POWER SYSTEM ANALYSIS

 

Power System Analysis is an important component of Electrical Engineering and in the modern day an increasingly complex  activity  with changes noticed in Generation and distribution of Electric Power.The field of Power System Analysis converges conventional Electrical  Engineering  with Power Electronics and Information system platforms. 

In the seventh semester we had a course on Power System Analysis  and it would be better if practitioners in this field also get an opportunity to share experiences and insight to the recepients.The entire area of Power Systems is fairly well managed in a country like India which has more than a century of experience in generation and distribution of Electrical Power. Two problems beset the area of Power system Analysis. The first component is to match the increasing demand for power. The second is to ensure quality of  Power, the third function is to ensure reduction in wastage and finally to keep the system from breakdowns and other disruptions.

At a global level Power System Analysis is to address the economics of Power. Basically matching the supply and demand at a rational price ,this is a problem at engulfs humanity and such a domain would invariably involve the import and export of Power. It would also involve domestication of Power which means effective local generation and distribution of Power over very short distances.. for instance the use of  Solar power. One of the major components of Power consumption in the future would be that Automobiles of all kinds might work on Batteries which need periodic charging.

Maintaining the Quality of Power is another component of PSA(Power System Analysis)..in an AC system ensuring the correct Voltage, Frequency and Power Factor. This is where computerization is going to make in-roads. I think to a very large extent PSA as we see today is in a very nascent condition with no real-time assessment of Power though we have progressed in this field in leap and bounds. Add to this the study of transients. Effects of lightning and all other forms of environmental   disturbances  on Electrical Power Systems. PSA of this kind is carried out through a DAS(Data Acquisition System);a low voltage  system properly insulated taps  EPI(Electrical Power Information) from various points and feeds it into a central computer device which registers Voltage, Frequency, Power factor and transients. Any abnormality anywhere can be instantly noticed for corrective action. DAS  helps in the proper management of Power System factors.DAS needs complex parallel wiring and care and a central control station with reporting systems almost on a daily basis.

DAS  mentioned above also helps in tracking wastage largely by controlling Power Factor in large industrial installations  and tracking  wastage of power by domestic installations. The Power Factor  is studied periodically at large power distribution zones to bring it into acceptable levels even by restructuring the load if necessary. Domestic wastage of power  is also a source of power wastage  which can be tracked even at a minute level by such systems.

Break down and disruptions need constant  analysis and improvement. Trees falling on  Power Lines resulting in Short Circuit is  one of major causes of disruptions and  add to that other sources like over load , tripping of breakers and single phasing  and even birds creating short circuit by  grounding high tension lines. Zones where  such things happen are normally identified  and acted upon and underground cables  with proper notifications laid. 

The above is the scope of PSA and to my observation has to be done more aggressively and at the same time the depth of the analysis also augmented that we know in the future..What problem is likely to happen and plan very much in advance all forms of corrective actions both complex and simple.

 

POWER FACTOR CORRECTION IN LARGE ELECTRICAL NETWORKS

POWER FACTOR  correction is an important component of Electrical Engineering concerning Alternating Currents.When DC is passed through a coil the coil only gives resistance. When AC is passed through the coil it gives a vector sum of resistance and reluctance. Reluctance is the Magnetic component of the opposition to the flow of Alternating current. Reluctance comes because of the self induction component because the coil creates an opposing electro-motive force or emf because of self-induction. What is self induction? Alternating current passing through a coil induces voltage in the coil opposing the flow of current which is called Self-induction.

When I was a student of Electrical Engineering I used to constantly read Edward Hughes,Vincent Del Toro and Charles Siskind in whose books the fundamental concepts of Electrical Engineering are dealt with in fine detail.Added to that the very experienced faculty at the Regional Engineering College Calicut (NIT) of our times Dr.Prabhakaran ,Dr. P P Gerwadis, Dr K P Mohandas and Dr. P S Srinivasan all of whom did involved teaching in their own style with commitment for a long stretch of time leaving Electrical Engineering indelible from my mind.

What are the consequences of  high inductance in an AC circuit. It increases current leading to power losses and creates heat from magnetization just like the heat created by a microwave -owen.It creates loss of power and adds to various forms of transients. It creates insulation failure and dis-orients electrical networks.

When an Alternating current is impressed upon a coil the current lags behind the voltage which literally means it struggles to catch-up with the Voltage. Larger the lag due to higher inductance lesser the fraction of useful power and higher the fraction of reactive power which is wasted in magnetisation and radiation of heat.

What is one of the solutions for this problem? Itis to shunt the circuit with an appropriate Capacitor. The Capacitor regulates voltage and reduces the lag of the earlier current passing through the coil literally absorbing reactive power and converting it into useful power.Such a measure reduces heat dissipation and increases circuit delivered power. The situation is similar to the relation between BHP,IHP and FHP in an engine. IHP is the integrated horse power the actual power created in the engine..FHP is the frictional horse power which creates heat and losses and BHP is Brake Horse Power the actual power delivered by the engine. FHP is akin to the reactive power in an electrical circuit which can be reduced by using Capacitor shunt which reduces this component.But how? Current through a Capacitor leads the Voltage.Capacitors block Voltage but its dielectric depending on the frequency passes current. Exactly opposite to inductive circuits in capacitive circuits Voltage tries to catch up with the current.

When I used to work in Electrical Maintenance long back I had developed a simple formula for arriving at the value of the Shunt Capacitor needed for any given Electrical network and also tested it with the hand book of Electrical Engineering and to my glee found that they match ditto.I was excited but left this area of Electrical Engineering for a short while to dabble with Information technology. Recently I tried to re-invent the formula few days back with some measure of success and I would like pundits of electrical engineering to put it to some form analysis to confirm if it works.

Note that large Electrical Networks are three phase and on the load side they have meters that indicate Current, Voltage and Power Factor and laso the Power. Our job is to note the Power factor and increase it to the level necessary.The basic analysis of such a situation can be done using a simple single phase diagram. 

The above is an illustration of the above discussed matter.The whole thing needs scrutiny and testing.Two circuits of a simple kind are shown which are r-l circuit and in diagram B they are shunted by a capacitor. Power and Voltage are held constant. The phasor diagrams are shown  and note the impedance diagram. ɸn is the new angle after correction and  cosɸn  is the new power factor.

NOTE  TANɸn = (XL - XC)  /   R

XC = Xl   -   R Tanɸn

XC IS CAPACITIVE REACTANCE
XL IS INDUCTIVE REACTANCE

SIDDIGANAPATHY BHAT AT REC NIT CALICUT

At REC NIT Calicut in 1982 there was a student in the seventh semester by name Siddi Ganapathy Bhat.The day my admission process was underway it took some time into the night and my father and myself were distraught and tired as getting back to Calicut city at that hour would be an onerous task. Siddi Ganapathy Bhat knowing our predicament suo-moto suggested that we could stay in his hostel room as his room mate was away.So we spent the night in his C hostel room on the first floor facing the D hostel.Much later I used to meet him in his room in the D hostel. Later I came to know he lectured Electrical Engineering for many years at some Engineering College in Karnataka State.His brother Narayan Bhat was later a student at REC NIT Calicut.

I must thank the concern he showed for us at that juncture which is noteworthy and may be without much precedence.