A few years ago, the Public Service Co. of New Mexico (PNM) adopted a program called FMEA (Failure Mode, Effects A Analysis) to identify weak points and reduce the number of transmission line trips both from the equipment and the human standpoint.

The FMEA program is a systematic engineering method for identifying vulnerabilities and potential failures in a method, process or system before they occur, and then eliminate them.

PNM (Albuquerque, New Mexico, U.S.) found it could make several improvements to equipment or a work process by taking a simple common-sense approach. A key element of the FMEA program is bringing the people involved with the problem area into the evaluation. PNM held meetings, studied the identified problems in detail and developed new methodology.

One area that kept registering as a potential problem for the transmission system was the control building, which houses the relays, meters and the communications systems needed to keep the station operating. It is the brain and central nervous system of the station, and it was a weak point.

Control Buildings

PNM has made continuous improvements to the control systems over the years, but the configuration of the building hasn't changed much since the first substations were introduced. There may be a separate room for batteries or communications equipment, but overall the control building was just a big room filled with panel-mounted racks of equipment.

In general, a foundation was poured and the building was constructed on site. It was either a concrete block design or a sheet-metal building arriving on site as a series of pallets. After the building was erected, the equipment was installed inside. Traditionally, the equipment was mounted in panels and then bolted together and arranged in narrow rows. The rows either faced all in the same direction (front to back) or they were paired sharing a common passageway (back to back) between them. The front of the panel displayed the relays, control devices, indication lights, meter faces and recording charts. The backs of the panels usually contained the test points, disconnect devices and a massive amount of cabling.

FMEA Findings

As PNM completed the FMEA process on the control building, it became apparent this was an area needing change. Meetings with the control and protection technicians and the engineers revealed the following key points:

• The typical control building was not a user-friendly place for the technicians and engineers working in this environment.

• The aisles between panels were typically narrow and crowded when test equipment and their associated wiring was present.

• Working space was cramped with no room to lay out drawings other than the floor.

• Lighting could be improved.

• Personnel were forced to work from both the front and the back of the panels at the same time during commissioning and testing.

• Trying to avoid sensitive equipment in crowded panels impacted concentration and increased stress levels.

The Future Was Now

The PNM team decided that the next switching station PNM constructed would have a “21st Century” control building designed to include the FMEA recommendations. As luck would have it, the Taiban Mesa Station was in the design phase as the FMEA recommendations were published. Taiban was a critical project to PNM with a very aggressive schedule (see T&D World, November 2003, “Wind Power”).

The engineering team designing Taiban was made up of personnel from PNM and GE Industrial Systems (Jackson, Mississippi, U.S.). The team was challenged to design a control building for the future today. This building should aid production but not impact it. If the control building was designed to enhance the work process, it should save time during the installing and commissioning phase of the construction and time was in short supply. The FMEA recommendations came along at an opportune time to make a difference in a decisive phase of design.

To make Taiban's building more user friendly, it was made larger. However, if future needs required enlarging the station, the building had to be able to handle the additional equipment without losing the advantage of the increased work space. There were two solutions: the building could be sized for the ultimate station size from the start or the building had to be designed to be expandable. A larger building initially would cost more up front, and what if the station never grew? A better approach would be an expandable building, but could PNM design an expandable building without a great deal of expense or mess? Sheet-metal buildings and concrete-block buildings can be expanded, but knocking out a wall would be dangerous to the equipment located inside. However, there was another type of building gaining acceptance in the market place, the prefabricated building.

Benefits of Prefabricated Buildings

The engineering team determined that the entire control building could be pre-engineered, preconstructed and pretested off site, including internal wiring and heating/air conditioning. The building would then be shipped to the station on trucks and placed on its foundation upon arrival. Once station service was connected to the building, it would be ready for occupancy.

PNM first selected a prefabricated building manufactured by Atkinson Industries Inc. (Pittsburg, Kansas, U.S.). Atkinson said it was possible to design the building so that one wall could be removed and another prefab section could be installed to increase the size. The expansion would take place quickly without any mess. Atkinson recommended a two-unit building design. The two sections would be shipped by truck to the station, bolted together and placed on the foundation. GE designed a pier foundation system that could be increased in size by placement of additional piers, allowing for a cost-effective expansion if necessary. Problem solved.

Human Factors Engineering

The next problem was the arrangement of the equipment panels. Typically the panels were bolted together to make up long rows. With the panels placed in a front-to-back configuration, engineers/technicians had to take turns working on rows to avoid having too many bodies in too small a space.

For the new building, the distance between rows was held at PNM's standard arrangement, but the panels were lined up in a back-to-back configuration. This kept the engineers/technicians working on the back on one lineup from the conflicting with technicians working on the front of the adjacent panels.

Another idea to reduce congestion was to place all the test jacks and isolation switches on the front of the panels. This way the test equipment would be in the front of the panel, and the technicians working on wiring would be in the back of the panel. Power outlets also were placed on the front of each panel, so test equipment could be plugged into outlets close to the work at hand.

The last problem area identified was working around the crowded, sensitive equipment, which increased worker's stress. Again, this was a problem that might be answered by two solutions: one, use a lot of panels and limit the amount of equipment in them; or two, install state-of-the-art technology in the panels. The team elected to install the new technology. If the technology reduced the amount of equipment and freed panel space, it had to diminish the workers stress levels by eliminating the congestion around sensitive relay packages. It might even save time and money. Taiban Mesa was a station developed for the ultra-modern New Mexico Wind Generation Center and its control building was going to be a 21st Century facility too.

21st Century Technology

FPL Energy (Juno Beach, Florida, U.S.) selected the location of its wind facility based on the location of PNM's 345-kV transmission line in eastern New Mexico. With the construction of the station, the single transmission line bisecting the wind farm became two, which caused a problem. The original plan had been to use the same protection scheme at the new station as at existing stations. The existing protection system consisted of three pilot relays operating through a computerized voting scheme. The GE Trip Security System (TSS) is a voting scheme based on two out of three relays agreeing before the line will trip. The TSS uses relays from three different manufacturers: one relay is no longer manufactured, one manufacturer could not meet the construction schedule, but the third relay was available. The Taiban engineering team, working with GE Multilin (Markham, Ontario, Canada), studied the problem in depth.

GE Multilin recommended PNM use its newly designed universal relay (UR) family for all the protection and control requirements. The UR family of digital-protective relays has the ability to be networked and integrated with existing hardware, regardless of manufacturer. It was ideal for this application since it was built on an expandable modular hardware platform, enabling it to support the system requirements. The UR modularity is much like the plug-and-play card architecture found in the personal computer. It also has a high-speed parallel bus providing a common power connection and a high-speed data-interface connection from the modules to the master processor. In addition, its FlexLogic, field-programmable logic allows for programming of complex schemes in the relays that can be modified without adding more hardware or wiring to accomplish the changes. It allowed the voting scheme logic to be moved into the relays instead of relying on separate devices. This eliminated the need to have separate voting scheme cabinets, which reduced equipment and saved time.

GE Multilin also suggested using the Utility Communication Architecture, a virtual wiring system allowing protection and control communications between the relay systems in conjunction with hard wiring. This flexible system was exactly what PNM needed to make the three stations coordinate with each other.

Also included was the GE enerVista Viewpoint system, a workflow-based monitoring, testing and troubleshooting program. Its function was to create a virtual interface within and without the Taiban Mesa system through SCADA and local control. The Human Machine Interface (HMI) provided for both local control and remote operation. It allowed local interaction between engineers/technicians and the control systems in the station. Personnel using the HMI can operate breakers, disconnect switches, monitor power flow, and check voltage and current on the lines terminating at the station. In addition to the control and monitoring functions, it can be used for data logging, metering, communications and alarm warning, to name a few. But HMI is more. It was really a “cyber” SCADA environment that responds to commands anywhere within the PNM control system.

Futuristic Control Building Reality

PNM's control building of the future was designed, constructed and commissioned in 2003. All of the recommendations for the physical improvements were implemented with good results. The state-of-the-art protection and control schemes reduced the amount equipment, which decreased the number of panels. It also simplified the installation work by using “virtual” wiring wherever possible.

Overall, it worked, it saved time and it saved money. To say it went smoothly would be preposterous. Any time you attempt an extremely aggressive schedule, problems will occur. Add new technologies to the mix, and it is guaranteed to cause problems, but nothing was serious enough to delay PNM's progress. In retrospect, a complex project of this nature was probably not the ideal place to undertake so radical a departure from the safe waters of tradition. At the same time, this type of a project created the opportunity for calculated risk taking and that gave way to some very creative engineering.

Gene Wolf, a contributing writer for T&D World, is a principal engineer with Public Service Company of New Mexico, where he is responsible for the design and construction of EHV station facilities. Wolf has a BSEE degree from Wichita State University and an MSEE degree from New Mexico State University. He is a senior member of IEEE and a registered professional engineer in the state of New Mexico.
gwolf@pnm.com