Time Synchronization in Electrical Systems

Precise Time Synchronization for Substation Automation purposes.

Time Synchronization in Power Plants

What is time synchronization and how does it work? Which solutions exist for power transmission and distribution systems? What is precision, accuracy and resolution and why should manufacturers and operators of equipment for electrical distribution networks care about these terms? This document has been created to answer these questions and offers you a comprehensive and easy-to-understand introduction. Read on ...

Time Synchronization Overview

Substation automation demands precise time synchronization for a variety of Intelligent Electronic Devices (IEDs). There are different possible approaches to achieve the required accuracy. Time synchronization for substations with integrated protection- and system control functions, as well as data collection require a target architecture that distributes synchronized time in several ways. Different solutions are possible and can be realized using MEINBERG timing equipment.

Electrical companies are turning into the biggest users and generators of
  • Operational Data
  • Administrative Data
They are the biggest users
  • of real time data
  • Operational data
Application of time synchronization in electrical systems Time Synchronization in:
  • SCADAs ->  Protocolization and registration
  • Communication equipment ->  Communication processors, protocol translators
  • Protection relays ->  Fault and performance analysis
  • Faultrecorders ->  Post mortem analysis, responsability, liability
  • Billingmeters AMR ->  Tarifswitching, load analysis
  • IEDs, RTUs, SOE, Sensors ->  Protocolization + registration
  • Servers, Routers, Switches ->  IT security!
  • Frequency deviation ->  Systemstability
  • Security monitoring ->  Physical security
  • Digital voice and video recording ->  Civil responsability, Law, Insurance companies

Synchronization of Equipment

Direct Synchronization

GPS Antenna Dedicated Clocks GPS167 rack and GPS163TD mounting rail for time synchronization
Right Arrow Resolution and precision:
  • 1 ms for events and faults in substation synchronization
  • PPS (Pulse per second as a hardware Gong)
  • 1 kPPs with 250 ns precision for sinchrophasor relays
    (Resolution of+/-5 µs)
Prot. Siemens ® Right Arrow
S/S equipment
Billing metering
SOE and fault recording
Frequency deviation
Δf, ΔT
Pulses PPS-PPM
1 kPPS

Syncronization over LAN

Resolution and Precision:
  • Depends on traffic on the network
  • Depends on distance and communication media
  • Range from submiliseconds to 5 -20 ms
Lantime NTP time server series M300, M600 and GPS170PCI GPS PCI-X slotcard
Right Arrow
Right Arrow Protocols
DNP 3.0
IEC 60870-x
IEC 61850  NEW! 
IEEE 1588-2002
UCA 2 (MMS) *

* UCA2 (Utility Communication Architecture) with MMS protocol(Manufacturing Message Specification)

Synchronization over LAN

  • External networks are gaining more significance in control and protection environments through:
    • LAN, WAN, MAN
    • Redundant LANs
    • Switches, routers, firewalls
    • Severs and clients
    • Communication over Internet and Intranets
    • Different medias
  • Transmission of secure data on insecure channel:
    • Confidenciality
    • Integrity
    • Authentication
  • Tools:
    • Encrypted tunnels
    • VPN

Synchronization Equipment from Meinberg

  • Clocks for SCADAs, RTUs, PLCs, relays, automation
    • PPH, PPM, PPS
    • Optical outputs
    • DCF, IRIG A/B Codes, etc.
    • Proprietary codes: SIEMENS, ABB, ION etc.
    • Frequencies/Amplitudes: Fixed and variable
    • Frequency measurement
    • PCI cards
    • Special signals and interfaces
    • Slave clocks
    • Wide AC and DC power supply ranges
    • Mounting on 19" Rack, DIN rail
    • Antenna with cable up to 300 meters, optical available

Examples of Use

Time Synchronization with GPS Satelllite Clock and LAN-CPU in Modular Case

IRIG-B DC Serial Data String Ethernet Fiber Optic
Time Synchronization with GPS170BGT and MEINBERG Time Code Diplexer via Fiber Optic,
Central Engine Room
Bay Controller
Metering and Control Devices
NTP over Lan
NTP over Lan
Ethernet over Fiber Optic / Multimode
IRIG-B DC Fiber Optic / Multimode
ION Code (TX) Fiber Optic / Multimode
Time Code Diplexer
3 circles with 8 relais
(e.g. General Electric) are possible
with LAN-CPU
and GPS Antenna
More Protection Relais are possible
NTP over LAN
Bay Controller
(e.g. BC1703ACP)
Protocol over LAN
Digital Power Metering
(e.g. ION 8300 RS485)

Time Synchronization with customized GPS Satellite Timing System

GPS Antenna / Surge Protection

Cable 10m

Cable 40m
MSTS1 RS232 (<15m)
IRIG-B (twisted pair)
ASCII RS485 9600 bd (twisted pair)
DCF Pulse
DCF Pulse
(24VDC external)
DCF Pulse
Digital Power Meter / e.g. ION 75502
(Industrial Ionisation Blower)
IRIG-B DC Serial Data String Pulse DC
1 MSTS = Meinberg Standard Time String
2 ION 7550 = ION Time String 9600 baud, RS485
Time Synchronization with customized GPS170BGT through different protocols (eg. RS485, RS232, DCF, IRIG-B, PPM )
Controller 1
Controller 2
Controller 3
Controller 4
Controller 5
Controller 6

Time Synchronization with GPS-Antenna Distributor GPSAV4

Time Synchronization with several GPS170BGT and antenna distribution over MEINBERG GPSAV4
IRIG-B DC Pulse DC Ethernet Serial Data String
GPS Antenna

Coaxial Cable 20m
Surge Protector
Antenna Diplexer
Coax. Cable
NTP over LAN
2xIRIG-B Protection Relais (e.g. GE Multilin)
8 x IRIG-B
(e.g. ION1 8600)
8 x DCF
GPS170BGT (additional)
GPS170BGT (additional)

Time Synchronization Terms and Glossary

What is Accuracy?

Accuracy (Precision)
  • Commonly based on UTC
  • Micro or nanoseconds
  • Referenced against the PPS in the GPS system
  • always given by the clock
  • e.g. +/- 250ns or 100 ns to PPS

What is Resolution?

  • The smallest possible time difference
    between two event recordings(in S/S = 1ms)
  • Chronological correctness
  • always depends on the end device
  • internal sampling rate
  • Processor and bus speeds


  • t 1 = 15:05:26:374
  • t 2 = 15:05:26:375
  • t 3 = 15:05:26:376

Usual signals for time synchronization in electrical systems:

  • IRIG-B mod
  • IRIG-B unmod
  • PPS

Each signal type has its own resolution

e.g. IRIG-B: The framerate is 1.0 second - but accuracies up to 1 μs can be achieved
  • B00x Resolution of 10 ms (dc level shift)
  • B12x Resolution of 1 ms (modulated 1kHz carrier)


A "free running clock" what does it mean?
  • Clock without external disciplining signal
  • Loss of GPS signal
  • GPS antenna or cable failure, damaged receptor
In the case of free running clock the oscillator maintains the accuracy with a certain precision for a certain time. Stability of a clock depends on the oscillator!! Oscillators of different qualities:
  • TCXO Temperature Controlled Oscillator
  • OCXO LQ-MQ-HQ Oven Controlled Oscillator
  • OCXO DHQ Double Oven Oscillator
  • Rubidium/ Cesium/ Other sources
Oscillator stability determines free running clock precision (without GPS).
  • Comparison in 1 day or 1 year time frames
  • The more stable an oscillator, the smaller the time deviaton of the free running system from UTC
Here you can find a comparison chart of our oscillators: Oscillators comparison

Internet adresses of IEDs and other related equipment manufacturers

ABB Automation
Basler Electric
Beckwith Electric
GE Industrial
GE Power Gen
Japan AE PSE(Hitachi)
Orion Italia
P&B Eng
Schneider Sepam
SEL Schweitzer Eng


Equipment for Electrical Systems and Power Plants

Relays - Protective
Motor Protection Relay
Motor Management Relay
Generator Management Relay
Blocking and Test Module
Feeder Relay
Transformer Management Relay
Feeder Management Relay
Advanced Line Protection System
Bus Differential Relay
Bus Differential Relay System
Percentage Differential with Harmonic Restraint
Bus Bar Protection
Controller System
Breaker Protection System
Capacitor Bank Protection and Control System
Offset Mho Directional-distance
Loss of Excitation Relay
Angle Impedance Relay
Reactance and Mho Phase Directional-distance
High Speed Differential Relay
Voltage-balance Relay
Instantaneous Overcurrent Relay
Remote CAN I/O Module
Line Distance Relay
Line Distance Protection System
Digital Breaker Failure
Digital Breaker Supervision
Distributed Digital Fault Recorder
Digital Distribution System
Digital Frequency Relay
Digital Generator Protection
Single Phase Digital Overcurrent Protection
Digital Line Protection System
Digital Multifunction System
Numerical Single-Phase and Three-Phase Reclosing System
Digital Transformer Protection
Transformer Tap Changer Controller
Terminal Boards
Multiple Feeder Management Relay
Bay Controller
Generator Management and Control System
Phase Packaged Directional-distance Relay
Substation Automation
Power Directional Relays
Ground Distance Relay
Automatic Synchronizing Relay
Auxiliary or Annunciator Relay
Multicontact Auxiliary Relay
Hinged Armature Auxiliary Relay
Single-shot Reclosing Relay
High Impedance Differential Module
Multicontact Hand Reset Auxiliary Relay
Time-overcurrent Relay
Time Delay Voltage Relay
Directional Overcurrent Relay
Directional Ground Overcurrent Relay
Phase Sequence and Undervoltage
Power Directional Protection Relay
TOC Relay with Voltage Restraint
Current Balance Relay
Percentage Differential Relay
Synchronism Check Relay
Phase and Ground Overcurrent Relay
Line Phase Comparison Relay
Line Current Differential Relay
Modular Low Voltage Motor Protection System
Line Protection System
Generator Backup/Out-of-Step Protection
Modular Microprocessor Relays
Digital Generator Protection Relay
High Impedance Busbar Differential Relay
Digital Overcurrent Relay
Digital Distribution System Family
Digital Feeder Relay
Machine Protection Relay
Generator Protection System
Digital Ground Protection
Voltage/Frequency M Family Relay
Voltage/Frequency MII Family Relay
Directional Power/Loss of Field
Directional Power Protection System
Digital Synchronism Check Relay
Intelligent MCC Controller
Low Voltage Motor Management System
Digital Multifunctional Protective Relay
Motor Protection Meter
Network Stability and Synchrophasor Measurement System
Auxiliary Relay
Voltage Unbalance Relay
Voltage Relay
Machine Field Ground Relay
Instantaneous Voltage Relay
Power Management Control System
PVD Differential Voltage Relay
High Speed Trip and Lockout Relay
Remote RTD Module
Static Timing Relay
Control and Transfer Switches Catalog
Master Control Switches
Static Breaker Backup Relays
Differential Voltage Relay
Control and Transfer Switches
Static Directional Comparison Blocking Relay
Static Digital Frequency Relay
Negative Sequence Overcurrent
Static Synchronism Check Relay
Feeder Management System
Synchronous Motor Protection & Control
STD Percentage Differential with Harmonic Restraint
Overexcitation Relay
Modular Power Reversal Relay
Modular Voltage Relay
Tripping and Blocking Rectifiers
Protection Relays
Universal Recloser Control
Wind Generator Protection System
Power Quality Meter
Electronic Power Meter
Instrument Transformers