A kA kA kA kA MA Active portion IP 00 999 k00 k99 1k0 9k9 10k 99k M10 M99 1M0 2M0 A kA kA kA MA MA Reactive portion IQ 00 999 k00 k99 1k0...

Страница 44: ...bbreviations 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 By pressing SELECT RESET the fault measurin...

Страница 45: ...applying auxiliary voltage to C8 D8 Software Reset The software reset has the same effect as the SELECT RESET push button see also communication protocol of RS485 interface The display can only be res...

Страница 46: ...uit 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 TR...

Страница 47: ...tage supply unit adjustable from 0 to 1 2 x Un Only for relays with directional feature timer to measure the operating time Accuracy class 10 ms switching device and test leads and tools 6 4 2 Example...

Страница 48: ...and earth current input circuits in the same manner Accuracy of earth current measuring 3 of measuring value or 0 1 of In for E type 0 01 of In for X type 6 4 5 Checking the relay operating time To c...

Страница 49: ...t relay with relay connection angle of 0 The re lay input currents and their corresponding reference voltages are shown in Table 6 1 also refer to 4 3 If the single phase test circuit as illustrated i...

Страница 50: ...upon the current input I1 The voltage source is to be con nected as provided for in Table 6 1 With an angle setting of 49o leading relay 2 must respond and LED lights up green If the angle is now cha...

Страница 51: ...or testing a relay with earth fault directional feature one of the input energizing quantity voltage shall be applied to the relay with a constant value within its effective range The other input ener...

Страница 52: ...e set to TR_B first value in the blocking menu of the protection functions Chapter 5 7 1 The appertaining Block Trip time should be longer than the set tripping time tI see chapter 5 4 18 Here too a c...

Страница 53: ...ked and the actual power factor may be calculated and compared it with the cos meter indication on the switchboard to verify that the relay is connected to the power system with the correct polarity 6...

Страница 54: ...nd in voltage circuit continuously 1 5 x UN 7 2 Common data Dropout to pickup ratio 97 Dropout to pickup ratio for phase current in range 0 2 x IN to 0 5 x IN 100 Returning time 30 ms Time lag error c...

Страница 55: ...05 10 EXIT inverse time 0 001 0 002 0 005 0 01 0 02 0 05 x IN 0 01 0 02 0 05 IN 0 01 0 02 0 05 0 1 0 2 0 5 1 0 2 0 5 0 10 20 s 0 01 0 02 0 05 0 1 0 2 5 from set value or 0 3 IN 0 3 IN SR 0 03 IN YR 3...

Страница 56: ...2 300 V UN 400 V 3 PHA e n 5 300 V 1 1 5 500 V 1 V 1 V 2 V 2 V 5 V 5 V 5 from set value or 0 5 UN 7 3 5 Block Trip time Block Trip 0 1 2 0 s EXIT 0 01 0 02 0 05 0 1 s 1 or 10 ms 7 3 6 Switch failure...

Страница 57: ...IEC 255 4 or BS 142 Normal Inverse Type A 0 14 1 Very Inverse Type B 13 5 1 Extremely Inverse Type C 80 1 Long Time Inverse 120 1 RI Inverse Time 1 0 339 0 236 RXIDG characteristic 5 8 1 3 Where t tri...

Страница 58: ...1 Determination of earth fault direction MRl3 ER XR Measurement of active current component for compensated systems IE x cos Measurement of reactive current component for isolated systems IE x sin Ang...

Страница 59: ...ormal Inverse Type A Figure 7 2 Very Inverse Type B 1 2 3 4 5 6 7 8 910 20 I IS 0 1 1 10 100 1000 t s tI 0 05 0 1 0 2 0 3 0 4 0 5 0 6 0 8 1 0 1 4 2 0 3 0 4 0 6 0 8 0 10 0 1 2 3 4 5 6 7 8 910 20 I IS 0...

Страница 60: ...C Figure 7 4 RI Inverse 1 2 3 4 5 6 7 8 910 20 I IS 0 01 0 1 1 10 100 1000 t s tI 0 05 0 05 0 1 0 1 0 2 0 3 0 4 0 5 0 6 0 8 1 0 10 0 1 4 2 0 3 0 4 0 6 0 8 0 1 2 3 4 5 6 7 8 910 20 I IS 0 1 1 10 100 t...

Страница 61: ...gure 7 6 RXIDG characteristic 1 2 3 4 5 6 7 8 910 20 I IS 0 1 1 10 100 1000 10000 t s tI 1 0 2 0 10 0 8 0 6 0 5 0 4 0 3 0 0 8 0 6 0 5 0 4 0 3 0 2 0 1 0 05 1 2 3 4 5 6 7 8 910 20 I IS 0 1 1 10 100 t s...

Страница 62: ...ntacts Number of relays dependent on relay type Contacts 2 change over contacts for trip relay 1 change over contact for alarm relays Technical data subject to change without notice 1 10 I IN 0 01 0 1...

Страница 63: ...tive 1 A 5 A 1 solid grounded 1 A 1 5 A 1 solid grounded 1 A sensitive 5 A E1 E5 X1 X5 S1 S5 Y1 Y5 Directional feature in earth path none Rated voltage2 100 V in earth circuit 230 V 400 V R1 R2 R4 Hou...

Страница 64: ...tion parameter Relay type MRI3 I IE IX IRE IRX IR IER IXR IRER IRXR ER XR E X ISR IRSR SR Default settings Actual settings 2 parameter sets X X X X X X X X X X X Set 1 Set 2 Set 1 Set 2 I X X X X X X...

Страница 65: ...setting Actual settings Plugged No plugged X No function X Code jumper Low High range for reset input Low High range for blockage input Default settings Actual settings Default settings Actual settin...

Страница 66: ...Parameter set Set 1 Set 2 Set 1 Set 2 Set 1 Sete 2 Set 1 Set 2 I X X I X X IE X X IE X X tCBFP X X This technical manual is valid for Software version D01 9 03 MRI3 ER IER IRER D20 3 03 MRI3 XR IXR IR...

Страница 67: ...Manual MRI3 GB Woodward DOK TD MRI3 Rev A 67...

Страница 68: ...ermany Postfach 10 07 55 P O Box D 47884 Kempen Germany Phone 49 0 21 52 145 1 Internet www woodward com Sales Phone 49 0 21 52 145 216 or 342 Telefax 49 0 21 52 145 354 e mail salesEMEA_PGD woodward...

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