Refrences » Time Synchronization in Electrical Systems

Precise Time Synchronization for Substation Automation purposes.


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
  • Time Synchronization Equipment
  • Examples of use
  • Time Synchronization Terms and Glossary

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

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

* 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

Time Synchronization with customized GPS Satellite Timing System

Time Synchronization with GPS-Antenna Distributor GPSAV4

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