Sam Crisafulli & Darren Zenko, Matrikon, USA

The importance of effective management of plant assets in the power industry should never be underestimated. Meridian Energy, New Zealand’s largest renewable energy electricity generator, certainly agrees following the implementation of a custom designed plant asset management system.

Meridian Energy is New Zealand’s largest state-owned renewable energy electricity generator, providing approximately 30 per cent of the country’s total generation. The company currently operates nine hydro stations in the South Island, New Zealand’s largest wind farm in the North Island, and a wind turbine in Wellington. Meridian supplies 200 000 residential, commercial and industrial customers throughout New Zealand.

With assets valued at over NZ$4 billion ($2.9 billion), Meridian takes asset management seriously. As a state-owned enterprise, Meridian is charged with managing the business in an effective and profitable manner, while preserving the capability of their assets for future generations. To achieve this balance the company has a continuous improvement programme in place, using best-practice management and maintenance methodologies in combination with leading edge technology.

Centralizing operation control

Many of Meridian’s assets were commissioned in the 1960s, and like many hydro sites of this vintage they are approaching an age where they require renewal or refurbishment, or at the very least an increased amount of care in order to prevent critical generating assets being forced out of service or, in the worst case scenario, suffering expensive or catastrophic failure.

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In addition to aging plants, Meridian also faced the worldwide phenomenon of experienced engineers and technical staff retiring, or simply choosing to move as the workforce has become more mobile. The difficulty with this, other than obvious recruitment issues, is the loss of the intellectual property that those leaving take with them after a lifetime in the industry.

In 2001 Meridian completed an ambitious five-year programme to upgrade plant wide monitoring and control networks and to centralize control-room operations in the town of Twizel on the South Island. Meridian’s entire plant is now remotely managed from a single location, a solution that partially addressed staffing and accessibility issues, but has raised new challenges.

A consequence of moving staff away from generation sites and into a central control room was that these experienced professionals were no longer at the power stations, and were out of physical contact with the equipment in their care. The most basic and fundamental condition monitoring system available – that based on sight, hearing, smell and touch – was therefore taken out of the maintenance equation.

It was recognized that without the in-depth knowledge and physical presence of experienced of staff at the station, powerful diagnostic tools would have to be provided to monitor the plant condition. Meridian had some very good systems and processes in place and a wealth of maintenance data, but these were described as “data rich, information poor”. The flow of raw sensor and alarm data from Meridian’s dispersed assets needed to be translated into clear, useful information about the plant’s condition and performance.

To address this, the company’s Generation Improvement team, led by Garth Dibley, began planning a system that would provide early warning of deterioration of critical equipment, perform basic analysis to turn data into information and provide predictive capability – in other words a plant asset management (PAM) system.

Key to the implementation of such a system was its integration with Meridian’s existing computerized maintenance management system – Maximo – and the existing plant historian. Meridian had invested heavily in these maintenance systems, in terms of both money and time and effort of capturing almost eight years of maintenance history. Unless the planned system could use the data the benefits would not be realised for many years.

Meridian began a tender process and selected Matrikon to deliver an integrated PAM solution. As Matrikon advanced control engineer Finn Peacock puts it, “When two intimately related systems such as a Computerized Maintenance Management System (CMMS) and a PAM system can not talk to each other, then human intervention is required and this defeats the objective of having a PAM system. A classic case of developing an IT system that actually creates more work.”

An integrated solution

Meridian’s PAM is designed around a central control system that ‘plugs into’ modular adaptors for the systems and software it needs to integrate with. The complete PAM system incorporates custom implementations of Matrikon’s proven off-the-shelf ProcessSuite products to gather and analyze incoming data, implement the mathematical models used in the diagnostics and provide web-based system access and visualization. ProcessSuite comprises:

  • ProcessGuard provides PAM’s real time alarm and event visualization and analysis, replaces multiple alarm printers, monitors operations and operator workload and provides tools for efficiently eliminating nuisance alarms.
  • ProcessMonitor is an advanced data-analysis and online industrial computing platform designed for troubleshooting difficult process problems and faults, provides an interface for implementing the mathematical models used in the diagnostics.
  • ProcessDoctor continuously monitors assets in real time, identifying and prioritizing poor performers.
  • ProcessNet provides flexible web-based access to the PAM system control centre and its dashboards.

In addition, Object Connections’ Common Knowledge is deployed to provide the development environment for implementing the business logic that classifies the results for the mathematical models, providing the diagnostics. The resulting three-tiered system is integrated under the custom PAM control centre.

Meridian’s customized PAM system has a integrated three-tiered system
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Plant assets provide the system with their condition information, the results of many online and offline automated and semi-automated tests. Plant data are analyzed with mathematical asset models, classified and collated with business logic, and plant dashboards are updated showing condition and predicted days to failure.

The sequence of events when a non-normal condition is detected or predicted
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In the case of a non-normal condition being detected or predicted, an email is sent automatically to the right people, recommending specific action to be taken – the whole process works in concert with the existing CMMS. The PAM system was successfully commissioned in early 2006, with a dashboard and transformer model monitoring Meridian’s fleet of 34 unit transformers. Following the success of this first-phase implementation, the plant’s turbines are now under the protection of PAM, with the governors being deployed within a month or so and the generators later this year.

Current & long term benefits

According to Meridian engineer Mark Williams, “To date the biggest success that has come out of PAM is a substantially increased visibility of transformer condition. Prior to the PAM implementation, transformer condition monitoring data relied on individuals to enter the test results into Maximo and then others to analyze that data and publicize the results in sufficient detail to flag any issues in a timely fashion. Any changes in staff, either in Meridian, the maintenance contractor or the laboratory providing the results, and a test result could easily be missed or analysis deferred.”

Peacock said: “Manual tests are prone to human error, and if tests and inspections are not linked directly into the CMMS, then it is difficult to track any missed or inaccurate manual measurements. The end result is that manually recorded results can very easily go out of date and eventually you may be relying on old data to interpret the condition of a transformer.”

Now, all unit transformer condition monitoring data go to one place – PAM – that automatically analyzes the raw data and, in a short time frame, notifies appropriate people via email with the results of that analysis and any recommended remedial action. “It is also worth noting,” says Williams, “that in developing the PAM models specialist expertise has been utilized to improve Meridian’s transformer condition monitoring programme and job plans have been substantially upgraded. The tests we carry out use international standards. In the case of transformers, IEEE standards and industry best practice.”

These best-practice testing and monitoring procedures are made possible by PAM’s integration with the plant’s existing Maximo CMMS and engineering knowledge of the equipment.

Meridian’s technology & process strategist Neil Gregory explains the value extracted from the PAM system in the very short time it was commissioned. “We really didn’t and still don’t expect PAM to pick up catastrophic conditions on a daily basis, but we do expect, and get, very early warning of changes in condition which we would not get without the system. Of course some of these changes could be significant and if undetected may go on to have catastrophic consequences.”

Solution to a global problem

There are numerous examples of transformer failures as the worldwide fleet of transformers approaches the latter part of their design life. According to Gregory, asset owners have three basic choices. They can replace the asset based on age, risking the loss of several years of useful remnant life, they can replace on failure, an unacceptable option for such large critical assets such as transformers, or they can take better care of the assets now and realise benefits into the future.

“The PAM system is a cost-effective means of maintaining visibility of the health of assets critical to the business, whether this be transformers or any other piece of equipment”, says Gregory.