Why reactive power is useless

Source: Consolidated Edison. As shown in the above image, picture a horse that is pulling a railcar from the side of the track. Although the horse is tied diagonally, the railcar can only move along the rails. As this angle becomes larger, the ratio between real power and reactive power declines until the horse is pulling directly away from the tracks, not moving the railcar at all.

Reactive power is essential to power flow because it helps to regulate voltage. Referring back to the river analogy, without a riverbed to push against for forward motion there could be no water flow.

Producing reactive power, sometimes referred to as imaginary power , requires power plant capacity while yielding no direct economic value—think of the horse pulling the railcar diagonally. For integrated monopoly utilities, running power plants to produce reactive power is compensated through the rate base.

For merchant generators, reactive power takes away from plant capacity that could produce real power instead. As such, reactive power needs to be compensated as an ancillary service. On July 14, a historical power outage occurred in the Northeastern US and Canada that affected an estimated 55 million people in eight states and one province. Among the reasons for this enormous system failure, a severe shortage in reactive power has been cited as an important factor.

In the hours leading to the blackout, demand for reactive power was particularly high due to large volumes of long-distance transmission streaming through Ohio into Canada. At the same time, the supply of reactive power was dangerously low in part because there was a lack of incentive to produce reactive power.

Reactive power failures have also contributed to blackouts in the West and in France In a direct current DC circuit, the power is of constant intensity and can only flow in one direction. Whereas, the reactive power is the useless power which only flows between the source and load. The other differences between the active and reactive power are explained below in the comparison chart. The right-angled triangle shown below shows the relation between the active, reactive and apparent power.

Measures the power factor of the circuit. The power which is dissipated or do the useful work in the circuit is known as the active power. It is measured in watts or megawatts. The active power is denoted by the capital alphabet P. Inadequate reactive power in electrical power system network has been a major reason in power outages in worldwide.

As discussed, insufficient quantity of reactive power causes voltage collapse that ultimately leads to the shutdown of generating stations and various equipments.

Most inductive loads such as motors, transformers, ballasts and induction heating equipments require reactive power in order to produce a magnetic field. In every electrical machine, a part of input energy, i. However, it leads to lower the power factor. In order to achieve the high power factor , capacitors are generally connected across these devices to supply the reactive power. This is a small note on the significance of reactive power.

Hope you get an idea on this concept. Perhaps, you have a great knowledge on this topic, so please feel free to add any comments, experiences and more information about this topic in comment section below. Related Posts:. I am hooked to your website. I would post some practical challenges Iv encountered in. I am a Construction Supervisor with background as a High Zvoltage Journryman Lineman, my throry training is limited to need to know infor for safety and functionality. It just so happens that I sm in the middle of a large Transmission Sub Capacitor project and I really enjoyed this article.

Thanks for your time and expertise! I certainly gained a bit of understanding and insight. Glad to know it helps at least someone… Looking forward to gain some knowledge from you as well… Thanks. The reactive power concept is now clear. I wants to know this concept through vector diagram. If you have such kind of data then send me on my email is rupeshsuthar ymail. Sir Is the load also produce reactive power. If so what will happen and how can it be removed.

Thanks to the publisher. I have learned alot from this article. I have gotten most of the answers to the questions i have been wanting to ask but no 1 to ask.

Your email address will not be published. Notify me of follow-up comments by email. Notify me of new posts by email. Electrical Technology 21 8 minutes read.

Since VARs represent energy that is continually circulated back and forth between the source and load, the only power consumed is due to losses. That is a small amount and is measured as watts when it occurs on the consumer side of the meter. On the utility side of the meter, the losses are a concern for the utility. The utility is also concerned with the use of transmission capacity to carry current that is not delivering power.

Only synchronous generators and capacitors can provide VARs to magnetic loads. If capacitors are connected near the magnetic loads, that avoids the associated transmission losses and frees up generating, transmission and distribution capacity to provide more real power.

Only synchronous generators and inductors can accept VARs from excess capacitance. Since utilities are not expecting excess capacitance, they are not prepared to add inductance. The synchronous generators may have difficulty with that kind of load. The result would be excess voltage. Since the statement is not entirely correct, there is no proof. Understanding what can happen requires studying the "V curves" for synchronous generators.

It is also necessary to understand the various limits on the safe operating conditions for synchronous generators and transmission system component. In order to overcome voltage drops in the transmission system, the voltage at the generator must be higher on a percentage basis than the voltage seen by a customer.

If the customer had been "consuming VARs," adding capacitors would reduce the current and voltage drop in the transmission lines. That would tend to increase the voltage at the meter, but the utility would adjust the generator to keep the customer voltage within limits.

If the customer begins to supply vars, that would tend to make the voltage higher at the customer location. To some extent, VARs supplied by one customer may be absorbed by other customers.