How to deal with low power factor (PF) in DG sets? - Part 2

Robust Power Factor correction systems have been designed by expert power electronics developers as per the given limitations and system boundaries (in Part 1). The newly designed systems deploy the principles of the conventional Automatic Power Factor Corrector (APFC) but they differ significantly on aspects like the control logics and subsequently the controller hardware that are cutting-edge and sophisticated. In common language, this corrective mechanism is known as reactive power consumption whereby a mirror image of the tracked power factor is formed to correct it in real time.

To put this into effect you would need the below things:

1.      Thyristors with solid state relays - As the name itself suggests and unlike the conventional magnetic induction relays, these are made up of solid state electronics (semiconductors) that are helpful in eliminating transient currents and reducing the time lag between the consecutive switchovers of capacitors.

2.      Multiple current sensors-A current transformer should be available for every electrical phase of the layout. It will virtually balance the load and correct the power factor on every phase line.

3.      Microprocessor-based controllers - The additional phase-wise data parameters and the calculation of power for correction determination have rendered micro controller based controllers slow and sluggish. That is why hardcoded PLCs or faster microprocessors work better than them.

Advantages of correcting the Power Factor with the above advanced methods:

1.      More alternator efficiency- The copper losses that are associated with an alternator are directly proportional to the square of the current that it delivers. Thus, the correction of power factorwill lead to lesser current per unit power and reduce the associated copper loss.

2.      Reduced overheating and voltage fluctuations - There’ll be reduction in the currents in the total system. Due to this, overheating and voltage fluctuations in the windings and the transmission network due to the shuttling of loads is greatly reduced. This further saves T&D losses.

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Low power factor in dg sets – Part 1

The state of power supply has been erratic for a long time and many areas in the country are still struggling for a reliable source of electricity. Especially the industries that need uninterrupted power supply for economic sustainability have shown a tremendous rise in moving to diesel generators as an important source of electricity and not just a temporary arrangement. With the increase in usage and desirability of diesel generators the need to find ways to improve their efficiency and power factor (PF) is also on the rise.

What are the causes of low power factor?

Different load sizes that come with different power factor effects is the primary cause for the overall reduction in the power factor of an electrical layout. But various other reasons contribute to power factor output being low and in a significant way. The reasons are primarily connected to the fundamental limitations of a power generator.

A diesel power generator is a source of power that doesn’t have a network of sources and loads to load it. Thus, it has a limited capacity to fulfill sudden and large demands of reactive power. To build more on this limitation, the below can be associated as reasons why there is lower power factor in dg sets:

1.      Over sized dg sets

Designers of a plant usually tend to oversize a dg set or limit its loading owing to a largely existent myth that 0.8 is the ‘designed’ PF for dg sets. This essentially leads to liberally sized diesel guzzlers that do not deliver the full version of their economic capability. The alternator of a dg set is same as its larger variants connected to utility power turbines with scaled down proportions. Which means that it by design has the capability to deliver the exact amount rated as its KVA (kilovolt-ampere). So, 0.8 is not a design variable but it’s more like a thumb rule inferred from the average power factor in any industrial electrical layout with a general set of inductive - PF values .8 to .85, non-linear – Power Factor values .5 to .65 and linear (unity PF) - 0.80.

2.      Phase loading that’s unbalanced

Most of the industrial electrical layouts have loads that are liberally connected on various power phase lines because physical limitations of the process layouts are simpler to visualize when compared to the electrical balancing on every line. This doesn’t seem to be a problem when it comes to the grid connected situation where the primary connection of a phase maintains the sync in the remaining from the utility side owing to a grid’s macro effect. But in the case of a dg set that’s’ captive, syncing the phases is not even a function built into its power electronics.

3.      The load of compensation

From various reports on the effect of different power factors on dg sets and detecting safe zones it has become evident that close to unity Power Factor is achievable and safer but low Power Factor for greater periods has more negative impact.

This is part one of a two-part series. In the second part, learn how to correct dg sets with low Power Factor.

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The Causes of Power Failures

Within a short span of two centuries, electricity has become indispensable to our day to day lives. Be it official work, entertainment, economy, healthcare or even simple activities of our livelihoods, we are totally dependent upon the constant supply of electrical power. In such scenarios, even a temporary loss of electricity can affect us greatly. It may lead to a relative chaotic situation, monetary setbacks may be faced, there may also be a possibility of loss of life. Power stoppage can especially cause mayhem when it comes to life-support systems such as in hospitals and nursing homes or in co-ordination facilities like traffic control, railway stations and airports.

Fortunately, most life support facilities have power backup which takes over automatically in the case of a power outage. Power backup is also increasingly being utilized in corporate offices, mining, manufacturing, businesses, and now even in residential complexes with the growing dependence on computers and electronics in everyday lives. So, though loss of power in small scale settings may not be lethal, it can still result into loss of data, missed deadlines, decreased productivity levels and also cause loss of revenue.

Thus, it is very important to know about the possible causes of power failure in order to be armed at all times, to protect ourselves and our businesses from its ill effects. When we have identified all that can possibly go wrong, it would be easier to ensure that adequate safeguards have been put into place.

 

Shared below are some of the major causes of power failure: -

1.       Weather conditions :- 

Power failures are majorly caused due to weather conditions. Lightning, wind, rain, snow and even dust are the various natural phenomenon that can cause power failure. While it is very difficult to guard against major power failures caused due to natural calamities as floods and storms, it is relatively easier to safeguard electrical systems from water and dust. Water can lead to short circuits and power outages. The damage caused due to water in electrical circuits are pretty expensive and thus it makes sense to ensure protection from it. Electrical switchboards, wires, and circuits should be protected and not exposed to water. Dampness and excessive moisture can lead to serious damages. Living in areas with higher levels of humidity makes it important to invest in specially sealed circuit protection devices. 

Dust can also wreak havoc with electrical systems and lead to short circuits and power failures. Areas that are exposed to dust and sandstorms are in dire need to ensure that the electrical circuits are protected from dust exposure at all times. Sealed circuit boxes can be helpful in ensuring protection of your critical electrical equipment and prevent power failures.

Natural disasters have historically been the root cause of the world’s most severe power outages. Floods, tsunamis, earthquakes, windstorms, and other severe weather conditions can completely destroy critical power infrastructure and result in outages that leave extensive geographic regions without power for months.

 2.       Short Circuits :-

‘Short circuit’ is the most commonly used term to describe the cause of power failure. At the same time, the term is also most bandied about without understanding the meaning very well. So, let us explain what exactly is a short circuit.

Short circuit occurs when electric current travels along a path which is not the intended path for it in an electrical circuit. Due to this, there is an excessive electric current which damages the circuit, cause fire and even an explosion to the extent that it’s one of the main causes of electrical fires all over the world. 

3.       Blackouts:-

‘Blackout’ refers to a total loss of electrical power in a given geographical area. It is also the severe most form of power outage that can occur. Depending upon what is the main cause of a blackout, restoring power is usually a very complex task for utilities and power stations and, repair time frames greatly depend upon the configuration of the affected electrical network.

4.       Brownouts:-

A brownout refers to a drop in the power supply. It is called, ‘brownout’ as it leads to a drop in voltage which causes the lights to dim. Brownout is not a total power failure, but it can adversely affect your electrical equipment. Induction and three-phase electrical motors (like the ones used in industrial diesel generators) are at greater risk during brownouts as they can get overheated and their insulation can be damaged. In case your main power supply is inconsistent and you’ve been experiencing brownouts frequently, you must invest in power back up system like diesel generators. They will automatically take over and provide your equipment with necessary electrical power whenever the voltage drops.

5.       Power Surges:-

Power surges are a bane when it comes to electrical systems. It can rapidly overheat and thus damage expensive electrical equipment. Surge protectors and circuit breakers can readily provide the much needed protection from such surges.

6.       Electrical treeing:-

Electrical treeing affects high power installations like transformers and high power voltage cables. If there are any impurities and mechanical defects in the equipment used in high voltage installations, then it can lead to partial electric discharges in the equipment. The process of damaging manifests in a tree-like pattern and hence the name ‘electrical treeing’. If over a period of time it goes undetected, it can continually degrade the equipment and eventually result into a complete breakdown.

To combat electrical treeing, one must only use top quality materials designed to handle the electric load. Maintenance by trained engineers can also help to identify and fix electrical treeing before a major breakdown.

Other Causes:-

When animals such as large birds come into contact with electric lines, power outages are bound to occur. Additional causes of power failures are primarily man made. Example, road accidents and accidents at construction spots with power poles and lines, maintenance issues and human error.

We at Mahindra Powerol offer solutions to combat these issues of Power failures. Visit us at www.mahindrapowerol.com to know more.