Power Quality Page
Power Quality is defined in different ways by different people. There is not a clear definition in the industry but for the purposes of this page we will define Power Quality as:
"Any deviation beyond 5% of the specified voltage within a power system from source to load".
This is a very wide statement, but it does not include what I call the other side of power quality and that is the quality of your grounding system. This will be covered on the Grounding Page.
Electrical Power is delivered at Alternating Current 60 Hertz at several different voltage levels accross the United States. Alternating current enables easy distribution as well as the ability to easily isolate elctrical busses through magnetically coupled transformers. Even simple industrial networks will include multipile isolated buses.
Each bus is configured to serve a specific amount of load at a specific voltage. Many systems have two voltages depending of they are connected to a center tap or in a Wye configuration. Ultimately our power quality problems are not seen until the load that the power source serves interrupts what we are using the energy for in the first place. Lets start with the end device and think about the differnt problems that we can have.
1. We could loose our energy source completely.
2. The voltage could sag from its accepted tolarance for a long term duration.
3. The voltage could swell from accepted tolarance for a long term duration.
4. The Power Factor could become highly inductive.
5. The frequency could become noisy.
6. Short voltage spikes could cause insulation breakdown.
7. Short voltage sags could cause equipment to shutdown.
All of these things are real power quality issues that need to be addressed on each bus that makes up an electrical system. Every transformer derives a new source of energy so every transformer bus has the potential to allow any of these power quality issues to exist. Some are dependent upon the input energy source such as loss of power, sags and swells. The rest of the issues are typically caused within the transformer secondary bus and is more related to the load and distribution equipment that it serves than the source.
The problem with identifying a power quality problem starts with understanding the other half of the circuit or the Ground. Often the ground is not considered a current carrying conductor or part of the path providing the energy, but due to safety factors it must be considered as it is a place for energy to flow when things are not right with the system. If the grounding system is set up properly, then equipment and system problems will usually identify themselves by tripping an alarm or operating a circit breaker. But it is when grounding systems are not set up correctly that unexplainable occurances start happening as voltages form across points that are not to have any voltage present.
Power Quality issue can be measured with sophisticated meters available on the market today. Many of which are capable of collecting data continuously at high frequency sample rates obtaining several hundred data points per cycle. Lesser Meters monitor the power and stores to memory only those events that were preselected for it to find. The lower the cost of the meter, the less that it will capture in regards to Power Quality. But this primarily covers the voltage supplied by the source.
But what about the ground? The ground is made up of unrefined conductors and connections and materials that are conductive, but at the same time these parts are ubiquitous to the entire system. Every device that uses electricity is connected to the ground in one way or another. Simply ignoring ground with a floating system nevery achieves the intended results becuase when any part of the electrical system insulation fails, it becomes energized and could cause devistating consequences for the loads connected.
Because the Power system is so carefully put together with refined components that are desinged to conduct, and grounding systems are put together hap hazardly usually with no regard for their purpose, grounding systems tend to be more of a problem than power supply systems.