4 Steps to Efficiently Upgrade Control Systems at Power Plants

Power generation in India comes from three main categories: the central sector, the state sector and the private sector. The latter produces nearly 50% of the power generated in the country; India’s total installed generation capacity is 395 gigawatts (GW) as of February 2022.

Nearly 60% of power generation comes from fossil fuels, with coal alone contributing 51.6%. Renewable energy sources account for more than 38% of capacity — including 11.8% from hydro — and nuclear power provides the final 1.7% of generation.

Even with renewable energy sources rapidly coming online, existing coal plants in India will need to continue operating for years to come. Current rules call for coal-fired power plants to curtail sulfur dioxide and nitrous oxide emissions by implementing appropriate technology. While this was originally to be in place by 2017, the Ministry of Power extended the deadline to 2022.

Upgrading coal plants in India could take several different paths: adopting new technologies to reduce emissions, switching from coal to natural gas to fuel power generation, or upgrading control systems.

A Systematic Approach to Improvements

Everything has an expiration date — even control systems. Operators need to watch for indicative signals, because the decision to upgrade a power plant triggers a cascade of necessary steps.

Experienced engineers know the complications of dealing with aging control systems, including either a lack of support or very expensive support from the vendor, limited or nonexistent availability of parts, and lost documentation. That’s not to mention the day-by-day degradation of overall performance. When operators ignore those indicative signals, eventually the systems fail or break down beyond repair.

A well-thought-out control system upgrade strategy can help avoid those outcomes.

Control system upgrades require a systematic approach. Many components might require improvements; the following are often important aspects to keep in mind:

• Downtime of the plant
• Security
• Ease of troubleshooting
• Expandability
• Cost
• Documentation

Planning upgrade implementations with minimal downtime calls for creativity. These four steps offer some guidance:

1. Study the existing system in detail: Take a close look at the system to determine what needs to be replaced or is creating problems. Sometimes the controller is the main culprit, sometimes it’s I/O cards. Occasionally the SCADA system can be at issue. Replacing a programmable logic controller (PLC) without replacing the SCADA system, or vice versa, might address the concerns. Sometimes the complete system needs to be replaced. Identifying the root cause of the problems is essential.

2. Understand the system: A control system integrator or consultant can help with this task, but the end users of the system must have their own understanding of the system’s operation. One power plant could be utilizing several different makes and models of PLCs. Switching to a single vendor, when possible, could reduce inventory and the plant’s dependence on multiple vendors. Details like which PLC controls which motors, and which objects on SCADA are associated with which PLC, are important to know.

3. Downtime possibilities: This can be the trickiest part in the upgrade phase. Management will expect to know how much downtime could be required to accomplish the proposed solution. A full shutdown to perform the upgrade would be simplest but is usually impractical. For more pragmatic options, think logically and seek answers to these questions:
   • • If the plant has multiple units, could implementation be performed unit by unit?
     • What approach would serve common systems like utilities or balance of plant?
     • Is there a common control room?
     • How many systems or instruments can be replaced to take fullest advantage of this downtime?
     • Can the same cables be used, or do they need to be replaced? (Most of the time, replacement is not required.)
     • Can the same marshalling cabinets and/or the same control system cabinets be used?

Additionally, running the plant in local control, or hand mode, during the control system upgrade might be possible. Although running the entire plant manually for the duration of a complete control system startup is rarely an option, running a small, internal subsystem manually just long enough to modify a subsystem is typically feasible.

4. Establish phases for the upgrade: This is necessary in drawing up a complete plan for the upgrades. Phasing helps in many ways. This could involve replacing one PLC of many in the facility, moving one small subsystem — controlling a small portion of the plant — from an aging PLC to a new one, or converting just a few graphic screens. Involving control systems integrators or consultants during this step is a great idea, as they can review your system and help determine which functionalities could be grouped together.

Building on the Benefits

Technology upgrades can be a win-win solution to enhance the capability of a control system and extend the productive life of a plant. Once operators start updating outdated systems with new parts, chances are the benefits will so outweigh the costs that the operators will look forward to each progressive upgrade.

The team at Burns & McDonnell India — in collaboration with the company’s U.S.-based offices — has seen such successes firsthand in performing a variety of upgrade projects, large and small, in recent years. These have included replacing a plant’s Allen-Bradley PLC with an Emerson Ovation distributed control system (DCS); producing all engineering deliverables to convert a plant to burning 100% natural gas, including field instrumentation and control system upgrades; and building a power generator’s PLC logic based on Control Narrative.

Take some time to consider the biggest technology pain points associated with equipment obsolescence. Then consider the productivity gains that could come with a new controller or a SCADA system that is more robust, feature-filled and better documented.

Operators know their systems better than anyone else, and they are usually in position to determine the right time to pursue an upgrade. To keep power plants productive, they must consider control system upgrades to provide more stability, new and enhanced features, and streamlined access to replacement parts in the future.

Newer distributed control systems have enhanced features to optimize safety, performance, controllability and reliability. A thorough control system assessment evaluates the risks and analyzes the potential benefits.