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					18   ABB review 3|11
Advanced power
grid protection
Next generation teleprotection solutions

RoMEo CoMINo,                                                    isturbances and faults in          tion equipment and a telecommunica-
MIChAEl STRITTMATTER –                                           power systems can result in        tions system ➔ 1. Teleprotection acts
Teleprotection is vital for the reliability                      severe voltage collapses and       as a physical interface between the
and economy of modern electric power                             power blackouts, affecting         telecommunication infrastructure and
systems. With the emerging deploy-                   entire regions or even countries. Due to       the protection relays. It is therefore
ment of non-deterministic Ethernet/IP                its heavy reliance on electric power,          essential for the conveyance of signals
technology in wide-area communication                modern society cannot accept such              generated by protection relays (“com-
networks, utilities around the world                 power outages –
are concerned that protection signaling,             neither for their
which ensures fast and selective                     impact on public         Protection systems must meet
isolation of faults in the power network,            life nor for their
might be compromised. Thanks to                      economical conse-        sensitivity, time response,
the company’s vast experience in
teleprotection and utility communica-
                                                     quences. It is there-
                                                     fore vital to avoid
                                                                              selectivity and reliability speci-
tions, ABB has been able to drive the                major disturbances       fications in order to satisfy
development of new interfaces for                    by all possible
its teleprotection platform NSD570,                  means. A key ele-        fault clearing requirements.
allowing secure, reliable and depend-                ment for the isola-
able operation of protection signaling               tion and fast clearing of faults is a sound    mands”), and to ensure that their
equipment over Ethernet/IP WAN                       protection practice.                           response time and selectivity needs
networks for the first time.                                                                        are met in case of power system fault
                                                     Protection systems must meet sensi-            conditions.
                                                     tivity, time response, selectivity and reli-
                                                     ability specifications in order to satisfy     Performance criteria for tele-
                                                     fault clearing requirements. Protection        protection: security, dependability
                                                     schemes, in particular for high-voltage        and transmission time
                                                     transmission lines, rarely meet all these      Since any telecommunication system
                                                     requirements without using telecommu-          is subject to various forms of inter-
                                                     nications.                                     ference and impairment (such as jitter
                                                                                                    and bit errors in digital networks or
                                                     The typical protection-system archi-           corona noise and attenuation variations
Title Picture
                                                     tecture on a high-voltage transmis-            on a power line carrier channel), the per-
Utlities are concerned that protection signaling
in substations might be at stake due to non-deter-   sion line consists of three main com-          formance of the teleprotection equip-
ministic Ethernet communication.                     ponents: protection relays, teleprotec-        ment under these disturbed channel

                                                                                                           Advanced power grid protection   19
 Disturbances may neither simulate a
 command that was not transmitted (security),
 nor unduly delay or suppress a command
 that was transmitted(dependability).

1 Typical protection system architecture

         Substation A                                                                                                    Substation B
                                                                   High-voltage line

         Protection                Teleprotection                                            Teleprotection               Protection
         equipment/                 equipment/                                                equipment/                  equipment/
          function                    function                                                  function                   function

                                                                 Teleprotection system

                                                    conditions is characterized by the terms     time requirements, as defined in the
                                                    security, dependability and transmission     IEC 60834-1 standard [1].
                                                                                                 Security, dependability, transmission
                                                    An important criterion is the available      time and bandwidth (or data rate) are in-
                                                    bandwidth on analog links and the            terrelated parameters. The combination
                                                    data rate of digital or Ethernet channels.   of high security and high dependability
                                                    The higher the bandwidth or data             with short transmission time and narrow
                                                    rate, the lower
                                                    the    transmission
                                                    time that usually           ABB’s next generation
                                                    can be achieved
                                                    with the teleprot-          tele protection equipment of
                                                    ection equipment.
                                                                                type NSD570 is ready to
                                                    For the protection          allow Ethernet connectivity
                                                    system, it is of ut-
                                                    most importance             by means of a 10/100 Mbps
                                                    that disturbances
                                                    in the telecom-
                                                    munication chan-
                                                    nel must neither simulate a command at       bandwidth (or low data rate) are conflict-
                                                    the receiving end when no correspond-        ing requirements. As a result, the em-
                                                    ing command signal was transmitted           phasis must either be on dependability
                                                    (security), nor unduly delay or even sup-    or on security, or on transmission time,
                                                    press a command that was actually            depending on the protection scheme
                                                    transmitted (dependability).                 used, ie, whether protection signaling is
                                                                                                 applied in permissive tripping, direct trip-
                                                    In this regard, all teleprotection equip-    ping or blocking schemes.
                                                    ment must comply with relevant secu-
                                                    rity, dependability and transmission

20   ABB review 3|11
2 NSD570 Ethernet WAN Interface type G3lE

Another important criterion is the avail-        –   Power line carrier (PLC) links
ability of the communication channel             –   Fiber-optic links                                 Teleprotection
itself, in order to perform the required         –   Copper wires / pilot cables
function at any moment in time within a          –   Microwave-radio links                             systems normally
given interval [2]. The availability level for
a telecommunication system used for              The physical property of the interface be-
                                                                                                       rely on telecommu-
teleprotection should be at least 99.99          tween the teleprotection equipment and                nication channels
percent. To achieve this critical objective,     the communication terminal is either an
a profound knowledge of the applied              analog circuit with voice frequency band-             that provide a
telecommunication technology is essen-
tial. Moreover, an appropriate network
                                                 width, or a digital/optical circuit with a
                                                 certain data rate, eg 64 kbps ➔ 3.
                                                                                                       deterministic signal
design, implementation of self-healing or                                                              transmission delay
recovery mechanisms and necessary re-            ABB’s next generation teleprotection
dundancy and back-up methods are es-             equipment NSD570 offers a complete                    and have a con-
sential.                                         set of interfaces to the telecommunica-
                                                 tion system as mentioned above, and
                                                                                                       stant bandwidth.
Beside the availability of the communica-        enables Ethernet connectivity by means
tion channel, the electromagnetic com-           of a 10/100 Mbps interface, which will be
patibility (EMC) of the teleprotection sys-      discussed later in this article.
tem and its immunity against interference
from fast transient bursts and other out-        Is Teleprotection compromised with
side disturbances is critical. The entire        deployment of Ethernet/IP based
design of the teleprotection system and          networks?
respective hardware has to be such that          Teleprotection systems rely on telecom-
it can withstand interference precisely at       munication channels that provide a de-
the moment of a fault in the power sys-          terministic signal transmission delay and
tem, ie, at the time when its ability to reli-   have a constant bandwidth or bit rate
ably transmit commands is most required.         over time, without any delay variation.
                                                 Static multiplexing techniques such as
Teleprotection via different telecom-            plesiochronous digital hierarchy (PDH) 1
munication media and channels
Various types of transmission media can be
used for teleprotection. As point-to-point
                                                 1 A plesiochronous digital hierarchy (PDH) network
communication links are still commonly              is a network in which different data streams are
used, the following media prevail today:            nearly, but not quite perfectly, synchronized.

                                                                                                          Advanced power grid protection   21
3 Transmission media and communication channels available with                                                         4 The challenge – teleprotection over Ethernet/IP networks

                                          PLC          Power       PLC                                                                            Station B
                                                        line                                                                                                                     Station C
                                      MUX              Radio       MUX






                                      MUX              -   -       MUX                                                                                                                 NSD570

                                                                                                                         Station A

                          op igita g

                                                                     an igita al

                           d alo
                            tic l

                                                                       d tic

                                                                        alo l



 Protection                           -                                        -                          Protection                                      Ethernet/IP
 commands                                          Optical                                                commands                                         network
                                                    fibre                                                               NSD570
                                      analo                                g
                                               g                   analo
                                                   -           -                                                                      Station E
                                he                 Copper                                 et                                                                                          Station D
                                     rn                                              rn
                                          et        wires                       he

                                                   IP based
                                                    network                                                                          NSD570

                                                                                               and synchronous digital hierarchy (SDH)              – NSD570 Management LAN Interface
 ABB, as leading                                                                               networks comply with this requirement                  type G3LM
                                                                                               and have been deployed for decades by
 provider of tele-                                                                             utilities in their wide-area communication           NSD570 Ethernet WAN Interface

 protection solu-                                                                              networks.                                            type G3lE
                                                                                                                                                    – New line interface for transferring of
 tions, has devel-                                                                             With the emerging deployment of statis-                up to eight simultaneous/independent
                                                                                               tical multiplexing transmission technolo-              commands over Ethernet/IP net-
 oped a new set                                                                                gies that use bandwidth-on-demand                      works ➔ 3.

 of interfaces for                                                                             or “best effort” techniques, utilities
                                                                                               around the world are concerned that the
                                                                                                                                                    – Channel monitoring and alarming
                                                                                                                                                      functions similar to the existing
 the NSD570 plat-                                                                              stringent performance requirements of                  NSD570 line interfaces (channel
                                                                                               teleprotection systems might be com-                   quality and availability, end-to-end
 form to allow pro-                                                                            promised when using these new com-                     delay, terminal addressing).

 tection signaling                                                                             munication technologies. This is a par-
                                                                                               ticular concern where utilities rely on              NSD570 Management lAN Interface

 and remote man-                                                                               third-party telecommunication services,
                                                                                               for which the communications channels
                                                                                                                                                    type G3lM
                                                                                                                                                    – Successor of existing management
 agement over                                                                                  are not under the full control of the utili-           interface for remote access, with

 Ethernet/IP net-                                                                              ties themselves.                                       additional features such as SNMP
                                                                                                                                                      (Simple Network Management
 works.                                                                                        As a consequence, in situations where
                                                                                               Ethernet/IP-based networks are used
                                                                                                                                                      Protocol) and VLAN (Virtual Local
                                                                                                                                                      Area Network) support, improved
                                                                                               for protection signaling, a solution is                cyber-security measures such as
                                                                                               required that allows to monitor the avail-             authentication and logging.
                                                                                               ability and quality of the WAN (wide-                – For the remote supervision/manage-
                                                                                               area network) communication channel,                   ment of the teleprotection units in a
                                                                                               and to alarm the protection equipment                  rack and further units accessible via
                                                                                               if the reliable transmission of com-                   the RS-485 station bus. The latter
                                                                                               mands to the remote end cannot be                      permits several racks to be intercon-
                                                                                               ensured ➔ 4.                                           nected ➔ 5.

                                                                                               Innovative solutions for next-genera-                Both modules offer an electrical port
                                                                                               tion teleprotection                                  (10/100 Mbps) and an optical port
                                                                                               ABB, as leading provider of teleprotec-              (100 Mbps) with exchangeable small form-
                                                                                               tion solutions, has developed a new set              factor pluggable (SFP) transceivers for
                                                                                               of interfaces for the NSD570 platform to             connection to the Ethernet/IP network ➔ 6.
                                                                                               allow protection signaling and remote
                                                                                               management over Ethernet/IP net-                     NSD570 Ethernet WAN interface
                                                                                               works ➔ 2. The innovative solutions con-             (G3lE) -– reliable protection signaling
                                                                                               sist of the following two modules:                   solution over Ethernet/IP networks
                                                                                               – NSD570 Ethernet WAN Interface type                 Instead of simply converting the existing
                                                                                                  G3LE                                              synchronous 64 kbps channel of the

22   ABB review 3|11
5 Secure remote access of NSD570                                                    6 New G3lE/G3lM plug-in module for ABB’s teleprotection platform

        RS-485 station bus                          Substation     Substation


      One NSD570
      equipped with
      LAN-interface          S/S-LAN                  Gateway

                                       Corporate intranet
                                        global Internet


NSD570 digital system to Ethernet pack-                     ping packets, but at the lower rate set for    Comprehensive tests were conducted
ets, a protocol was developed in order to                   guard-packets. If the command is re-           on the new G3LE type NSD570 Ethernet
reduce latency and bandwidth require-                       moved by the protection relay, guard           interface in a network built up of ABB’s
ments.                                                      packets are sent from then on.                 Ethernet type AFS switch family. Even
                                                                                                           with simulated burst traffic of varying
Beside the actual teleprotection com-                       The reception of only one correct trip-        packet size and traffic overload on sec-
mands, the payload content of such a                        ping packet at the remote NSD570 trig-         tions of the network, the transmission
packet comprises several data fields that                   ger the configured relay interface outputs     time did not exceed 4 ms, and averaged
enable the measurement of various key                       in accordance with the commands re-            approximately 2.5 ms.
performance parameters including trans-                     ceived in the packet.
mission time and packet loss rate.                                                                         To verify reliable operation even under
                                                            Priority settings for time-critical            severely disturbed Ethernet/IP network
The entire payload is protected by an au-                   teleprotection commands                        conditions, ie, with packet loss rates
thentication algorithm (patent pending),                    As teleprotection commands are time-           (PLR) of up to 10 percent and above, the
which addresses various cyber-security                      critical, they should be transmitted as        dependability (referred to as Pmc or prob-
issues.                                                     fast as possible through the network.          ablility of missing a command) was mea-
                                                            Both IP and Ether-
Channel supervision continuously                            net offer means to
monitors quality and availability                           set priorities and       All user activity is logged in
A packet-switched network is vulnerable                     handle high-priori-
to various factors that can negatively                      ty traffic accord-       order to detect security
affect transmission time.                                   ingly. The NSD570
                                                            Ethernet supports
                                                                                     relevant system manipulations
The NSD570 Ethernet continuously                            Ethernet/IP priority     at an early stage.
monitors the channel’s availability and                     settings with the
quality using “guard” packets that are                      following parameters: ToS – setting the        sured. At various PLR levels, a significant
sent at user-configurable intervals.                        type of service field on IP layer 3, and       number of tripping commands were
Alarms are generated if the measured                        VLAN tagging – ID and priority setting of      sent, the number of commands not re-
transmission time or packet-loss rate ex-                   the Ethernet frame on layer 2.                 ceived within a specified transmission
ceeds user-configurable thresholds, or if                                                                  time (Tac) was recorded and thus the re-
the channel is lost completely.                             Proven performance under severe                sulting P mc was calculated. For compari-
                                                            network conditions                             son, the measurement of the depend-
Ensure dependable command                                   The worst-case requirement for security        ability is based on the bit error rate (BER),
transmission                                                (referred to as Puc or probability of an un-   which can be derived from the corre-
As soon as a command is received from                       wanted command) of tripping commands           sponding packet loss rate PLR ➔ 7.
the protection relay, the NSD570 Ether-                     transferred in digital communication
net WAN interface starts sending multi-                     systems according to IEC 60834-1 is            These test results, in conjunction with
ple “tripping” packets at short intervals.                  Puc < 1E-08. For the new protocol imple-       additional field trials in utility Ethernet/IP
This ensures fast reception of packets at                   mented in the NSD570, a P uc of < 1E-18        networks, confirmed that ABB’s innova-
the remote NSD570, even under very                          can be proven mathematically.                  tive Ethernet WAN interface type G3LE
bad channel conditions (ie, high packet                                                                    meets and exceeds the requirements as
loss). Following this initial sequence, the                                                                set for “Digital” teleprotection equipment
NSD570 Ethernet continues to send trip-                                                                    according to IEC 60834-1.

                                                                                                                   Advanced power grid protection     23
 An appropriate
                       7 Excerpt of test results (NSD570 Ethernet WAN interface, type G3lE)

 Ethernet/IP             Dependability
                         Channel condition –
                                               Pmc <     1E-02       1E-02      1E-03         1E-03       1E-04

 network design          Packet Loss Rate
                         Channel condition –
                                               PLR <     1%          2%         3%            10%           10%

 is a prerequisite       Bit Error Rate
                         Max. actual
                                               BER <     1.1E-05     2.3E-05    3.5E-05       1.2E-04    1.2E-04

 as is engineering       Transmission time     Tac ≤     4 ms        5 ms       6 ms          8 ms        10 ms

 that guarantees
 the requested         Assuring reliable command transmission         tion of Ethernet-based            local      area
                       requires both an appropriate Ethernet/IP       networks in substations.
 maximum packet        network design and a setup guaran-

 loss rate and         teeing the specified packet loss rate
                       and latency between the two NSD570
                                                                      Currently, IEC 61850 intra-substation
                                                                      Ethernet bus communication is used for
 minimum latency.      terminals are not exceeded. If this
                       requirement is not satisfied, NSD570
                                                                      control and automation signals only. Pro-
                                                                      tection signals are still hard-wired from
                       will immediately report the network im-        relay to relay or from relay to teleprotec-
                       pairment.                                      tion device. However, the new NSD570
                                                                      module type G3LS has been designed to
                       NSD570 management lAN interface                accept “GOOSE messages” 3 according
                       (G3lM) – secure remote connection              to IEC 61850-8-1 from protection relays
                       and monitoring                                 with GOOSE interface in future.
                       Together with the G3LE Ethernet WAN
                       interface, a new NSD570 Management             Moreover, new IEC working groups have
                       LAN interface type G3LM was also intro-        been formed to discuss and define the ex-
                       duced, enabling remote access on               tension of IEC 61850 for inter-substation
                       NSD570 teleprotection equipment over           communication. In March 2010, a techni-
                       Ethernet/IP networks. The integrated           cal report for this WAN communication
                       SNMP agent serves network manage-              was released under IEC 61850-90-1 [3].
                       ment stations with
                       alarm and equip-
                       ment information         Solution is fully integrated, ie
                       using the open
                       standard SNMP in-        no external devices that need
                                                their own power supply and
                       At the same time,        user/management interface
                       several     features
                       were integrated to       are required.
                       achieve the highest
                       possible level of cyber security and en-       As per the “gateway approach” described
                       able customers to operate the NSD570           in this report, the GOOSE protection sig-
                       teleprotection system supporting new           nals in WAN communication can be trans-
                       standards such as NERC CIP. A tech-            ferred to the remote NSD570 via any ana-
                       nique called Secure Socket Layer (SSL)         log, digital/optical or Ethernet channel ➔ 3.
                       is used for encryption and authentication
                       of the user access. Furthermore, a new         Mixed operation of “legacy” and IEC 61850
                       user administration system now allows          protection relays is possible with G3LS
                       individual user accounts to be set up and      GOOSE LAN interface:
                       access rights to be assigned to users in-
                       dividually. All user activity is logged, in    GOOSE and contact type commands
                       order to detect security-relevant system       can be signaled in parallel over the same
                       manipulations at an early stage.               NSD570 link. Additionally, GOOSE mes-
                                                                      sages from one substation can be re-
                       NSD570 ready for future applications           leased via contact type command out-
                       of IEC 61850                                   puts in the remote substation.
                       The introduction of IEC 61850 2, the in-
                       ternational standard for substation com-
                       munication, has driven the implementa-

24   ABB review 3|11
                                                 Customers planning to migrate their
                                                 WAN communication network infrastruc-               With the latest
                                                 ture to Ethernet/IP based networks are
           Bit Error Rate
           Critical Infrastructure Protection    well supported by the NSD570 architec-              innovations of
  EMC      Electromagnetic Compatibility
                                                 ture. They can use digital and Ethernet
                                                 line interfaces in parallel for example, to
                                                                                                     ABB, NSD570
  GOOSE Generic Object Oriented Substation
                                                 build up confidence in the new medium.              offers a future-
                                                 For this purpose, a cost-efficient “1+1”
  IEC      International Electrotechnical
           Commission                            path protection operating mode is pro-              proof platform that
           Internet Protocol
           Local Area Network
                                                 vided, with no need to duplicate the relay
                                                 interfaces to the protection devices. The
                                                                                                     can be integrated
  MUX      Multiplexer                           setup requires only a second line inter-            into Ethernet/IP
  NERC     North American Electric Reliability   face for the redundant path, plugged into
           Corporation                           the same rack.                                      WAN networks or
  PDH      Plesiochronous Digital Hierarchy
  PLC      Power Line Carrier                                                                        into a substation
           Packet Loss Rate
           Synchronous Digital Hierarchy
                                                                                                     LAN network by
           Small Form-factor Pluggable
           Simple Network Management
                                                                                                     simply replacing/
                                                                                                     adding one
           Type of Service
           Virtual Local Area Network
  WAN      Wide Area Network

Thus, ABB’s NSD570, with its open ar-
chitecture, is ready to evolve in line with
both the IEC 61850 standards for intra-
and for inter-substation communication.

With ABB’s latest innovations, NSD570
offers a future-proof platform that can be
integrated into Ethernet/IP WAN or into a
substation LAN network by simply re-
placing/adding one module. NSD570 is a
true all-in-one system for communication         Romeo Comino
line and protection interface require-           Michael Strittmatter
ments.                                           ABB Power Systems
                                                 System Group Utility Communications
The solution is fully integrated, ie no ex-      Baden, Switzerland
ternal devices that need their own power
supply and user/management interface   
are required.

The large installed base of “legacy” pro-        References
                                                 [1] IEC publication 60834-1 “Teleprotection
tection relays with contact-type com-
                                                     Equipment of Power Systems – Performance
mand inputs/outputs can be used over                 and Testing – Part 1: Command Systems”.
all existing communication media, even           [2] Protection using Telecommunications, Cigré
in parallel with new IEC 61850 “GOOSE”               Joint Working Group 34/35.11, August 2001
                                                 [3] IEC publication 61850-90-1 “Use of IEC 61850
protection relays via the same NSD570
                                                     for the communication between substations”.
link. In this respect, NSD570 also sup-
ports the step-by-step retrofit of sub-
stations with IEC 61850, ie the inter-           Footnotes
connection of “legacy” substations with          2 See also the ABB Review Special Report on
IEC 61850 substations via existing                  IEC 61850, downloadable from
NSD570 teleprotection channels.
                                                 3 GOOSE: Generic Object Oriented Substation
                                                    Events is a control model defined by IEC 61850
                                                    for transferring event data.

                                                                                                       Advanced power grid protection   25

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