Virtual Solar also Known as Virtual Net Metering explained

    

    Virtual solar usually refers to virtual net metering (VNM) or community/group solar arrangements where the electricity produced by a solar system is not consumed on the same rooftop as the system. Instead, the solar plant (located onsite at a separate location or on a shared rooftop) feeds power into the grid, and the utility allocates monetary or energy credits from that generation to one or more electricity consumers’ bills. In short, you gain the financial benefits of solar (lower bills, renewable energy credits) without having panels on your own roof. 

Virtual Solar Explained

How does it help consumers use solar energy?

1. Access for people who can’t install panels - Renters, apartment dwellers, shaded roofs, heritage buildings, or businesses with no spare roof space can still benefit from solar through a virtual share.

2. Economies of scale - A single, larger plant is often cheaper per kWh than many small rooftop systems — lower development, operation and maintenance costs. 

3. Simplified billing (credits) - The utility’s billing software credits each linked consumer’s electricity account with a portion of the solar generation (either as kWh credits or rupee credits), reducing their monthly bill. That means the generated solar energy is used financially, even if the electrons flow through common wires. [pivotenergy.net]

4. Flexibility for organisations - Corporations, public bodies, or housing societies can pool demand and assign shares — useful for campuses or multi-site companies. 

Let's look at it with an example - 

    Imagine a 100 kW off-site solar plant that generates 100,000 kWh/year. The utility credits the plant’s output to three consumers in the same license area:

• Consumer A: 40% share → 40,000 kWh credited
• Consumer B: 35% share → 35,000 kWh credited
• Consumer C: 25% share → 25,000 kWh credited

If the retail electricity price is ₹8 per kWh, the annual bill reduction (credit value) would be -

• A - 40,000 × ₹8 = ₹320,000 saved/year
• B - 35,000 × ₹8 = ₹280,000 saved/year
• C - 25,000 × ₹8 = ₹200,000 saved/year

Total credit value = 100,000 × ₹8 = ₹800,000 — the plant’s generation value is fully allocated among the three consumers. This shows how consumers “utilise” generated solar energy financially, even when panels are not on their own roofs. (Numbers used here are illustrative; actual generation, allocation rules and billing rates vary by project and utility.) [pivotenergy.net]

How the mechanism typically works - 

1. A developer or group installs a solar system (off-site, rooftop of a public building, or a central plant).

2. The system exports power to the distribution grid.

3. The utility measures generation and, according to approved VNM/group-metering rules, assigns credits proportionally to each registered consumer’s account.

4. Credits offset consumption in the monthly bill (sometimes with limits on rollover or settlement rules). 

Is the government using this in schemes? 

Yes. In India, central agencies and state regulators have recognised and promoted virtual/group net metering -

    

    The Ministry of New & Renewable Energy (MNRE) has issued guidance and a Standard Operating Procedure (SOP) for implementation of Virtual Net Metering and Group Net Metering (SOP published 23 Feb 2023). MNRE has also issued clarifications about the applicability of central financial assistance (CFA) for systems installed under Virtual Net Metering arrangements. These moves show the government formally supports VNM/GNM as an implementation model for rooftop and shared solar. [Source - Ministry of New and Renewable Energy]

    Several state distribution utilities and program portals (e.g., PM Surya Ghar / rooftop portals) now include provisions or guidance for group/virtual metering in their rooftop solar programmes and application flows. Policy write-ups by think-tanks and research bodies (CEEW, etc.) explain how these models are being detailed in state regulations and utility procedures. [Source - PMSuryaghar]

Practical caveats & what consumers should check - 

• Same license/utility area - VNM/GNM usually requires participants to be within the same distribution license area and meet the utility’s eligibility rules. [Source - CEEW]
• Allocation and settlement rules - how credits are calculated (kWh vs rupee), rollover, banking, expiration, and limits on matching demand can vary by state/utility. Read the local VNM/GNM tariff order or SOP. [Source - Ministry of New and Renewable Energy]
• Contract and ownership - Who owns the plant (consumer cooperatives vs. RESCO vs. third-party developer), who claims Renewable Energy Certificates (RECs), and responsible for maintenance should be clear in contracts. [Source - pivotenergy.net]

        Virtual solar (virtual net metering) lets people share and get billed credits for solar generation from a shared or off-site plant — making solar available to renters, apartment residents, and organisations with limited roof space — and it’s an approach formally supported and operationalised in India through MNRE guidance and state/utility implementations. 

Records keeping of a Junior Engineer (Electrical) office placed under in Distribution Sector

A Junior Engineer (JEN) - 

    Acts as the backbone of the distribution system—ensuring uninterrupted power supply, routine maintenance, maintaining records, releasing new connections, conducting vigilance, etc.

Field Duties of a Junior Engineer - 

• Monitor and regulate the power supply in the designated area.
• Inspect and maintain 11 kV feeders and 33/11 kV GSS (grid substations) regularly.
• Respond promptly to faults, outages, and consumer complaints.
• Supervise and coordinate the work of field staff (linemen, helpers, contractors).
• Manage and account for materials used in maintenance and repairs.
• Conduct preventive maintenance of transformers, breakers, and feeders.
• Authorise and verify new service connections to consumers.
• Maintain safety procedures and make sure that laws are followed.

Essential Records Maintained by a Field JEN -

Record keeping of the JEN Office

        A junior engineer is also the custodian of all official records and materials. 

A. Stock Register -

• Records all materials received and issued (e.g., cables, poles, insulators, meters, transformers).
• Facilitates effective inventory control and audits.

B. Meter Movement Register (MMR)

Tracks the movement of meters:

  - Issued to the site.

  - Installed at consumer premises.

  - Faulty meters returned for repair or scrapping.

  - Stock in and stock out.

C. Meter Change Order Register (MCO)

• Documents orders for replacing defective meters.
• Includes consumer details, as well as old and new meter particulars.

D. Service Connection Order Register (SCO)

• Maintains comprehensive records of new service connections.
• Contains application numbers, consumer details, sanctioned load, connection date, and meter number.

E. RC/DC Register (Reconnection/Disconnection)

     Records instances of supply disconnections (due to non-payment, theft, or maintenance) and subsequent reconnections.

F. Net Meter Solar Feasibility Register (Feeder-wise)

    Conducts feasibility assessments for solar net-metering applications, feeder-wise, to ensure adherence to feeder capacity limits.

G. Transformer Register

Logs all 11/.4 kV distribution transformers in the field -

  - Location,

  - Capacity,

  - Commissioning date,

  - Failure and replacement history.

Etc..

H. VCR Register (Vigilance Control Register)

    Records instances of electricity theft, inspection reports, penalties imposed, and follow-up actions.

I. Estimate Register

    Keeps a record of all cost estimates prepared for new works, system extensions, and equipment installations.

J. Master Data File

    A single file or folder to organise all correspondence, such as circulars, government orders, internal memos, operational instructions, and safety notices.

Record Registers of the JEN office

Materials Managed in the Field -

    As part of field operations, the JEN supervises and records the following materials:

• Poles (RCC, PCC, steel)
• Conductors (ACSR, AAAC)
• Insulators and clamps
• Distribution transformers
• Stay sets and earthing components
• Meters (single-phase, three-phase, smart meters)
• LT/HT cables and fuses
• Protective equipment (breakers, isolators, lightning arresters)

etc..

  All materials must be documented in the stock register and properly accounted for.

Urban Cess in Electricity Bills Explained Simply

      Urban Cess is a type of tax collected by the electricity department (on behalf of the state government) from consumers living in urban areas to fund the development and maintenance of urban infrastructure.

Urban Cess

        It is not a charge for the electricity you use, but an extra amount levied to support civic amenities—like street lighting, roads, drainage, public spaces, and upkeep of urban areas. So, think of it as a contribution toward improving and maintaining your town or city’s facilities.

Why is Urban Cess Charged? 

Compared to rural areas, urban environments need more services and upkeep because -

• Higher population density
• More electricity infrastructure
• Roads, streetlights, and drainage systems
• Waste management
• Parks, public buildings, etc.

        The state government needs funds to provide these services and maintain the infrastructure.

         Instead of raising all the money from general taxes, they collect urban cess directly from electricity consumers living in municipal or urban areas, because nearly everyone there uses electricity.

How Much is Urban Cess?

        The rate of urban cess varies from state to state and is decided by the respective state government’s policy. In Rajasthan (for example), it is usually charged as a small percentage of your energy charges or a fixed amount per kilowatt (kW) of sanctioned load.

Does the Public Benefit from Urban Cess? 

    Yes—at least in principle. The funds collected through urban cess are meant to be used for urban development projects, such as

• Installing and maintaining streetlights
• Building and maintaining public toilets
• Repairing city roads and footpaths
• Improving drainage and sewerage systems
• Keeping public parks and spaces clean
• Upgrading electrical infrastructure (like poles, wires, transformers) in city areas

      

      So, when you pay urban cess, you’re contributing to making your city a better, cleaner, and safer place to live. However, sometimes the benefits may not be immediately visible to everyone, because these are collective services and depend on how effectively the funds are used by the urban local bodies.

Urban Cess at a Glance

      While urban cess might feel like an extra burden on your electricity bill, it’s essentially your share of responsibility to maintain and improve your city’s infrastructure.

     Although small in amount, when collected from millions of consumers, it provides significant funds to municipalities and local bodies to keep the urban environment functional and pleasant.

Understanding Electricity Duty in Bills

    When consumers in Rajasthan receive their electricity bills from Jodhpur Vidyut Vitran Nigam Limited (JdVVNL), many come across various components like energy charges, fixed charges, fuel surcharge, and a lesser-known component – Electricity Duty (ED). 

Electricity Bill

What is electricity duty?

    Electricity Duty (ED) is a state government levy imposed under the Rajasthan Electricity (Duty) Act, 1962. It is not a charge by the discom (like JdVVNL), but rather a tax collected on behalf of the Rajasthan State Government for the consumption of electrical energy.

    This duty contributes to the state’s revenue and is meant to support the infrastructure, development, regulation, and oversight of electricity supply in Rajasthan.

Why is the electricity duty included in the Bills?

    Electricity Duty is mandated by state law, and every licensed electricity distribution company, such as JdVVNL, is required to collect it from consumers and remit it to the government. It is calculated based on actual energy consumed (in kWh) and varies for different consumer categories such as domestic, commercial, industrial, and agricultural users.

    Electricity Duty in Rajasthan is a mandatory state tax collected through your JdVVNL electricity bill. Though often overlooked, it forms a crucial part of the overall billing structure and contributes to the development and regulation of electricity infrastructure in the state. 

Emergence and Impact of Smart Meters in India

     India, with its vast and diverse electrical infrastructure, has been quick to adopt smart metering as part of its energy reform and digitalization efforts. The Ministry of Power, through Energy Efficiency Services Limited (EESL) and REC Ltd., has launched various initiatives under the Smart Meter National Programme (SMNP) to replace traditional meters with smart meters.

Key Drivers in India -

Smart Meter

1. AT&C Loss Reduction -

   With over 20% losses in some states, smart meters aim to reduce aggregate technical and commercial losses by accurate billing and tamper detection.

2. Prepaid and Postpaid Flexibility

   Consumers can now choose prepaid models, helping Discoms improve cash flow and operational efficiency.

3. Remote Reading in Rural Areas

   Eliminates the need for physical meter reading in difficult terrains using GSM and 4 G-based communication.

4. Integration with AMI (Advanced Metering Infrastructure) -

   India is moving toward large-scale AMI implementation, where thousands of smart meters communicate with data concentrators and Head-End Systems (HES) for seamless energy data management.

Key Projects and Milestones in India-

• EESL Deployment -More than 5 million smart meters have been installed in states including Rajasthan, Uttar Pradesh, Bihar, Delhi, and Haryana.
• Smart Grid Pilots - Under the NSGM (National Smart Grid Mission), cities like Panipat, Chandigarh, and Mysuru have demonstrated successful AMI integration.
• Private Sector Push - Companies like L\&T, Genus Power, and Secure Meters are actively manufacturing and deploying BIS-certified smart meters.

Challenges in Indian Context -

1. Communication network reliability in remote areas
2. Initial cost of deployment and infrastructure
3. Consumer awareness and resistance
4. Interoperability among vendors and protocols
5. Data privacy and cybersecurity concerns

Future of Smart Meters in India -

• The government plans to deploy 250 million smart meters by 2030 as part of the PAN India rollout.
• Integration with Solar and Net-Metering - Enabling bidirectional energy flow tracking.
• AI and ML for Demand Response - Using smart meter data for predictive analytics and load balancing.
• Blockchain for Energy Transactions—Decentralized energy trade among prosumers.

        A significant change in how power is measured, controlled, and marketed is represented by smart meters. While the technology is universal, its application in India has been both challenging and transformative. With continuous innovation, policy support, and consumer participation, India is poised to become a global leader in smart grid technologies.

Emergence of Smart Meters in the Power Sector - A Technical Insight

Introduction to Smart Meters-

    A smart meter is an advanced energy metering device equipped with embedded electronics and communication modules to record energy consumption in real-time or near real-time. It enables two-way communication between the meter and the utility provider using technologies such as RF mesh, cellular (GPRS/4G), PLC (Power Line Communication), or Wi-Fi.

A Smart Meter

In simple words -

    Simply put, a smart meter is a digital electricity meter that tells you how much electricity you’re using and when you're using it. Unlike traditional meters, it can automatically send readings to your electricity provider and receive commands remotely.

Components of a Smart Meter (With Technical Explanation) - 

1. Energy Metering Integrated Circuit (IC) -

Function - This is the core metrology component responsible for measuring voltage, current, power factor, frequency, real, reactive, and apparent power.

Technical Insight - Modern ICs like the ADE7758 or STPM33 integrate multi-phase support and high-accuracy ADCs to digitally sample electrical parameters and calculate consumption using advanced algorithms.

2. Microcontroller Unit (MCU) -

   Function - Acts as the brain of the meter, processing data from the metering IC and managing communication, control, and logic.

  Technical Insight - MCUs such as ARM Cortex-M series are preferred due to their low power consumption, high processing speed, and support for encryption and protocol stacks.

3. Communication Module -

   Function - Makes it easier for data to move back and forth between utility servers and smart meters.

Types and Technologies - 

• RF Mesh - Best for urban and densely populated areas.
• PLC - Suitable for low-voltage distribution networks.
• Cellular (GSM/GPRS/4G) - Wide-area communication used in India’s rural and urban deployments.
• Wi-Fi/Bluetooth - Mainly for home automation interfaces.

4. Non-Volatile Memory (NVM)-

   Function - Stores metering data, firmware, and logs.

  Technical Insight - EEPROM or Flash memory ensures retention of critical data during power failures.

5. Display Interface -

 Function - Shows real-time parameters like voltage, current, power, units consumed, and alerts.

Technical Insights - LCD/LED screens controlled via SPI/I²C protocols; some even integrate touch or scroll buttons for user interaction.

6. Tamper Detection Sensors -

Function - Detects tampering attempts like magnetic interference, current reversal, and physical opening.

Technical Insight - Uses current comparison logic, reed switches, and Hall sensors to detect and warn in real time.

7. Relay/Switching Circuit -

Function - Allows the power source to be remotely disconnected and reconnected.

Technical Insight - Uses solid-state relays (SSRs) or electromechanical relays controlled by the MCU to disconnect loads up to 60 A or more.

Advantages of Smart Meters -

1. Real-time consumption monitoring.
2. Automatic billing with reduced human errors.
3. Remote disconnection/reconnection.
4. Load profiling and demand forecasting.
5. Real-Time Theft and Tamper Detection.
6. Enhanced consumer awareness and energy saving.

     Smart meters are not just a technological upgrade - they represent a fundamental transformation in how energy is measured, monitored, and managed across the globe. Their ability to provide real-time consumption data, enable two-way communication, detect tampering, and support remote operations makes them indispensable for building resilient and efficient power infrastructure.

    Globally, smart meters are paving the way for smarter energy grids, greater integration of renewable energy sources, and more empowered consumers. They enhance operational efficiency for utilities, reduce energy losses, support dynamic pricing, and help in load balancing and demand-side management. In developed countries, they are central to smart city initiatives; in developing nations, they offer a path to reduce losses, improve billing transparency, and drive energy equity.

Power Transformer Failures - Causes, Protection Strategies, and Technological Solutions

The Cost of Transformer Failures -

    In India, power transformers are a critical infrastructure in the transmission and distribution system. Despite their robust design, hundreds of transformers fail or catch fire each year, resulting in -

• Energy loss
• Grid instability
• Downtime of feeders and substations
• Massive financial losses for DISCOMs (distribution companies)

Power Transformer Protection

    According to industry data, transformer failures cost Indian DISCOMs hundreds of crores annually, including replacement cost, service interruption, penalties, and manpower.

Causes of Transformer Failure -

1. Overloading - Transformers exceeding 80–85% loading over extended periods cause insulation deterioration.

2. Poor maintenance and oil contamination - Moisture and impurities in transformer oil reduce dielectric strength.

3. Short circuits or transient faults. 

4. Lack of protection relays or faulty relay settings.

5. High ambient temperature and inadequate cooling.

6. Lightning surges or switching overvoltages.

7. Ageing and mechanical vibration.

8. Fire risks stemming from oil leaks and combustible environments.

Technical Methods to Prevent Transformer Failure -

1. Load Management & Monitoring -

• Install online transformer load monitoring systems using IoT-based current and voltage sensors.
• Implement load shedding algorithms during peak hours or automatic feeder balancing.

Equation for load capacity -

•  S = (√3×V×I) / 1000 (kVA)

Where S = apparent power, V = line voltage, I = current

It should be ensured that the actual S ≤ 80% of - nameplate rating.

2. Online Dissolved Gas Analysis (DGA) -

Use DGA sensors to monitor transformer oil for fault gases like -

• Hydrogen (H₂)
• Acetylene (C₂H₂)
• Methane (CH₄)
• Ethylene (C₂H₄)

    DGA forecasts internal arcing, thermal overload, and insulation degradation prior to failure.

3. Temperature and Thermal Protection -

Install -

• Winding temperature indicators (WTI)
• Top oil temperature sensors
• Digital thermographic scanning during preventive maintenance.

Thresholds -

• Alarm at 80°C
• Trip at 95°C (winding)

4. Protection Relays and SCADA Integration -

• Use Numerical Differential Protection Relays (87T) for internal faults.
• Integrate with SCADA or RTU (Remote Terminal Units) to provide real-time data and alarms.

5. Use of Vacuum or SF₆ Circuit Breakers -

• Replacing oil circuit breakers at substations with vacuum or SF₆ CBs enhances arc quenching and safety.
• Fast-acting breakers prevent faults from propagating and damaging transformers.

6. Routine Testing and Preventive Maintenance -

• IR (Insulation Resistance) Testing
• Tan-Delta and Capacitance Test
• Transformer Turns Ratio (TTR) Test
• Bushing CT and OLTC testing

    Routine preventive schedules reduce the probability of sudden catastrophic failures.

Fire-Fighting Protection Systems for GSS and Transformers

1. Dry-Type and Fire-Retardant Transformers -

    In urban zones, use dry-type cast resin transformers or mineral oil alternatives like FR3 ester-based oils which are -

• Biodegradable
• Non-toxic
• Have high fire point (>300°C)

2. Automatic Fire Detection and Suppression System (AFDSS) -

    Install thermo-sensitive linear heat-sensing cables (LHSC) across GSS transformers and oil tanks. The system includes -

• UV/IR flame detectors
• Nitrogen or clean-agent gas suppression
• Deluge water spray systems for cooling

Smart integration - Link with SCADA or fire panel; trigger alerts and isolate supply instantly.

3. Infrared Imaging and AI Monitoring -

    AI-powered security cameras and infrared sensors identify anomalous heat zones (red-hot) on transformers in real-time. Algorithms predict fire risks using thermal trend analysis.

4. Oil Leakage Detectors -

    Use float-type or capacitive sensors to detect minor oil leakage that may escalate into fire hazards if not addressed.

Financial Savings and Cost-Benefit Analysis for Power Sector Companies- 

Latest Technologies in Transformer Protection

1. Digital Twin Modelling Predictive diagnostics through virtual simulations.
2. IoT-Enabled Smart Transformers with Remote Control.
3. Edge computing-based condition monitoring.
4. AI + ML fault detection algorithms trained on historical failure data.
5. Drone-based thermography for difficult terrains and EHV substations.

What Engineers and Transmissions, and DISCOMs Can Do -

1. Implement failure root cause analysis post every major fault.
2. Train ground staff in oil sampling, relay settings, and fire safety drills.
3. Schedule quarterly thermography and bushing checks.
4. Digitize old substations with sensorized retrofitting.
5. Establish Central Monitoring Centers for transformer health analytics.

        Transformer failures in India can be significantly reduced through proactive technical upgrades, intelligent monitoring, and reliable fire suppression systems. With climate change and increasing electrical loads, electricity companies must modernise transformer protection infrastructure to reduce financial losses, increase grid reliability, and ensure public safety.

Power Factor Explained

Power Factor (PF) is the ratio of real power (P, in kilowatts, kW) used by a load to do useful work to the apparent power (S, in kilovolt-amperes, kVA) drawn from the grid.

  PF = P/S = cos φ = Active Power / Apparant Power

- φ = the phase angle between the waveforms of voltage and current.

• Real power (P) does the work (lighting, heating).
• Reactive Power (Q) (in kVAR) oscillates between source and load, creating magnetic fields (motors, transformers).
• Apparent Power (S) combines both - S² = P² + Q².

Layman’s Analogy - 

Imagine water flowing through a hose - 

• Real power is like the water you actually use (to water plants).
• Reactive power is when water flows back and forth in the hose without actually watering anything (only creating pressure).
• All of the water in the hose, both wasted and helpful, is known as apparent power.
• A good PF (near 1) means almost all water goes to your plants.
• A poor PF (low) means lots of water just sloshes and doesn’t water.

What Happens with Good v/s Poor Power Factor?

What can be done for Power Factor Improvement- 

• Use PF Correction Devices - Capacitor banks or smart PF controllers.
• Choose PF‑Certified Appliances - Look for motors and appliances with PF > 0.9.
• Regular Maintenance - Keep motors and compressors clean for optimal magnetics.
• Balance Loads Across Phases - (in three‑phase systems) to avoid neutral overloading.

- GGJ

Comparison between Dry-type copper wound and Dry-type aluminum wound Transformers

Dry Type Transformer

Dry-Type Copper Wound Transformer - A dry-type copper wound transformer is a transformer that uses copper conductors in its windings and relies on air or resin insulation instead of oil for cooling. Known for their high electrical conductivity, durability, and efficiency, these transformers are ideal for critical and long-term installations where performance and reliability are key.

Dry-Type Aluminum Wound Transformer - A dry-type aluminum wound transformer uses aluminum conductors in the windings and is similarly air- or resin-insulated, eliminating the need for oil. These transformers are lighter and more cost-effective, making them suitable for installations where budget and ease of handling are more important than maximum efficiency.

1. Conductor Material 

Copper

• Higher electrical conductivity (\~59.6 MS/m)
• Requires a smaller conductor cross-section

Aluminum -

•  Lower conductivity (\~36 MS/m)
•  Requires a larger conductor size for the same current

Best - Copper

2. Resistance

Copper -

•  Lower electrical resistance
•  Reduces I²R losses

Aluminum -

• Higher resistance
• More heat and power loss

Best - Copper

3. Heating & Thermal Performance -

Copper-

• Better heat dissipation
• Lower temperature rise
• Less thermal expansion

Aluminum -

• Heats up more
• Higher thermal expansion (can cause joint issues)

Best - Copper

4. Efficiency -

Copper -

• Higher energy efficiency
• Better for long-term power savings

Aluminum - 

• Slightly lower efficiency

Best - Copper

5. Losses - 

Copper -

• Lower copper (I²R) losses

Aluminum - 

• Higher copper losses

Best - Copper

6. Size and Weight - 

Copper - 

• Compact winding size
• Heavier due to high density

Aluminum - 

• Larger windings
• Lighter and easier to handle

Best - Aluminium (for weight-sensitive setups)

7. Life Expectancy - 

Copper - 

• Longer lifespan
• Stronger mechanical strength
• Less prone to oxidation

Aluminum - 

• Shorter lifespan
• Higher risk of connection issues over time

Best - Copper

8. Oil & Insulation (Dry-Type Specific)-

Both - Use air or resin for cooling, no oil required, environmentally friendly

Best - Equal

9. Indoor/Outdoor Suitability - 

Copper - 

• Excellent in harsh outdoor environments

Aluminum - 

• Acceptable, but more prone to corrosion

Best - Copper

10. Mechanical Strength & Reliability -

Copper -

• Stronger
• Withstands vibrations and short-circuits better

Aluminum - 

• Softer metal
• Lower mechanical endurance

Best - Copper

11. Cost Consideration

Copper - 

• Higher initial cost
• Lower lifetime cost due to durability and efficiency

Aluminum - 

• Lower initial cost
• Higher total cost due to greater losses

Best - Aluminium (when budget is a constraint)

12. Installation & Handling - 

Copper -

• Heavier and harder to move/install

Aluminum - 

• Facilitated transportation and installation owing to reduced weight

Best - Aluminum

13. Accuracy (Voltage Regulation)-

Copper -

• Lower voltage drop
• Tighter voltage regulation

Aluminum - 

• Higher voltage drop under load

Best - Copper

So, lets check in below-

Factors                   /                         Suitable

..................................................................................................................................

In Efficiency                             -           Copper        

Mechanical Strength & Life  -           Copper        

Heating & Thermal Stability -          Copper       

Price                                           -          Aluminum

Weight & Portability               -          Aluminum

Durability outdoors                 -         Copper  

Handling & Transport             -         Aluminum

Final Recommendation - 

• Choose a copper-wound transformer for high efficiency, long life, critical loads, and reliable performance.
• Choose an aluminum-wound transformer for budget-conscious applications, lighter installations, or temporary use.

- GGJ

Impact on electrical system if the Transformer is given 100 % Solar Load

    

The electrical system on the solar load

 Let us consider the case first - 

    I have a 100 KVA distribution transformer installed near my house (considering PF 0.9). The total solar load applied by households in that area is 90 kW, which will be fed through this 100 kva transformer. The parameters are -

1. Transformer rating = 100 kVA  
2. Power Factor = 0.9 (lagging, assumed typical for residential loads)  
3. Rated real power = 100 × 0.9 = 90 kW
4. Total solar load on system= 90 kW

    As per the condition, let's say all 90 kW solar generation is connected to feed into the transformer (i.e., export to the grid or supply local loads).

What Happens Technically When 90 kW Solar Is Connected?

1. Loading of Transformer - The transformer is rated 90 kW at PF 0.9. If all 90 kW solar starts generating at peak - 

1.  The transformer is operating at full real power capacity.
2.  But in real life, transformers also handle reactive power (kVARs), so apparent power can exceed 100 kva.

Risk Involved - If the local load is low (at night or on holidays), this full 90 kW might be pushed back to the grid, causing reverse power flow.

2. Reverse Power Flow - Transformers are usually not designed for continuous reverse flow unless specially specified.

- If generation > local consumption, surplus power flows back from LV to HV side, i.e., from 415 V to 11 kv in India.

Impacts -

• Overheating of the transformer due to reverse magnetisation.
• Protection malfunctions (relay settings typically designed for forward load).
• Can lead to overvoltage on the 11 kv feeder, especially if other transformers also have high solar.
• Utilities may limit solar penetration per transformer (usually 30-50 % of kva capacity); however, in JdVVNL, AVVNL, JVVNL, Rajasthan  norms its 80 % of the Transformer capacity.) 

3. Voltage Rise on LT Side -

• The LT line's voltage increases as a result of solar power.
• With 90 kW connected and minimal local consumption:
• LT voltage can exceed permissible limits (say > 240 V phase-to-neutral).
• May trip inverters due to overvoltage (anti-islanding protection).
• Uneven PV output can cause voltage fluctuations, especially if single-phase inverters are used.

4. Thermal Overload Risk -

• The transformer is designed for typical residential loads, with diversity and non-peak coinciding.
• 90 kW solar = non-coincident, simultaneous injection → actual load on transformer may exceed thermal limit.
• Temperature rise in windings, insulation degradation → shortens transformer life.

5. Power Quality Issues -

• If many inverters operate simultaneously - 
• It may introduce harmonics and voltage flicker.
• Also results in unbalanced loads (if solar is not equally spread across 3 phases), neutral heating, and voltage imbalance.

Solutions & Measures -

1. Limit Solar Capacity on DT -

• Follow solar hosting capacity guidelines and respective acts and norms to be followed with discipline. 
• Generally, max 30–50% of transformer capacity or as applicable by various discom norms of different states.
• For 100 kVA DT → limit solar to 30–50 kW (or as decided by the distribution company norms across states).

2. Upgrade Transformer -

- If demand justifies -

•  Upgrade to a 100 kVA or 160 kVA transformer.
•  Ensure it supports bi-directional power flow.

3. Install LT Side Voltage Regulation -

• Use on-load tap changers (OLTC) or line voltage regulators.
• Monitor and stabilise the voltage rise due to solar.

4. Install Reverse Power Relays or Limiters -

• Prevent dangerous export by tripping or curtailing excess generation.
• Or install net metering + export limiters.

5. Phase Balancing -

• Ensure solar connections are equally distributed across the 3 phases.
• Prevents overloading of a single phase and neutral heating.

6. Real-time Monitoring System -

IoT or SCADA monitoring of ----

•  Transformer loading
•  Voltage at the LT side
•  Solar injection
•  Reverse power

7. Energy Storage (Optional but Effective) -

• Use battery storage to store excess daytime generation.
• Reduces grid injection and stabilises voltage.

Types of Solar Rooftop Plates - Working, Specifications, Capacity & Lifespan

        With the rise in demand for renewable energy, solar rooftop systems have become a widely adopted solution for both residential and institutional electricity needs. At the core of these systems are solar plates—commonly known as solar panels—which convert sunlight into electricity. The selection of the right solar panel type depends on efficiency, installation area, budget, and desired output.

Solar Rooftop Plates - Working, Specifications, Capacity & Lifespan

Working Principle of Solar Rooftop Plates -

    All solar panels work on the photovoltaic effect. When sunlight hits the surface of a solar cell, photons in the sunlight dislodge electrons in the silicon-based semiconductor material. These free electrons flow through an electric circuit, generating direct current (DC), which is later converted into alternating current (AC) via an inverter for use in homes or institutions.

Types of Solar Rooftop Panels (Plates)

1. Monocrystalline Solar Panels (Mono-Si)

Made from a single crystal structure of high-purity silicon, these panels are known for their sleek black appearance and high efficiency.

- Efficiency - 18% to 22%

- Temperature Coefficient - 0.3% to -0.5% per °C (lower is better)

- Power Output - 320W – 600W (per panel)

- Lifespan - 25–30 years

- Best For - Limited rooftop space, high-efficiency requirements

- Cost - Higher than other types, but provides better ROI over time

Advantages -

- High power output per square meter

- Better performance in low-light and high-heat environments

2. Polycrystalline Solar Panels (Poly-Si)

    These panels are speckled and have a bluish colour because they are made of many silicon pieces that have been melted and put into moulds.

- Efficiency - 15% to 17%

- Temperature Coefficient - ~ -0.4% per °C

- Power Output - 250W – 400W (per panel)

- Lifespan - 20–25 years

- Best For - Larger rooftops, budget-friendly installations

- Cost - Cheaper than monocrystalline

Advantages -

- Cost - effective for large-scale installations

- Stable performance under average sunlight

3. Thin-Film Solar Panels (TFSP) -

    These are made by depositing one or more layers of photovoltaic material on a substrate like glass, plastic, or metal. Amorphous silicon (a-Si) and cadmium telluride (CdTe) are common materials.

- Efficiency: 10% to 12% (can go up to 14% with advanced models)

- Temperature Coefficient - 0.2% to -0.3% per °C

- Power Output - 100W – 300W (per panel)

- Lifespan - 10–20 years

- Best For - Curved or non-traditional roofs, lightweight applications

- Cost - Medium to low

Advantages -

- Flexible and lightweight

- Better performance in shaded or partially sunlit conditions

4. Bifacial Solar Panels -

    These panels can absorb sunlight from both the front and rear surfaces, increasing overall energy yield, especially when installed on reflective surfaces (e.g., white rooftops).

- Efficiency - Up to 25%

- Power Output - 350W – 700W

- Lifespan - 25+ years

- Best For - High-reflectivity rooftops, institutional use

- Cost - Higher initial investment

Advantages -

- Generates more energy from the same area

- Ideal for government or commercial rooftops with higher demands

5. Half-Cut Cell Solar Panels -

    A variation of mono or polycrystalline panels where cells are cut into halves to reduce resistance and improve performance.

- Efficiency - 19% to 23%

- Power Output - 370W – 600W

- Lifespan - 25 years

- Best For - Areas with partial shading or high temperatures

- Cost -Slightly more than standard panels

Advantages -

- Less power loss due to shading

- Higher durability and energy output

Comparison Table -

Panel Type	Efficiency	Lifespan	Power Output	Cost	Best Use Case
Monocrystalline	18–22%	25–30 yrs	320–600W	High	Limited space, max output
Polycrystalline	15–17%	20–25 yrs	250–400W	Medium	Budget-friendly setups
Thin-Film	10–12%	10–20 yrs	100–300W	Low	Lightweight, flexible use
Bifacial	Up to 25%	25+ yrs	350–700W	High	Reflective rooftops
Half-Cut Cell	19–23%	25 yrs	370–600W	Medium	Shaded or hot climates

    Choosing the right type of solar rooftop plate involves understanding your roof’s area, orientation, budget, and power requirement. In Rajasthan’s sun-rich environment, monocrystalline or bifacial panels offer the best long-term value for government and institutional installations, while polycrystalline panels are ideal for cost-sensitive projects.

        Installing efficient solar panels not only lowers electricity bills but also contributes to environmental protection by reducing carbon emissions and promoting clean, renewable energy adoption.

Government Scheme - PM Surya-ghar Muft Bijlee Yojna, an initiative by the central government, aims for the installation of solar net metering for households, under which the government of India offers a subsidy. The scheme to promote renewable energy to cut much higher household bills and helps in the reduction in carbon emission.