SUPERVISORY CONTROL & DATA ACQUISITION SYSTEM (SCADA)

History

In 1993 it was determined that a Supervisory Control & Data Acquisition System (SCADA) system was needed to monitor the campus electrical supply and distribution system.  A study was conducted to determine which SCADA system would be most appropriate for Stanford University Power Systems.  We reviewed other utilities' SCADA and wall Map systems such as PG&E, Palo Alto, Santa Clara and Berkeley.  In addition, we contacted numerous vendors in order to better understand the different technologies available.  Most of the packaged systems involved the purchase of a complete SCADA system as opposed to the method of using single meters as the basic component.  We were aware that strategically placing these meters both in switch gear at the substations and building switchgear; an effective instant evaluation could be made regarding the status of the electrical power distribution system.

In 1994 the Utilities Division started installation of the campus SCADA system using Intelligent Electronic Devices (IEDs)  and a DOS based SCADA software package.  The Energy Management Control Systems (EMCS) group, which is a department in the Utilities Division, also needs data from building meters.  The IEDs provide communications to the SCADA software as well as an analog output signal (proportional to kW) which is read by the building EMCS.  The building EMCS (a Rosemont system) records this signal to track electrical energy demand and Kilo Watt Hours (KWH).

The SCADA software is a graphical package using a Window NT Operation System.  The system, manufactured by Power Measurement Ltd (PML), provides the programming necessary to incorporate actual AutoCAD campus maps and diagrams, and to display real time information on top of the graphic background.  Items such as: power system parameters, breakers and switches status, alarms, event logs & historical data logs; can be overlaid on the AutoCAD Single-Line Diagram. 

Additionally, this system allows the Facilities Operations - High Volt Technicians to view the big picture (a section of campus), and then tunnel down to a detailed view ( a single-line) as needed.  SCADA automatically generates alarms and monthly energy reports and is easily expandable as the needs grow. The new system is extremely flexible and is completely expandable as IED meters are added. 

Benefits

Present Benefits

The University needs have grown and the demands for reliable and accurate performance and trend data have increased. High Volt Technicians need to be able to remotely and instantaneously, identify electrical power loop feeder sections that are affected, and respond accordingly.  As discussed, when a particular section of the distribution system goes down, the operators are provided with instant information. This enables the system operators to provide individual building managers, researchers, department chairs and others, information on the problem.  In addition, the engineers are able to examine historical data for load trending, planning and  improving system performance.

In addition, the following functions are being utilized more and more as the SCADA system is expanded across campus.

• Manual meter reading is being replaced with automatic reporting

• Real time alarms and data give operators the information they need to respond quickly.

• The Utilities Division can be proactive in providing quality information to its customers.

Long Term Benefits and Future Needs

Power System Operators need to be able to continue to remotely and instantaneously, identify electrical power system failures at any location in the distribution system.  Accurate real time alarming and historical information is needed to continually meet the needs of a diverse community of energy users.  A continuation of the demands for high reliability and accurate performance and trending data is paramount.

Stanford has already been experimenting with the web based metering and plans to incorporate, and design custom features with off the shelf web based tools.  This will allow users within the university community to access specific information by using a web browser instead of expensive third party software (e.g., energy consumption report, performance data, etc...).

Summary

It is considered imperative that Stanford University become fully aware of the disposition of the Electrical System at all times in order to serve the academic mission with the least amount of disruptions.  Stanford requires accurate real-time alarming and historical information to continually meet the needs of a diverse community of energy users.  We need to prevent outages and other power problems proactively.  We have acquired a solid communications and highly reliable SCADA system.

SCADA System in Action

Fault Location

Prior to 1993, the method used to determine the magnitude of  a campus power failure such as which buildings were affected and what should be first priority to restore power to were determined by a combination of waiting, hoping, guessing, triangulation and luck.  

A triangulation scenario:

A power failure on the campus would usually start with a call being received from Maintenance Customer Service (MCS) or a building manager stating that a building, ( in some cases a number of buildings) had lost its electrical power.  Not knowing which branch of the circuit had failed; High-Volt Electricians would wait for a second call identifying another building power outage. Eventually, when a number of buildings without power were identified, by using a simple method of triangulation could be used to determine which area of the distributions system had failed.  This would be an elaborate procedure, sometimes taking several hours. High-Volt crews would be dispatched along the route of the distribution (all of which is underground at Stanford) and would selectively remove vault and manhole covers, observing the fault indicators on the distribution cables.  In time, the cause of these multiple building power failures were becoming more difficult to locate, consequently, fault location time, and subsequent restoration time could be several hours.  With the installation of SCADA technology, the excessive time spent investigating faults and problems is reduce substantially.

Outage Record

Post incident analysis is required to prevent reoccurrence of similar outages and power failures.

Position and Status of Breakers

Multiple use of HV switch contacts that are connected to the system, gives the system operators the ability to obtain instant and remote status changes.

Amperage on Feeder Cables

In addition to the fault location requirement, the High Volt Technicians  needed to able to record and evaluate the current use of specific distribution cables.  Switching operations required daily reports to enable them to transfer load to other feeders.  In the past obtaining this information required sending an electrician to the substation to record the feeder ammeters, a time consuming event. 

Substation Battery Status

Five banks of batteries are installed for breaker control, relay protection and tripping circuits.  Loss of the critical function of the battery system can be devastating for a switchgear breaker unit and inability to trip a faulted circuit can be a disaster.  Setting low voltage limits that alarm instantly, warns the maintenance personnel who can respond quickly and avert a major problem.

Switching and Paralleling Operations

Confirmation of the physical change in operator switch position was not available prior to the use of remote SCADA applications.

Power Quality

As needed, generally after an event, or upon query from building users power users power quality records are requested.   

Substation Security Fires and Door Alarms

Early on in the design of the SCADA application, it was determined that fire/smoke detectors were needed in all substation switch gear rooms.  This function, along with door alarm contacts, provides the system operators with the ability to respond instantly to these types of events.

Substation Primary Transformer Status

Most substation transformer status alarms and events are monitored by the system.  The annunciation and display of alarm conditions ensures timely investigation of the problem.  Remedial action can prevent future equipment damage and power outages.

Emergency Generator & Power Available Status

Stanford has an ongoing program to replace the Cogeneration Plant emergency feeders stand-alone generators.  Emergency generator breaker running and transfer switch transferred status is imperative to understanding the specific availability of the emergency source.  These monitored events provide the added assurance that all systems are working correctly.

Breaker Position Status at Building Voltage Level

Auxiliary breaker contacts on the main building, 208/480-Volt service boards are connected into the SCADA system.  These enable High Volt Technicians to be informed of a single or multiple building area power failure.

Hospital and Medical School Emergency Services Status

The Hospital emergency power feeders from the Cogeneration Plant are monitored to confirm the availability of the services, on a continual basis; this prevents the remote possibility that the service is not available.  As mentioned earlier, Stanford is presently designing a system of stand-alone generators to replace the Cogeneration Plant emergency feeders.