Executing a Power System Study at a pulp and paper mill

By Jeff MacKinnon, P.Eng., PE

There are a lot of different ways to successfully complete any power system study, but the best for any pulp and paper mill is likely a hybrid, with a lot of the time consuming activities being down with mill staff. The advantage of this system, is that when you have the scope of the project outlined, you can start gathering the necessary information before engaging a consultant.

Here are three thoughts around data gathering (the most costly part of a power system analysis) when you decide to get started with a power system analysis project at your pulp and paper mill.

Data Gathering

Typically the most time consuming part of developing a complete power system model is data gathering. This is something that is best done by the people that know the facility the best, and have the best grasp on the electrical safety program. A lot contractors will want to bring in outside help, but if the system is under operation this will increase the risk of an unscheduled shutdown as these inexperienced contractors are rooting around in MCC buckets trying to find wire sizes.

1 Start off with drawings

SLD drawing

Most of the information needed for a power system analysis, especially the short circuit study, can be found in the existing drawings:

  • single line diagrams
  • motor elementaries
  • General Arrangements (cable lengths)

If you couple this with other support documentation like cable lists and relay setting sheets, the biggest chunk of the information will be done. However, this doesn't mean you don't have to get out into the field and verify everything. Unfortunately, drawings and support documentation don't have all the current information, some examples that may be missing are:

  • fuse manufacturer
  • transformer impedance
  • cable length

These will need to be as-built in the field during the data gathering process, and recorded. As one of the deliverables, the affected drawings will be updated when the report is completed.

2 Ideally completed by the owner's staff

Based on the age and complexity of most forest product plants, we recommend that plant staff (preferably electrical workers) gather the information over a reasonable period of time. Electrical shop workers are routinely all over the mill, and adding a requirement to as-built information as a routine task will limit the back work, and is a good habit to be in for any case.

Accurate drawings shorten unplanned shutdown times.

One of the side benefits of having current drawings is when something does go wrong, you can troubleshoot from a drawing, and then implement solutions. If you are always worried the drawing is incorrect you ended up drawing out the circuit on a napkin (or any other scrap of paper) while you troubleshoot, all the while 5-10 people are looking over your shoulder "helping".

3 Best done during shutdowns

Speaking of shutdowns, opening up switchgear and MCC buckets is best down during planned shutdowns. Partial shutdowns are a normal part of a pulp and paper mill, by ensuring there are enough electrical workers on staff during the outage to support the data gathering effort.

Operating the MCC.

It is important to gather the data in a safe manner, ideally with the equipment de-energized. A shutdown allows you to access a large majority of the equipment de-energized, without affecting the rest of the plant process. While inspecting may not be a "working on" type task based on your energize work permit, finding some of the information may require manipulating wires, etc. For example, how often do you think you will see the wire gauge in a MCC bucket?

Next Steps

A power system analysis report is a critical tool for any pulp and paper mill in today's lean wood products economy. If you are interested in learning more about power systems you can join our Power System Newsletter here, when you do we will send you a technical spec that you can use with your next RFP.

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