Net metering in Solar Systems; On Grid and Off Grid system in Solar Power

🌞 Net Metering in Solar Power Systems

🔹 What is Net Metering?

Net metering is a billing arrangement provided by DISCOMs (Power Distribution Companies) that allows consumers (households, businesses, and industries) to generate electricity using solar PV systems and export surplus power to the grid.

A bi-directional net meter is installed, which records:

• Import → Electricity consumed from the grid.
• Export → Surplus electricity sent back to the grid.

The consumer is billed only for the net consumption (Import – Export). If exports exceed imports, the consumer may receive credits or payments from the DISCOM.

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🔹 Solar PV Power Generation Basics

• Solar Photovoltaic (SPV) modules convert sunlight into DC electricity.
• A Power Conditioning Unit (Inverter) converts DC to AC for household/industrial use.
• The system can be connected to:
1. On-Grid (Preferred) – Connected directly to the grid, no batteries required.
2. Off-Grid – Works independently with batteries for storage.

✅ Example (On-Grid):
If a factory requires 100 kW, and its solar system generates 5 kW, the net demand from the grid is only 95 kW.

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🔹 How Does a Grid-Connected Rooftop Solar System Work?

1. Solar PV Panels on rooftops capture sunlight → generate DC electricity.
2. Inverter converts DC to AC → connects to building distribution board.
3. Load Consumption → Solar power is consumed first, grid power supplements if needed.
4. Excess Power → Automatically exported to DISCOM grid.
5. Net Meter → Records both import & export.

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🔹 Advantages of Net Metering & Rooftop Solar PV

✔ Clean, renewable, and sustainable energy.
✔ Reduces electricity bills by offsetting grid consumption.
✔ Converts consumers into “prosumers” (producers + consumers).
✔ Cuts diesel costs where DG backup is used.
✔ Surplus energy contributes to the grid, improving local supply.
✔ No land required – rooftops are utilized.
✔ Minimal maintenance – only periodic cleaning of panels.

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🔹 Implementation Guidelines (Typical in India – Example: APTRANSCO/APDISCOMS)

• Applicable for 3-phase consumers.
• Certified switchgear & harmonic suppressors required for safety.
• Statutory approvals from CEIG (Chief Electrical Inspector to Government).
• Application submission to concerned DE/Operation.
• Technical feasibility & synchronization certificate issued by DISCOM.
• Meter specifications: Tri-vector, 0.2 class accuracy, MRI compatible.
• Insurance requirement: e.g., ₹5 lakhs coverage for safety risks.
• Billing: Spot billing with net metering software integrated into DISCOM systems.

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🔹 On-Grid vs Off-Grid – Quick Comparison

Feature	On-Grid Solar PV	Off-Grid Solar PV
Grid Connection	Yes (synchronized with DISCOM grid)	No (independent system)
Batteries Required	❌ Not required	✅ Required
Efficiency	Higher (no battery losses)	Lower (due to charging losses)
Power Backup	No (depends on grid)	Yes (battery backup available)
Cost	Lower	Higher (battery cost included)
Popularity	Widely adopted	Limited use (remote/off-grid)

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✅ In summary:
Net metering is the bridge between consumers and the power grid, allowing rooftop solar users to cut costs, earn credits, and contribute to clean energy adoption with minimal maintenance.

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Maximum Power Point Tracking in Solar Power; MPPT in Solar Power, MPPT working

Maximum Power Point Tracking is most powerfull concept in the field of Solar power . Let’s study about what is Maximum Solar power point tracking and it’s applications in Solar power systems.

A MPPT is an electronic DC to DC converter that optimizes the midst of the solar array (PV panels), and the battery bank to get the optimum use of Solar power. 

Why There is Need of MPPT

Solar cells are clean source of Energy. Most Solar PV panels are built to give nominal output voltage of 12 volts. But Solar cells designed for 12V can give output from 16V to 18V.  Mostly batteries are charged from about 13.2 to 14.4 volts. Now Solar panels can give output voltage ranging from 16V to 18V but batteries can be charged upto 13.2-14.4V.

Now lets assume that we have a solar panel having Capacity of 150 watt.

The Solar power panel is rated at 8.52 amps at 17.6 volts. (8.52 amps X 17.6 volts = 150 watts).

 i.e. Solar panel will give output voltage of 17.6 Volts at 8.52A. But this is Solar power panel output voltage. 

But batteries can be charged upto maximum of 14.4 volts. Now if we assume that battery is get charged to 14V then output we get is  8.52 A X 14 volts = 119.56 Watts. Now you see that you have paid for 150W and what you get is approx. 120W means there will be loss of 30W every hour. Now what we get if battery is only get charged to 12V.

Output at 12V will be 8.52A X 12V= 102.24 W now loss will become even higher.

The panel is rated at 150 watts at full sunlight at a particular temperature. If temperature of the solar panel is high, you may not get 17.4 volts output. At higher temperatures output voltage of solar panel will get reduced to 16 volts.  

Now question arises why not we install 15V output Solar panels??
Solar panels have to work under worst conditions in some times at that time if output voltage will be 15V then there are chances that batteries doesn't get charged.

How MAXIMUM POWER POINT TRACKING System Works:-

Panel tracking - this is where the panels are vis--vis a mount that follows the sun. The most common are the Zomeworks and Wattsun. These optimize output by as well as the sun across the declare for maximum sunlight. Panel tracking system will give output power increase of 15% in winter and 35% increase in summers.  MPPT is just opposite of the Panel tracking in case of seasonal variations i.e. MPPT will increase power output in winters then in summers. 

Since panel temperatures are much lower in winter, they will give more power. In winter more power needed from solar panels due to shorter days.

Maximum Power Point Tracking is and electronic system. The controller looks at the output of the panels, and compares it to the battery voltage. It as well as figures out what is the best capacity that the panel can to achievement the battery. It takes this and converts it to best voltage to profit maximum AMPS into the battery. Most take in hand looking MPPT's are concerning 93-97% efficient in the conversion. You typically acquire a 20 to 45% gift be in in winter and 10-15% in summer. Actual be in can change widely depending weather, temperature, battery verify of proceedings, and late growth factors.

Grid tie systems are becoming more popular as the price of solar drops and electric rates go occurring. There are several brands of grid-tie by yourself (that is, no battery) inverters comprehensible. All of these have built in MPPT. Efficiency is almost 94% to 97% for the MPPT conversion as regards the order of those.

How Maximum Power Point Tracking works

Here is where the optimization, or maximum adroitness lessening tracking comes in. Assume your battery is low, at 12 volts. A MPPT takes that 17.6 volts at 8.52 amps and converts it also to, consequently that what the battery gets is now 13.04 amps at 12 volts. Now you yet have in this area 156.5 watts, and everyone is glad.

Ideally, for 100% gift conversion you would acquire on the subject of 13.04 amps at 11.5 volts, but you have to feed the battery a far ahead voltage to force the amps in. And this is a simplified checking account - in actual fact the output of the MPPT row controller might adjust forever to become accustomed for getting the maximum amps into the battery.

 Typical Power Curve of a Solar Electric PanelOn the left is a screen shot from the Maui Solar Software "PV-Design Pro" computer program (click upon describe for full size image). If you see at the green extraction, you will see that it has a gifted pinnacle at the upper right - that represents the maximum doer twist. What an MPPT controller does is "see" for that alter mitigation, furthermore does the voltage/current conversion to have an effect on it to exactly what the battery needs. In authentic animatronics, that summit moves as regards for ever and a day behind changes in light conditions and weather.

A MPPT tracks the maximum expertise narrowing, which is going to be oscillate from the STC (Standard Test Conditions) rating asleep not far off from all situations. Under the whole icy conditions a 120 watt panel is actually gifted of putting gone more 130+ watts because the knack output goes taking place as panel temperature goes in addition to to - but if you don't have some exaggeration of tracking that carrying out narrowing, you are going to lose it. On the subsidiary hand numb each and every one hot conditions, the execution drops - you lose facility as the temperature goes happening. That is why you do less reach in summer.

MPPT's are most energetic out cold these conditions:

Winter, and/or cloudy or confusing days - in imitation of the supplementary realization is needed the most.

Cold weather - solar panels perform augmented at chilly temperatures, but without a MPPT you are losing most of that. Cold weather is maybe in winter - the era as soon as sun hours are low and you compulsion the behave to recharge batteries the most.

Low battery dispute - the degrade the fall in along in the middle of of charge in your battery, the more current a MPPT puts into them - again gone the totaling triumph is needed the most. You can have both of these conditions at the joined period.

Long wire runs - If you are charging a 12 volt battery, and your panels are 100 feet away, the voltage drop and faculty loss can be considerable unless you use utterly large wire. That can be certainly costly. But if you have four 12 volt panels wired in series for 48 volts, the proficiency loss is much less, and the controller will convert that high voltage to 12 volts at the battery. That with means that if you have a high voltage panel setup feeding the controller, you can use much smaller wire.

Ok, suitably now lead to the original investigate - What is a MPPT?

How a Maximum Power Point Tracker Works:

The Power mitigation tracker is a tall frequency DC to DC converter. They admit the DC input from the solar panels, involve it to tall frequency AC, and convert it urge around furthermore to to a every second DC voltage and current to exactly harmonize the panels to the batteries. MPPT's conduct yourself at the entire tall audio frequencies, usually in the 20-80 kHz range. The advantage of tall frequency circuits is that they can be expected past every tall efficiency transformers and little components. The design of tall frequency circuits can be altogether tricky because the problems taking into account portions of the circuit "broadcasting" just furthermore a radio transmitter and causing radio and TV interference. Noise coldness and suppression becomes totally important.

There are a few non-digital (that is, linear) MPPT's charge controls on the subject of. These are much easier and cheaper to construct and design than the digital ones. They make a purchase of add together efficiency somewhat, but overall the efficiency can modify a lot - and we have seen a few lose their "tracking reduction" and actually buy your hands on worse. That can happen occasionally if a cloud passed on summit of the panel - the linear circuit searches for the adjacent best want, but subsequently gets too far out upon the deep decline to locate it in imitation of more when the sun comes out. Thankfully, not many of these as regards a new.

The power ambition tracker (and all DC to DC converters) operates by taking the DC input current, changing it to AC, paperwork through a transformer (usually a toroid, a doughnut looking transformer), and later rectifying it consent to help to to DC, followed by the output regulator. In most DC to DC converters, this is strictly an electronic process - no genuine smarts are working except for some regulation of the output voltage. Charge controllers for solar panels mannerism a lot more smarts as animate and temperature conditions rotate constantly every one of hours of day long, and battery voltage changes.

Smart power trackers

All recent models of digital MPPT controllers understandable are microprocessor controlled. They know bearing in mind to footnote yourself the output that it is creature sent to the battery, and they actually shut all along for a few microseconds and "heavens" at the solar panel and battery and make any needed adjustments. Although not in fact auxiliary (the Australian company AERL had some as in front as 1985), it has been unaided recently that electronic microprocessors have become cheap plenty to be cost operating in smaller systems (less than 1 KW of panel). MPPT charge controls are now manufactured by several companies, such as Outback Power, Xantrex XW-SCC, Blue Sky Energy, Apollo Solar, Midnite Solar, Morningstar and a few others.

To know about Net metering concept in solar System visit link:-http://electrialstandards.blogspot.in/2015/05/net-metering-in-solar-systems.html

Capacitor in Series and Parallel; Parallel Capacitors; Series Capacitors

📘 Capacitors in Series and Parallel 

Just like resistors, capacitors can also be connected in series or parallel. But unlike resistors, the behavior of capacitors is exactly opposite:

• Resistors in series → total resistance increases

• Capacitors in series → total capacitance decreases

• Resistors in parallel → total resistance decreases

• Capacitors in parallel → total capacitance increases

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🔹 Capacitors in Series

• Net capacitance decreases.

• Formula:

$$\frac{1}{C_{eq}} = \frac{1}{C_1} + \frac{1}{C_2} + \dots + \frac{1}{C_n}$$

For two capacitors:

$$C_{eq} = \frac{C_1 \times C_2}{C_1 + C_2}$$

📌 Example:
C1 = 100 nF, C2 = 10 nF

$$C_{eq} = \frac{100 \times 10}{100 + 10} = 9.09 \, nF$$

• Key points:

  • Voltage rating adds up (useful when higher working voltage is required).

  • Charge stored is the same across all capacitors.

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🔹 Capacitors in Parallel

• Net capacitance increases.

• Formula:

$$C_{eq} = C_1 + C_2 + \dots + C_n$$

📌 Example:
C1 = 100 nF, C2 = 10 nF

$$C_{eq} = 100 + 10 = 110 \, nF$$

• Key points:

  • Working voltage stays the same as the lowest-rated capacitor.

  • Charge distribution depends on capacitance values.

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🔹 SI Prefixes for Capacitors

• 1 µF (microfarad) = 1,000 nF = 1,000,000 pF

• 1 nF (nanofarad) = 1,000 pF

• 1 pF (picofarad) = smallest practical capacitor unit

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⚠️ Notes

1. Polarity (for electrolytic capacitors):

   • Series → connect + of one to – of the next.

   • Parallel → connect all + together, all – together.

2. Voltage rating:
   Always choose a capacitor with a higher voltage rating than the applied voltage.
   Example: For 24V supply, use 35V capacitor instead of 16V.

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✅ Comparison Summary

Feature	Series Capacitors	Parallel Capacitors
Total Capacitance	Decreases (smaller than the smallest)	Increases (sum of all)
Working Voltage	Increases (adds up)	Same as lowest capacitor
Charge Distribution	Same across all	Divided based on C value
Best Use Case	Higher voltage handling	Higher capacitance storage

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Power factor Improvement formula; Additional KVAR required for Power factor improvment.

Power Factor Improvement with Capacitor Bank Sizing

Why Power Factor Improvement is Needed?

• Most industries operate with inductive loads (motors, pumps, lighting ballasts, welding machines, etc.), which lower the power factor.

• Typical industry power factor: 0.80 – 0.85.

• Low PF leads to:

  • Higher current flow in the system.

  • Energy losses (15–20%).

  • Utility penalties for reactive power consumption.

• Maintaining PF near unity (1.0) reduces losses and avoids penalties.

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Formula for Capacitor Bank Sizing

To calculate the required capacitor (kVAR) for PF correction:

$$\text{Q (kVAR)} = \text{P (kW)} \times \left[\tan(\cos^{-1} \, \text{PF}_{\text{initial}}) - \tan(\cos^{-1} \, \text{PF}_{\text{desired}})\right]$$

Where:

• P (kW) = Active load

• PF_initial = Present running power factor

• PF_desired = Target power factor (close to 1)

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Example Calculation

• Load = 200 kW

• Initial PF = 0.8

• Desired PF = 1.0

$$\text{Q} = 200 \times [\tan(\cos^{-1}(0.8)) - \tan(\cos^{-1}(1))]$$ $$\text{Q} = 200 \times [\tan(36.86°) - \tan(0°)]$$ $$\text{Q} = 200 \times (0.75 - 0) = 150 \, \text{kVAR}$$

✅ Answer: An additional 150 kVAR capacitor bank is required to improve PF from 0.8 → 1.0.

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Key Notes

• In practice, PF correction is usually done up to 0.95–0.99, not exactly 1.0, to avoid leading PF issues.

• Capacitor banks can be:

  • Fixed type (constant loads)

  • Automatic / APFC panels (variable loads)

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Electricity bill understanding/ Electricity bill simplified

Usually understanding electricity is made very simpler by power distribution companies. Whenever new electricity bill received then everyone reads through it to come to know what is the unit consumption this month and whether this consumption is increasing or decreasing everyone uses some trend analysis.

There are some certain terms which should everyone know before understanding electricity bill.

Before going in details please look at the bill mentioned above.

Sanctioned Load

When you look at the bill at the top most there is Name and address is printed on the bill. Then there is Sanctioned load which indicates what is the load sanctioned for Industrial or domestic customers. This is usually sanctioned depending upon load connected at the system .

Maximum Demand Indicator

Then there is MDI means Maximum demand indicator which indicates the Maximum demand for the current month billing period this Maximum demand should not exceed Sanctioned load. For Industrial customers if this maximum demand exceeds the sanctioned load certain amount of penalty will be charged to the customers if that MDI kept on exceeding sanctioned load for three billing cycles then load will be enhanced by power distribution companies depending upon maximum MDI of last three bills and security deposit amount will be charged by power discoms in that new bill. Same will be true for domestic customers but no penalty will be charged for exceeding maximum demand.

Power Factor:-

For domestic customers power factor is not of any importance as domestic customers are charged at KWH i.e. kilowatt hour. But for industrial customers Power factor is of prime importance as industrial customers are charged at  KVAH which is will be higher than KWH if power factor will be low. So Industrial customers should keep Power factor to as near possible to 1 so that power charges will be saved for lower power factor. You will easily see that if power factor will be 0.8 then electricity charges will be around 20% then when power factor kept at 1.

For knowing how much capacitor required for PF improvement please visit link:-
http://electrialstandards.blogspot.in/2015/03/power-factor-improvement-formula.html

CA and CRN no.

CA No. is customer account no. and CRN is customer relationship no.

Electricity charges:-

Then there is meter no. and KWH /KVAH reading at start of billing cycle and pend of billing cycle along with dates of billing cycle. For domestic customers there will be only KWH reading and for industrial customers there will be KWH as well as KVAH readings and customer will charged depending upon which will be higher.

Billing details:-

Then there is breakup of bill in which there are fixed charges, Billed units, Unite rate depending upon slabs of units, Then there are Slab-wise FPA/PPA charges i.e. FPA—Federal Power Act (US) / PPA—Power Purchase Agreement (electricity) , TOD charges i.e. Time of the day , this means that peak load hours and off peak load hours are described by Discoms.   Then there are surcharges, Electricity tax and at the last are Total charges to be paid by customers. TOD charges are applicable for industrial customers only. Certain rebate and higher charges are charged to customers against TOD for the time interval decided by discom’s. This will attract customer to lower their consumption during peak hours.

Past Dues/ Refund/ Subsidy:-

Then there is column for Arrears/Refunds, Late payment charges, Total payable charges, Rebate/Subsidy and finally new amount payable.

Bill amount Payable and due date of payment:-
In last bold letters there is amount payable for the current period along with due date of payment.

There are column’s for Security deposit with DISCOM for Sanctioned load.

And also there is column for Interest payment against Security deposit. This interest is usually adjusted in bill and same will be mentioned also.

Back side of electricity bill:-

Back side of bill is also very useful and provide very useful information  about electricity charges. There are various slabs mentioned against type of customers.

There is also information about last 6 months bill consumption and charges against that bills.

There is also information about customer complaint no. how to redress the complaints against discoms.

Electric Shock first aid; Saving life from electric shock

Electric Shock: Causes, Effects, and First Aid Steps You Must Know

Learn what happens during an electric shock, its severe effects on the human body, and essential first-aid steps like CPR and injury management to save lives.

Introduction

Almost everyone has experienced a mild electric shock at some point in life. An electric shock occurs when electric current flows through the human body. Since the body is composed of about 60–70% water, and water is a good conductor of electricity, our body also acts as a conductor. While small shocks may only cause discomfort, severe electric shocks can be life-threatening, leading to burns, heart problems, organ damage, or even death.

This article explains the effects of electric shock and the immediate steps to take as first aid to save lives.

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Effects of Electric Shock

Electric shocks can cause multiple health issues depending on voltage, current, and duration of contact. Some of the major effects include:

• Severe Burns – Skin and tissues may get damaged due to high current flow.

• Heart Problems – Shocks can disturb heart rhythm, leading to cardiac arrest.

• Damage to Internal Organs – Current can pass through muscles and nerves, causing hidden injuries.

• Death – Prolonged exposure or high-voltage shocks can be fatal.

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First Aid Steps for Electric Shock

1. Separate the Person from the Electric Source

• Immediately disconnect the power supply if possible.

• If switching off is not possible, use insulated objects such as wood, plastic, books, newspapers, or a dry chair to separate the person from the electrical source.

• Never touch the person directly while they are in contact with electricity, otherwise you may also get shocked.

⏱ Note: The quicker the person is separated from the source, the higher their chances of survival.

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2. Perform CPR if Necessary

If the person is:

• Unconscious

• Unresponsive

• Not breathing normally

then immediately perform CPR (Cardiopulmonary Resuscitation).

CPR for Adults

• Place both hands (one over the other) on the center of the chest.

• Push hard and fast (at least 100–120 compressions per minute).

CPR for Children (1–8 years)

• Use the heel of one hand only.

• Compress the chest to one-third of chest depth.

CPR for Infants (up to 12 months)

• Place the infant on their back.

• Perform gentle mouth-to-mouth breaths, covering both the nose and mouth.

• Use two fingers for chest compressions, pressing to one-third of chest depth.

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3. Check for Injuries and Get Medical Help

• After separating the person from electricity, check for burns, fractures, or breathing difficulties.

• Even if the person regains consciousness, take them to a hospital immediately for a full check-up, as internal injuries may not be visible.

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Final Thoughts

Electric shock is a serious medical emergency that requires immediate action. Knowing how to react—especially how to disconnect the victim from the current and perform CPR—can make the difference between life and death. Always remember: safety first, act quickly, and seek medical help without delay.

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Resistance in Series and parallel

Resistance in Series and Parallel – Concepts, Formulas & Applications

Resistance is the fundamental component in electrical circuits that opposes the flow of electric current. It plays a key role in converting voltage to current and current to voltage through Ohm’s Law:

$$V = I \times R$$

Where:

• $V$ = Voltage (Volts)

• $I$ = Current (Amperes)

• $R$ = Resistance (Ohms, Ω)

Depending on how resistors are connected in a circuit, their equivalent resistance changes. The two most common connections are Series and Parallel.

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🔹 Resistance in Series

When resistors are connected end-to-end, they form a series circuit.

Formula:

$$R_{eq} = R_1 + R_2 + R_3 + \dots + R_N$$

Key Characteristics:

• Current: Same through all resistors.

• Voltage: Divided across resistors (hence called a voltage divider).

• Equivalent Resistance: Increases as more resistors are added.

👉 Example:
If $R_1 = 10Ω$, $R_2 = 20Ω$, and $R_3 = 30Ω$,

$$R_{eq} = 10 + 20 + 30 = 60Ω$$

Applications:

• Used in voltage divider circuits.

• Simple current limiting in power supply circuits.

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🔹 Resistance in Parallel

When resistors are connected across the same two nodes, they form a parallel circuit.

Formula:

$$\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \dots + \frac{1}{R_N}$$

Key Characteristics:

• Voltage: Same across all resistors.

• Current: Divided among parallel branches (hence called a current divider).

• Equivalent Resistance: Always less than the smallest resistor in the network.

👉 Example:
If $R_1 = 10Ω$, $R_2 = 20Ω$, and $R_3 = 30Ω$,

$$\frac{1}{R_{eq}} = \frac{1}{10} + \frac{1}{20} + \frac{1}{30}$$ $$R_{eq} \approx 5.45Ω$$

Applications:

• Used where low resistance paths are needed.

• Widely applied in household wiring to keep voltage constant across appliances.

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🔹 Conductance in Parallel

In parallel circuits, it’s often easier to use conductance (G) instead of resistance.

$$G = \frac{1}{R}$$

• Units: Siemens (S)

• Equivalent conductance in parallel:

$$G_{eq} = G_1 + G_2 + G_3 + \dots + G_N$$

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✅ Quick Comparison

Feature	Series Circuit	Parallel Circuit
Equivalent Resistance	Sum of resistances (increases)	Less than smallest resistor (decreases)
Current	Same through all resistors	Divided among branches
Voltage	Divided across resistors	Same across each branch
Application	Voltage Divider	Current Divider

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🔗 Related Reads:

• Capacitors in Series and Parallel

• Electrical Power in Series and Parallel

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✅ Disclaimer: The above content is for educational purposes. Always follow electrical safety standards and consult professional guidelines while designing or working on electrical circuits.

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