George Municipality is utilising Adroit Technologies' supervisory control and data acquisition (scada) system to minimise system incidents and power outages, and to deliver the best possible service to its clients.
With a rapidly expanding residential and commercial area, reliable power supply to customers requires continuous monitoring, and to do this, George Municipality makes maximum use of numerical technology to monitor and control primary and secondary equipment.
Kobus Wilken, principal technician for the George Municipality - Directorate: Electrotechnical took about 80 man hours to integrate and implement the Adroit scada in 1996 when the organisation switched from a legacy Multiview system. He says: "It is a truly open automation system and has proven so over the past 10 years.
"It is very easy to 'build' an Adroit system. There are a huge amount of drivers available free of charge, except of course for a couple of OEM drivers which carry a once off minimal charge. Updates come out all the time, and can be downloaded off the Internet and installed."
The municipality has continuously upgraded to each new version of Adroit since its initial installation - all of these are managed by Wilken who says: "The most important aspect was that Adroit is a local company with support just a phone call away; or you can e-mail or remote dial up if there is a problem. It is also very easy to use and implement. They can even do on-site support."
The scada human machine interface (HMI) screens enable the operator to monitor and control all integrated equipment and facilitate quick deployment of personnel when trips or equipment failures occur. Wilken says: "There are a lot of images available with the package, but we drew our own graphics and images. It is vector based, so it is very easy to draw and add behaviours."
Trending of analog values such as MW, MVAR, currents, voltages and power factor are also available via the Adroit system to assist in managing daily demand as well as maximum peak periods.
George Municipality has a suburban supply area of 67,38 km² coupled with a rural supply area of 446,32 km²; including Wilderness, Thembalethu, Pacaltsdorp and Heroldsbaai. This places a maximum demand of 70 MW on the municipality, which is a 66 kV voltage level and then stepped down to 11 kV at six existing substations from Eskom. The municipality's larger substations are fully integrated into Adroit, without the use of RTUs.
George Municipality has a large installed base of protection and automation equipment from Schweitzer Engineering Laboratories, these include seven SEL-2030 communications processors, 105 SEL protection relays (of which 45 are already fully integrated into the scada system). Another 58 SEL relays have been purchased and are still to be installed and integrated to cope with the growing demand.
It uses the Adroit scada software platform to perform all the remote supervisory control and data acquisition functions, using typical communications network architecture. The communications processor is the heart of the system and acts as a communications processor, substation database, protocol gateway, programmable controller, port switch and synchronising time source.
In a substation environment, integration means providing communications pathways so that the individual intelligent electronic devices (IEDs) function as one unit monitoring, controlling, protecting, and automating the system. Devices within the substation have become more and more intelligent, performing multiple functions and containing measurement data, status, control, settings, historical information, and alarms.
Substation IEDs include protective relays, battery chargers, equipment monitors, weather stations, and many other devices. Each IED often performs the functions of several devices within a substation, but for a portion of the substation associated with a single bay or circuit breaker.
In George, a communications processor integrates the IEDs into the Adroit scada system. The communications protocol uses an SEL family link of binary and ASCII messages sometimes called SEL interleaved communications. This powerful protocol and the combination of IRIG-B on the 9-pin serial ports of the IEDs and communications processor enable the use of a single cable to provide functions in all of the basic integration areas.
Because the messaging is interleaved, an engineering connection does not halt the collection of status and measurement data for the scada. The ASCII engineering connection shares the cable with the binary data collection and control messages. "Using the SEL protocol, auto-configuration via the communications processor is possible," says Wilken. When connecting an SEL IED to the communications processor, the auto-configuration process can be initiated where the communications processor learns of the IED and what information and control points are available to it.
Other devices like the ABB DPU, REG DA and the Beckwith N2001 tap change controller are also connected to the communications processor at George Municipality. An ASCII string is generated inside the unit and sent to the IED at user-defined intervals. The data sent by the IED is then passed into the communications processor database and made available to an Adroit master. "Our system is licensed for one server and one node with 5000 scan tags. Licensing includes all protocols except a couple of OEM protocols, in our case DNP3.0," says Wilken.
George Municipality uses DNP3 as a master protocol to get all the scada functions. Two ports from the communications processor connects to the multiplexer in the substation, the data is then transmitted over the fibre-optic link between the multiplexer in the substation and that at the control centre. From the multiplexer in the control centre there is an Ethernet connection to the master computer, which serves as the DNP3 scada link, and a second serial connection to a serial to Ethernet transceiver that connects onto the Ethernet network, allowing authorised personnel to establish an engineering connection to the relays in the substation from the management offices.
Wilken says: "The maximum tags one can use are system limited, which means, if the server can handle it, so can Adroit. Our system currently uses about 2500 scan tags and 5100 tags overall. We do however scan in 32 bit values from most outstations which drastically decreases the amount of scan tags used."
The Adroit scada also provides an overview screen of the network. When one of the substations is selected a screen showing the detail of the station opens. On this screen the operator can see various analog values like the current in the feeder, the busbar voltage and the voltage of the DC tripping batteries.
Wilken says: "Adroit is connected on a LAN, mainly for the purpose of communicating with outstations. We can also access Adroit using PCanywhere from a remote location where full control is allowed, if you have the correct passwords of course." Some of the relays have the capability to monitor the voltage level of the tripping batteries if the voltage reaches a critically low level. An indication will be sent to the scada system thus enabling the operator to immediately send maintenance personnel to rectify the problem. Once the tripping battery voltage reaches a critically low level the relay can block any closing operations or spring rewinds and conserve the available battery energy for tripping.
The protection relays can be accessed from Adroit where settings can be reviewed or changed with the necessary passwords. All controls and acknowledgement of alarms are listed in the event log viewer creating a sequence of events list. "We log almost all analog values and these can be viewed on a graph within Adroit or exported to an Excel spreadsheet. Data reporting to databases is also a standard function. Example scripts are available to write to Excel spreadsheets," said Wilken.
This system also features an SMS function where certain events, prioritised in terms of criticality, will initiate the message to the on-duty operator. A trip on an overhead line with successful re-close will for instance not generate a SMS but as soon as the trip results in the relay locking out, an SMS will be generated. Although the SMS function is standard in Adroit, a script was used to verify message recipients. George Municipality is currently running 12 scripts, which Wilken wrote.
The Adroit scada at George Municipality is expanding every day as new equipment is added or upgraded to cope with demand. The organisation, for example, is currently upgrading to a hot standby system of redundancy. As the system expands and more IEDs were added, additional serial ports were also added to the master computer in the control centre. A total of 18 serial ports existed on the master computer.
To reduce the number of serial ports required George considering retrieving the scada data over an Ethernet network using the DNP 3.0 on Ethernet. This architecture is similar to that used for engineering access, whereby a serial to an Ethernet transceiver with multiple serial ports is connected to the Ethernet switch in the control centre, the serial ports are then connected to the various multiplexers. The only connection required for the master computer is an Ethernet connection to the switch, all scada functions and engineering access functions can then be performed using the IP port.
For more information contact Charles Hudgson, Adroit Technologies, 011 658 8100, [email protected], www.adroit.co.za
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