Woodward XR1 User manual
XR1 – Rotor Earth Fault Relay
Manual XR1 (Revision A)
Woodward Manual XR1 GB
2 DOK-TD-XR1 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 XR1 GB Woodward
DOK-TD-XR1 Rev.A 3
Content
1.Applications and features...........................................................................4
2.Design...........................................................................................................5
3.Function........................................................................................................6
4.Operation and settings................................................................................8
4.1Setting of DIP-switches .......................................................................................................9
4.2Setting of the tripping values.............................................................................................10
4.3Communication via serial interface adapter XRS1 ...........................................................11
5.Relay case and technical data..................................................................12
5.1Relay case.........................................................................................................................12
5.2Technical data...................................................................................................................13
Woodward Manual XR1 GB
4 DOK-TD-XR1 Rev.A
1.Applications and features
Protection relay XR1 of our PROFESSIONAL LINE is used for detection of rotor earth faults in syn-
chronous machines. The earth fault element detects high and low impedance earth faults in rotor
windings and is in two stage design (for alarm and trip).
When compared to the conventional protection equipment all relays of the PROFESSIONAL LINE
reflect the superiority of digital protection techniques with the following features:
High measuring accuracy by digital data processing
Fault indication via LEDs
Extremely wide operating ranges of the supply volt-age by universal wide-range power
supply
Very fine graded wide setting ranges
Data exchange with process management system by serial interface adapter XRS1 which
can be retrofitted
Extremely short response time
Compact design by SMD-technology
In addition to this, relay XR1 has the following special features:
Detection of high impedance earth faults in rotor windings and is in two stage design.
Short circuit and overvoltage proof measuring input for earth fault protection
Separately setting of trip delay for R< and R<<
Manual XR1 GB Woodward
DOK-TD-XR1 Rev.A 5
2.Design
Figure 2.1: Connections
Measuring paths
By using a measuring voltage, the protection relay ascertains the resistance of the test object via
terminals U1 and U2.
Auxiliary voltage supply
Unit XR1 needs a separate auxiliary voltage supply. Therefore a dc or ac voltage must be used.
Unit XR1 has an integrated wide range power supply. Voltages in the range from 19 - 390 Vdc or
36 - 275 Vac can be applied at connection terminals A1 and A2.
Contact positions
Figure 2.2: Contact positions of the output relays
Woodward Manual XR1 GB
6 DOK-TD-XR1 Rev.A
3.Function
A single earth fault on the field windings of a synchronous generator produces no immediate da-
maging effect. It must be detected and removed because of the possibility of a second earth fault
that could short a part of the field winding and cause severe damage.
XR1 provides an alarm and a trip element for the rotor earth fault protection.
The insulation resistance measurement system of the XR1 can be used for synchronous genera-
tors of both types, with and without brushes.
It works with a low frequency alternating test voltage (1 Hz, ±24V) which is connected via slip rings
to the main exciter 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 capacit-
ance (CE) which can reach values up to 1 µF on large generators. The test voltage is fed via one
current limiting resistors (RV) to both ends of the field winding.
Figure 3.1: Measuring principle of the earth current
The insulation resistance measurement is based on the subsequent measurement of the shunt re-
sistor 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.
Manual XR1 GB Woodward
DOK-TD-XR1 Rev.A 7
Figure 3.2 explains the measuring principle:
Figure 3.2: Measuring principle
Woodward Manual XR1 GB
8 DOK-TD-XR1 Rev.A
4.Operation and settings
All operating elements needed for setting parameters are located on the front plate of the XR1 as
well as all display elements.
Because of this all adjustments of the unit can be made or changed without disconnecting the unit
off the DIN-rail.
Figure 4.1: Front plate
For adjustment of the unit the transparent cover has to be opened as illustrated. Do not use force!
The trans-parent cover has two inserts for labels.
Figure 4.2: How to open the transparent cover
LEDs
LED „ON“ is used for display of the readiness for ser-vice (at applied auxiliary voltage Uv). LED R<
and R<< signal pickup (flashing) or tripping (steady light) of the corresponding function.
Test push button
This push button is used for test tripping of the unit and when pressed for 5 s a check-up of the
hardware takes place. Both output relays are tripped and all tripping LEDs light up.
Manual XR1 GB Woodward
DOK-TD-XR1 Rev.A 9
4.1 Setting of DIP-switches
The DIP-switch block on the front plate of the XR1 is used for adjustment of the nominal values and
setting of function parameters:
DIP-switch OFF ON Function
1
2
3
4 active blocked Rotor earth fault warning
5 active blocked Rotor earth fault tripping
6
7 x1 x2 Multiplier for tR<
8 x1 x2 Multiplier for tR<<
Table 4.1: Functions of DIP-switches
Blocking of rotor earth fault warning element
When DIP-switch 4 is in „ON“-position, the rotor earth fault warning element is blocked.
Blocking of rotor earth fault trip element
When DIP-switch 5 is in „ON“-position, the rotor earth fault trip element is blocked.
Woodward Manual XR1 GB
10 DOK-TD-XR1 Rev.A
4.2 Setting of the tripping values
The PROFESSIONAL LINE units have the unique possibility of high accuracy fine adjustments. For
this, two potentiometers are used. The coarse setting potentiometer can be set in discrete steps of
20 kΩor 5 kΩ. A second fine adjustment potentiometer is then used for continuously variable set-
ting of the final (0 - 20 kΩor 0 - 5 kΩ. Adding of the two values results in the precise tripping value.
Rotor earth fault alarm R<
The rotor earth fault alarm can be set in the range from 20 - 140 kΩwith the aid of the potentiome-
ter illustrated on the following diagram.
Example:
A tripping value of 92 kΩis to be set. The set value of the right potentiometer is just added to the
value of the coarse setting potentiometer. (The arrow of the coarse setting potentiometer must be
inside of the marked bar, otherwise no defined setting value).
Figure 4.3: Adjustment example
Rotor earth fault tripping R<<
The rotor earth fault tripping can be set in the range from 0 - 30 kΩwith the aid of the potentiome-
ter illustrated on the following diagram (R<< min = 2Ω)
Example:
A tripping value of 18 kΩis to be set.
Figure 4.4: Adjustment example
Time delay tR<
With the aid of DIP-switch 7 the time delay at rotor earth fault alarm tR< can be adjusted conti-
nuously variable in the range from 0 - 25 s or 0 - 50 s.
Time delay tR<<
With the aid of DIP-switch 8 the time delay at rotor earth fault tripping tR<< can be adjusted conti-
nuously variable in the range from 0 - 10 s or 0 - 20 s.
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