Siemens SIPROTEC 4 7XT7100-0 A00/EE Series User manual

C53000-B1174-C128-7
SIPROTEC 4/5
Injection Unit 7XT71
(for Rotor Ground Fault Protection, 1 Hz to 3 Hz)
7XT7100-0*A00/EE
Product Information
(valid from hardware version /EE)

Disclaimer of Liability
This document has been subjected to rigorous tech-
nical review before being published. It is revised at
regular intervals, and any modifications and amend-
ments are included in the subsequent issues. The
content of this document has been compiled for infor-
mation purposes only. Although Siemens AG has
made best efforts to keep the document as precise
and up-to-date as possible, Siemens AG shall not
assume any liability for defects and damage which
result through use of the information contained
herein.
This content does not form part of a contract or of
business relations; nor does it change these. All obli-
gations of Siemens AG are stated in the relevant con-
tractual agreements.
Siemens AG reserves the right to revise this docu-
ment from time to time.
Document release: C53000-B1174-C128-7.00
Edition: 09.2016
Product version: /EE
Copyright
Copyright Siemens AG 2016. All rights reserved.
The disclosure, duplication, distribution and editing of
this document, or utilization and communication of the
content are not permitted, unless authorized in writ-
ing. All rights, including rights created by patent grant
or registration of a utility model or a design, are
reserved.
Registered Trademarks
SIMATIC®, SIMATIC NET®, SIPROTEC®, DIGSI®,
SICAM®, SIMEAS®, SINAUT®, OSCOP®, and
DAKON®are registered trademarks of
SIEMENS AG. An unauthorized use is illegal.
All other designations in this document can be trade-
marks whose use by third parties for their own pur-
poses can infringe the rights of the owner.
NOTE
For your own safety, please observe the warnings and safety instructions con-
tained in this document.
NOTE
This Product Information contains important information about the
Injection Unit 7XT71.
It is part of the product supplied, and the information in it should be considered
more up-to-date than any other information if uncertainties arise.

1SIPROTEC 4/5, Injection Unit 7XT71, Product Information
C53000-B1174-C128-7, Edition 09.2016
Table of Contents
1 Information for Your Safety 2
2 Statement of Conformity 4
3 Used Symbols 5
4 Ordering Information 6
5 Application 7
6 Design 9
7 Dimensions and Connections 12
8 Assembly and Connection Notes 17
9 Commissioning 22
10 Maintenance and Repair 29
11 Storage and Transport 30
12 Technical Data 31
13 Block Diagram 38
14 Connection Diagrams 39

2SIPROTEC 4/5, Injection Unit 7XT71, Product Information
C53000-B1174-C128-7, Edition 09.2016
1 Information for Your Safety
This manual does not constitute a complete catalog of all safety measures required
for operating the equipment (module, device) in question, because special operat-
ing conditions may require additional measures. However, it does contain notes
that must be adhered to for your own personal safety and to avoid damage to prop-
erty. These notes are highlighted with a warning triangle and different keywords in-
dicating different degrees of danger.
DANGER
Danger means that death or severe injury will occur if the appropriate safety mea-
sures are not taken.
✧Follow all instructions to prevent death or severe injury.
WARNING
Warning means that death or severe injury can occur if the appropriate safety
measures are not taken.
✧Follow all instructions to prevent death or severe injury.
CAUTION
Caution means that minor or moderate injury can occur if the appropriate safety
measures are not taken.
✧Follow all instructions to prevent minor injury.
NOTICE
Notice means that damage to property can occur if the appropriate safety mea-
sures are not taken.
✧Follow all instructions to prevent damage to property.
NOTE
is important information about the product, the handling of the product, or the part
of the documentation in question to which special attention must be paid.

3SIPROTEC 4/5, Injection Unit 7XT71, Product Information
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Personnel Qualified in Electrical Engineering
Commissioning and operation of the equipment (module, device) described in this
manual must be performed by personnel qualified in electrical engineering only. As
used in the safety notes in this manual, electrically qualified personnel are those
persons who are authorized to commission, release, ground and tag devices, sys-
tems, and electrical circuits in accordance with safety standards.
Use as Prescribed
The equipment (device, module) must not be used for any other purposes than
those described in the catalog and the Technical Description. If it is used together
with third-party devices and components, these must be recommended or ap-
proved by Siemens.
If the device is not used in accordance with this product information, the intended
protection function is impaired.
Correct and safe operation of the product requires adequate transportation, stor-
age, installation, and assembly as well as appropriate use and maintenance.
During the operation of electric equipment, it is unavoidable that certain parts of this
equipment will carry hazardous voltages. Severe injury or material damage can oc-
cur if appropriate measures are not taken:
• Before making any connections, ground the equipment at the grounding termi-
nal.
• Hazardous voltages can be present on all switching components connected to
the power supply.
• Even after the supply voltage has been disconnected, hazardous voltages can
still be present in the equipment (capacitor storage).
• Equipment with current transformer circuits must not be operated while open.
• The limit values indicated in the manual and the product information must not
be exceeded; this also refers to testing and commissioning.

4SIPROTEC 4/5, Injection Unit 7XT71, Product Information
C53000-B1174-C128-7, Edition 09.2016
2 Statement of Conformity
This product complies with the directive of the Council of the European Commu-
nities on harmonization of the laws of the Member States relating to electromag-
netic compatibility (EMC Council Directive 2014/30/EU) and concerning electrical
equipment for use within specified voltage limits (Low Voltage Directive
2014/35/EU).
This conformity has been proved by tests performed according to the Council
Directive in accordance with the product standard EN 60255-26 (for EMC direc-
tive) and with the product standard EN 60255-27 (for Low Voltage Directive) by
Siemens AG.
The device is designed and manufactured for application in an industrial environ-
ment.
The product conforms with the international standards of IEC 60255 and the
German standard VDE 0435.

5SIPROTEC 4/5, Injection Unit 7XT71, Product Information
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3 Used Symbols
Table 3-1 Used Symbols
No. Symbol Description
1 Direct current
IEC 60417-5031
2 Alternating current
IEC 60417-5032
3 Direct and alternating current
IEC 60417-5033
4 Three-phase alternating current
5 Ground (earth)
IEC 60417-5017
6 Protective conductor
IEC 60417-5019
7 Caution, risk of electric shock
8 Caution, risk of danger
ISO 7000-0434

6SIPROTEC 4/5, Injection Unit 7XT71, Product Information
C53000-B1174-C128-7, Edition 09.2016
4 Ordering Information
Ordering code for your order:
Fig. 4-1 Ordering Code
7XT7100- 0
8
A0 0
1211109
Injection Unit
In housing for panel surface mounting B
E
In housing for panel flush mounting

7SIPROTEC 4/5, Injection Unit 7XT71, Product Information
C53000-B1174-C128-7, Edition 09.2016
5 Application
Large generators require a high sensitivity of the rotor ground fault protection. The
influence of the rotor ground capacitance must largely be eliminated, and the sig-
nal-to-noise ratio to the harmonics (for example 6th harmonic) of the excitation de-
vice must be increased.
This type of machine protection is implemented in the SIPROTEC family using the
Injection Unit 7XT71 in combination with the Resistor Unit 7XR6004 and the Multi-
functional Machine Protection 7UM62/Generator Protection 7UM85. This combina-
tion of devices continuously monitors the rotor ground resistance to ensure the
sensitive rotor ground fault protection. From hardware version /DD, the
Injection Unit 7XT71 can be connected to up to 2 devices 7UM62 or 7UM85. This
enables the protection function to be assigned to 2 protection groups increasing the
functional redundancy.
The square-wave generator of the Injection Unit 7XT71 generates a low-frequency
square-wave voltage of approximately ±50 V that can be adjusted in the device via
a DIP switch in increments of 0.5 Hz, from 0.5 Hz to 4.0 Hz. The Resistor Unit
7XR6004 injects a square-wave voltage between the rotor winding of a generator
and the ground brushes.
The square-wave voltage injected in the rotor winding causes a permanent charge
reversal of the rotor ground capacitance. The ground current enters the measuring
circuit of the Injection Unit 7XT71 where it is galvanically separated and injected
into the measuring input of the 7UM62 or 7UM85. If no fault is present (Rground 
infinite), the rotor ground current approximates zero after charging the ground ca-
pacitance. If a fault is present, the ground resistance and the series resistance of
the Resistor Unit 7XR6004 and the supply voltage determine the stationary current.
Simultaneously, the Injection Unit 7XT71 acquires the polarity reversal caused by
the square-wave voltage (square-wave voltage and square-wave frequency) and
injects it as galvanically separated control signals into the control input of the
7UM62/7UM85.
The 7UM62/7UM85 monitors the rotor ground circuit for interruptions by evaluating
the rotor ground current during the polarity reversals.
The sensitivity of the rotor ground fault protection can detecting fault resistances of
up to 80 k.
An AC/DC wide-range power supply unit processes the auxiliary voltage for the de-
vice modules in the Injection Unit 7XT71.

8SIPROTEC 4/5, Injection Unit 7XT71, Product Information
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NOTE
7UM62:
The SIPROTEC manual 7UM62, order no. C53000-G1176-C149 provides a de-
tailed description of the measurement method in combination with the 7UM62.
7UM85:
The SIPROTEC manual 7UM85, order no. C53000-G5040-C027 provides a de-
tailed description of the measurement method in combination with the 7UM85.