Siemens 9700 Using Time Synchronization

Using Time Synchronization

Time synchronization allows you to synchronize the internal clocks of

multiple networked Siemens Energy & Automation devices. When your

devices’ clocks are synchronized, all data logs will have timestamps that are

relative to a uniform time base. This allows you to perform accurate

sequence-of-events and power quality analyses.

Time synchronization is achieved by broadcasting the time across the

network of IEDs. When the source of the time broadcast initially connects to

the devices, the time signal is interpreted as the absolute time, and the

devices’ clocks are reset. During normal operation time signals are sent out

periodically, and each 9700 Power Meter will continually assess its ability to

remain synchronized with the incoming broadcasts. Over a brief period of

time the 9700 Power Meter learns how its internal timing differs from that of

the broadcast source, and adjusts its timekeeping to compensate. Very

accurate time synchronization can be achieved with this method.

Devices that are not continuously connected to the time source (i.e. modem

sites) will be synchronized each time they are connected. The longer the

duration between connections, the larger the error in time synchronization

can be. In the extreme case this can result in missing or duplicated logs. If

this occurs, GPS receivers can be installed at the remote sites, a direct

WinPM connection can be implemented, or the time between connections

can be reduced. As a remote device’s clock is reset upon connection if its

clock is out of synchronization by one or more seconds, increasing the

frequency of connections will typically ensure records are not duplicated or

lost.

Different time sync methods can be used to provide different levels of

accuracy. WinPM can be used for systems where time synchronization is

not critical. In this configuration, each device’s clock is synchronized to the

time broadcast by the WinPM Communications Server workstation. For

applications where highly accurate synchronization is required, an

additional serial network is installed at the site, and a GPS receiver is used

to broadcast the time synchronization signal.

Using a GPS receiver, the 9700 Power Meter can be synchronized to within ±

1ms of Universal Time, or within ± 2ms (typical) of other 9700 Power Meter

devices on the network.

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If the time on a device is out

by one second or more

when a time sync signal is

received, the device’s clock

is reset to the broadcast

time.