TN-101
Nov-2016
TECHNICAL NOTE
Summary
I
Sequence of Events Recording
(SER) System Architectures
1588
SM
Modern power systems rely on precision timing.
Sequence of Events Recording (SER) systems use
1-ms time-stamp resolution to provide essential
information about power system events.
PTP (Precision Time Protocol defined in IEEE 1588)
uses hardware-assisted time-stamping to achieve
required accuracy over Ethernet, finally making
“high-resolution” time sync simple and affordable.
This document describes simple, scalable system
architectures using PTP with products from Cyber
Sciences. In addition, various options are described
for integrating devices using legacy time protocols.
Introduction
Precision timing is essential for modern industrial/commercial power systems. For
years Electrical Power Monitoring Systems (EPMS) have helped facility engineers
manage their power infrastructure and the cost, quality, safety and reliability of
this important resource. In the past, the clocks of ”Intelligent Electrical Devices”
(IEDs) were set over Ethernet, with accuracy no better than 1 second. Modern EPMS
require 1-ms time-stamping, implying time synchronization of 100 µs. Until recently,
separate cabling was needed to achieve this “hi-res” time, limiting the benefits to
only the largest projects. Today, Precision Time Protocol (PTP), defined in IEEE 1588TM
makes hi-res time synchronization over Ethernet simple and affordable for all.
System Components
A typical SER system includes a GPS antenna mounted on the roof or other external
location allowing line-of-sight access to multiple satellites. A GPS receiver or satellite
time reference decodes the antenna’s GPS time data and outputs a precise time
signal using one or more protocols, as needed. PTP achieves precise time synchronization over the same Ethernet network used for data communications. Some IEDs do
not yet support PTP, and so other time protocols may still be needed, using dedicated cabling. These “legacy protocols” include IRIG-B (several variations), DCF77, ASCII
serial (RS-485) and 1per10 (one pulse every 10 seconds). When legacy protocols are
involved, then the number of devices to be synchronized, the protocols supported,
and the distances involved all affect system architecture. Even if these are unavoidable, PTP can simplify the system design by eliminating extra cabling between
power equipment lineups as well as some converters and repeaters.
GPS
Antenna
EPMS
0.000
Ethernet
0.000
0.000
0.000
0.000
SER system architecture concept drawing
Precision Timing for Reliable Power. Simplified.SM
TN-101 | Nov-2016
TECH NOTE—SER System Architectures
IEEE 1588: PRECISION TIME
PROTOCOL (PTP)
Introduction to IEEE 1588-2008
THE “SIMPLE PTP” PROFILE (SPTP)
The Simple PTP Profile—Based on IEEE 1588 Default Profile
IEEE Std 1588 defines the Precision Time Protocol (PTP) with a goal of achieving very
high precision for time-synchronization over a packet-based network such as Ethernet. PTP takes advantage of special Ethernet hardware for precise time-stamping of
the Ethernet frame send and receive time and prescribes a very precise mechanism
to correct for delays introduced in the network path from the master clock (time
reference), through multiple levels of switches, to the slave clocks (time consumers).
CyTime SER-3200/2408 Event Recorders use a “Simple PTP” Profile (dubbed “SPTP”)
optimized for commercial/industrial power system applications (including data
centers, hospitals and microgrids). SPTP is intended to achieve time sync over Ethernet with accuracy of 100 µs max, taking advantage of the same Ethernet network
infrastructure used for power monitoring—without requiring special PTP-compliant
Ethernet switches (transparent clocks). There is no need for special prioritization of
PTP packets in managed switches, nor any constraints on network topology. To accomplish time synchronization, SPTP uses the PTP delay request-response mechanism (sometimes called “End-to-End). Other simplifications include using UTC as its
timescale (instead of TAI) and longer message intervals (e.g., updates every 32s) to
minimize network traffic.
The name “Simple PTP” Profile is proposed by Cyber Sciences; however, it is not proprietary. SPTP is actually based on the IEEE 1588 “Default Profile” defined in Annex J.
Devices using SPTP are interoperable with others set to use this profile.
Comparison Table: PTP Profiles
2
IEEE 1588 (All Profiles)
“Simple PTP Profile (SPTP)”
Power Profile (C37.238)
GENERAL
SIMPLE
STRICT
Target accuracy: nanoseconds
Target accuracy: 100 µs
Target accuracy: 1 µs
All clock types
Master and Slave-only
All clock types except boundary
Unicast or Multicast
Multicast
Multicast
802.3 (layer 2), UDP/IPv4, UDP/IPv6
UDP/IPv4
802.3 only (layer 2)
PTP-compliant switches
No special switches required
PTP-compliant switches required
End-to-end or Peer-to-peer
End-to-end (E2E) only
Peer-to-peer (P2P) only
1-step or 2-step
2-step
1-step or 2-step
Variable delay requests
32 seconds
Variable delay requests (typically 1 second)
TLV, MIB, VLAN tags optional
None
TLV, MIB, VLAN tags req’d.
Does not address max no. of slaves
Designed to support 200+ PTP slaves
Does not address max no. of slaves (< 40?)
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TN-101 | Nov-2016
TECH NOTE—SER System Architectures
LEGACY TIME-SYNC PROTOCOLS
Legacy Precision Time Protocols
IRIG-B—time codes typically distributed at low
levels (5 Vdc) and wired point-to-point. IRIG-B
has 100 pulses per second and transmits a
complete date/time every second, although the
year may or may not be included. The two most
common variations:
•
•
Amplitude Modulated IRIG-B (1kHz carrier)
Unmodulated, DC Level Shift (DCLS)
DCF77—time protocol similar to IRIG-B with
equivalent accuracy but distributed at 24 Vdc
via multi-point wiring. DCF77 has one pulse per
second (1 PPS) and transmits a complete date/
time every minute.
Others—Other protocols include 1per10 (one
pulse every 10 seconds) used by Sepam relays by
Schneider Electric; and ASCII over RS-485, used by
ION7550/7650 and PM8000 meters by Schneider
Electric and 9510/9610 meters by Siemens.
The type(s) of devices to be synchronized usually dictates the choice of time-sync
protocol required, and the protocol(s), distances and number of devices may introduce constraints on system architectures. Power system devices support various
time-sync protocols, each with its own advantages. However, combining several
types of devices in a single GPS time-sync system brings real-world complexity. First,
let’s consider the key characteristics of the most common time-sync protocols.
The IRIG time codes were originally developed by the US military and are widely
used by US electric utilities and others. Using 100 pulses per second, a complete
date/time string is transmitted once every second. The two most common variations:
•
•
Modulated IRIG-B (1kHz carrier)
Unmodulated IRIG-B, DC Level Shift (DCLS)
Point-to-Point. The IRIG 200-04 standard does not define specific signal levels, but
both IRIG-B types are typically distributed at TTL levels (5Vdc) via point-to-point wiring, either via coaxial cable or twisted pair. This may be suitable for a small number
of devices over short distances.
Multi-Point Wiring (Daisy-Chain). To synchronize a larger number of devices, a
daisy-chain topology is often preferred, using twisted-pair cabling rather than coax.
However, at 5Vdc, distances and number of devices are limited.
Hybrid Solutions. One way to circumvent the device and distance limitations of
IRIG-B at 5Vdc: hybrid architectures distribute the IRIG-B signal at 24Vdc (along
with 24Vdc control power) using a multi-point (daisy-chain) connection to “IRIG-B
Distribution Modules” which in turn convert the signal back to the expected 5Vdc for
point-to-point connection to up to 8 IRIG-B devices.
DCF77 is a standard time protocol well-suited to power applications as it supports
multi-point wiring over long distances. It also requires less processor overhead than
IRIG-B, yet offers equivalent accuracy. Its 24 Vdc pulse provides a complete date/
time string once every minute. However, it may not be supported by all applicable
devices, in which case multiple networks are needed.
1per10 is a time-sync protocol used by Sepam relays by Schneider Electric. One
pulse every 10 seconds (24 Vdc nominal) provides a precise time-sync reference enabling the devices to maintain highly accurate time. This is used in conjunction with
date/time information provided over an Ethernet network.
ASCII over RS-485 is a time-sync protocol used by ION7550/7650 meters by Schneider Electric and 9510/9610 meters by Siemens. These meters use a proprietary ASCII
protocol (“ASCII + Quality”) defined by Arbiter systems. They can be synchronized
from an Arbiter clock’s RS-485 serial port (not IRIG-B) or from the RS-485 time-sync
output of a CyTime SER-3200/2408 Event Recorder by Cyber Sciences.
Time-Sync over Ethernet. Undoubtedly, the simplest way to distribute date/
time from a central clock to all devices would be over the same Ethernet network
already connecting the devices to the supervisory monitoring system. Two common
protocols for this are Network Time Protocol (NTP) and Modbus TCP. However, the
accuracy with either of these is not sufficient for 1ms SER time-stamping.
One IED relying on NTP may be accurate to 10 ms while another (from a different
manufacturer or model, 32-bit vs. 64-bit processors, etc.) may only be accurate to
250 ms. Even if IEDs use sophisticated statistical algorithms to minimize the errors
inherent with NTP, accuracy is affected by network traffic and processor loading and
is ultimately not deterministic. For precision time synchronization over Ethernet,
these limitations must be overcome. Precision Time Protocol (PTP) does this.
© 2011-2016 Cyber Sciences, Inc. All rights reserved.
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3
TN-101 | Nov-2016
TECH NOTE—SER System Architectures
TIME-SYNC PROTOCOLS
BY DEVICE
STR-100
Satellite Time Reference
Acutime 360
GPS Antenna Input
Modulated
IRIG-B Input
OR
BNC-to-screwterminal adapter
24 Vdc
control power
An added variable with IRIG-B is whether or not the
year is included. If IRIG-B input is used, the STR-100
must be configured with the current year. Full date/
time is transmitted via its DCF77 outputs.
STR-100
Satellite Time Reference
CH 1
CH 2
DCF77 Output
(or 1per10)
DCF77 Output
SER-3200 / SER-2408
Sequence of Events Recorder
}
(optional)
24V levels
PLX-5V or
PLX-24V
EZC-DCF77 or
EZC-IRIG-B
Unmodulated IRIG-B
or DCF77 Input
PTP, NTP or Modbus TCP
Time Source
(over Ethernet)
(optional)
(optional)
IRIG-B,
DCF77
or 1per10
OUT
OR
24 Vdc
control power
CyTimeTM SER-3200 (or SER-2408)
Sequence of Events Recorder
STR-IDM
IRIG-B Distribution Module
24V IRIG-B plus 24 Vdc power
(from PLX-24V or
STR-100/IRIG-B
ASCII / RS-485 OUT
(or Inter-SER IN/OUT)
24V IRIG-B plus 24 Vdc power
(to next STR-IDM)
STR-IDM
IRIG-B Distribution Module
Unmodulated IRIG-B
Outputs (x8)
(5V levels)
Trigger output on event
Trigger Output for Waveform Capture by Meter
Meter
WFC Trigger
CyTime SER, with Trigger Output for Waveform Capture
4
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In addition to precise time synchronization via PTP, a second form of synchronization
provides critical data for power system analysis. The SER-3200/2408 can be configured to output a trigger pulse for any detected status change. Typically, this is used
with a compatible power meter to capture voltage and current waveforms associated with the event, both pre- and post-event.
Whether the power meters themselves have the benefit of high-res time sync or not,
it is easy to correlate the waveforms with the precise timestamp by the SER device,
making the SER’s I/O a logical extension of the power meter’s own capabilities.
© 2011-2016 Cyber Sciences, Inc. All rights reserved.
TN-101 | Nov-2016
TECH NOTE—SER System Architectures
System Building Blocks
PRACTICAL IMPLEMENTATION
OF PTP TODAY
The CyTime SER-3200/2408 Event Recorders are the first Cyber Sciences products
that support PTP. For both models, PTP functionality is enabled through an optional
license key. (Only hardware versions B1 and later support the PTP option.)
EPMS
The PTP license enables both PTP master and PTP slave functionality in the SER, and
user setup determines whether the device functions as a PTP master or PTP slave (or
neither, and is simply installed for future use).
Ethernet
PTP Master
SER-3200
(or SER-2408)
PTP
In addition to PTP, the SER-3200/2408 offers several time-sync input and output
options, as well as trigger output for waveform capture by a meter or relay. Various
building blocks are described below, with emphasis on SER time-sync inputs and
outputs for interoperability with other devices. And unlike some legacy time-sync
systems described previously, these building blocks form systems that are scalable
to the largest installations.
PTP Slaves
SER-3200
(or SER-2408)
SER-3200
(or SER-2408)
SER-3200
(or SER-2408)
SYSTEM ARCHITECTURE
SER-3200/2408: PTP Master and Slaves
In the application shown below, the first SER serves as PTP master (grandmaster);
all other SERs sync automatically using PTP over the Ethernet network. Unlike NTP,
which requires each client to be configured with the IP address of at least one NTP
server (and possibly update interval), no configuration is needed for the PTP slaves.
The SER serving as grandmaster may use any convenient time source: IRIG-B, DCF77,
NTP or Modbus TCP. If the requirement is simply to ensure that all devices are synchronized with each other (and not necessarily to GPS time), the first SER may even
accept periodic updates from an EPMS server using Modbus TCP. GPS antenna or
receiver is optional. However, most systems benefit from having all clocks synchronized with high accuracy to a reference time source traceable to a known standard,
such as GPS. Specific system examples follow.
or
TIME
SOURCE
or
or
IRIG-B
EPMS
server
DCF77
NTP
Modbus TCP
set the first SER’s time...
PTP
MASTER
MENU
Ethernet
ENTER
SER-3200-PTP
(or SER-2408-PTP)
PTP
SLAVES
IRIG-B or
DCF77 or
1per10
PTP
all other SERs sync
automatically via PTP
MENU
ENTER
SER-3200-PTP
(or SER-2408-PTP)
MENU
ENTER
MENU
SER-3200-PTP
ENTER
SER-3200-PTP
(or SER-2408-PTP)
(or SER-2408-PTP)
EPMS
device
ASCII / RS-485
Set the first SER, all others sync automatically using PTP
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5
TN-101 | Nov-2016
TECH NOTE—SER System Architectures
PTP SYSTEM: SER Master and Slaves
(DCF77 input to first SER)
TIME
SOURCE
In the example shown below, the first SER accepts DCF77 as its time source (from an
STR-100 connected to a GPS antenna) and serves as PTP master (grandmaster); all
other SERs sync automatically using PTP over the Ethernet network.
Acutime 360
Antenna
EPMS
server
STR-100
Satellite Time Reference
DCF OUT
PWR
GPS INTERFACE
DCF
SYNC
CH 1
STAT
CH 2
DCF77
EZC-DCF77
PTP
MASTER
MENU
Ethernet
ENTER
SER-3200-PTP
(or SER-2408-PTP)
PTP
SLAVES
IRIG-B or
DCF77 or
1per10
PTP
MENU
ENTER
MENU
ENTER
MENU
ENTER
EPMS
device
(up to 200 PTP slaves)
SER-3200-PTP
SER-3200-PTP
(or SER-2408-PTP)
(or SER-2408-PTP)
SER-3200-PTP
ASCII / RS-485
(or SER-2408-PTP)
PTP time sync system: the first SER accepts DCF77 time sync (from STR-100), serves as PTP master for all other SERs
PTP SYSTEM: SER Master and Slaves
(IRIG-B input to first SER)
TIME
SOURCE
In the example shown below, the first SER accepts IRIG-B as its time source (from
a third-party clock) and serves as PTP master (grandmaster) for all other SERs. The
clock also provides NTP time-sync for the EPMS server.
GPS
Antenna
EPMS
server
Coax cable
GPS Clock
(by others)
NTP
IRIG-B
EZC-IRIG-B
PTP
MASTER
MENU
Ethernet
ENTER
SER-3200-PTP
(or SER-2408-PTP)
PTP
SLAVES
IRIG-B or
DCF77 or
1per10
PTP
MENU
ENTER
MENU
ENTER
MENU
ENTER
EPMS
device
(up to 200 PTP slaves)
SER-3200-PTP
(or SER-2408-PTP)
SER-3200-PTP
(or SER-2408-PTP)
SER-3200-PTP
(or SER-2408-PTP)
ASCII / RS-485
PTP time sync system: the first SER accepts IRIG-B time sync (from 3rd-party clock), serves as PTP master for all other SERs
6
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© 2011-2016 Cyber Sciences, Inc. All rights reserved.
TECH NOTE—SER System Architectures
TN-101 | Nov-2016
PTP SYSTEM: SER Master and Slaves
(IRIG-B input to master plus standby)
As stated previously, PTP clocks are self-organizing, in that they establish a hierarchy
of interconnections based on messages exchanged. Slaves automatically sync to the
master (grandmaster). A second, redundant (optional) grandmaster-capable clock
can stand by in passive mode and function as grandmaster if the first is unavailable.
In the example below, the first two SERs accept IRIG-B as time source (from a thirdparty clock); the first SER serves as PTP master (grandmaster) and the second SER
remains in passive (standby) mode.
In addition to providing a backup to the primary PTP master to increase system
reliability, this architecture also provides a built-in path for scalability in case it is
needed in future expansions. The next section continues this discussion.
TIME
SOURCE
GPS
Antenna
EPMS
server
Coax cable
GPS Clock
(by others)
NTP
IRIG-B
EZC-IRIG-B
PTP
MASTER
EZC-IRIG-B
IRIG-B
MENU
Ethernet
ENTER
MENU
SER-3200-PTP
SER-3200-PTP
(or SER-2408-PTP)
PTP
SLAVES
PTP MASTER
(STANDBY)
ENTER
(or SER-2408-PTP)
IRIG-B or
DCF77 or
1per10
PTP
MENU
ENTER
MENU
ENTER
MENU
ENTER
EPMS
device
(up to 200 PTP slaves)
SER-3200-PTP
(or SER-2408-PTP)
SER-3200-PTP
(or SER-2408-PTP)
SER-3200-PTP
(or SER-2408-PTP)
ASCII / RS-485
PTP time sync system: the first SER accepts IRIG-B time sync (from 3rd-party clock), serves as PTP master for all other SERs
PTP Scalability
IEEE 1588 Interoperability:
Cyber Sciences has tested its CyTime SERs (PTP
slaves) with several third-party clocks as PTP masters with good results. However, some third-party
clocks did not perform well as systems scaled to
larger number of PTP slaves. For this reason, Cyber
Sciences recommends against using third-party
PTP masters unless specific testing has been done.
Cyber Sciences is a member of the InterOperability
Laboratory of the University of New Hampshire,
which is dedicated to ensuring interoperability of a
wide range of technologies, including IEEE 1588.
© 2011-2016 Cyber Sciences, Inc. All rights reserved.
CyTime Event Recorders have been tested under real-world network conditions and
are proven to maintain hi-resolution time in large systems with over one hundred
devices. Even much larger systems are expected to function satisfactorily, but if
extreme network conditions prove otherwise, there is a simple solution. Instead of
bringing IRIG-B or DCF77 to just one SER serving as a single grandmaster, the same
time signal can be connected to a second SER to serve as a second grandmaster, using a different domain number. Half of the slave devices would simply be set to this
second domain number, resulting in two logical PTP systems, independent of each
other. In this way, PTP is scalable for virtually any size project.
Third-party clocks as PTP grandmaster
For small systems (up to 10 PTP slaves), it may be possible to use a third-party GPS
clock as PTP master instead of a CyTime SER. The GPS clock must be configured to
use PTP options and settings compatible with the Simple PTP Profile (SPTP) used
by the SERs. Normally, selecting the 1588 Default Profile is sufficient. In addition, it
may be necessary to increase the grandmaster’s Delay Request Interval. Consult the
GPS clock manufacturer for specifications on the maximum number of PTP slaves it
can support, as well as recommended adjustments to any other settings. In general,
Cyber Sciences recommends using SERs as both PTP master and slave.
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TN-101 | Nov-2016
TECH NOTE—SER System Architectures
PTP-ENABLING DEVICES WITH
LEGACY PROTOCOLS
No PTP? No Problem
Need to sync meters or relays that don’t support PTP? No problem. CyTime Event
Recorders offer ways to integrate these devices by converting the PTP time reference to the legacy protocol(s) required, effectively making them “PTP-enabled.” Even
though some additional factory wiring is needed, the cost and complexity of field
wiring between lineups is eliminated through the use of PTP.
The supported legacy protocols are:
●● IRIG-B (Unmodulated)
●● DCF77
●● 1per10
●● ASCII serial time code (over RS-485)
Time-sync Output: Unmodulated IRIG-B (< 8 devices)
The SER-3200/2408 can be configured to output the most common form of IRIG-B:
Unmodulated, or DC Level Shift (DCLS) at 5 Vdc nominal, via a PTP Legacy Interface
(PLX-5V) connected to its top DB-15 port. This IRIG-B time code includes the full
date/time, including the year (IRIG code “B006”), and is compatible with most meters
and relays that support IRIG-B.
Daisy-chain wiring, Belden 8760 cable or
equivalent, 1000 ft (300m) max total length.
Ethernet LAN
PTP
PLX-5V
IRIG-B
PTP SLAVE
(Time source = PTP)
(Time-sync out = IRIG-B)
MENU
ENTER
...
IRIG-B
IRIG-B
up to 7
devices
SER-3200-PTP
(or SER-2408-PTP)
Time-sync Output: Unmodulated IRIG-B (8 or more devices)
For reliable distribution over longer distances or to a number of devices, this same
IRIG-B code can be output at 24 Vdc using a PLX-24V, wired to one or more Cyber Sciences STR-IDM IRIG-B Distribution Modules for step-down to 8 conventional IRIG-B
signals (at 5 Vdc).
Daisy-chain wiring, Belden 8770 cable or
equivalent, 2000 ft (600m) max total length.
IRIG-B (24V DCLS) + 24Vdc power
STR-IDM
STR-IDM
Ethernet LAN
PTP
PLX-24V
MENU
ENTER
SER-3200-PTP
STR-IDM
STR-IDM
IRIG-B (5V DCLS)
PTP SLAVE
(Time source = PTP)
(Time-sync out = IRIG-B)
To next STR-IDM (4 total)
1 to 4 STR-IDM
modules per PLX
IRIG-B
...
up to 8
devices
IRIG-B
IRIG-B (5V DCLS)
IRIG-B
...
up to 8
devices
IRIG-B
(or SER-2408-PTP)
8
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TN-101 | Nov-2016
TECH NOTE—SER System Architectures
PTP-ENABLING DEVICES WITH
LEGACY PROTOCOLS (cont.)
Time-sync Output: DCF77
The SER-3200/2408 can be configured to output the standard DCF77 signal (24 Vdc)
via the PTP Legacy Interface (PLX-24V). This protocol is most commonly used by
PowerLogic CM3000/4000 series meters from Schneider Electric and Power Xpert
PXM 4000/6000/8000 meters from Eaton.
Daisy-chain wiring, Belden 8760 cable or
equivalent, 2000 ft (600m) max total length.
Ethernet LAN
PTP
PLX-24V
DCF77
PTP SLAVE
(Time source = PTP)
(Time-sync out = DCF77)
MENU
DCF77
ENTER
...
DCF77
up to 16
devices
SER-3200-PTP
(or SER-2408-PTP)
Time-sync Output: 1per10
The PTP Legacy Interface PLX-24V is also used to output one pulse every 10 seconds
(at 24 Vdc). This signal is most commonly used by Sepam 20/40/80 protective relays
from Schneider Electric.
Daisy-chain wiring, Belden 8760 cable or
equivalent, 2000 ft (600m) max total length.
Ethernet LAN
PTP
PLX-24V
1per10
PTP SLAVE
(Time source = PTP)
(Time-sync out = 1per10)
MENU
ENTER
1per10
1per10
up to 16
devices
SER-3200-PTP
(or SER-2408-PTP)
Time-sync Output (ASCII / RS-485)
Note: Only one protocol can be selected for output
via the PLX connector (IRIG-B, DCF77 or 1per10).
However, for maximum flexibility, the ASCII / RS-485
output is enabled by default any time an SER is
configured with time source = PTP. Thus, an SER can
output one of these protocols (via the PLX connector)
and output the ASCII / RS-485 signal as well.
Ethernet LAN
...
The SER-3200/2408 has a built-in RS-485 communications port that can be used
to output the ASCII serial code (Time + Quality) required by some power meters,
such as ION 7550/7650 and PM8000 from Schneider Electric and 9510/9610 from
Siemens. The SER is configured to accept PTP as its time source and enabled as timesync master generating ASCII RS-485 output to one or more devices. In most cases,
one SER will sync one meter, making it easier to treat the two as one logical device.
If desired, up to 16 devices can be synchronized from one SER over RS-485.
Daisy-chain wiring, Belden 9841 cable or
equivalent, 4000 ft (1200m) max total length.
PTP
PTP SLAVE
(Time source = PTP)
(Time-sync out = ASCII)
MENU
ENTER
ASCII
SER-3200-PTP
...
1 to 16
devices
ASCII
RS-485
termination
(or SER-2408-PTP)
© 2011-2016 Cyber Sciences, Inc. All rights reserved.
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TN-101 | Nov-2016
TECH NOTE—SER System Architectures
SYSTEM EXAMPLE
One system architecture using PTP is illustrated below. A Cyber Sciences STR-100
Satellite Time Reference accepts a GPS input from a Trimble Acutime 360 smart GPS
antenna. The STR-100 outputs DCF77 to the first CyTime SER-3200 Event Recorder,
and this in turn serves as PTP grandmaster for all other PTP slaves, also CyTime SERs.
Several variations are possible for time-sync to the relays and meters:
●● Hi-res time-sync via PTP: If the devices support PTP, enable this feature and set
them to use the IEEE 1588 Default Profile (or equivalent individual settings).
●● Hi-res time-sync via legacy protocol from an SER: Sync via a legacy protocol
(IRIG-B, DCF77, ASCII, etc.) from an SER-3200. The SER-3200 uses PTP as its own
time source, and then syncs relay/meter using a dedicated cable, with time-sync
output according to the protocol required by the relay/meter.
●● Std-res time-sync via Ethernet: Distribute time to relays and meters over Ethernet via NTP or Modbus TCP. The SER-3200 trigger output on status changes will
ensure proper synchronization for waveform analysis, and so Ethernet sync may
be sufficient for these devices.
In any case, redundant field-wiring is avoided between all of the power distribution equipment enclosures, eliminating most of the cost and complexity problems
described earlier.
EPMS
SOFTWARE
GPS
Antenna
WEB
BROWSER
Switch
Ethernet
STR-100
Relay
Relay
Relay
Relay
Meter
Relay
SER-3200
SER-3200
Meter
Meter
Meter
SER-3200
Meter
Meter
SER-3200
MV SWGR
Meter
SER-3200
SER-3200
Meter
SER-3200
GEN SWGR
Meter
SER-3200
Meter
SER-3200
Meter
SER-3200
PDP 1
LV SWGR 1
Meter
SER-3200
UPS 1
PTP SYSTEM EXAMPLE—High-resolution time-sync over Ethernet using PTP
10
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Meter
SER-3200
LV SWGR n
Meter
SER-3200
© 2011-2016 Cyber Sciences, Inc. All rights reserved.
Meter
SER-3200
PDP n
Meter
SER-3200
UPS n
TN-101 | Nov-2016
TECH NOTE—SER System Architectures
SYSTEM EXAMPLE
(PTP PLUS LEGACY PROTOCOLS)
Another PTP-enabled system architecture is illustrated below. In this case, the GPS
receiver/clock is located outside the first power equipment lineup (for example, in
the networking equipment rack). Since most MV protective relays do not yet support
PTP, this example shows their time-sync using dedicated cabling for IRIG-B.
The first CyTime SER-3200 Event Recorder accepts IRIG-B in this example, and again
serves as PTP grandmaster for all other PTP slaves (CyTime SERs).
As in the previous example, several options are possible to time-sync relays/meters:
●● Hi-res time-sync via PTP: If the devices support PTP, enable this feature and set
them to use the IEEE 1588 Default Profile (or equivalent individual settings).
●● Hi-res time-sync via legacy protocol from an SER: Sync via a legacy protocol
(IRIG-B, DCF77, ASCII, etc.) from an SER-3200. The SER-3200 uses PTP as its own
time source, and then syncs relay/meter using a dedicated cable, with time-sync
output according to the protocol required by the relay/meter.
●● Std-res time-sync via Ethernet: Distribute time to relays and meters over Ethernet via NTP or Modbus TCP. The SER-3200 trigger output on status changes will
ensure proper synchronization for waveform analysis, and so Ethernet sync may
be sufficient for these devices.
In addition, the use of PTP to achieve high-res time sync greatly simplifies building
out the system in phases. Each subsequent building or section simply obtains its
precision time reference from the GPS source in the original build. If the PTP devices
ever reach such a large number that performance is impacted, the PTP system could
simply be reconfigured (settings change) to use multiple domains.
GPS
Antenna
EPMS
SOFTWARE
= IRIG-B (DCLS)
WEB
BROWSER
Switch
Clock
Relay
Relay
Relay
Relay
Ethernet
Meter
Relay
SER-3200
SER-3200
Meter
Meter
Meter
Meter
SER-3200
Meter
SER-3200
MV SWGR
Meter
SER-3200
SER-3200
Meter
SER-3200
GEN SWGR
Meter
SER-3200
Meter
SER-3200
Meter
SER-3200
PDP 1
LV SWGR 1
Meter
SER-3200
UPS 1
SECOND PTP SYSTEM EXAMPLE—High-resolution time-sync over Ethernet using PTP, with interface to IEDs using legacy protocols (e.g., IRIG-B)
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© 2011-2016 Cyber Sciences, Inc. All rights reserved.
Meter
SER-3200
LV SWGR n
Meter
SER-3200
Meter
SER-3200
PDP n
Meter
SER-3200
UPS n
11
TN-101 | Nov-2016
TECH NOTE—SER System Architectures
LEGACY SYSTEM ARCHITECTURES
These “Legacy System Architectures” are provided for reference to support older
systems without PTP.
SYSTEM L1—All DCF77 Devices
The STR-100 Satellite Time Reference accepts an input from Trimble Acutime 360
smart antenna or modulated IRIG-B and outputs two DCF77 output channels, each
of which can sync up to 16 devices.
Trimble AcutimeTM 360
Smart GPS Antenna
= Acutime Interface
= Modulated IRIG-B
= DCF77
STR-100
Satellite Time Reference
Satellite Time Reference
DCF OUT
PWR
GPS INTERFACE
DCF
SYNC
CH 1
STAT
CH 2
CH 1
CH 2
RS-422 signal,
Antenna interface cable: CAB-ACU-xxx
xxx = length (50, 100, 200 or 400 feet)
OR
Modulated
IRIG-B
Daisy-chain wiring, Belden 8760 cable or
equivalent, 2000 feet (600m) max total length.
DCF77
24Vdc
up to 16
devices
(per channel)
EZC-DCF77
DCF77
DCF77
DCF77
MENU
DCF77
EZC-DCF77
up to 16
devices
EZC-DCF77
DCF77
MENU
ENTER
MENU
SER-3200/2408
ENTER
SER-3200/2408
Event Recorder
DCF77
ENTER
SER-3200/2408
Event Recorder
Event Recorder
System architecture # L1: STR-100 provides precision time reference for multiple devices via DCF77.
SYSTEM L2—DCF77 plus 1per10
STR-100 channel 2 is configurable for DCF77 (default) or 1per10, as shown below.
Trimble AcutimeTM GG
Smart GPS Antenna
= Acutime Interface
= Modulated IRIG-B
= 1per10
STR-100
Satellite Time Reference
Satellite Time Reference
DCF OUT
PWR
GPS INTERFACE
DCF
SYNC
CH 1
STAT
CH 2
CH 1
CH 2
OR
Modulated
IRIG-B
RS-422 signal,
Antenna interface cable: CAB-ACU-xxx
xxx = length (50, 100, 200 or 400 feet)
= DCF77
Daisy-chain wiring, Belden 8760 cable or
equivalent, 2000 feet (600m) max total length.
1per10
up to 16
devices
24Vdc
1per10
1per10
1per10
1per10
DCF77
EZC-DCF77
up to 16
devices
EZC-DCF77
EZC-DCF77
DCF77
MENU
ENTER
SER-3200/2408
Event Recorder
MENU
ENTER
SER-3200/2408
Event Recorder
MENU
DCF77
ENTER
SER-3200/2408
Event Recorder
System architecture # L2: STR-100 provides precision time reference for multiple devices via DCF77 and 1per10.
12
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TN-101 | Nov-2016
TECH NOTE—SER System Architectures
CABLE RECOMMENDATIONS
The table below summarizes the cable types recommended in this technical note.
They are provided only as a guideline. Consult device manufacturers’ literature and
verify that any cable meets the requirements of your project before ordering materials.
TIME-SYNC PROTOCOLS—CABLE SUMMARY
Time Protocol
Max. # of
Devices
Max.
Distance
Recommended
Cable
Description
IRIG-B, unmodulated (5V DCLS)
4
1000 feet
(300 m)
Belden 8760
(or equiv.)
Shielded, twisted-pair cable, copper, #18
AWG, 300V rms
IRIG-B, modulated
4
300 feet
(100 m)
Belden 8760
(or equiv.)
Shielded, twisted-pair cable, copper, #18
AWG, 300V rms
DCF77
16
2000 feet
(600 m)
Belden 8760
(or equiv.)
Shielded, twisted-pair cable, copper, #18
AWG, 300V rms
1per10 (1 pulse every 10 sec.)
16
2000 feet
(600 m)
Belden 8760
(or equiv.)
Shielded, twisted-pair cable, copper, #18
AWG, 300V rms
IRIG-B, unmodulated, @ 24 Vdc plus
24 Vdc power (to/from STR-IDM or PLX)
8
2000 feet
(600 m)
Belden 8770
(or equiv.)
Shielded, 3-conductor cable, copper, #18
AWG, 300V rms
IRIG-B, unmodulated, over RS-485
(SER Inter-Device)
32
4000 feet
(1200 m)
Belden 9841
(or equiv.)
Shielded, twisted-pair cable, copper, #24
AWG, 300V rms
DCF77, over RS-485 sub-network
(SER Inter-Device)
32
4000 feet
(1200 m)
Belden 9841
(or equiv.)
Shielded, twisted-pair cable, copper, #24
AWG, 300V rms
ASCII, over RS-485 sub-network
(from SER-3200/2408 time-master)
16
4000 feet
(1200 m)
Belden 9841
(or equiv.)
Shielded, twisted-pair cable, copper, #24
AWG, 300V rms
Trimble Acutime 360 smart GPS
antenna interface cable (RS-422)
1
400 feet
(120 m)
Acutime 360
Interface Cable
Shielded, six-twisted-pair cable, #22 AWG,
with 12-pin connector on one end. Available
in lengths of 50, 100, 200 and 400 feet.
Antenna interface cable between
STR-100s when sharing an antenna
7
1000 feet
(300 m)
Belden 8723
(or equiv.)
Shielded, two-twisted-pair cable, copper, #22
AWG, 300V rms
CABLE TERMINATION
For SER Inter-Device (RS-485) time-sync sub-networks, Cyber Sciences recommends
using a 120 Ohm resistor (1/4 watt) across the twisted-pair, per the EIA standard. The
termination, as the name suggests, should be placed at the end of the network, after
the last device on the daisy-chain.
Due to the nature of the signal and baud rates associated with DCF77, 1per10 and
IRIG-B time protocols, line termination is normally not required. If cable distances
are near their maximum limits and signal reflections are suspected to affect reliable
operation, line terminations may be added as follows:
If desired, Cyber Sciences recommends using a 100 Ohm resistor (1/4 watt) across
the signal pair, in series with a 0.01 µF (microfarad) capacitor. This will minimize
reflections of the time-code pulse.
PRACTICAL CONSIDERATIONS
© 2011-2016 Cyber Sciences, Inc. All rights reserved.
The suggested distance limits and max devices suggested in this document are
based on standard specifications, factory testing and field experience. While some of
the recommendations may be conservative, few are absolute limits. While it may be
technically feasible to exceed such guidelines, the total distance and number of devices on a given segment should probably be kept as small as possible for practical
reasons. For example, rather than combine 30 or more devices on the same chain,
it may be better to split these into two segments if possible, simply to avoid costly
troubleshooting later.
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13
TN-101 | Nov-2016
SUMMARY
TECH NOTE—SER System Architectures
Summary
Modern power monitoring systems require 1-ms time-stamping, and so “hi-res” time
sync (accuracy <100 µs) is required. SER devices record the exact time of power
system events (to 1 ms), enabling root-cause analysis, identifying slow breakers and
allowing operators to verify proper system operation. Until recently, separate cabling
(often involving multiple protocols) was needed, limiting the benefits to only the
largest projects.
Precision Time Protocol (PTP), defined in IEEE 1588TM enables hi-res time sync over
Ethernet. Simple PTP (SPTP) makes PTP relevant for commercial/industrial power
systems, extending the benefits of precision timing to a broader market, even those
previously forced to compromise to keep costs low. The PTP-enabled solution is simple, affordable and completely scalable, from a few devices to the largest installation.
This document presented examples of the most cost-effective system architectures
and showed typical applications of CSI products. Since some relays and meters do
not yet support PTP, CSI provides ways for these to be “PTP-enabled” too.
REFERENCES
References
[1] IEEE Std 1588™-2008, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems.
For More Information
Tech Note: Hi-res Time Sync using PTP/1588 (TN-100)
Tech Note: IRIG-B Time Codes (TN-102)
Tech Note: DCF77 Time Protocol (TN-103)
Tech Note: 1per10 Time Protocol (TN-104)
CyTime SER User’s Guide (IB-SER-01)
CyTime SER Reference Guide (IB-SER-02)
EZC Instruction Bulletin (IB-EZC-01)
PLX Instruction Bulletin (IB-PLX-01)
STR-100 Instruction Bulletin (IB-STR-01)
[2] IEEE Std C37.238-2011, IEEE Standard Profile for Use of IEEE 1588™ Precision Time
Protocol in Power System Applications
[3] Kennedy, Robert A., P.E., “GPS Time Synchronization: How precision timing and
sequence of events recording will make the Smart Grid even smarter,” Electrical Construction & Maintenance (EC&M) magazine, August 19, 2011, pp. 18-20.
http://ecmweb.com/computers-amp-software/gps-time-synchronization
[4] Brown, PE, Bill, and Mark Kozlowski, “Power System Event Reconstruction Technologies for Modern Data Centers,” Square D Critical Power Competency Center. Aug. 2006.
[5] Dickerson, Bill, P.Eng., Arbiter Systems, Inc. “Time in the Power Industry: How and
Why We Use It.” http://www.arbiter.com/solutions/event-time-and-reconstruction.php
STR-IDM Instruction Bulletin (IB-IDM-01)
The service marks, “Precision Timing for Reliable Power. Simplified.” and “I-Heart-1588”,
CyTime, and the Cyber Sciences stylized logo are trademarks of Cyber Sciences.
All other trademarks are the property of their respective owners.
MADE IN USA
Cyber Sciences, Inc. (CSI)
229 Castlewood Drive, Suite E
Murfreesboro, TN 37129 USA
Tel: +1 615-890-6709
Fax: +1 615-439-1651
14
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RoHS
Pb
Lead-Free
I
1588
SM
Doc. no: TN-101 Nov-2016
(supersedes doc. dated May-2016)
© 2011-2016 Cyber Sciences, Inc. All rights reserved.