In the first part of the Power System Study series I told you what a power system study is, and in the second I described what power system analysis I consider critical for every facility, plant, building, etc, no matter how large or small.
- Short Circuit
- Protection Coordination
- Incident Energy
- Load Flow
Now, assuming you have these studies in your hands, what do you do with them? In Part 3 I will give ideas on why power system studies are important for your facility and business, and how different areas of you company can benefit from a comprehensive power system study.
Who can leverage a power system study
It’s not just engineers
Once you have a power system study in place you can starting thinking about how to leverage it and make decisions to improve your facility.
There are four perspectives that the study can be viewed from, and most companies have them. Whether it is one person with many hats, or groups of dedicated personelle.
- Capital projects.
With the Incident Energy report in hand, critical information can be added to the Arc Flash Risk Assessment and areas that are found to be high risk can be looked at closely. Mitigation techniques can be implemented in these areas starting with eliminating the risk entirely, or adding engineering controls that lower the incident energy to an acceptable range. This may be a relatively simple setting change in a relay, or replacing an old protection scheme with a modern relay with multiple sets of settings. One for normal operation and another for energized work.
Management will integrate this information into the facility’s electrical safety program, and the general safety program. They can update the risk assessments associated with their electrical system.
Second,operations can use the reports to identify areas that are a higher risk to cause outages, and determine how the system reacts to faults. The two studies of particular interest are the protection coordination and incident energy.
The protection coordination lets the operator know what areas of the facility will be affected in the case of an outage, and if the area is too large, or not large enough, modifications can be made to optimize the selective coordination scheme.
The incident energy study helps the workers on the floor stay prepared, within the greater electrical safety program.
Maintenance will look at the short circuit and load flows to help prioritize where preventative maintenance budgets should be focused. The short circuit study will determine if there is any existing equipment that is over-dutied. Meaning that it is not designed to handle the fault currents that it could be subjected to in the event of a bolted fault. If there is any over-dutied equipment identified, maintenance will start the process of replacing, or mitigating the fault currents by changing system configuration, such as not operating with transformers in parallel, or adding current limiting reactors that increase the short circuit impedance on the system.
The load flow report can help schedule maintenance schedules for major equipment such as motors and distribution transformers. If a newer transformer is close to its design load most of the time, versus a older transformer being lightly loaded, the probability of failure may lean toward replacing the newer transformer before the older one. Without the load information the older transformer would be replaced sooner, costing more from the maintenance budget if the newer transformer failed around the same time.
Finally capital projects can use the model to make improve decisions for capital improvements. When capital improvements are in the early stages, modifications to the greater power system, other than the new equipment being added, is sometimes neglected. This oversight may increase the cost greatly when the service entrance needs to be replaced, or other major changes have to be made.
With a current short circuit and load flow study, most of these issues can be accounted for early in the capital project cycle and power system improvements can be accounted for at the start. Without a current power system study you will not know, and it will likely cost too much to have one completed just for a capital project budgeting.
Along the same lines the model can be used to save money, one way is by making improvements to the power system to increase efficiency.
Utilities, especially when they are dealing with a large load, may have power factor and demand changes that are much higher that the energy charge. With a load flow study in hand, it is a relatively easy task to determine where pf correction could be added to keep the PF charges low, or if there are any buses in particular that can be controlled differently to prevent new demand charges.
This concludes our three part series on Power System Studies. If you missed Part 1 on Monday, it defines what a Power System Study is, and Wednesday I talked about what the critical power system studies every facility needs.
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