Woodward MRR1 User manual

MRR1 – Multifunctional Generator Rotor
Protection Relay
Manual MRR1 (Revision A)

Woodward Manual MRR1 GB
2 DOK-TD-MRR1 Rev.A
Woodward Governor Company reserves 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 Woodward Governor Company unless otherwise expressly undertaken.
© Woodward 1994-2008

Manual MRR1 GB Woodward
DOK-TD-MRR1 Rev.A 3
Contents
1.Introduction and application.......................................................................4
2.Features and characteristics ......................................................................4
3.Design...........................................................................................................5
3.1Connections ........................................................................................................................5
3.1.1Output relays ...................................................................................................................5
3.1.2Blocking input ..................................................................................................................5
3.1.3External reset input .........................................................................................................5
3.2Display.................................................................................................................................6
3.3LEDs....................................................................................................................................7
4.Working principle.........................................................................................8
4.1Rotor earth fault protection..................................................................................................8
4.2Excitation current supervision ...........................................................................................10
5.Operation and settings..............................................................................12
5.1Setting and measuring values...........................................................................................12
5.2Setting procedure..............................................................................................................13
5.2.1Pickup value and tripping delay ....................................................................................13
5.2.2Setting of slave address................................................................................................13
5.2.3Reset .............................................................................................................................14
5.3Blocking of protective functions and assignment of the output relays ............................15
5.3.1Blocking of protective functions.....................................................................................15
5.3.2Assignment of the output relays....................................................................................16
6.Relay testing and commissioning............................................................17
6.1Power-On ..........................................................................................................................17
6.2Testing the output relays...................................................................................................17
6.3Checking the set values ....................................................................................................17
6.4Secondary injection test ....................................................................................................17
6.4.1Test equipment..............................................................................................................17
6.4.2Example of a test circuit ................................................................................................18
6.4.3Checking the insulation measuring circuit.....................................................................18
6.4.4Checking the excitation current circuit ..........................................................................18
6.4.5Checking the pickup value and reset value ..................................................................19
6.4.6Checking the tripping delay...........................................................................................19
6.5Real injection test..............................................................................................................19
6.6Maintenance......................................................................................................................19
7.Technical data............................................................................................20
7.1Measuring input circuits ....................................................................................................20
7.2Common data....................................................................................................................20
7.3System data and test specifications..................................................................................20
7.4Setting ranges and steps ..................................................................................................21
7.5Order Form........................................................................................................................22

Woodward Manual MRR1 GB
4 DOK-TD-MRR1 Rev.A
1.Introduction and application
The generator rotor protection relay MRR1 com-bines rotor earth fault protection, excitation over-
and undercurrent protection as well as rotating diode failure protection.
Thus providing a powerful protection regarding the rotor of synchronous generators, covering the
following ANSI codes:
37 DC undercurrent relay
40 Field relay
58 Rectification failure relay
64 Ground detector relay
76 DC over current relay
The MRR1 is recommended for synchronous generators and motors above 1 MVA rating.
The rotor earth fault element detects high- and low resistance earth faults of the rotor winding. It is
equipped with two stages, one for alarm, one for trip.
The excitation current protection element super-vises the DC excitation current of brushless excitor
machines. The protective functions are: Undercurrent, over current and ripple detection for diode
failure protection.
2.Features and characteristics
Besides features described in the general MR-description, MRR1 provides:
Detection of high impedance earth faults with a test frequency of 0.5 Hz
Short circuit and overvoltage proof measuring input for the earth fault protection
Excitor current measurement galvanically isolated via Hall-transducer, measuring range
0 to 20 A
Display of insulation resistance
Display of the excitation current
Excitation current over- and undercurrent protection with independent settings for current
and delay time
Detection of diode failures by supervision of the ripple component of the excitation current
Two stage supervision of the rotor insulation resistance with independent settings for
resistance and time delay
Two trip relays, one for excitation under- and over current, one for diode failure detection
Digital inputs for blocking and for remote reset
Programmable function of the blocking input
Programmable assignment of protective functions to output relays
Remote interfacing via RS485

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DOK-TD-MRR1 Rev.A 5
3.Design
3.1 Connections
Figure 3.1: Connection diagram
3.1.1 Output relays
The MRR1 has 5 output relays. Relays 1 and 2 are provided with two change-over contacts each,
the other relays with one change-over contact each.
Function of relays 1 - 4 is programmable. Status of self-supervision is indicated by relay 5. The
relays are allocated to the following contacts :
Output relay 1: C1, D1, E1 and C2, D2, E2
Output relay 2: C3, D3, E3 and C4, D4, E4
Output relay 3: C5, D5, E5
Output relay 4: C6, D6, E6
Output relay 5: Self-supervision (internal fault of the relay) C7, D7, E7
All relays are normally off, only the self-supervision relay is normally on.
3.1.2 Blocking input
When required to inhibit the selected functions to be blocked, the auxiliary voltage has to be
switched to D8/E8 (please also refer to chapter 5.3.1).
3.1.3 External reset input
See chapter 5.2.2

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3.2 Display
Function
Anzeige in LED / colour
Measuring
values
Measuring value of the insulation resistance kR green
Measuring value of the excitation current A Iegreen
Ripple component of the excitation current % Irgreen
Setting val-
ues
Insulation resistance alarm element kRWgreen
Tripping time for insulation resistance alarm element s tRW red
Insulation resistance trip element kR< green
Tripping time for insulation resistance trip element s tR< red
Setting for excitation undercurrent element A Ie< green
Delay time setting for excitation undercurrent element s tIe< red
Setting for excitation over current element A Ie> green
Delay time setting for excitation over current element s tIe> red
Setting for ripple component of the excitation current % Irgreen
Delay time setting for the ripple component element s tIR red
Slave address for the RS485 interface RS yellow
Table 3.1: Possibilities for indication by the display
Functions can be called via push button ENTER.
For changing to the next value use push button <SELECT/RESET>.

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DOK-TD-MRR1 Rev.A 7
3.3 LEDs
All LEDs (except LED RS) are two-colored. The LEDs on the left side, next to the alphanumerical
display light up green during measuring and red after tripping.
The LEDs beyond the push button <SELECT/RESET> are lit green during setting and inquiry pro-
cedure of the setting values which are printed on the left side next to the LEDs. The LEDs will light
up red after activation 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 (RS485).
Figure 3.2: Front plate

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4.Working principle
4.1 Rotor earth fault protection
A single earth fault on the field windings of a synchronous generator produces no immediate dam-
aging effect. It must be detected and removed be-cause of the possibility of a second earth fault
that could short a part of the field winding and cause severe damage.
MRR1 provides an alarm and a trip element for the rotor earth fault protection.
The insulation resistance measurement system of the MRR1 can be used for synchronous genera-
tors of both types, with and without brushes.
It works with a low frequency alternating test voltage (0,51 Hz, ±24V) which is connected via slip
rings to the main excitor winding and to rotor earth (ref. to connection diagram).
The low frequency of the test voltage is used to avoid malfunction due to the field-to-earth
capacitance (CE) which can reach values up to 1 µF on large generators. The test voltage is fed
via two current limiting resistors (RV) to both ends of the field winding. If only one end of the field
winding can be connected, the terminals A3 and A4 should be paralleled.
The earth current is measured via shunt resistor RM.
Figure 4.1: Measuring principle of the earth current
The insulation resistance measurement is based on the subsequent measurement of the shunt
resistor voltage of two consecutive half cycles, i.e. positive and negative test voltage.
From the differential voltage between the positive and negative measuring voltage at the end of
each half cycle the insulation resistance is calculated. Thus avoiding wrong measurement due to
the earth capacitance and possible voltage offsets.

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DOK-TD-MRR1 Rev.A 9
Figure 4.2 explains the measuring principle:
Figure 4.2: Measuring principle

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10 DOK-TD-MRR1 Rev.A
4.2 Excitation current supervision
Failures in the excitation system of a synchronous generator may cause severe damage to the ro-
tor of the generator as well as undesirable operating conditions:
Failure Effect
AVR failure; undercurrent
in parallel operation
Excessive reactive current flow to the generator
System stability endangered
AVR failure; undercurrent
in single operation
System under voltage if
System stability endangered
AVR failure; over current
in parallel operation
Excessive reactive current flow to the system
Thermal overload of the exciter winding
AVR failure; over current
in single operation
System overvoltage if in single operation
Thermal overload of the exciter winding
AVR failure; over current Rotor damage due to overheating
Rotating diode open Increased excitation current
overheating of the rotor system
Rotating diode short Excessive excitation current
severe overheating of the rotor system
Table 4.1: Effects of different failures
Excitation current supervision:
The excitation current supervision comprises of three elements: under- and over current and ripple
component measurement. Those elements cover above mentioned failures of the generator
excitation system.
Undercurrent protection:
The undercurrent protection is a definite time element. The current setting (Ie<) should be chosen
at about 70% of the no load excitation current of the generator. The time delay tIe< should be set to
a value well above the AVR response time (e.g. 2 s), to allow transient de-excitation of the genera-
tor due to voltage regulator action.
If required the MRR1 may be blocked by connecting supply voltage to terminals D8/E8. This might
be necessary during start up of the generator.
Over current protection:
The over current protection is a definite time element. The current setting (Ie>) should be chosen at
about 120% of the nominal excitation current of the generator. The time delay tIe> should be set to
a value well above the AVR response time and required short circuit times (e.g. 3 s), to allow
transient over excitation of the generator due to voltage regulator action.

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DOK-TD-MRR1 Rev.A 11
Diode failure protection:
The diode failure protection is based on the measurement of the ripple component of the excitation
current related to the mean value of the excitation current as per following formula:
󰇛%󰇜, 
,

· 100
Typical values for Ir:
All diodes all right: Ir ≈15...20%
One diode open: Ir ≈110%
One diode short: Ir ≈200%
The setting of Ir> should be chosen at about 40% to 50%. The tripping time tIr should be instanta-
neous or with only a small delay, e.g. 200 ms. In case of a diode short the rotor system is extreme-
ly endangered!
Hint!
The required settings depend on various factors like:
- Required power factor of the generator
- Required minimum short circuit duration etc.

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12 DOK-TD-MRR1 Rev.A
5.Operation and settings
5.1 Setting and measuring values
By pressing push button <SELECT/RESET> al-ways the next value in sequence is displayed. At
first measuring values are shown followed by the setting values. If the relay is in trip condition, dis-
play of setting values can only be achieved after pressing push button <ENTER>. Display of mea-
suring and setting values is ended and the relay resets when push button <SELECT/RESET> is
pressed for a certain time. In the display “WW" appears again.
Measuring value LED
R Insulation resistance green
IeExciter current green
I
r
Ripple component of the exciter current green
Table 5.1: Measuring values
Setting values LED
RWPickup value of insulation resistance supervision (warning) green
tRW Tripping delay for R< red
R< Pickup value of insulation resistance supervision (trip) green
tR< Tripping delay for R<< red
Ie< Pickup value exciter undercurrent element green
tIe< Tripping delay for I< red
Ie> Pickup value exciter over current element green
tIe> Tripping delay for I> red
Ir Pickup value for ripple current supervision green
tI
r
Tripping delay for tI
r
red
RS Slave address of the serial interface yellow
Table 5.2: Setting values

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DOK-TD-MRR1 Rev.A 13
5.2 Setting procedure
Before changing a parameter a password has to be entered first (see chapter 4.4 of description
"MR-digital multifunctional relay).
The gradual changing procedure is clearly explained in the following table:
Display Procedure Relevant push
button
Actual
value
Value change <+> or <->
Changed value Initiate storing yes:<ENTER>
no: <SELECT>
SAV? Checkback: really storing? yes:<ENTER>
no: <SELECT>
PSW? Enter password, a combination of 4 push
buttons
<ENTER>, <+>, <-> or
<SELECT/RESET>
SAV! When password correct: storing of new
parameter
Hold <ENTER> for 2 s
Table 5.3: Changing of parameters and storing
5.2.1 Pickup value and tripping delay
For each element the pickup value and tripping de-lay can be adjusted. When the set pickup value
is either exceeded or falls below, the corresponding LED flashes. After elaps of the tripping delay
trip of the relay is initiated. Should the duration of pickup be shorter than the set tripping delay, this
is signaled by periodical flashing of the corresponding LED. This indication can be cancelled by
pressing push button <SELECT/RESET>.
Complete blocking of an element :
An element is blocked when the parameter is set to EXIT by pressing repeatedly push button <->
or <+>.
Warning only:
Should only excitation of an element be intended and not tripping, the respective trip delay can be
set to EXIT by push button <+> (pressed repeatedly) and then pickup only is indicated by the
LEDs.
5.2.2 Setting of slave address
When pressing push buttons <+> and <-> the slave address can be set in the range from 1 - 32,
hereby LED RS lights up.

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5.2.3 Reset
MRR1 has the following 3 possibilities to reset the display as well as the output relays at jumper
position J3 = ON.
(see also chapter 4.2 of description "MR-Digital Multifunctional Relays".
Manual reset
by pressing push button <SELECT/RESET> for some time (approx. 3 seconds.)
Electrical reset
by applying aux. voltage to C8/D8
Software reset
software reset has the same effect as the <SELECT/RESET> push button. Please also
refer here to the communication protocol of RS 485 interface.
Resetting the display is only possible when there is no pickup anymore (otherwise signal "TRIP"
will still remain in the display and the relays remain activated). Resetting the relay does not change
the preset parameters.

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DOK-TD-MRR1 Rev.A 15
5.3 Blocking of protective functions and assignment of the
output relays
By pressing the <ENTER> and <TRIP> push buttons simultaneously the menu for blocking of pro-
tective functions and assignment of the output relays is activated. The assignments can either be
done by using the push buttons on the front plate or via serial interface RS485. The assignment
mode can be terminated at any time by pressing <SELECT/RESET> push button for some time
(3s).
5.3.1 Blocking of protective functions
After activating the menu for blocking of protective functions the following functions can be blocked
selectively:
Earth fault protection (warning)
Earth fault protection (trip)
Excitation undercurrent
Excitation over current
Rotating diode failure protection
By repeatedly pressing the <SELECT/RESET> push button, the functions to be blocked are
selected one after another. The corresponding LED lights up simultaneously. The display shows
"BLOC" or "NO_B". BLOC means this function is blocked, if auxiliary voltage is applied to the
external blocking input. NO_B means applying aux. volt-age to the external blocking input has no
influence on this protection function.
Blocking or not blocking a function can be selected with the push buttons <+> or < > and be stored
with <ENTER> after input of the password. Storage of the new setting to be done as shown in table
5.3.
Display Blocking function Selection with push button
BLOC yes <+>
NO_B no <->
Table 5.4: Effect of the blocking input
With the default setting all functions shown in above table are blocked via input D8/E8.
After all functions have been displayed and push button <SELECT/RESET> has been pressed, the
relay switches over to the assignment mode of the output relays.

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16 DOK-TD-MRR1 Rev.A
5.3.2 Assignment of the output relays
Unit MRR1 has five output relays. The fifth output relay is provided as permanent normally on
alarm relay for self supervision. Output relays 1 - 4 are normally off and can be assigned as alarm-
or trip-ping relays to the different supervision 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 simi-
lar to the setting of parameters, however, only in the assignment mode. By pressing push buttons
<ENTER> and <TRIP> simultaneously, the assignment mode is selected.
The assignment of the relays will be done as follows:
LEDs RW, R<, Ie< , Ie> are two-colored and light up green when the output relays are assigned as
alarm relays and red as tripping relays.
Definition:
Alarm relays are activated at pickup of the re-lay.
Tripping relays are only activated after elapse of the tripping delay.
After the assignment mode has been activated, first LED Rel and RW light up green. Now one or
several of the four output relays can be assigned to the insulation resistance supervision as alarm
relays. At the same time the selected alarm relays for the insulation resistance supervision are in-
dicated on the display. Indication "1_ _ _" means that output relay 1 is assigned to this element.
When the display shows "_ _ _ _", no alarm relay is assigned to this element.
The assignment of output relays 1 - 4 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 RW lights up red. The output relays
can now be assigned to this element as tripping relays.
Relays 1 - 4 are selected in the same way as
described before. By repeated pressing of the <SELECT/RESET> push button and assignment of
the relays all supervision elements can be as-signed separately to the output relays. The as-
signment mode can be terminated at any time by pressing the <SELECT/RESET> push button for
some time (abt. 3 s).
Display Function Assigned relay
LED Colour 1 2 3 4
RWgreen _ _ _ _ Warning
red _ 2 _ _ Tripping x
R<green _ _ _ _ Warning
red 1 _ _ _ Tripping x
Ie< green _ _ _ _ Warning
red _ _ 3 _ Tripping x
Ie> green _ _ _ _ Warning
red _ _ 3 _ Tripping x
I
r
green _ _ _ _ Warning
red _ _ _ 4 Tripping 
Table 5.5: Default assignment of the output relays
Note:
The function of jumper J2 described in general description "MR Digital Multifunctional Re
lays" has no function. For relays without assignment mode this jumper is used for
parameter setting of alarm relays (activation at pickup or tripping).
A form is attached to this description where the setting requested by the customer can be
filled-in. This form is prepared for telefax transmission and can be used for your own
reference as well as for telephone queries.

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DOK-TD-MRR1 Rev.A 17
6.Relay testing and commissioning
The following test instructions should help to verify the protection relay performance before or dur-
ing commissioning of the protection system. To avoid a relay damage and to ensure a correct relay
operation, be sure that:
the auxiliary power supply rating corresponds to the auxiliary voltage on site.
the rated values of the relay correspond to the plant data on site
all signal circuits and output relay circuits are connected correctly.
6.1 Power-On
NOTE!
Prior to switch on the auxiliary power supply, be sure that the auxiliary supply voltage corresponds
to the rated data on the type plate.
Switch on the auxiliary power supply to the relay and check that the message "WW" appears on
the display and the self supervision alarm relay (watchdog) is energized (Contact terminals D7 and
E7 closed).
6.2 Testing the output relays
NOTE!
Prior to commencing this test, interrupt the tripping circuit to the circuit breaker if tripping is not de-
sired.
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 mes-
sage 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 but-
ton <SELECT/RESET>.
6.3 Checking the set values
By repeatedly pressing the push button <SELECT/RESET>, all relay set values may be checked.
Set value modification can be done with the push button <+>< > and <ENTER> (refer to chapter 5).
6.4 Secondary injection test
6.4.1 Test equipment
Voltmeter and ammeter with class 1 or better
Auxiliary power supply with the voltage corresponding to the rated data on the type plate
Single-phase voltage supply unit
Timer to measure the operating time (Accuracy class 10 ms)
Switching device
Test leads and tools
Adjustable resistance (0 - 2201 M/0.6 W)

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6.4.2 Example of a test circuit
Figure 6.1 shows a simple example of a test circuit with variable current source for testing the re-
lay.
Figure 6.1: Test circuit
6.4.3 Checking the insulation measuring circuit
For checking the insulation measuring circuit a resistor with a defined value is simply connected to
terminals A2 - A3/A4 (A3 and A4 are to be bridged). By pressing push button <SELECT/RESET>,
measuring value R is displayed. This value must be identical with the de-fined value.
6.4.4 Checking the excitation current circuit
For checking the measuring values a current must be injected (terminals B1 - B2) which is below
the set pickup current of the MRR1. After renewed pressing the <SELECT/RESET> push button,
measuring value le is displayed and can be checked by using an ammeter.
Example : For this test circuit the dc current is generated from a single-pulse rectification. If a cur-
rent of IAV = 5A is fed to the MRR1, this value has to be indicated at the display. By repeatedly
pressing the <SELECT/RESET> push button, measuring value Ir is displayed.
Due to the conversion factor for single-pulse rectification of 0.318, the peak value at an average of
IAV = 5A comes to 15.73A. The ripple is calculated by using the following formula :
%,   , 
  · 100%
The measuring value Ir resulting from this is 314 %.

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6.4.5 Checking the pickup value and reset value
For testing these values a current smaller than the adjusted pickup value has to be injected (ter-
minals B1 - B2). The current is now to be increased until the relay picks up, which is indicated by
lighting up of LEDs le and le>. At the same time the output relay selected by the parameter setting
mode (see chapter 5.3.2) trips. The value shown at the ammeter must not vary more than
2 % from the adjusted pickup value of the MRR1. The resetting value is ascertained by slowly de-
creasing the test current until the output relay re-leases. Check that the resetting current is 0.98
times smaller than the operating current. This method is also to be used for the insulation
measuring circuit.
6.4.6 Checking the tripping delay
For checking the tripping delay a timer is to be connected to the trip output relay contact. The timer
should be started simultaneously with the test current injection in the current input circuit and
stopped at the instant the relay trips. The test cur-rent should be 1.5 times the operating current.
The tripping delay measured by the timer should not vary more than 3 % or less than 150ms from
the adjusted tripping delay.
For checking the insulation measuring circuit the same method can be used. The permissible
tolerance for this is 3 % or less than 1s from the adjusted tripping delay.
6.5 Real injection test
Generally, a test with real exciter current could be carried out in the similar manner as the injection
test with current sources above described. Since the cost and potential hazards are very high for
such a test, especially if staged fault tests are in-tended, these tests are usually limited to very
important protective relays in the power system.
Because of its powerful combined indicating and measuring functions, you have still the possibili-
ties to test the MRR1 relay in the manner of a primary injection without extra expenditures and time
consumption.
In actual service, for example, the measured cur-rent values may be compared with the ammeter
on the switch-board panel to verify that the relay works and measures correctly.
6.6 Maintenance
Maintenance testing is generally done on site at regular intervals. These intervals vary among us-
ers depending on many factors: e.g. the type of protective relays employed; the importance of the
primary equipment being protected; the user's past experience with the relay, etc.
For electromechanical or static relays, maintenance testing will be performed at least once a year
according to the experiences. For digital re-lays like MRR1, this interval can be substantially longer.
This is because:
The MR-relays are equipped with very wide self-supervision functions, so that many faults
in the relay can be detected and signalized during ser-vice. Important: The self-supervision
output relay must be connected to a central alarm panel!
The combined measuring functions of MR-relays enable supervision the relay functions
during service.
The combined TRIP test function of the MR-relay allows to test the relay output circuits.
A testing interval of two years for maintenance will, therefore, be recommended.
During a maintenance test, the relay functions including the operating values and relay tripping
times should be tested.

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7.Technical data
7.1 Measuring input circuits
Insulation resistance measuring:
Measuring aux. voltage UH: 24 V
Measuring frequency: fH= 0.51 Hz
Measuring resistance range: 1 kto 1 M
Max. input voltage: 600 V DC
Exciter DC current measuring
Max. continuous current: 20 A DC
Nominal current IN 10 A DC (measuring range: up to 25A DC)
Power consumption in current circuit: <1 VA
7.2 Common data
Dropout to pickup ratio >98%
Returning time: ≤30ms
Minimum operating time: ≤100ms
Weight: ca.1.5kg
Mounting position: any
Influences:
Temperature influence at
-20°C up to 70°C: ±2.5%
Auxiliary voltage: none
7.3 System data and test specifications
Insulation test voltage as per EN60255-6
Voltage test as per IEC255-5
2 KV DC for the terminals A2/A3/A4 for earth (C9)