WHITE  PAPER  

C37.94 - Installation & Maintenance 1. INTRODUCTION

Power   utility   companies   constantly   monitor   high   voltage   power   lines   in  order  to  ensure  a  secure  and  uninterrupted  supply  of  electricity.  Protection  relays   are   used   at   substations   and   other   critical   locations   controlled  through   communications   links   in   order   to   isolate   faults,   protecting  equipment   and   plant.   The   communications   channels   used   for   protection  applications  demand  the  highest   level  of  availability  with  very   low  delays.  Legacy   Telecom   networks   historically   have   been   interconnected   using  metallic   circuits   the   problem   being   that   the   substation   environment   is  characterised   by   high   levels   of   electromagnetic   fields,   which   can   disturb  transmissions  on  copper  wires.  

To   avoid   the   problems   electromagnetic   fields   can   have   on   transmission  circuits   it   is   recommended   to   use   optical   links   using   the   IEEE   C37.94  standard.   The   IEEE   C37.94   standard   defines   the   rules   to   interconnect  teleprotection  and  multiplexer  devices  from  different  manufacturers  using  optical  fibres.    

All   rights   reserved.  No   part   of   this   document  may   be   stored,   copied   or   transmitted,   by   any  means,  without   the  permission   in   written  of   the   Legal  Owner  

©  2014  ALBEDO  Telecom  

Figure  1   Protection  of  high  voltage  power  lines  is  a  fundamental  task  of  power  utility  companies  to  deliver  a  secure  and  uninterrupted  supply  of  electricity.  

2  /  6  

2. PROTECTION OF HIGH VOLTAGE PoWER LINES

Authorities   use   a   teleprotection   schema   to   enable   substations   to  communicate  with  one  another  to  selectively  isolate  faults  on  high  voltage  lines,   transformers,   reactors   and   other   important   elements   of   electrical  plant.   This   requires   the   continuous   exchange   of   data   over   the   utilities  telecommunication   network   in   order   to   assure   correct   operation.   It   is  imperative  that  the  telecom  network  therefore  should  always  be  in  perfect  condition  in  terms  of  availability,  performance,  quality  and  delay.  

Telecom   networks   in   the   past   have   used   transmission   circuits   that   were  vulnerable   to   electromagnetic   and   radio   interference   (EMI/RFI),   signal  ground   loops,   and   ground   potential   rise.   Communications   circuits  vulnerable   to   interference   and   disturbance   are   not   acceptable  where   the  reliable  transport  of  teleprotection  protocols  is  required.    

The   electrical   substation   environment   is   usually   characterised   by   a   high  level  of  electromagnetic  fields  caused  by  the  high  voltages  and  currents  in  power   lines.  Moreover,   during   times  when  high   voltage   fault   conditions  occur   electromagnetic   disturbances   can   rise   significantly   causing  communication   errors   on   copper   based   communication   circuits.   The  reliability  of  the  communications  link  interconnecting  the  protection  relays  is  critical   and   must   be   resilient   to   the   effects   encountered   in   these   high  voltage  areas  such  as  high  frequency  induction  and  ground  potential  rise.  

Substation 1 Substation 2

Multiplexer E1, PDH, SDH Protection Channels Voice, Data, Video

Figure  2   Teleprotection  architecture  using  C37.94  in  normal  operation.  

Multiplexer E1, PDH, SDH

Protection Channels Voice, Data, Video

High Voltage

Power Relay Power Relay

Fiber Optics IEEE C37.94

Fiber Optics IEEE C37.94

PDH SDH

3  /  6  

To   prevent   these   issues   the   electrical   distribution   industry  moved   to   optical  fibres   to   connect   protection   relays   installed   in   substations.   Fibre   optic  connections   do   not   have   a   ground   path   and   are   therefore   immune   to  the   interferences   caused   by   electrical   noise.   T h e   u s e   o f  fully  optical  links  from  power  relays   to  multiplexers  using  the  IEEE  C37.94  standard  has  become  widespread  in  the  industry.  

Protection   schemes   using   IEEE   C37.94   interfaces   can   transport   signals  across   fault   tolerant   networks   of   different   kinds   including   PDH/SDH   and  Packet  networks.  These  fault  tolerant  networks  help  increase  the  reliability  and   availability   of   communications   circuits   helping   ensure   critical  teleprotection  data  interchanges.  

3. THE IEEE C37.94 STANDARD

Teleprotection  systems  must  isolate  faults  very  quickly  to  preventing  dam-­‐  age   to   the   network   and   power   outages.   The   IEEE   committee   defined   the  C37.94  as  a  programmable  n   x  64   kbps   (n=1...12)  multimode  optical   fibre  interface   to   provide   transparent   communications   between   teleprotection  relays   and   multiplexers   for   distances   of   up   to   2   km.   Later   on   the  industry   a l s o   adopted  monomode  optical  fibre  as  well  in  order  to  reach  longer  distances.  

The  standard  defines  the  protection  and  communications  equipment  inside  a   substation   using   optical   fibres,   the   method   for   clock   recovery,   jitter  tolerances   allowed   in   the   signals,   physical   connection   method,   and   the  actions   the   protection   equipment   must   follow   when   any   kind   of  network   anomalies  and  faults  occur.  Many  protection  relay  manufacturers  including  ABB,  SEL,  RFL,  RAD  and  others  have  already  implemented  C37.94.  Teleprotection  equipment  often  offers  a  choice  of  WAN  transmission  interfaces   including  IEEE  C37.94  compliant  fibre  interfaces,  G.703,  64Kbps  co-­‐directional,  E1  and  increasingly  Ethernet.  

Figure  3   Ether.Genius  is  a  multi  technology  tester  equipped  with  all  the  features  to  install  and  troubleshoot  C37.94  teleprotection  systems  and  Gigabit  Ethernet,  SyncE,  PTP,  E1  and  Datacom  services.

C37.94

4  /  6  

4. C37.94 Testing

Before   C37.94   interfaces   and   circuits   are   handed   over   for   protection  purposes   they   should  be   tested   and   verified   that   they  meet   the   required  standards  and  requirements.  There  is  a  major  difference  between  point-­‐to-­‐point  C37.94  circuits  and  multiplexed  channels  running  over  SDH  or  Packet  based   transmission   networks   although   both   require   testing   to   ensure  correct  operation.    

Direct  point-­‐to-­‐point  C37.94  circuits  perform  very  well  and  are  easy  to  test  because   they   are   symmetrical,   have   a   fixed   latency   and   do   not   share  bandwidth   with   other   applications.   On   the   other   hand   C37.94   interfaces  that   are   multiplexed   and   transported   over   synchronous   digital   hierarchy  (SONET/SDH)  or  packet  networks  are  not  symmetrical,  have  variable  delays  and   also   carry   other   data   that   can   impact   on   the   transmission   of   critical  protection  data.  

Bit Error Rate (BER) Testing

A   BER   test   verifies   the   ability   to   deliver   error   free   data   between   two  network  ports.  This  test  is  widely  deployed  in  communications  networks  as  it  can  detect  a  number  of  issues  occurring  anywhere  between  two  point  on  a  network  including:  

• Noise   interfering   with   the   transmission   medium   and   networkdevices.

• Failing  or  marginal  components  in  active  network  devices.• Marginal  electrical  signals  or  power  in  lasers  on  fibre  connections.• Framing   errors   due   to   issues  with   communications   clocks   causing

framing  errors  and  lost  data.• Interruptions  due  to  network  switching  and  other  events.• Delays   and   loss   of   data   due   to   network   overloads   or   buffer

overflow  in  network  and  multiplexer  devices.

A  BER  test  can  be  run  for  a  short  period  of  time  or  over  a  number  of  hours  in   order   to   expose   cyclical   network   events,   such   as   changing   bandwidth  usage  patterns  in  the  utility’s  network  or  random  events  like  the  switching  of  high-­‐voltage   lines.  Depending  on  the  transmission  technology  deployed  longer   periods   of   testing   may   be   required   if   for   example   microwave   or  wireless   links   are   used   or   when   a   packet   based   (Ethernet)   transport  network  is  being  used.  

Network Delay/Latency

Multiplexed   and   Packet   networks   normally   suffer   from   some   form   of  network   delay   and   latency.  Network   delays   can   have   serious   implications  on  the  performance  of  protection  systems  and  it   is  vital  to  be  able  to  test  that  any  network  delays  are  within  the  required  specification.  

Through  the  use  of  a   loopback  device  it   is  possible  to  measure  the  round-­‐trip  delay  between  two  ports  on  a  network  and  by  halving  the  delay  

5  /  6  

estimate   the  one-­‐way  delay.   This   assumes  however   that   the   transmission  path   between   the   two   points   is   symmetrical,   in   reality   when   there   are  multiplexers  and  other  network  equipment  in  the  path  this  is  unlikely  to  be  the  case.  The  probability  of  asymmetrical  network  delays  increases  further  when   packet   based   (Ethernet)   networks   are   used   or   when   wireless,  microwave  or  transport  circuits  are  deployed.  

With   the   use   of   the   Global   Positoning   System   (GPS)   now   being   a   viable  option  for  portable  and  hand-­‐held  test  equipment  it  is  possible  to  measure  the  one-­‐way-­‐delay  (OWD)  between  two  network  points.  Performing  a  OWD  test  means  that  the  delay/latency  can  be  measured  independently  in  each  direction  allowing  for  checks  of  network  asymmetry.  

Substation 1 Substation 2

Multiplexer E1, PDH, SDH Protection Channels Voice, Data, Video

Multiplexer E1, PDH, SDH

Protection Channels Voice, Data, Video

Figure  4   Teleprotection  system  installation  and  maintenance  with  ALBEDO  Ether.Genius.  

Interface Conformance

Although   a   BER   test   helps   to   verify   that   a   transmission   path   is   error   free  and   a   OWD   test   can   check   network   latency   and   delay,   checking   the  interface   for   compliance   helps   to   ensure   that   both   the   protection   relays  and   communications   equipment   are   able   to   interoperate   and   can  communicate  with  each  other.  

High Voltage

Power Relay Power Relay

Errors, Alarms G.821 performance

Frame/Unframed BERFrequency (Hz, ppm, max)

One-Way delay (GPS)Round Trip Delay

Optical Power Fiber Optics

IEEE C37.94 Fiber Optics

IEEE C37.94

SDH

6  /  6  

These   tests   include  basic   communications   checks   such  as   clock   frequency  and   deviation   measurements,   clock   recovery   and   optical   power  measurement.  Having  the  ability  to  carry  out  tests  such  as  these  in  addition  to   BER   and   delay   tests   can   help   save   considerable   time   when  troubleshooting  C.37.94  communication  issues  and  problems.  

5. ALBEDO ETHER.GENIUS AND C37.94

Ether.Genius  provides  a  fully  integrated  test  set  to  verify  protection  systems  using  C37.94   interfaces.  A  handheld   multi   technology   tester,  Ether.Genius  can   operate   up   to   24h   hours   on   batteries   and   can   verify   networks   and  services  based  on  Gigabit  Ethernet  (GbE),  Synchronous  Ethernet  (SyncE),  E1,  Datacom,  Precision  Time  Protocol  (PTP,   IEEE   1588v2),  Jitter/Wander,  One-­‐way-­‐delay  using  GPS,  Round  trip  delay  and  Optical  Power  measurements.  

Field  engineers  can  use  Ether.Genius  to  turn  up  new  C37.94  deployments,  or  to  troubleshoot  and  perform  maintenance  tests  on  teleprotection  relays  and   multiplexers.   Ether.Genius   can   perform   bit   error   rate   testing   (BERT),  events   monitoring,   one-­‐way-­‐delay   measurements   using   GPS,   round   trip  delays  and  optical  power  measurements.  

Figure  5   Albedo  Ether.Genius  multi-­technology  tester  for  installation  and  maintenance  telecom  networks  

7  /  6  

Ethernet Testing

Interfaces • Dual RJ-45 port for electrical connection 10/100/1000BASE-T; PoE detection and PoE transparency• 2 x SFPs ports: 10BASE-T, 100BASE-TX, 100BASE-FX, 1000BASE-T, 1000BASE-SX, 1000BASE-LX, 1000BASE-ZX and 1000BASE-BX• Autonegotiation: Bit rate at 10, 100, and 1000 Mbit/s, Disable autonegotiation and direct set up• EtherType II (DIX v.2), IEEE 802.3, IEEE 802.1Q, IEEE 802.1ad; IEEE 802.2–LLC1, IEEE 802.3–SNAP; IPv4 (RFC791), IPv6 RFC2460)

Generation (8 streams)

• MAC address: Source / Destination, Default / User defined, Single / Range• VLAN: Single VLAN support, Q-in-Q stacking, VID, DEI, S-VLAN, C-VLAN, and Priority codepoint• Type / Length: Generation/Analysis, Jumbo frames with MTU up to 10 kB• Bandwidth Profile: Constant, in bit/s and frames/s, Periodic Burst, in high/low traffic, Ramp, in high/low traffic, Poisson• Loopback: L1to L4 layers, filtering conditions, broadcast and ICMP frames control• Single, burst, rate, random, FCS error insertion in pass-through mode• Unframed Layer 1 (IEEE 802.3-2008 Annex 36A): High, Low, Mixed Frequency Test, Long, Short (NCITS TR-25-1999): RPAT, JJTPAT, SPAT• Framed Layer 2-4 BERT; PRBS: 2e11-1, 2e15-1, 2e20-1, 2e23-1, 2e31-1 and inverted, All 1, all 0, ud. (32 bits), SLA Payload Y.1731• RTD and VF tone generation

Filters for Statistics (up to 8 simultaneously)

• Ethernet Selection: MAC address, Type/Length, C-VID, S-VID, CoS and Priority with selection mask• IPv4 and IPv6 Selection: address, protocol, DSCP, Flow (v6): single value or range. UDP Selection: port: single value or range

Traffic Statistics

• Top 16 talkers: Sour/Dest MAC / IPv4 / IPv6 addresses, VID (VLAN), C-VID (Q_in_Q), S-VID (MPLS)• Ethernet Frame Counts (RFC 2819): VLAN, Q-in-Q, Priority, Control, Pause, BPDUs• Tx/Rx Uni-Multi-Broadcast, Errors, Undersized, Oversized, Fragments, Jabbers, Runts, (Late) Collisions, Sizes, MPLS stack length• Bandwidth Statistics: (in bit/s, frame/s,%) Rate, Max, Min, Aver, Occupancy, Unicast, Multicast, Broadcast• IPv4 & IPv6 counts: (in bit/s, frame/s,%) Unicast, Multicast, Broadcast, Errors, TCP, UDP, ICMP

Results

• Twisted Cable: MDI/MDI-X status, Open, Cable Length Test, Short, Polarities, Pair Skew. PoE: voltage and current• SFP: Presence current interface, Vendor, Part number, Optical power (over compatible SFP)• Frame Delay (FTD) Y.1563: Min/Max/Med/Mean; Delay Variation (FDV) RFC1889: Peak; Jitter Curr/Max/Min/Mean• Frame Loss (FLR) Y.1563, Duplicated: Out-of-Order packets (RFC 5236)• Availability: SES and Y.1563 PEU; BER: Count, seconds with errors, Pattern losses, pattern loss seconds

RFC-2544 & Y.1564 • RFC 2544: Throughput, Latency, Frame Loss, Back-to-back, Recovery• eSAM: test up to 8 non-color or 4 color aware services. Configuration: CIR, EIR, max. throughput for each service• Tests (CIR, EIR and policing) with FTD, FDV, FLR and availability• Performance test with FTD, FDV, FLR and availability results for all services

ICMP • RFC 792: IP ping / Traceroute, Generation of ICMP echo request: Dest. IP address, Packet length, Generation interval• Analysis of ICMP echo reply: Round trip time, Lost packets, Time-To-Live Exceeded, Port unreachable

Ergonomics

Hand-held Instrument • Display 480 x 272 TFT, Soft LEDS, 223x144x65 mm, IP rating 54; Weight: 1.2 kg USB and Ethernet ports, Serial Port RS-232C• Rechargeable Batteries continuous working up to 10 hours; Operating 0ºC ~ 50º C Storage -20ºC ~ 70ºC; Humidity 5% ~ 95%

SyncE and PTP testing

E1 & Datacom testing

Network Testers Network   Testers   is   a   leading   supplier   of   solutions   and   professional   services   for   the   Management,   Performance,   and   Testing   of  Networks.    

Formed   originally   from   the   UK   sales   operations   of   Albedo   Telecom   and   Testbook,   Network   Testers   today   offers   leading   solutions   from  not  only  these  two  vendors  but  also  some  of  the  most  innovative,  up  and  coming  companies  in  the  network  testing  and  assurance  space.  

Selected  Products  

T3  Innovation  Arc  Chaser  

21st  Century  Dual  Mode  TDR   for  Testing  and  Monitoring  Energised  and  Unenergised  Cables.  

The   Arc   Chaser   Dual   Mode   TDR   is   capable   of   finding   faults   (Opens,   Shorts,  Arc  Faults)  on  fully  energised  cables  up  to  600  Volts.    

Arc   Chaser   can   monitor   live   cables   for   intermittent   conditions,   capturing  these  “events”  and  reporting  where  and  when  they  occur.  Using   advanced   Spread   Spectrum   Time   Domain   Reflectometry   (SSTDR),  Arc  Chaser  is  capable  of  accuracy  to  fault  of  better  than  1%.  <More  Details>  

Albedo  AT-­‐2048  2M/Datacom  

Low  Cost  E1,  Datacom,  Jitter/Wander  Testing.  

Albedo  AT-­‐2048  is  the  ultimate  tester  for  Field  Engineers  who  install  commission   and   trouble-­‐shoot   E1   and   Datacom   circuits.   The   AT-­‐2048   is   an   excellent   tester   for   network   operators,   contractors   and  enterprise   users   that   have   to   manage   fixed   and   mobile   networks   that  are  using  E1  and  Datacom  backhaul  circuits.  <More  Details>

Shepherds  Barn  Shepherds  Close  Weston  on  the  Green  Ox25  3RF  Oxfordshire  United  Kingdom  T:    01865  601008  E:  sales@network-­‐testers.com