RECOLECCIÓN DE DATOS

The ACE3600 system can use a GPS receiver precise time measurement application for synchronization purposes, to synchronize the RTU with other SCADA systems.

The ACE3600 RTUs use GPS timing receivers equipped with a 1 Pulse per Second (PPS) output. The receivers are connected to an RTU port. In case of a satellite failure, the time is manufactured internally and the receiver indicates its inability to trace the satellite.

The recommended GPS receiver is the Synergy Systems SynPaQ/E GPS Sensor with M12+

Timing Receiver which must be purchased from a Synergy vendor. Along with the timing receiver, a data/power cable and antenna should be purchased. For details on connecting to the GPS receiver, see Appendix A in this manual.

RTU Site Configuration

Open the STS site configuration and configure any one of the serial or plug-in ports to RS_232, Async, GPS receiver. Only ONE per RTU can be configured as GPS receiver.

The other parameters are automatically set as shown below.

The default parameters values are set for the Oncore M12+T receiver, but may be changed, as necessary.

Clock Functions and Synchronization

Link Parameters for PI1/PI2 or SI1/SI2

Time period to get data from GPS (sec) <8-60> [10]:

This field defines the interval between two time updates from the GPS receiver. . Note that a drift of 30 ppm per day in ACE3600 RTU is 1.78 milliseconds per minute. Setting the clock every 10 seconds will prevent this drift.

The GPS advanced parameters explained in ACE3600 STS User Guide, Appendix A Site configuration parameters. The most important parameters are shown below:

Advanced Link Layer

Offset in milliseconds Default: 0

Range: 0- 86400000

The field defines the time offset to add for GPS time in the Universal Time Coordinate (UTC). The range is 0-86400000 msec.

This parameter is for testing purpose and should be left as 0. For adding local time offset set it in time zone section of advanced parameters.

Powerup with factory defaults Default: Disable Range: Disable/Enable

If Enabled the GPS receiver will power up with defaults from factory, taking it longer to obtain time.

Set GPS in position Hold (Timing only) Default: Enable Range: Disable/Enable

This parameter should be enabled for M12+T timing receiver and disabled for non- timing receivers.

If enabled, in order to perform precise timing, the GPS receiver position is

determined and then the receiver is put into Position-Hold mode where the receiver no longer solves for position. With the position known, time is the only remaining unknown.

When in this mode, the GPS receiver only requires one satellite to accurately determine time. If multiple satellites are tracked, then the time solution is based on an average of the satellite measurements.

Clock Functions and Synchronization

Advanced Physical Layer

RTS Always ON Default: No

Range: Yes/No.

This parameter should be left as NO since RTS has no meaning in GPS.

Polarity of PPS Input signal Default: Active LOW

Range: Active LOW/Active HIGH This parameter determines the PPS (Pulse per second) polarity in DCD input. For M12+T it is set as LOW.

After setting the GPS parameters and downloading the configuration to the RTU, the unit starts updating its time accordingly. You may use the Get Site Time & Date utility to verify the RTU time.

GPS Diagnostics and Verification

The system flag, ClockValid, is included in the Reserved Flags (system) table. A value of

‘1’ indicates that a GPS receiver is connected to the RTU and the receiver is updated from the satellite. When ClockValid=1 the RTU updates its time from the GPS, and ignores any synchronization words received from other systems, from the Site Time & Date utility, or through the ladder diagram language. ClockValid=0 indicates that the GPS receiver is not connected to the RTU, or that the GPS is connected and a satellite connection failure has occurred. Following system power-on, it takes up to 15 minutes for the GPS receiver to start reading the satellite time.

The ladder controlled GpsOfs value is included in the Reserved Values (system) table.

This value enables the user to update the MOSCAD unit to Daylight Savings Time.

The GpsOfs default value is ‘0’, and it may be either positive or negative according to the specific time changes (measured in hours). This value is added to the local offset from universal time ‘Offset in milliseconds’ value, defined in the port Advanced Properties window.

When the GpsOfs is set, the RTU time is updated starting from the next GPS report, except following a “cold restart”, which may last up to one minute.

Verify the GPS time using STS SW Diagnostics, device GPS level 1. or using device NTP level 1 to see that time is synchronized, and level 3 to see the local time.

NTP Advanced Parameters for GPS

The NTP advanced parameters affect the GPS. In ACE3600 the GPS is regarded as an NTP clock source over RS232. The defaults are suitable for GPS, yet the following parameters enable warning messages when losing time synchronization (when ClockValid is 0.):

Clock Functions and Synchronization

Time sync lost before declare ‘no sync’ in sec

Default: 120

The number of seconds to wait before declaring ‘no sync’, when no reply is received from the NTP server after a poll.

During this wait period, polling is increased.

If ‘no sync’ is declared, the ClockValid flag in the Reserved Flags database system table is set to Nr (see the next parameter.) If GPS is configured, ‘no sync’ occurs when no valid satellite status is received for this period of time.

Notify error logger when losing sync Default: Yes Range: Yes/No

Whether notification should be sent to the Error Logger when declaring ‘no sync’. By default this parameter is "Yes", meaning a message is logged into error logger when getting into "no sync" state after being in sync. If ‘no sync’ occurs again, no message is logged until the user retrieves SW Diagnostics device NTP level 10.