But when you extend your network with fiber optic, you introduce network latency. There are converters that convert the IRIG-B coaxial signal to fiber optic. Yes, IRIG-B can be distributed to many devices and distributed over large distances. Some people think, вЂњI can reduce my hardware costs by specifying fewer clocks in the system, more distributed clocks, and shorter networks!вЂќ If the clocks on the internal mechanisms were off by a couple milliseconds, you might not be able to definitively tell which one occurred first because your time base is incorrect. Having a 1 millisecond time resolution you can count on ensures that when you root cause and analyze events, you can trust the information in your report. In electrical systems, a cycle of electricity is about 16 milliseconds.

IRIG-B has a resolution of 1 millisecond. Using timestamps served over Ethernet is like trying to solve a crime without any facts. Common side effects of Ethernet like network latency and collisions almost always cause time synchronization issues. When you send a message out via Ethernet, you donвЂ™t actually know when it will be received by the CPU. The reason the electrical industry shouldnвЂ™t use computers acting as NTP servers to serve time out to the CPUвЂ¦is because it serves it over Ethernet.Д®thernet is nondeterministic. In contrast is a common network protocol for synchronization of time called NTP вЂ“ network time protocol. Once the signal is sent out from the clock, we know exactly how long it will take to arrive and be recognized by the pieces of equipment connected to the clock. IRIG-B exists because itвЂ™s deterministic. This distribution occurs through a protocol used in electrical and automation industries, called IRIG-B, which uses a coaxial cable. ItвЂ™s important that your GPS clock distributes its time to the PLC sequence of events modules and other devices in the system. GPS is a known time base accepted throughout the world. CPUs, redundant CPUs, and computer clocks tend to drift if they arenвЂ™t synced to a common time base. In order to know what events occurred first to last, itвЂ™s important that any pieces of hardware reporting events to your SCADA system are on a common time base. How would you do that if the timing was seconds or even milliseconds off? If something beyond normal operation happened in your system, youвЂ™d want to see the exact point in time the system realized there was a loss of source power. The cycle of electricity is 60 cycles per second. In electrical systems, events occur very quickly. One of the first things an owner/consultant would want to look at is the SCADA system to determine which events occurred in what sequence. Say the controls scheme fails, or the system doesnвЂ™t sequence properly. Time synchronization is most important when it comes to root causing or diagnosing a problem with controls or controlled hardware. Why is time synchronization so important?

Its responsibility is to determine when to open and close certain breakers to make sure power continues to flow downstream. Feeder breakers are fed power by one of the two sources at all times.

This PLC is always looking upstream to make sure: In this main-tie-main scenario weвЂ™re going to look at the importance of a PLC thatвЂ™s controlling the main and tie breakers. IвЂ™m going to explain why, with a little diagram of a double ended substation. Time synchronization is often overlooked in mission critical power when specifying hardware, proper controls, and data acquisition.

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