Hitachi Relion 670 Series User guide

Relion 670/650 SERIES
Communication set-up, 670/650 series
Version 2.2
Application Guide

Document ID: 1MRK505382-UEN
Issued: June 2023
Revision: K
Product version: 2.2
© 2017 - 2023 Hitachi Energy. All rights reserved

Copyright
This document and parts thereof must not be reproduced or copied without written permission from
Hitachi Energy, and the contents thereof must not be imparted to a third party, nor used for any
unauthorized purpose.
The software and hardware described in this document is furnished under a license and may be used
or disclosed only in accordance with the terms of such license.
This product includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit
(https://www.openssl.org/). This product includes cryptographic software written/developed by: Eric
Young ([email protected]) and Tim Hudson ([email protected]).
Trademarks
ABB is a registered trademark of ABB Asea Brown Boveri Ltd. Manufactured by/for a Hitachi Energy
company. All other brand or product names mentioned in this document may be trademarks or
registered trademarks of their respective holders.
Warranty
Please inquire about the terms of warranty from your nearest Hitachi Energy representative.

Disclaimer
The data, examples and diagrams in this manual are included solely for the concept or product
description and are not to be deemed as a statement of guaranteed properties. All persons
responsible for applying the equipment addressed in this manual must satisfy themselves that each
intended application is suitable and acceptable, including that any applicable safety or other
operational requirements are complied with. In particular, any risks in applications where a system
failure and/or product failure would create a risk for harm to property or persons (including but not
limited to personal injuries or death) shall be the sole responsibility of the person or entity applying
the equipment, and those so responsible are hereby requested to ensure that all measures are taken
to exclude or mitigate such risks.
This document has been carefully checked by Hitachi Energy, but deviations cannot be completely
ruled out. In case any errors are detected, the reader is kindly requested to notify the manufacturer.
Other than under explicit contractual commitments, in no event shall Hitachi Energy be responsible
or liable for any loss or damage resulting from the use of this manual or the application of the
equipment.

Conformity
This product complies with the directive of the Council of the European Communities on the
approximation of the laws of the Member States relating to electromagnetic compatibility (EMC
Directive 2004/108/EC) and concerning electrical equipment for use within specified voltage limits
(Low-voltage directive 2006/95/EC). This conformity is the result of tests conducted by Hitachi
Energy in accordance with the product standard EN 60255-26 for the EMC directive, and with the
product standards EN 60255-1 and EN 60255-27 for the low voltage directive. The product is
designed in accordance with the international standards of the IEC 60255 series.

Table of contents
Section 1 Introduction....................................................................................................5
1.1 This manual...........................................................................................................................5
1.2 Intended audience.................................................................................................................5
1.3 Product documentation......................................................................................................... 5
1.3.1 Product documentation set..................................................................................................5
1.3.2 Document revision history...................................................................................................6
1.3.3 Related documents............................................................................................................. 7
1.4 Document symbols and conventions.....................................................................................9
1.4.1 Symbols...............................................................................................................................9
1.4.2 Document conventions........................................................................................................9
Section 2 Telecommunication networks and line differential protection................ 11
2.1 Overview..............................................................................................................................11
2.2 Telecommunication network types.......................................................................................11
2.3 Telecommunication networks with symmetric or fixed routes..............................................12
2.3.1 Maximum time deviation between internal clocks............................................................. 13
2.3.1.1 Setting the maximum time deviation............................................................................ 13
2.3.1.2 Reference clock deviation from the set maximum time deviation................................ 14
2.3.2 Longer route switching interruptions ................................................................................ 15
2.3.3 Detecting accumulated time delay changes with echo timing...........................................15
Section 3 Common time synchronization.................................................................. 17
3.1 Design of the time system (clock synchronization)............................................................. 17
3.2 Time synchronization using a built-in GPS receiver............................................................18
3.3 Time synchronization using IRIG-B.....................................................................................19
Section 4 Analog and binary signal transfer for line differential protection...........21
4.1 Communication channels for line differential protection......................................................21
4.2 Communication between channels via Line data communication module..........................22
4.3 Configuration of analog signals...........................................................................................22
4.3.1 Configuration of analog inputs...........................................................................................23
4.3.2 Configuration of output signals..........................................................................................24
4.4 Configuration of redundant channels.................................................................................. 25
4.5 Link forward.........................................................................................................................27
4.5.1 Application configuration ACT...........................................................................................28
4.6 Configurations with power transformers in the protected zone........................................... 29
4.6.1 Line differential protection L3CPDIF, L6CPDIF, LT3CPDIF, LT6CPDIF............................ 29
4.6.1.1 Power transformers in the protected zone................................................................... 29
4.6.2 Line differential protection L4CPDIF................................................................................. 31
4.6.2.1 Possible configurations................................................................................................ 31
4.7 Setting examples.................................................................................................................32
4.7.1 Line differential protection L3CPDIF, L6CPDIF, LT3CPDIF, LT6CPDIF............................ 32
4.7.2 Line differential protection L4CPDIF................................................................................. 41
1MRK505382-UEN Rev. K Table of contents
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4.7.2.1 Setting example with a two-end power line .................................................................41
4.8 Configuration of binary signals............................................................................................45
4.8.1 Operation principle............................................................................................................ 45
4.8.2 Configuration of binary inputs and outputs........................................................................46
4.8.2.1 Configuration of binary inputs and outputs via ACT.....................................................46
4.8.2.2 Configuration of binary inputs and outputs via SMT.................................................... 48
4.8.3 Binary output signals.........................................................................................................51
4.8.4 Setting guidelines..............................................................................................................54
4.8.5 Settings............................................................................................................................. 58
Section 5 Communication set-up................................................................................63
5.1 Communication alternatives................................................................................................63
5.2 Communication channels....................................................................................................63
5.3 Fibre-optic communication interfaces with C37.94 protocol................................................65
5.4 Galvanic X.21 line data communication (X.21-LDCM)........................................................68
5.4.1 Introduction .......................................................................................................................68
5.4.2 Design............................................................................................................................... 68
5.4.3 Functionality...................................................................................................................... 70
5.4.4 Technical data................................................................................................................... 70
5.4.5 Communication via built-in X.21 galvanic interface...........................................................71
5.4.5.1 Service settings for the line differential protection IED with X.21 galvanic interface....71
5.4.5.2 PDH telecommunication via C37.94 interface to external transceiver C37.94-X.21.... 71
5.5 PDH telecommunication via C37.94 interface to transceiver 21-216..................................72
5.5.1 Communication requirements........................................................................................... 72
5.5.2 Communication structure via C37.94 interface to transceiver 21-216...............................73
5.5.3 Setting up transceiver 21–216...........................................................................................73
5.5.4 Power-up and LED statuses with transceiver 21–216.......................................................75
5.5.5 Service settings.................................................................................................................76
5.5.5.1 Service settings for the line differential protection IED.................................................76
5.5.5.2 Service settings for transceiver 21–216.......................................................................77
5.5.6 Earthing ............................................................................................................................77
5.5.7 Communication structure for laboratory testing.................................................................78
5.6 PDH/SDH telecommunication via C37.94 interface to transceiver 21-219 ........................ 79
5.6.1 Communication requirements........................................................................................... 79
5.6.2 Communication structure with transceiver 21-219 port synchronized from SDH
master clock...................................................................................................................... 79
5.6.3 Communication structure with PDH/SDH port synchronized from transceiver 21-219..... 80
5.6.4 Setting up transceiver 21–219...........................................................................................81
5.6.5 Power-up and LED statuses with transceiver 21–219.......................................................83
5.6.6 Service settings.................................................................................................................84
5.6.6.1 Service settings for the line differential protection IED.................................................84
5.6.6.2 Service settings for transceiver 21–219.......................................................................85
5.6.7 Earthing ............................................................................................................................85
5.6.8 Communication structure for laboratory testing.................................................................86
5.7 Communication status and fault tracing.............................................................................. 86
5.7.1 Communication status on the line differential protection IED............................................86
5.7.2 Detecting communication faults on transceiver 21-216.....................................................89
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2Communication set-up, 670/650 series
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5.7.3 Detecting communication faults on transceiver 21-219.....................................................89
5.7.4 Detecting communication faults through loop-back testing...............................................90
Section 6 Appendix...................................................................................................... 93
6.1 Sample specification of communication requirements........................................................ 93
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4

Section 1 Introduction
1.1 This manual GUID-AB423A30-13C2-46AF-B7FE-A73BB425EB5F v21
This manual contains application examples for the set-up of the communication software and
hardware. The manual is covering functionality that may not be available in the customers' actual
product.
1.2 Intended audience GUID-C9B8127F-5748-4BEA-9E4F-CC762FE28A3A v11
This manual addresses the personnel responsible for commissioning, maintenance and taking the
IED in and out of normal service.
The commissioning personnel must have a basic knowledge of handling electronic equipment. The
commissioning and maintenance personnel must be well experienced in using protection equipment,
test equipment, protection functions and the configured functional logics in the IED.
1.3 Product documentation
1.3.1 Product documentation set GUID-3AA69EA6-F1D8-47C6-A8E6-562F29C67172 v16
IEC07000220-4-en.vsd
Planning & purchase Engineering Installing Commissioning Operation Maintenance Decommissioning Deinstalling & disposal
Application manual
Operation manual
Installation manual
Engineering manual
Communication
protocol manual
Cyber security
deployment guideline
Technical manual
Commissioning manual
IEC07000220 V4 EN-US
Figure 1: The intended use of manuals throughout the product lifecycle
The engineering manual contains instructions on how to engineer the IEDs using the various tools
available within the PCM600 software. The manual provides instructions on how to set up a PCM600
1MRK505382-UEN Rev. K Section 1
Introduction
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© 2017 - 2023 Hitachi Energy. All rights reserved

project and insert IEDs to the project structure. The manual also recommends a sequence for the
engineering of protection and control functions, as well as communication engineering for IEC 61850.
The installation manual contains instructions on how to install the IED. The manual provides
procedures for mechanical and electrical installation. The chapters are organized in the chronological
order in which the IED should be installed.
The commissioning manual contains instructions on how to commission the IED. The manual can
also be used by system engineers and maintenance personnel for assistance during the testing
phase. The manual provides procedures for the checking of external circuitry and energizing the IED,
parameter setting and configuration as well as verifying settings by secondary injection. The manual
describes the process of testing an IED in a substation which is not in service. The chapters are
organized in the chronological order in which the IED should be commissioned. The relevant
procedures may be followed also during the service and maintenance activities.
The operation manual contains instructions on how to operate the IED once it has been
commissioned. The manual provides instructions for the monitoring, controlling and setting of the
IED. The manual also describes how to identify disturbances and how to view calculated and
measured power grid data to determine the cause of a fault.
The application manual contains application descriptions and setting guidelines sorted per function.
The manual can be used to find out when and for what purpose a typical protection function can be
used. The manual can also provide assistance for calculating settings.
The technical manual contains operation principle descriptions, and lists function blocks, logic
diagrams, input and output signals, setting parameters and technical data, sorted per function. The
manual can be used as a technical reference during the engineering phase, installation and
commissioning phase, and during normal service.
The communication protocol manual describes the communication protocols supported by the IED.
The manual concentrates on the vendor-specific implementations.
The point list manual describes the outlook and properties of the data points specific to the IED. The
manual should be used in conjunction with the corresponding communication protocol manual.
The cyber security deployment guideline describes the process for handling cyber security when
communicating with the IED. Certification, Authorization with role based access control, and product
engineering for cyber security related events are described and sorted by function. The guideline can
be used as a technical reference during the engineering phase, installation and commissioning
phase, and during normal service.
1.3.2 Document revision history GUID-34B323E4-1319-4D42-80CE-29B0F2D36E2C v8
Document
revision
Date Product version History
- 2017–05 2.2.0 First release for product version 2.2
A 2017–10 2.2.1 Ethernet ports with RJ45 connector added.
B 2018–03 2.2.1 Document enhancements and corrections
C 2018–06 2.2.2 Technical data updated for PSM. Case dimensions
updated.
D 2018–11 2.2.3 Functions CHMMHAI, VHMMHAI, DELVSPVC,
DELISPVC and DELSPVC added. Updates/
enhancements made to ZMFPDIS, ZMFCPDIS,
CCRBRF, REALCOMP, PTRSTHR and FNKEYMDx.
Ordering section updated.
E 2019-05 2.2.3 PTP enhancements and corrections
F Document not released
Table continues on next page
Section 1 1MRK505382-UEN Rev. K
Introduction
6Communication set-up, 670/650 series
Application Guide
© 2017 - 2023 Hitachi Energy. All rights reserved

Document
revision
Date Product version History
G Document not released
H 2020-09 2.2.4 Minor document enhancements and corrections
J 2021-06 2.2.5 Minor document enhancements and corrections
K 2023-06 2.2.6 Minor document enhancements and corrections
1.3.3 Related documents GUID-94E8A5CA-BE1B-45AF-81E7-5A41D34EE112 v10
Documents related to REB670 Document numbers
Application manual IEC: 1MRK505370-UEN
Commissioning manual IEC: 1MRK505372-UEN
Product guide 1MRK505373-BEN
Technical manual IEC: 1MRK505371-UEN
Type test certificate IEC: 1MRK505373-TEN
Documents related to REC670 Document numbers
Application manual IEC: 1MRK511401-UEN
Commissioning manual IEC: 1MRK511403-UEN
Product guide 1MRK511404-BEN
Technical manual IEC: 1MRK511402-UEN
Type test certificate IEC: 1MRK511404-TEN
Documents related to RED670 Document numbers
Application manual IEC: 1MRK505376-UEN
Commissioning manual IEC: 1MRK505378-UEN
Product guide 1MRK505379-BEN
Technical manual IEC: 1MRK505377-UEN
Type test certificate IEC: 1MRK505379-TEN
Documents related to REG670 Document numbers
Application manual IEC: 1MRK502071-UEN
Commissioning manual IEC: 1MRK502073-UEN
Product guide 1MRK502074-BEN
Technical manual IEC: 1MRK502072-UEN
Type test certificate IEC: 1MRK502074-TEN
1MRK505382-UEN Rev. K Section 1
Introduction
Communication set-up, 670/650 series 7
Application Guide
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Documents related to REL670 Document numbers
Application manual IEC: 1MRK506369-UEN
Commissioning manual IEC: 1MRK506371-UEN
Product guide 1MRK506372-BEN
Technical manual IEC: 1MRK506370-UEN
Type test certificate IEC: 1MRK506372-TEN
Documents related to RET670 Document numbers
Application manual IEC: 1MRK504163-UEN
Commissioning manual IEC: 1MRK504165-UEN
Product guide 1MRK504166-BEN
Technical manual IEC: 1MRK504164-UEN
Type test certificate IEC: 1MRK504166-TEN
Documents related to RES670 Document numbers
Application manual IEC: 1MRK511407-UEN
Commissioning manual IEC: 1MRK511409-UEN
Product guide 1MRK511410-BEN
Technical manual IEC: 1MRK511408-UEN
Type test certificate IEC: 1MRK511410-TEN
Documents related to RER670 Document numbers
Application manual IEC: 1MRK506375-UEN
Commissioning manual IEC: 1MRK506377-UEN
Product guide 1MRK506378-BEN
Technical manual IEC: 1MRK506376-UEN
Type test certificate IEC: 1MRK506378-TEN
670 series manuals Document numbers
Operation manual IEC: 1MRK500127-UEN
Engineering manual IEC: 1MRK511398-UEN
Installation manual IEC: 1MRK514026-UEN
Communication protocol manual, DNP3 1MRK511391-UUS
Communication protocol manual, IEC 60870-5-103 1MRK511394-UEN
Communication protocol manual, IEC 61850 Edition 1 1MRK511392-UEN
Communication protocol manual, IEC 61850 Edition 2
and Edition 2.1
1MRK511393-UEN
Communication protocol manual, LON 1MRK511395-UEN
Communication protocol manual, SPA 1MRK511396-UEN
Point list manual, DNP3 1MRK511397-UUS
Accessories guide IEC: 1MRK514012-BEN
Table continues on next page
Section 1 1MRK505382-UEN Rev. K
Introduction
8Communication set-up, 670/650 series
Application Guide
© 2017 - 2023 Hitachi Energy. All rights reserved

670 series manuals Document numbers
Cyber security deployment guideline 1MRK511399-UEN
Connection and Installation components 1MRK513003-BEN
Test system, COMBITEST 1MRK512001-BEN
Application guide, Communication set-up 1MRK505382-UEN
1.4 Document symbols and conventions
1.4.1 Symbols GUID-2945B229-DAB0-4F15-8A0E-B9CF0C2C7B15 v13
The electrical warning icon indicates the presence of a hazard which could result in
electrical shock.
The warning icon indicates the presence of a hazard which could result in personal injury.
The caution hot surface icon indicates important information or warning about the
temperature of product surfaces.
The caution icon indicates important information or warning related to the concept
discussed in the text. It might indicate the presence of a hazard which could result in
corruption of software or damage to equipment or property.
The information icon alerts the reader of important facts and conditions.
The tip icon indicates advice on, for example, how to design your project or how to use a
certain function.
Although warning hazards are related to personal injury, it is necessary to understand that under
certain operational conditions, operation of damaged equipment may result in degraded process
performance leading to personal injury or death. It is important that the user fully complies with all
warning and cautionary notices.
1.4.2 Document conventions GUID-96DFAB1A-98FE-4B26-8E90-F7CEB14B1AB6 v9
• Abbreviations and acronyms in this manual are spelled out in the glossary. The glossary also
contains definitions of important terms.
• Push button navigation in the LHMI menu structure is presented by using the push button icons.
For example, to navigate between the options, use and .
• HMI menu paths are presented in bold.
For example, select Main menu/Settings.
• LHMI messages are shown in Courier font.
For example, to save the changes in non-volatile memory, select Yes and press .
• Parameter names are shown in italics.
For example, the function can be enabled and disabled with the Operation setting.
• Each function block symbol shows the available input/output signal.
1MRK505382-UEN Rev. K Section 1
Introduction
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• the character ^ in front of an input/output signal name indicates that the signal name may
be customized using the PCM600 software.
• the character * after an input signal name indicates that the signal must be connected to
another function block in the application configuration to achieve a valid application
configuration.
• Dimensions are provided both in inches and millimeters. If it is not specifically mentioned then
the dimension is in millimeters.
Section 1 1MRK505382-UEN Rev. K
Introduction
10 Communication set-up, 670/650 series
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© 2017 - 2023 Hitachi Energy. All rights reserved

Section 2 Telecommunication networks and
line differential protection
2.1 Overview
GUID-8EC49FAE-5EFE-4C17-AD2A-F1824B2518B4 v1
Telecommunication networks have two main application areas for multi-terminal line differential
protection IEDs with up to five line ends:
• Networks with symmetric or fixed routes using echo timing (back-to-back systems included)
• Networks with unspecified route switching using accurate global time derived from the Global
Positioning System (GPS)
Echo timing can be used as a fall-back system in the latter application area if the GPS
reference is lost in one or more IEDs,
.
GUID-0C62EF3A-999C-4EEF-BE48-CC4DF1DCD8D9 v1
With networks using symmetric or fixed routes and echo timing, the internal clock in each local line
differential protection IED operates as a master and the internal clock in each remote line differential
protection IED operates as a slave. Time deviations between the internal clocks are monitored
continuously, and compensated for with echo messages between all ends at 40 ms intervals over the
telecommunication network. After start-up, it takes approximately 15 seconds to reach full
synchronization of the internal clocks. Time deviation between the internal clocks is compensated for
to be within 1 μs of relative time.
The internal clock also functions as a real time clock for other protection and monitoring
functions such as event timing, but this is totally separate from the line differential
protection function.
With networks using unspecified route switching, reference for the internal clock comes from global
time provided by, for example, a built-in GPS receiver. The internal clock in each line differential
protection IED is thus set according to the GPS systems' global time. Inaccuracy depends on the
connection time to the GPS system. After start-up (cold start), a software calibration procedure is
carried out. After less than one hour, all internal clocks' real time deviation from the global time has
decreased to 1 μs.
There can be only one master clock in the telecommunication network for the synchronization of
multiplexers, transceivers and differential protection relays' communication modems. This clock can
also be a GPS clock but the telecommunication network synchronization is totally separate from the
line differential protection IED's internal clock synchronization.
2.2 Telecommunication network types GUID-3AA2C8C6-62B7-42E4-AD80-0479BAFF21C6 v1
There are two main types of telecommunication networks used by electric power utilities:
Plesiochronous Digital Hierarchy (PDH) networks and Synchronous Digital Hierarchy (SDH)
networks (see Figure 2). These networks are mostly owned by the utilities, but it is also possible to
lease communication links from external companies.
PDH networks are used with 64 kbit/s communication. Proper synchronization of PDH networks must
be available so that hey can be used with protection applications. SDH networks are used with 2
Mbit/s communication.
1MRK505382-UEN Rev. K Section 2
Telecommunication networks and line differential protection
Communication set-up, 670/650 series 11
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IEC07000240 V2 EN-US
Figure 2: Telecommunication networks for electric power utilities
2.3 Telecommunication networks with symmetric or fixed
routes GUID-36D8D02D-E63A-4DFC-83C0-1C37708390AD v1
It is possible to use networks with fixed routes where symmetric time delay is applied, or networks
with fixed route switching where both directions have a symmetric time delay even after route
switching has been performed. In these types of networks, different channel delay times are
automatically compensated for, and echo timing can be used. If a fixed route has specified
asymmetry, this can be compensated for by using the AsymDelay parameter.
The maximum interruption time for route switching and echo timing (for example when a
communication channel is lost) without affecting the synchronization of internal clocks is 2 s. The
protection function gets blocked for the duration of the interruption. The 2 s time limit is derived from
the stability of the internal clocks. If route switching takes longer than that, the protection function
gets blocked until the internal clocks are re-synchronized. Proper re-synchronization of the internal
clocks takes an additional 15 seconds after the channel is restored.
From protection point-of-view, route switching interruptions should be < 50 ms (normally route
switching takes < 0.1 ms). The maximum time delay in a telecommunication network can be set to 40
ms (default delay being 20 ms). In echo timing mode, this time represents round-trip delay divided by
two. If the channel delay is longer than the set value, the protection function gets blocked.
The recommended value for maximum time delay when using echo timing is 20 ms.
The protection function also gets blocked if the maximum time deviation (MaxtDiffLevel) between the
line differential protection IEDs' internal clocks is higher than ±200-2000 μs (see Figure 3). Blocking
of the function lasts until the internal clocks' deviation reaches the set value range. Time required for
new synchronization depends on the interruption time.
Section 2 1MRK505382-UEN Rev. K
Telecommunication networks and line differential protection
12 Communication set-up, 670/650 series
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IEC07000221 V2 EN-US
Figure 3: Three-end application (protection master/slave)
2.3.1 Maximum time deviation between internal clocks GUID-20739D2E-572A-4D7B-83F3-3F55B7177681 v1
2.3.1.1 Setting the maximum time deviation GUID-787C8FBC-2B88-4488-AE46-3F58A7C5A4B1 v1
Maximum time deviation between internal clocks is set using the MaxtDiffLevel parameter in the
respective (one to five) line differential protection IEDs. The setting is done on the local HMI or via
PCM600 (see Figure 4). Maximum time deviation depends on:
• Jitter and wander in the telecommunication network: typically ±100-200 μs in PDH networks and
±50 μs in SDH networks (< ±100 μs according to telecommunication standards).
• Acceptable small asymmetric delay: typically ±50–100 μs. A constant (fixed) asymmetric delay
in the duplex channels can be adjusted by setting the asymmetric delay on the local HMI or via
the parameter setting tool (PST) which is part of PCM600.
• Buffer memory in the telecommunication network: typically < +100 μs (buffer memories should
be avoided).
• Clock drift during two seconds: < ±100 μs.
IEC10000062 V1 EN-US
Figure 4: Setting the MaxtDiffLevel in PCM600
1MRK505382-UEN Rev. K Section 2
Telecommunication networks and line differential protection
Communication set-up, 670/650 series 13
Application Guide
© 2017 - 2023 Hitachi Energy. All rights reserved

The setting range for MaxtDiffLevel is ±200-2000 μs, and it must be coordinated with reference to the
sensitivity of the protection function. This setting is only relevant for echo timing.
MaxtDiffLevel is defined and measured at a sudden change in time difference between the line ends
induced by route switching. If the set value for MaxtDiffLevel is exceeded, the protection function
gets blocked. To avoid unwanted trips produced by a number of small changes below the set value,
these small changes are summated and checked to be below MaxtDiffLevel.
The line differential protection IED has no supervising function that could detect the difference
between asymmetric delay, buffer memory delay, telecommunication network jitter and wander, and
internal clock drift. The sum of these factors is supervised by observing the deviation between the
internal clocks in all IEDs.
GPSSyncErr denotes GPS synchronization error, and it is activated when GPS global time and
internal clock time deviate by more than 16 μs. If activated, the differential protection function can be
set to be blocked or the echo mode can be set to be activated.
In an SDH network (≥ 2 Mbit/s) with an acceptably small asymmetric delay, for example G.703 E1,
maximum time deviation of 2 x ±300 μs can be used. In a PDH network (n x 64 kbit/s) with a buffer
memory of for example 100 μs, typical maximum time deviation is 2 x ±400 μs. The actual setting
value is to be calculated accordingly.
2.3.1.2 Reference clock deviation from the set maximum time deviation
GUID-0FC23ED9-2CDB-48EE-ADDB-81D39E334F56 v1
Reference clock deviation lower than the set maximum time deviation
Route switching that causes the virtual difference between the internal clocks of respective line
differential protection IEDs to be lower than the set maximum time deviation due to asymmetry in the
communication channel delay, jitter and wander, and buffer memory, does not cause a
communication failure alarm or blocking of the protection function. The deviation is considered to be
within the accuracy requirements, and will be compensated for by the normal synchronization
mechanisms of the internal clocks.
If route switching takes longer than 2 s, master and slave IEDs start to re-synchronize after a 4 s
delay incorporating the new channel asymmetry. Synchronization adjusts the internal clock
differences of differential protection IEDs at different line ends to be within ±1 μs. Time
synchronization messages are evaluated every 5 ms. If maximum time deviation is set to ±200 μs, it
takes approximately 10 seconds to reach new synchronization. Synchronization reaches the ±1 μs
accuracy after an additional 10-15 seconds.
Reference clock deviation higher than the set maximum time deviation
Route switching that causes the virtual difference between the internal clocks of respective line
differential protection IEDs to be higher that the set maximum time deviation (±200-2000 μs) due to
asymmetry in the communication channel delay, jitter and wander, and buffer memory, causes the
blocking of the internal clock synchronization. If this deviation lasts under 2 s, the protection function
still remains in operation. The total stability time of 2 seconds stems from the route switching being
supervised during 50 internal clock synchronization messages that are sent every 5 ms but evaluated
every 40 ms.
If deviation between the internal clocks is higher than the set limit after 2 s, a communication failure
alarm is issued and the protection function gets blocked. After communication channels are restored,
a re-synchronization with initial 20 μs clock adjustment steps takes place for each clock
synchronization message. The clock adjustment steps gradually decrease as the internal clock
differences are reduced.
Section 2 1MRK505382-UEN Rev. K
Telecommunication networks and line differential protection
14 Communication set-up, 670/650 series
Application Guide
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