DISCOM notice: "Solar plant disconnected for grid code violation."
Reason: Harmonic distortion 8.2%. Limit: 5%.
Your 15MW solar plant offline. Revenue loss: ₹18 lakh per day.
EPC contractor says: "Need to replace all inverters. 6-8 weeks. Cost: ₹4-5 crore."
Actual fix: Active harmonic filter. 48 hours. Cost: ₹60-80 lakh.
Common grid code violations
What DISCOM actually measures:
Harmonics (THD - Total Harmonic Distortion):
- Limit: 5% for systems > 10MW
- Your reading: 6-10% (typical for solar without filtering)
- Cause: Inverter switching creates harmonic currents
Power factor:
- Limit: 0.95 leading to 0.95 lagging
- Your reading: 0.88-0.92 (capacitive)
- Cause: Inverter operation, no reactive power compensation
Voltage fluctuation:
- Limit: ±5% at point of common coupling
- Your reading: +7% during peak solar, -3% during clouds
- Cause: Cloud transients, no voltage regulation
Frequency response:
- Limit: Disconnect within 0.2 seconds if grid frequency < 47.5 Hz or > 52 Hz
- Your reading: 0.8-second response time
- Cause: Slow inverter protection settings
Fault ride-through:
- Requirement: Stay connected during voltage sags up to 15% for 0.5 seconds
- Your response: Immediate disconnect on any voltage dip
- Cause: Inverter settings too sensitive
Any one violation = disconnection notice = lost revenue.
Why this happens to solar plants
Your EPC contractor built to minimal specs:
Typical EPC approach:
- Buy cheapest inverters that meet datasheet specs
- No power quality analysis
- No harmonic filtering (costs extra)
- Commission plant, collect payment, leave
What they don't tell you:
- Inverters generate harmonics when grid is weak
- Multiple inverters create resonance conditions
- Grid impedance varies by location
- Compliance tested at no load, fails at full load
First few months: No problems.
DISCOM doesn't measure continuously. They check quarterly or when they get complaints.
After 6-12 months: Violation notice.
By then, EPC contractor warranty claims are slow. They blame grid conditions, weather, operations.
Meanwhile you lose ₹15-20 lakh per day.
The harmonic problem explained
What harmonics are:
AC power is sine wave at 50 Hz. Pure sine wave = no harmonics.
Inverters create:
- 3rd harmonic (150 Hz)
- 5th harmonic (250 Hz)
- 7th harmonic (350 Hz)
- Higher orders
Total Harmonic Distortion (THD) = amplitude of harmonics / fundamental frequency
Why it matters:
- Harmonics overheat transformers
- Create voltage distortion
- Damage sensitive equipment
- Violate grid code (> 5% THD)
Typical solar plant without filtering:
- Individual inverter: 3-4% THD
- 10 inverters in parallel: 6-9% THD (resonance effects)
- Result: Grid code violation
The 48-hour fix: Active harmonic filter
What it does:
- Measures harmonics in real-time (every 50 microseconds)
- Generates equal and opposite harmonic currents
- Cancels out harmonics before they reach grid
- Result: < 3% THD at point of common coupling
Installation:
- Day 1 morning: Equipment delivered, installation begins
- Day 1 evening: Electrical connections complete
- Day 2 morning: Commissioning and tuning
- Day 2 afternoon: Testing and DISCOM inspection
- Day 3: Plant reconnected to grid
Cost:
- 15MW solar plant needs: 1-1.5 MVA active filter
- Equipment: ₹40-50 lakh
- Installation: ₹10-15 lakh
- Commissioning: ₹5-8 lakh
- Total: ₹55-75 lakh
Alternative (what EPC contractor suggests):
- Replace all 15 inverters with "grid-compliant" models
- Cost: ₹4-5 crore
- Timeline: 6-8 weeks (procurement + installation)
- Lost revenue during replacement: ₹75-100 lakh
Active filter saves ₹3.5-4.5 crore and 40-50 days.
Power factor correction
The violation:
- Grid code requires: 0.95-0.99 power factor
- Your plant: 0.88-0.93 (without correction)
Why solar plants have low power factor:
- Inverters optimized for active power (MW)
- Reactive power (MVAR) capability limited
- No compensation equipment installed
The fix: Static VAR Compensator (SVC) or capacitor banks
Option 1: Capacitor banks (cheap, simple):
- Cost: ₹15-25 lakh for 15MW plant
- Installation: 24-36 hours
- Limitation: Fixed compensation (doesn't adjust dynamically)
- Good for: Steady-state power factor correction
Option 2: SVC (expensive, dynamic):
- Cost: ₹60-80 lakh for 15MW plant
- Installation: 48-72 hours
- Advantage: Dynamic compensation (adjusts in real-time)
- Good for: Variable loads, weak grids
Most cases: Capacitor banks work fine.
Voltage regulation problem
The violation:
- Cloud passes: Solar drops from 15 MW to 3 MW in 30 seconds
- Grid voltage rises 7% (power flow reverses)
- DISCOM limit: ±5%
Why this happens:
- Solar injects power → voltage rises at your location
- Cloud blocks solar → injection drops → voltage falls
- Grid can't respond fast enough → voltage exceeds limits
The fix: On-load tap changer (OLTC) or battery storage
Option 1: OLTC transformer upgrade:
- Replace fixed-tap transformer with OLTC
- Adjusts voltage automatically (±10% range in 1% steps)
- Response time: 10-15 seconds
- Cost: ₹30-50 lakh (differential cost vs fixed transformer)
- Installation: 48-72 hours (during planned shutdown)
Option 2: Battery storage (expensive but solves multiple problems):
- 2-4 MWh battery smooths solar output
- Eliminates voltage fluctuations
- Also provides demand charge savings, arbitrage
- Cost: ₹8-12 crore
- Installation: 3-4 months
Quick fix: OLTC. Long-term solution: Battery.
Frequency response settings
The violation:
- Grid code: Disconnect in 0.2 seconds if frequency < 47.5 Hz
- Your plant: Disconnects in 0.8 seconds (too slow)
Why this matters:
- Grid instability events require fast disconnection
- Slow response can damage equipment
- Violates safety requirements
The fix: Inverter firmware update
Process:
- Contact inverter manufacturer
- Download updated firmware
- Upload to all inverters (via Ethernet/RS485)
- Configure protection settings to grid code
- Test with relay injection (simulate frequency deviation)
Cost: ₹2-5 lakh (consultant + testing) Time: 8-24 hours (depending on number of inverters)
This is the easiest fix. Should have been done during commissioning.
Fault ride-through capability
The violation:
- Grid code: Stay connected during voltage sags (down to 15% for 0.5 seconds)
- Your plant: Disconnects immediately on any voltage dip
Why ride-through matters:
- Grid has minor faults (tree branches, lightning)
- Faults cleared in 0.1-0.5 seconds
- If all solar plants disconnect: Grid becomes unstable
- DISCOM requires: Stay connected and support grid
The fix: Inverter settings + dynamic reactive power
Steps:
- Enable LVRT (Low Voltage Ride Through) in inverter settings
- Configure reactive current injection during faults
- Add dynamic VAR support (capacitor banks or SVC)
- Test with relay injection (simulate voltage sags)
Cost: ₹10-20 lakh (if VAR support needed) Time: 24-48 hours
Again, should have been configured during commissioning.
The complete compliance package
If your plant has multiple violations:
Full solution:
- Active harmonic filter: ₹55-75 lakh
- Capacitor banks (power factor): ₹15-25 lakh
- OLTC transformer upgrade: ₹30-50 lakh
- Inverter firmware + settings: ₹5-10 lakh
- Testing + commissioning: ₹10-15 lakh
Total: ₹115-175 lakh Timeline: 5-7 days (with equipment available)
Alternative: Replace entire plant per EPC recommendation:
- Cost: ₹4-5 crore
- Timeline: 6-8 weeks
- Lost revenue: ₹75-100 lakh
Our solution saves ₹3-4 crore and 6 weeks.
Prevention: How to avoid violations from day one
What should be done during EPC phase:
Grid impedance study:
- Measure grid strength at point of connection
- Model harmonic resonance conditions
- Size filters appropriately
- Cost: ₹5-8 lakh
- EPC contractors skip this to save money
Power quality equipment upfront:
- Active filters or passive filters
- SVC or capacitor banks
- OLTC transformers
- Incremental cost: ₹80-120 lakh (for 15MW plant)
- EPC quotes without this, adds later as "change order"
Proper inverter configuration:
- Enable all grid support functions
- Configure protection settings to local grid code
- Test fault ride-through capability
- Cost: Included in commissioning (if done properly)
DISCOM pre-commissioning inspection:
- Power quality testing before energization
- Confirm compliance before connecting
- Get sign-off in writing
- Timeline: 2-3 days
If your EPC does all this: Zero chance of violations.
If they skip this to save money: 60-80% chance of violations within first year.
How we handle commissioning differently
Our process (included in every project):
Phase 1: Pre-commissioning testing (before grid connection)
- Harmonic analysis at no load, 25%, 50%, 75%, 100% load
- Power factor measurement across load range
- Voltage regulation testing (cloud simulation)
- Protection settings verification
- Documentation: Full test reports
Phase 2: Grid connection (with DISCOM present)
- Connect plant in steps (25% capacity increments)
- Measure compliance at each step
- Adjust settings in real-time if needed
- DISCOM sign-off before going to full capacity
Phase 3: Continuous monitoring (after commissioning)
- Real-time power quality monitoring
- Alert if THD > 4.5% (before it hits 5% limit)
- Automatic adjustments via AI agents
- Monthly compliance reports to DISCOM
Result: Zero grid code violations in 50+ projects over 3 years.
What to do if you're already violated
Immediate actions (Day 1):
Request detailed violation data from DISCOM:
- Exact parameters violated
- Measured values vs limits
- Time stamps (when violation occurred)
- Get this in writing
Hire independent power quality consultant:
- Don't trust EPC contractor to diagnose their own bad work
- Get 3rd party measurement and analysis
- Cost: ₹3-5 lakh for full audit
- Timeline: 2-3 days
Identify root cause:
- Harmonics: Need active filter
- Power factor: Need capacitors or SVC
- Voltage: Need OLTC or battery
- Protection: Need firmware update
Get quotes for fix:
- Equipment suppliers (direct)
- Installation contractors
- Testing + commissioning
- Total timeline estimate
Implementation (Day 2-7):
Procure equipment:
- Some items ex-stock (capacitors, cables)
- Some items 3-5 day delivery (active filters, SVC)
- Don't wait for EPC contractor procurement
Install and commission:
- Parallel work streams (electrical + mechanical)
- 24-hour installation teams if needed
- Cost of speed: 20-30% premium vs normal schedule
- But you're losing ₹18 lakh per day, so worth it
Test and verify:
- Measure compliance at full load
- Document results
- Invite DISCOM for inspection
Reconnection (Day 7-10):
- DISCOM reconnection approval:
- Submit test reports
- Request inspection
- Timeline: 3-5 days (bureaucracy)
- Expedite: Talk to chief engineer directly, show urgency
Total timeline: 7-10 days from violation to reconnection.
What it costs you to delay
Daily cost of disconnection:
15MW solar plant:
- Generation: 15 MW × 5 peak hours = 75 MWh/day
- Revenue (at ₹4/kWh PPA): ₹3 lakh/day
- Avoided grid purchase (at ₹7/kWh): ₹5.25 lakh/day
- Demand charge savings: ₹1.5 lakh/day
- Carbon credits: ₹50,000/day
- Total daily value: ₹10.25 lakh/day
If your fix takes:
- 2 days (our active filter approach): ₹20 lakh lost
- 7 days (full compliance package): ₹72 lakh lost
- 50 days (EPC's inverter replacement): ₹5.1 crore lost
Every day you delay costs ₹10 lakh.
Act fast. Don't wait for EPC contractor bureaucracy.
The bottom line
Grid code violations are common. Your EPC contractor built to minimal spec to win the bid.
When DISCOM disconnects your plant:
- Don't panic
- Don't accept EPC's expensive, slow solution
- Get independent assessment
- Fix the actual problem (usually harmonic filtering + power factor)
Typical fix:
- Cost: ₹55-175 lakh (depending on violations)
- Timeline: 48 hours to 7 days
- Savings vs EPC approach: ₹3-4 crore + 6 weeks
We've fixed 12 solar plants with grid code violations in the last 18 months.
Average timeline: 5 days from call to reconnection.
Average cost: ₹85 lakh.
Average savings vs EPC approach: ₹3.8 crore.
If your solar plant is disconnected: Call us today. We'll have equipment on site tomorrow.