Reactive energy penalty though the compensation panel works: what should we monitor?

[DataStream]

Last month our electricity bill included a reactive energy charge for the first time. The compensation panel is running, the controller display shows a power factor around 0.98 whenever I check it, and the contactor steps switch in and out.
We now have energy analyzers on the main incomer and the compensation panel. Which values should I watch to find out what is going wrong, and when does it actually happen?

[Technical Support]

A good power factor at the moments you look at the controller doesn't mean the power factor is good over the whole billing period. Reactive energy charges are usually based on the energy accumulated over time, so short or recurring problem periods can be enough. Continuous monitoring helps you find *when* it happens.
What to monitor
1. Power factor at the main incomer, not only at the compensation controller. The incomer is closest to what the utility meters.
2. Reactive power (kVAr) per phase. An imbalanced load can leave one phase under-compensated while the average looks fine.
3. Reactive power at the compensation panel, to see how much the panel is actually delivering at each moment.
Typical patterns and what they point to
- Poor power factor at night, weekends or holidays: at low load, cables, transformers and lightly loaded motors can dominate. The panel's smallest step may be too large, or the panel may be over-compensating and pushing the plant into capacitive territory. Check whether the reactive energy is inductive or capacitive; both can be charged.
- Poor power factor when certain machines start: the panel may be too slow, or its total capacity may no longer match the plant after new equipment was added.
- Gradually worsening over weeks: capacitors lose capacity with age and heat. Steps that are switched in but deliver less kVAr than their rating are a common cause.
- Sudden change on one day: a blown fuse, a failed contactor or a step disabled in the controller.
Steps
1. Collect data from the incomer and compensation analyzers for at least one to two weeks, including a weekend.
2. Compare the periods with poor power factor against your production schedule and shifts.
3. Check the inductive/capacitive direction during those periods.
4. Have the compensation panel inspected for the steps and capacitors involved.
5. After the fix, keep monitoring and compare with the next bill.
Note that the exact penalty limits and calculation method depend on your utility and tariff, so use your bill and contract as the reference for the limits.
For reference, power factor and compensation monitoring on the transformer, generator and compensation panels was part of GreenSoft's 17-analyzer energy project at Forschner Turkey: https://greensoft.ai/news/greensoft-...-line-diagram/