Developing a great sequence of operations: Additional answers

Applications, repairs and risk reduction, failure modes, retrofits, documentation and project scope are among additional information provided for developing a critical power sequence of operation. Take related training with a quiz for one continuing education unit (CEU).

By Zach Goldsworthy October 22, 2020
Courtesy: Siemens Industry

Emergency parallel switchgear is vital to a building’s resiliency or for processes inside, and the sequence of operation (SoO) for starting and stopping emergency parallel switchgear rarely receives the same level of attention. Sequence of operation parts, including considerations and what makes a good SoO, were covered in an Oct. 8, hour-long training course on the topic. Also covered was how transfer switches could be prioritized based on code and operation of the sequence of operation system.

A live question and answer (Q&A) session followed the training, “Developing a great sequence of operations” produced by CFE Media and Technology, owner of Control EngineeringPlant EngineeringConsulting-Specifying Engineer, and CFE Edu online training.

Additional answers to questions not addressed in the Q&A follow below. Answering the seven questions below was one of the instructors for the presentation (archived through December), Zach Goldsworthy, LEED AP BD&C, national healthcare market leader, Siemens Industry Inc.

Seven answers for sequence of operations applications

1. Regulatory requirements aside, how many other applications might benefit from electrical sequence of operations and why?

Any electrical distribution that has automated operation should have a sequence of operation developed, which should include different operations/sources along with failure scenarios.

2. Even though the sequence of operation is automated, can we still have manual operation?

Yes, the manual operation option is best practice and allows additional flexibility. It is also recommended that additional or follow up training is included.

3. If sequence of operations changes because of equipment failure are there requirements for time for repairs to reduce risk?

There are no published or required times for equipment to be repaired but best and recommended practice is as soon as possible to minimize the risk to the facility, occupants and community. This is also why many facilities require levels of redundancy.

Seven modes of sequence of operation for emergency parallel switchgear are normal operation, loss of normal source, retransfer sequence, failure modes, load shed, load bank and monthly generator test. Courtesy: Siemens Industry

Seven modes of sequence of operation for emergency parallel switchgear are normal operation, loss of normal source, retransfer sequence, failure modes, load shed, load bank and monthly generator test. Courtesy: Siemens Industry

4. Are there often overlooked details you’d like to point out about sequence of operations?

Unfortunately, failure modes are not always thoroughly considered. Most systems have a single sequence that does not consider other variations. Additionally, if the system is expected to be response to failures or modes, the detailed sequence allows the system to be more responsive and resilient.

5. Are retrofit considerations different than working with new equipment? In what ways?

Yes, retrofit projects need to take into account existing conditions and the overall ability of the emergency parallel switchgear and related equipment; this would include generators to parallel or in older transfer switches the ability to be shed.

6. What are documentation requirements or best practices for sequence of operations? Does it vary by industry or by application?

At the beginning of the project a comprehensive one-line diagram along with a thorough understanding of the facility is critical for understanding the full scope. At the end of the project, thorough as-builts and narrative are required.

I also recommend reviewing the as-builts and sequence of operation at the end of the project with the complete team. The facility type or industry does not change the best practice recommendations but it is more important in critical power facilities, such as data centers, healthcare, and other areas, including critical industrial applications where power loss would be costly or dangerous.

7. Is there anything else you would like to explain or emphasize?

Thorough site investigation and review of the project scope are critical for a successful sequence of operation. Engagement with the manufacturer is also recommended to understand the impacts of the layout or configuration on emergency parallel switchgear and related equipment.

– Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media and Technology,


KEYWORDS: Sequence of operations, emergency parallel switchgear


Review risk considerations related to sequence of operation for emergency parallel switchgear and related equipment used in critical power applications.

Consider sequence of operation failure modes, retrofit and repairs.

Learn about documentation best practices for sequence of operations.


Need a refresher course on sequence of operations for emergency parallel switchgear?

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Zach Goldsworthy
Author Bio: Zach Goldsworthy, LEED AP BD&C, Siemens Industry Inc.