IED Time Synchronization

John Levine, P.E.Levine Lectronics and Lectric

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Why do we need to synchronize our relays?

Relays at all three locations tripped. All three had different times. Are these events related???

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Definitions

• the marking of an event with respect to a reference origin. GPS time signals, based on the atomic clock in GPS satellites, are the reference origin.

Time

• a measurement of duration between events.Time interval

• a time system adopted in 1972. UTC is based on the weighted combination of atomic clocks located around the world. UTC occasionally changes by the addition of leap seconds.

Coordinated Universal Time

(UTC)

• High-precision atomic coordinate time standard, basis for UTC. 35 seconds ahead of UTC.

International Atomic Time (TAI)

• the measure of the number of events that occur within a time interval, such as the number of oscillations of a voltage waveform within one second

Frequency

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GPS

• GPS Satellite Navigation System uses precise time measurements to measure the distance between a receiver and satellites

• GPS satellites use atomic clocks for accuracy

• GPS satellites are the source of timing signals for clock applications

• ±100 nanosecond accuracy

• GPS time is not UTC time• UTC time adds leap seconds,

GPS does not• GPS time is 16 seconds ahead

of UTC

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NTP / SNTP

• Network time protocol (NTP) networking protocol for clock synchronization between devices operating over packet-switched, variable-latency data networks.

• Calculates round trip delay• Doesn’t accurately cover

switch delays, network traffic, reconfigurations

• Benefits to NTP• Uses SCADA Ethernet network • Good enough for SOE

• Detriments to NTP• Accuracy in the ms range• Not sufficient for

synchrophasors

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IRIG-B • IRIG Formats developed by U.S.

Military• IRIG-B is 1 specific format used in

utility and industrial applications

• IRIG-B is an analog signal• Uses voltage pulses on copper

wire • Pulses indicate time from fractions

of second from midnight, date from January 1st

• Benefits of IRIG-B• Proven• Sub- μs accuracy

• Detriments of IRIG-B• Number of devices, distance

limited by voltage drop• Redundancy difficult• Requires careful wiring design• Must have an antenna for each

clock location

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IEEE 1588

IEEE Std. 1588 - 2008 IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems.• a.k.a. “PTP” or “Precision Time Protocol”

• Message based protocol for packet based networks

• Nano-second accuracy possible

• Uses TAI time

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Challenges to network time synch

Ethernet switches• Buffering adds delays• Pause frames add delaysMultiple master clocks possible• Determining the master clock

Network segmentation• Determining the master clock

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How 1588 works (peer-to-peer)C37.238

Message based synchronization to measure peer delays

• Best Master Clock (BMC) algorithm determines the best Master to use

• BMC runs continuously for network changes

• Synchronize through message transactions by measuring peer-to-peer delays between devices• Each Peer measures delay

between devices using Pdelay_Req and Pdelay_Resp

• Switches measure queuing delay internally

• Calculations are between devices

t1

t2

t3

t4

Pdelay_Req

Pdelay_Resp

Pdelay_Resp_Follow_Up

Delay = (t2-t1 + t4-t3)/2

Clock A Clock B

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IEEE 1588 architecture (peer-to-peer)

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Modern Time Synchronization by GE

Add 1588 capabilities for future expansion while supporting in-

service IRIG-B devices

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Redundant clocks for reliability

• All devices have clocks

• All 1588 clocks run BMC• Will choose best clock source

based on BMC algorithm, switch configuration

• Clock in individual devices will choose the second clock if the first clock is unavailable. • Redundancy for critical

applications like wide area control through synchrophasors, process bus

MultiSync 100 Overview

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MultiSync 100 1588 GPS Clock

• Time synchronization Inputs:• GPS antenna (BNC port), • 1588 over network (the RJ-45 port)

• Time synchronization outputs:• 1 RJ-45 Ethernet port

• 1588 and NTP/SNTP simultaneously• 1588 or 1588/C37.238

• 2 TTL ports (BNC connectors)• IRIG-B (DC Shift), with IEEE 1344 extensions• Multiple other analog time synch profiles

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Protocols Supported

• IRIG-B (Un-modulated, DCLS - C37.118)• DC level shift un-modulated• IEEE 1344 extension (C37.118)• Modified Manchester

• User defined pulses

• NTP/ SNTP (IEC 61850)

• IEEE 1588-2008• (Supports Power Profile - C37.238-2011)

• DCF77

• SNMP v1, v2c & v3

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Clock capabilities

• Time:• Support for UTC time, local time

settings, DST settings• Configurable Alarms

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MultiSync 100 hardware

• Compact size

• DIN-rail mount

• Universal power supply • (36 – 300V DC)

• IP30 Ingress

• IPC 610 Class 3 boards

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MultiSync 100 Hardware – cont.

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Configured in Software

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Security

• Password protection

• User authentication

• Data encryption

• RBAC

• User groups

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Where the MultiSync 100 fits