Woodward ESDR 4T User manual

37138C
ESDR 4T
Current Differential Protection Relay
Manual
Manual 37138C

Manual 37138C ESDR 4T - Current Differential Protection Relay
WARNING
Read this entire manual and all other publications pertaining to the work to be performed before install-
ing, operating, or servicing this equipment. Practice all plant and safety instructions and precautions.
Failure to follow instructions can cause personal injury and/or property damage.
The engine, turbine, or other type of prime mover should be equipped with an overspeed (overtempera-
ture, or overpressure, where applicable) shutdown device(s), that operates totally independently of the
prime mover control device(s) to protect against runaway or damage to the engine, turbine, or other ty-
pe of prime mover with possible personal injury or loss of life should the mechanical-hydraulic gover-
nor(s) or electric control(s), the actuator(s), fuel control(s), the driving mechanism(s), the linkage(s), or
the controlled device(s) fail.
Any unauthorized modifications to or use of this equipment outside its specified mechanical, electrical,
or other operating limits may cause personal injury and/or property damage, including damage to the
equipment. Any such unauthorized modifications: (i) constitute "misuse" and/or "negligence" within
the meaning of the product warranty thereby excluding warranty coverage for any resulting damage,
and (ii) invalidate product certifications or listings.
CAUTION
To prevent damage to a control system that uses an alternator or battery-charging device, make sure
the charging device is turned off before disconnecting the battery from the system.
Electronic controls contain static-sensitive parts. Observe the following precautions to prevent dam-
age to these parts.
•Discharge body static before handling the control (with power to the control turned off, contact a
grounded surface and maintain contact while handling the control).
•Avoid all plastic, vinyl, and Styrofoam (except antistatic versions) around printed circuit boards.
•Do not touch the components or conductors on a printed circuit board with your hands or with
conductive devices.
OUT-OF-DATE PUBLICATION
This publication may have been revised or updated since this copy was produced. To verify that you
have the latest revision, be sure to check the Woodward website:
http://www.woodward.com/pubs/current.pdf
The revision level is shown at the bottom of the front cover after the publication number. The latest
version of most publications is available at:
http://www.woodward.com/publications
If your publication is not there, please contact your customer service representative to get the latest
copy.
Important definitions
WARNING
Indicates a potentially hazardous situation that, if not avoided, could result in death or serious injury.
CAUTION
Indicates a potentially hazardous situation that, if not avoided, could result in damage to equipment.
NOTE
Provides other helpful information that does not fall under the warning or caution categories.
Woodward reserves the right to update any portion of this publication at any time. Information provided by Woodward is believed to be
correct and reliable. However, Woodward assumes no responsibility unless otherwise expressly undertaken.
© Woodward
All Rights Reserved.
Page 2/46 © Woodward

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 3/46
Revision History
Rev. Date Editor Changes
NEW 02-11-26 Tr Release
A 03-02-29 TP Minor corrections
B 04-11-22 TP Minor corrections
C 07-03-01 TP Sealing parameters added; minor corrections
Contents
CHAPTER 1. GENERAL INFORMATION..........................................................................................5
CHAPTER 2. ELECTROSTATIC DISCHARGE AWARENESS..............................................................7
CHAPTER 3. WIRING ..................................................................................................................8
Wiring Diagram .......................................................................................................................................9
Power Supply ........................................................................................................................................10
Measuring Inputs...................................................................................................................................11
Discrete Inputs ......................................................................................................................................12
Relay Outputs .......................................................................................................................................13
CHAPTER 4. FUNCTIONAL DESCRIPTION ...................................................................................14
Introduction ...........................................................................................................................................14
Measurement Inputs .............................................................................................................................15
Differential Current Monitoring ..............................................................................................................16
Tripping Characteristic................................................................................................................16
Electrical Restraint of Inrush Current and Overexcitation with Transformers ............................18
Self-Monitoring ......................................................................................................................................18
Configuration.........................................................................................................................................18
Inputs and Outputs................................................................................................................................19
Control Inputs..............................................................................................................................19
Relays .........................................................................................................................................19
CHAPTER 5. DISPLAY AND OPERATING ELEMENTS....................................................................20
Short Description of LEDs and Buttons ................................................................................................20
LEDs......................................................................................................................................................21
Buttons ..................................................................................................................................................21
LC-Display.............................................................................................................................................22
CHAPTER 6. CONFIGURATION...................................................................................................24
Introduction ...........................................................................................................................................24
Basic Data.............................................................................................................................................24
Configuration Access ............................................................................................................................25
Configuring the Relay............................................................................................................................27
Nominal Data ........................................................................................................................................29
General Data...............................................................................................................................29
Data for Differential Protection....................................................................................................29
Differential Protection............................................................................................................................30
Modifying the Tripping Characteristic .........................................................................................31
Modifying the Electrical Restraint ...............................................................................................32

Manual 37138C ESDR 4T - Current Differential Protection Relay
CHAPTER 7. COMMISSIONING................................................................................................... 33
Prerequisite........................................................................................................................................... 33
Pre-Adjustments ................................................................................................................................... 33
Testing with Secondary Values ............................................................................................................ 33
Differential Current Testing Using Single-Sided Three-Phase Supply ...................................... 34
Commissioning Using Primary Values ................................................................................................. 34
Testing for Correct Connection ..................................................................................................35
Testing with Cyclical Swapping..................................................................................................35
Renewed Test with the Correct Connection .............................................................................. 36
APPENDIX A. DIMENSIONS ....................................................................................................... 37
APPENDIX B. TECHNICAL DATA ............................................................................................... 38
APPENDIX C. LIST OF PARAMETERS ......................................................................................... 39
APPENDIX A. SERVICE OPTIONS .............................................................................................. 41
Product Service Options....................................................................................................................... 41
Returning Equipment for Repair........................................................................................................... 41
Packing a Control ....................................................................................................................... 42
Return Authorization Number RAN ............................................................................................ 42
Replacement Parts ............................................................................................................................... 42
How to Contact Woodward................................................................................................................... 43
Engineering Services............................................................................................................................ 44
Technical Assistance............................................................................................................................ 45
Figures and Tables
Figures
Figure 3-1: Wiring diagram.......................................................................................................................................................9
Figure 3-2: Power supply.........................................................................................................................................................10
Figure 3-3: CT (transducer) inputs...........................................................................................................................................11
Figure 3-4: Discrete inputs.......................................................................................................................................................12
Figure 3-5: Relay outputs ........................................................................................................................................................13
Figure 4-1: Protection principle...............................................................................................................................................15
Figure 4-2: Characteristic ........................................................................................................................................................17
Figure 5-1: Front panel............................................................................................................................................................20
Figure 6-1: Sealing ..................................................................................................................................................................26
Figure 6-2: Operating/idle current ...........................................................................................................................................27
Figure 7-1: Dimensions............................................................................................................................................................37
Page 4/46 © Woodward

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 5/46
Chapter 1.
General Information
The ESDR 4T is a three-phase current differential protection relay for generators, motors and transformers in
block connection (protected object). The currents flowing in the individual conductors are each measured using a
current transformer on both sides of the protected object. They form the protection area boundary or zone. All
two or three-phase short-circuits and line-to-earth faults within this protection area are detected by the ESDR 4T
as fault currents which cause tripping. The unit does not trigger if fault currents occur outside the protection
zone. In this way, a selective protection is guaranteed.
All 6 measuring currents are measured in electrical isolation. The unit calculates the differential current and re-
straint current internally for each phase separately. The following settings are taken into account for this:
•Transformer vector group
•Rated current of the protection object on the low-voltage side
•Rated primary current of the current transformer on the high and low-voltage side
•Voltage transformation of the transformer
The ESDR 4T consists of a basic unit plus various options. The model designation is determined as follows:
ESDR 4T 0 5 -h0018 B/ -ABDEF..Z
Options according to the option list.
These option labels may be found in the operation instructions. The de-
scription of each function will include if it is a standard function or
available only as an option.
Mounting [B]..Front panel mounting
[M]..Rear wall mounting
Hardware variation
Special types; e.g. other relays
Current transformer, secondary [1] = ../1 A
[5] = ../5 A
Potential transformer, secondary
[0] = N/A
[1] = 100 Vac
[4] = 400 Vac
Type
Examples:
ESDR 4T01B (standard unit, no voltage measuring and ../1 A CT input, for front panel mounting)

Manual 37138C ESDR 4T - Current Differential Protection Relay
Intended Use The unit must only be operated for the uses described in this manual. The prerequisite for a proper
and safe operation of the product is correct transportation, storage, and installation as well as careful operation
and maintenance.
NOTE
This manual has been developed for a unit fitted with all available options. Inputs/outputs, functions,
configuration screens and other details described, which do not exist on your unit may be ignored.
The present manual has been prepared to enable the installation and commissioning of the unit. Due to
the large variety of parameter settings, it is not possible to cover every possible combination. There-
fore, this manual is only a guide. In case of incorrect entries or a total loss of functions, the default set-
tings can be taken from the enclosed list of parameters.
Page 6/46 © Woodward

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 7/46
Chapter 2.
Electrostatic Discharge Awareness
All electronic equipment is static-sensitive, some components more than others. To protect these components
from static damage, you must take special precautions to minimize or eliminate electrostatic discharges.
Follow these precautions when working with or near the control.
1. Before performing maintenance on the electronic control, discharge the static electricity on your body to
ground by touching and holding a grounded metal object (pipes, cabinets, equipment, etc.).
2. Avoid the build-up of static electricity on your body by not wearing clothing made of synthetic materials.
Wear cotton or cotton-blend materials as much as possible because these do not store static electric char-
ges as much as synthetics.
3. Keep plastic, vinyl, and Styrofoam materials (such as plastic or Styrofoam cups, cup holders, cigarette
packages, cellophane wrappers, vinyl books or folders, plastic bottles, and plastic ash trays) away from
the control, the modules, and the work area as much as possible.
4. Opening the control cover may void the unit warranty.
Do not remove the Printed Circuit Board (PCB) from the control cabinet unless absolutely necessary. If
you must remove the PCB from the control cabinet, follow these precautions:
•Ensure that the device is completely de-energized (all connectors must be disconnected).
•Do not touch any part of the PCB except the edges.
•Do not touch the electrical conductors, connectors, or components with conductive devices with your
hands.
•When replacing a PCB, keep the new PCB in the protective antistatic bag it comes in until you are
ready to install it. Immediately after removing the old PCB from the control cabinet, place it in the
protective antistatic bag.
CAUTION
To prevent damage to electronic components caused by improper handling, read and observe the pre-
cautions in Woodward manual 82715, Guide for Handling and Protection of Electronic Controls, Printed
Circuit Boards, and Modules.

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 8/46 © Woodward
Chapter 3.
Wiring
CAUTION
A circuit breaker must be provided near the unit and in a position easily accessible to the operator.
This must also bear a sign identifying it as an isolating switch for the unit.
NOTE
Inductive devices connected to the system (such as operating current coils, undervoltage tripping
units, or auxiliary/power contacts) must be connected to a suitable interference suppressor.
The following chart may be used to convert square millimeters [mm²] to AWG and vice versa:
AWG mm² AWG mm² AWG mm² AWG mm² AWG mm² AWG mm²
30 0.05 21 0.38 14 2.5 4 25 3/0 95 600MCM 300
28 0.08 20 0.5 12 4 2 35 4/0 120 750MCM 400
26 0.14 18 0.75 10 6 1 50 300MCM 150 1000MCM 500
24 0.25 17 1.0 8 10 1/0 55 350MCM 185
22 0.34 16 1.5 6 16 2/0 70 500MCM 240

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 9/46
Wiring Diagram
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
Current IL1 transducer set 2
Current IL2 transducer set 2
Current IL3 transducer set 2
Current IL3 transducer set 1
Current IL2 transducer set 1
Current IL1 transducer set 1
35
Subject to technical modifications.
L1 L2 L3
Transducer set 1 (high voltage side)
3025 26 27 28 29
T
G
Transducer set 2 (low votlage side)
36 33 34 31 32
18
Acknowledgement
Relay 1
Relay 2
Relay 3
Ready for operation
Relay 4
0 Vdc
24 Vdc
Common
Configuration off
61 2 3 4 5
2003-07-14 | ESDR 4T Wiring Diagram e4tww-2903-ap.skf
12111097 8 13 161514 17
Blocking
19
Protected object
G
Possible
protected objects:
Block
differential protection
Generator
differential protection
The transducer ratio is adjustable
in the display.
The transducer ratio is adjustable
in the display.
ESDR 4T - Current Differential Protection Relay
N/C
N/C
Figure 3-1: Wiring diagram

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 10/46 © Woodward
Power Supply
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
24 Vdc (+/-25 %)
1314
24 Vdc
0 V
Power supply
Figure 3-2: Power supply
Terminal Description Amax
13 +24 V DC, 10 W 2.5 mm²
14 0 Vdc reference voltage 2.5 mm²

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 11/46
Measuring Inputs
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
WARNING
Before detaching the secondary current transformer connections or those on the unit, you should en-
sure that the current transformer secondary is short-circuited.
NOTE
One side of the secondary of all CTs must be earthed. The earth connection should be made on the
side of the secondary facing the protected object. The polarity of the CTs must be in accordance with
the following diagram.
Star point
Transducer set 1
(high voltage side) Block connection Transducer set 2 (low voltage side)
Differential
current
monitoring
Transducer
set 1
Differential
current
monitoring
Transducer
set 2
L2
L1
L3
G
l (s2)
k (s1)
L2
l (s2)
k (s1)
l (s2)
k (s1)
l (s2)
k (s1)
L3
L2
L1
l (s2)
k (s1)
l (s2)
k (s1)
25 26 30292827 35 36 33 34 31 32
L1
L3
Generator diff. prot.
G
Protection object
Figure 3-3: CT (transducer) inputs
Terminal Measurement Description Amax
25 Measured current L1, Transducer input s2 (l) 4 mm²
26 Measured current L2, Transducer input s1 (k) 4 mm²
27 Measured current L2, Transducer input s2 (l) 4 mm²
28 Measured current L2, Transducer input s1 (k) 4 mm²
29 Measured current L3, Transducer input s2 (l) 4 mm²
30
CT set 1
../1 A
or
../5 A Measured current L3, Transducer input s1 (k) 4 mm²
31 Measured current L1, Transducer input s2 (l) 4 mm²
32 Measured current L1, Transducer input s1 (k) 4 mm²
33 Measured current L2, Transducer input s2 (l) 4 mm²
34 Measured current L2, Transducer input s1 (k) 4 mm²
35 Measured current L3, Transducer input s2 (l) 4 mm²
36
CT set 2
../1 A
or
../5 A Measured current L3, Transducer input s1 (k) 4 mm²

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 12/46 © Woodward
Discrete Inputs
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
Signal device
Signal device
Signal device
Blocking
Acknowledgment
Configuration
18 to 250 V (ac/dc)
171518151915
Figure 3-4: Discrete inputs
Terminal Associated
common Description (according to DIN 40 719 section 3, 5.8.3) Amax
A B
Make contact
17 Configuration off 2.5 mm²
18 Acknowledgement 2.5 mm²
19 15 Blocking 2.5 mm²

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 13/46
Relay Outputs
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
max. 250 Vac
AB
Relay output
Relay output
external device
external device
external device
CDE
Relay output
external device
external device
FGH
Figure 3-5: Relay outputs
Terminal Amax
Root Make-contact
A B
Description
7 8 Relay 3 - Ready for operation 2.5 mm²
Make-
Contact Root Break- contact
CDE
3 2 1 Relay 1 - Trip 2.5 mm²
6 5 4 Relay 2 - Trip 2.5 mm²
Root Make-
contact Break- contact
F G H
11 10 12 Relay 4 - Warning 2.5 mm²

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 14/46 © Woodward
Chapter 4.
Functional Description
Introduction
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
The ESDR 4T is a three-phase current differential protection relay for generators, motors and transformers in
block connection (protected object). The currents flowing in the individual conductors are each measured using a
current transformer on both sides of the protected object. They form the protection area boundary or zone. All
two or three-phase short-circuits and line-to-earth faults within this protection area are detected by the ESDR 4T
as fault currents which cause tripping. The unit does not trip if fault currents occur outside the protection area. In
this way, a selective protection is guaranteed.
All 6 measuring currents are electrically isolated. The unit calculates the differential current and restraint current
internally for each phase separately. The following settings are taken into account for this:
•Transformer vector group
•Rated current of the protection object on the low-voltage side
•Rated primary current of the current transformer on the high and low-voltage side
•Voltage transformation of the transformer
During the calculation, the star connections on the windings are arithmetically converted into delta layouts to
eliminate the zero-sequence system. The different relationships between the current transformer ratios and the
voltage transformation can lead to relatively different currents even when there are no faults. In order to manage
defined ratios, the measured value on the high-voltage side is standardized so that it can be compared with the
measured value on the low-voltage side. The reference side is the low-voltage side, therefore the configured rated
current on the low-voltage side must be referred to. It is recommended that the generator rated current be used as
the reference value for unit connections.
NOTE
The measured values of the differential protection are shown as percentage values related to the con-
figured rated current.

Manual 37138C ESDR 4T - Current Differential Protection Relay
The unit monitors six (6) measured currents via isolated inputs. The unit calculates internally the restraint current
(Is) and the differential current (Id) separately for each phase. The actual values of the calculated parameters (Dif-
ferential current Idund Restraint current IS) are shown on the display either as absolute values or as a percentage
of the generator rated current (selectable in locked input mode).
Theoretically the currents Iaand Ibare equal, both in fault-free operation and outside the protection zone (Figure
4-1-a).The difference is zero and the differential protection does not initiate. However, in practice current differ-
entials do occur (= spurious currents), even in fault-free operation. They result, for example, from summation or
phase angle errors in the CTs, which are influenced by deviating burden values. These spurious currents remain
small inside the operating range, but increase with increasing load and are especially high when one or more CTs
become saturated (e.g. in the case of an external short circuit). In order to prevent a tripping of the relay due to
spurious currents, the trigger threshold is not held statically constant but increases in relation to the restraint cur-
rent Is. Spurious currents need to be taken into account when adjusting the trip characteristic.
When a fault occurs inside the protection area (Figure 4-1-b), unequal currents flow in the CTs, which result in a
current differential. If this exceeds the differential protection threshold, the relay will trip.
G
I I
I
L
G
I I
I
L
a
a)
b
b)
a b
Schematic circuit diagrams (single phase version):
a) Fault outside the protection area
b)Fault inside the protection area
Figure 4-1: Protection principle
The circuit diagram above serves to explain the protection concept for in phase and equal currents. The differen-
tial current and restraint currents are determined arithmetically.
Measurement Inputs
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
The unit records six current values for the current differential protection.
For differential current measurement, the unit forms the sum of two values (restraint current IS) and the deviation
(differential current Id). The actual value of the values determined (differential current Idand restraint current IS)
is shown as a percentage on the display with reference to the rated current.
© Woodward Page 15/46

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 16/46 © Woodward
Differential Current Monitoring
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
The monitoring of the differential current is carried out in two stages.
The first monitoring stage serves as a warning and can be enabled or disabled. Should the adjustable warning
characteristic be exceeded, a text appears in the display and a relay contact is enabled. The pick-up time and the
dropout delay of the relay output are adjustable. The warning stage of the monitoring is auto-resetting.
The second stage of monitoring (main stage) serves to initiate tripping. In contrast to the first stage, it offers the
possibility to monitor the overstepping of an adjustable tripping characteristic (Id < In) and additionally, a fixed
tripping-threshold of 100%, relative to the generator rated current (Id> In). The trigger-delay for each limit value
may be independently adjusted, thus allowing a shorter triggering time at higher differential currents. When one
or both tripping characteristics are exceeded, a text display is initiated and two relay contacts are energized. The
tripping characteristics possess a 2% hysteresis relative to the generator rated current.
The signal relay is only automatically reset if the function "auto-acknowledge relay" in the Entry field on the
screen is configured to "ON". Otherwise, the resetting is carried out by pressing the "Clear" button on the front of
the unit or via the discrete input terminal 18 "Reset".
Tripping Characteristic
The following figure shows the tripping and warning characteristics (with sample values for X12, Y1,and Y2). It
represents the tripping and warning thresholds (Y) relative to the restraint current (X) The coordinates P
(X12/Y2) and P (X12/Y1) the positions of the corner points. The selection of these positions is dependent on the
generator being protected. The following gives the ranges of tripping and warning thresholds:
IS/ IN0 to X12 The threshold Idis independent of the restraint current..
IS/ INX12 to 5 × INThe threshold Idis dependent on the restraint current. A change of 100% in the
restraint current causes an increase of 10% in the tripping threshold.
IS/ IN> 5 × INThe threshold Idstays constant at 85%.
Different characteristics can be chosen for the first and second monitoring levels, whereby the horizontal position
(X-coordinate) is valid for both stages. The vertical position (Y-coordinate) can be chosen separately for each
monitoring level. This results in a fixed difference in thresholds of the first and second monitoring levels for each
restraint current Is.
The unit can measure currents up to 5 × INaccurately. Depending on the vector group there can be a deviation in
measuring the different currents and the unit can trip. The message "range exceeded" is displayed when tripping
due to these currents occurs. Currents larger than 5 × INwill only result in tripping if a short circuit is within the
protected area. If the short circuit is outside the protection area, only the generator would be drive the currents
measured by the CTs.

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 17/46
Monitoring step 1
(X12 = 100 % / Y1 = 10 %)
Monitoring step 2
(X12 = 100 % / Y2 = 35 %)
Protected
object
100 200
Characteristic gradient (fixed) = 10 %
Monitoring step 2, fixed limit (100 %)
X12, Y2 and Y1: adjustable
N
I
100
P (X12/Y2) P (X12/Y1)
Y = I
d
[%]
a
I
300 400
2004-02-12
ESDR 4 Characteristic e4ww-0704-kenn.skf
500
S
I
[%]
I
N
X =
-
+I
ba
I
b
I=
I
S
II=I
bad
2
Monitoring step 1 fixed limit (85 %-Y2+Y1) Monitoring step 2 fixed limit (85 %)
1
21 2
=
35 10
Figure 4-2: Characteristic

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 18/46 © Woodward
Electrical Restraint of Inrush Current and Overexcitation with Transformers
Certain transformer operational conditions can cause differential currents without there actually being a fault pre-
sent at the protected object. This includes energizing the transformer and operating in overexcitation mode.
When a transformer is energized, a current inrush flows in on one side which can be variably high depending on
the instantaneous value of the supply current. If a long high-voltage line has a transformer at the end that is being
energized, overvoltages can occur and overexcite the transformer, inducing increased currents on one side. As
the currents only flow one-sided in both cases, a differential current will be measured which results in false trip-
ping.
During an inrush current there are typically high proportions of 2nd order harmonics present. However during
overexcitation there are predominantly 5th order harmonics present. The harmonics component is determined in
the ESDR 4T using the digital Fourier transformation (= DFT) and this is used as the criteria for electrical re-
straint against false tripping.
To activate the electrical restraint of an inrush current or an overexcitation, enable the "Stabilization Rush" func-
tion in the configuration mode by configuring as ON and set an operate margin in the next screen. The operate
margin must be set for rush detection. This limit must be set so that it is not exceeded in normal operation. But it
must be exceeded if an inrush current occurs. The proportion of 2nd harmonics in normal operation and in the
starting current depends in part on the type of transformer construction and the starting torque. As such, no gen-
eral operate margin can be given here. The documentation contains notes stating that the proportion of 2nd order
harmonics when there is inrush current is always over 50 % and always under 30 % when there is a short-circuit.
Only step 1 of the differential current tripping can be stabilized; step 2 causes constant tripping. When electrical
restraint is activated you should ensure that the time lag for monitoring the differential current 1 is at least
0.08 seconds.
Self-Monitoring
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
The unit is equipped with an operational readiness message for self-monitoring. It is available externally via a
contact assembly. The ready for operation signal is disabled if the unit's supply voltage drops below approxi-
mately 19 Vdc or if there is an internal malfunction.
Configuration
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
The operating parameters may be entered in through the buttons on the front panel. To change these parameters,
the control must be in the configuration mode. The control unit will continue to operate while in the configura-
tion mode. This may result in the control unit accidentally issuing a breaker open command if the parameters are
changed while in the operation mode.

Manual 37138C ESDR 4T - Current Differential Protection Relay
© Woodward Page 19/46
Inputs and Outputs
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
Control Inputs
Configuration off
Terminal 17 When this input is energized, the unit remains in Display mode and cannot be
changed to Configuration mode. The Configuration mode is enabled if this terminal
is de-energized.
Acknowledgement
Terminal 18 If this input remains energized for at least 1 s, the faults detected in monitoring
level 2 are reset. This means that the relays will be de-energized and the text display
will be deleted from the screen as long as the monitored currents are not exceeding
the configured threshold level.
Blocking
Terminal19 When this input is energized, the differential protection is disabled. This means that
the differential current is not monitored, relays cannot be enabled and text is not dis-
played.
Relays
Relay 1
Terminals 1/2/3 The function of this relay may be configured. Refer to Configuring the Relay on
page 25 for details.
Relay 2
Terminals 4/5/6 The function of this relay may be configured. Refer to Configuring the Relay on
page 25 for details.
Ready for operation
(Relay 3)
Terminals 7/8
This relay is enabled when the unit is operational and the differential current is being
monitored. The relay becomes disabled if the monitoring is deactivated through any
of the following reasons:
• the internal self-monitoring has detected a malfunction of the unit. A correct func-
tioning of the unit cannot be guaranteed and corrective action may be necessary.
• the digital input "Blocking" is energized
• the parameter "Monitoring" is configured to "Off"
An additional function may be assigned to this relay. Refer to Configuring the Relay
on page 25 for details.
Relay 4
Terminals 10/11/12 The function of this relay may be configured. Refer to Configuring the Relay on
page 25 for details.

Manual 37138C ESDR 4T - Current Differential Protection Relay
Page 20/46 © Woodward
Chapter 5.
Display and Operating Elements
The foil covering of the front panel consists of coated plastic. All keys are comprised of touch sensitive mem-
brane elements. The display is a Liquid Crystal display (LC-display), comprised of two rows of text that are 16
characters each and are indirectly illuminated (green). The contrast of the display can be continuously adjusted
by means of a rotary potentiometer on the left hand side.
Monitoring
Differential Current
Protection
ON
A
larm
I
s
I
a
I
b
+
2
=
I
a
I
b
I
d=
Protected
Object
I
a
I
b
[ ]
Operating and Alarm Messages
L1 L2 L3
Release
Variable Release Characteristic
X
Y
10%
I
d
N
I
I
s
N
I
Lock
I
s
I
d
1
2
412 13 14
5
3
Figure 5-1: Front panel
Short Description of LEDs and Buttons
≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡
LEDs
No.. Designation Function
1I
SRestraint current
2I
dDifferential current
3Monitoring ON Monitoring activated
4Alarm Alarm initiated
Buttons
No. Designation Function
12 Message↓Scroll message
12 Select Confirm selection
13 Display↓Scroll display
13 Digit↑Increase digit
14 Clear Clear (Reset) of fault message
14 Cursor→Move cursor one position to the right
Miscellaneous
No. Designation Function
5LC-Display LC-Display