Time Synchronisation of Mark VI System

In a plant where many control systems are used for specific dedicated purposes, it is essential that all their individual times are synchronised. Mark VI System used for Gas Turbine Control has the facility to synchronise its time with other systems via the Network Time Protocol (NTP) system. After connecting all Controllers and HMIs into the same network and establishing communication among them, the next requirement was to get the system time-synchrnised with the Plant GPS enabled Master Clock system. And it was the first time.

So first of all it was necessary to get the scheme clear. It became clear that unlike DCS Processors, Mark VI Controllers do not have direct time signal input facility. Rather one or more of its HMIs can be made Time Masters which will receive time signal input from the main time source (e.g. GPS system) and work as servers for time signal in its own network. Since all the Controllers and other HMIs are on the same network, they will become client to the time server and become time-synchronised with the time server.

To begin with we planned to make a single unit (Unit-1) out of two units ready with time-synchrinisation. So the devices on the Mark VI network were -

• Mark VI Control Panel for Unit-1
• Local HMI for Unit-1 panel (GT1_SVR)
• Remote HMI for both the units (CRM1_SVR)

Next when we made a list of the pre-requisites for implementing the scheme it was somewhat like this -

• Fully established communication among the controllers and the HMIs - which was ready
• Network Time Protocol software installed on the HMIs -which was also ready
• A receiver for time signal called Time Card capable of receiving IRIG-B time signal - it was installed on the CRM1_SVR which was to be configured as the time server. In our case the Time Card was bc635PCI time module installed at a PCI Slot supplied by Symmetricom. This card was identified by the Operating system through its driver. The connection was to be made through a 15-pin 'D' connector.
• 'D' Connector to BNC adapter - it was required because the IRIG-B signal was available from the Master Clock system via co-axial cable, and this was also supplied with the time card.

In addition to these, the HMI with the time card was also having two other software namely Symmetricom Demonstration Driver bc635CPP and TrayTime whose utilities, at the beginning, we were not so sure about.

So everything was ready and only the implementation was left. We started with the internal configuration of the Mark VI system which we divided into 3 steps and did like this -

1. Configuring Mark VI Controller (in the M6B file): "Unicast" selected at the NTP tab on the device (G1) properties and servers UDH names were specified. The primary server was the remote server i.e. UCRM1_SVR and the backup server was the local server i.e. UGT1_SVR.
2. Configuring CRM1_SVR (HMI with the time card): 
• First NTP server was configured from Control Panel by selecting it as a Time "Master (supply time to clients)" and operating mode as "Unicast."
• Next the time card was configured at the Turbine Control Interface from Control Panel. At the Time Hardware tab, appropriate time card was selected (in our case BC635PCI) and in the Satellite Time Source section Timecode was selected as "IRIG-B, Modulated" and Timebase as "UTC".
3. Configuring GT1_SVR (HMI without the time card): For this only NTP was required to configure from Control Panel by selecting it as a Time "Client" and operating mode as "Unicast." In addition the Server was to be provided, for which the PDH name of the Primary Time Master, i.e. CRM1_SVR was provided.

With these the internal configuration was over. Now it was time to connect the IRIG-B cable to the time card via the BNC to 'D' adapter. After the connection the utility of the software bc635cpp became apparent. The bc635cpp program allows the user to access the bc635PCI card and demonstrates the board functionality. And with this we saw that the time card was receiving time signal from the time source.

The next step was to set the HMI system time as per the acquired time which will further be synchronised thoughout the network. Then it was the time for the software TrayTime. This system tray utility queries the bc635PCI and set the system clock on a periodic basis. That was it. It was to be kept running to sync the system time with the acquired time after a certain interval. Then we checked one by one and found that all the controllers and HMIs were showing the same time in synchronisation.