Quick Facts
What ABT and ABT meter are
ABT (Availability Based Tariff) is the framework that governs inter-utility electricity trading in India, including how utilities settle scheduling, deviations, frequency control, and reserves. ABT operates at 15-minute granularity, with charges and credits based on a combination of scheduled and actual generation.
An ABT meter is the specialised energy meter that records electricity in 15-minute time blocks to support ABT-based settlement. ABT meters are installed at:
Inter-state transmission interfaces (between states).
Large generating stations.
Independent Power Producer (IPP) substations.
SECI-procured solar plants.
Inter-utility exchange points.
For utility-scale solar plants connected to inter-state transmission, ABT meters are essential infrastructure. The meters’ 15-minute data feeds the grid operator’s scheduling and settlement systems.
ABT framework overview
ABT separates electricity transactions into three components:
Fixed charge (capacity charge): Paid based on the generator’s declared capacity availability.
Energy charge: Paid for actual energy delivered.
UI (Unscheduled Interchange) charge: Penalty or incentive for deviations from scheduled output.
The 15-minute time blocks are the unit for these settlements. Each block has its scheduled and actual values, with deviations calculated per block.
For solar plants, ABT settlement involves:
Day-ahead scheduling: Forecast generation submitted the previous day.
Real-time monitoring: Actual generation tracked by ABT meter.
Deviation calculation: Difference between scheduled and actual.
UI charge or payment: Per grid frequency at the time of deviation.
The framework incentivises accurate forecasting and stable generation. For solar plants with variable output, scheduling accuracy is challenging.
ABT meter specifications
ABT meters meet specific technical requirements:
Accuracy class: 0.2S (highest available per IS 13779). This is significantly more accurate than trivector meters (typically 0.5S or 1.0).
Time synchronisation: GPS or NTP synchronisation. Accurate to seconds for precise 15-minute block timing.
Communication: Real-time data via GPRS, Ethernet, or dedicated fibre. Continuous data flow to the grid operator.
Data storage: Sufficient memory to record months of 15-minute block data.
Time-of-day registers: Within the 15-minute block framework, ToD designations are tracked.
Reverse flow: Bidirectional measurement for solar export.
Tamper detection: Extensive event logging including cover opening, magnetic field exposure, and abnormal current/voltage patterns.
Battery backup: Maintains time, configuration, and recent data during outages.
Display: Multiple parameters accessible through scrolling display.
ABT meter in solar plants
For utility-scale solar plants:
Installation: At the plant’s interconnection point to the transmission network.
Configuration: Bidirectional measurement (solar export is the dominant flow; import for plant station service).
Communication: To the relevant Regional Load Dispatch Centre (RLDC) or State Load Dispatch Centre (SLDC).
Data: Used for:
Real-time generation tracking by the grid operator.
Scheduling and deviation settlement.
Plant performance verification.
Billing for sold energy.
For SECI tenders, the ABT meter’s data is the basis for monthly invoice to SECI.
ABT and solar curtailment
When the grid is overcongested or local demand is low, the grid operator may curtail solar output:
Operator issues a curtailment order via dispatch system.
The plant reduces output (often through inverter Q-control or capacity reduction).
The ABT meter records the actual (reduced) generation.
The curtailed energy is logged but not billed.
For grid reliability, must-run status for solar provides protection: solar plants are typically not curtailed except in extreme grid conditions.
ABT scheduling for solar
Day-ahead scheduling for solar involves:
The plant submits hourly forecast generation for the next 24 hours.
The grid operator approves the schedule.
The next day, the plant’s actual generation is compared to the schedule in 15-minute blocks.
Deviations between actual and scheduled trigger UI charges.
For solar plants, forecasting accuracy depends on weather forecasting quality. Modern AI-based forecasts achieve 5% to 10% mean absolute error on day-ahead solar generation forecasts.
The 15-minute deviation settlement aligns with these forecasting capabilities. Small deviations are common and incur modest UI charges or credits.
ABT meter ownership and operation
For inter-state generators:
The generator typically owns and maintains the meter.
The grid operator (POSOCO/NLDC) accesses the meter data through dedicated communication.
The CT and PT secondary connections are sealed by the grid operator.
Periodic meter calibration is verified by the grid operator’s auditing.
For utility-utility interfaces:
The transmission utility (Powergrid or state STU) typically owns the meter.
The DISCOM accesses data for billing inter-state imports.
For solar IPPs:
The meter is part of the plant’s electrical interface design.
EPC contractor specifies and installs per IPP procurement.
DISCOMs and grid operators verify and approve the installation.
Major Indian ABT meter suppliers
Larsen and Toubro Electrical and Automation.
ABB.
Schneider Electric.
Siemens.
Genus Power.
Elmex.
Secure Meters.
Indian DISCOMs and IPPs typically standardise on specific brands for their installations.
Common ABT meter mistakes
Treating ABT meter as just another trivector meter. ABT requires specific accuracy and communication features.
Underestimating the 15-minute settlement granularity. The fine time resolution affects how deviations are calculated.
Forgetting communication continuity. ABT requires near-real-time data flow; communication failures are settlement issues.
Skipping calibration verification. Long-term meter drift accumulates significant settlement errors.
Mismatching CT/PT ratios with meter expectations. The configuration must match precisely.
Best practices
For utility-scale solar plant design, include ABT-grade metering as part of the electrical interface.
For meter selection, verify Class 0.2S accuracy and GPS time synchronisation.
For communication, plan for primary and backup data paths to the grid operator.
For O&M, include ABT meter calibration in periodic plant audits.
For scheduling, invest in accurate weather forecasting and AI-based generation prediction.
For dispute resolution, maintain detailed records of meter data, schedules, and deviations.
Standards and references
ABT meters follow IS 13779 (Class 0.2S accuracy), IS 16444 (smart meter standard), CEA Connectivity Regulations 2019, and CERC ABT framework. Specific requirements are detailed in CERC orders.
Related glossary terms
Key takeaways
An ABT (Availability Based Tariff) meter records electricity import and export in 15-minute time blocks, supporting India’s inter-utility settlement framework. ABT meters are used at inter-state transmission interfaces, large generating stations, IPP substations, and utility-scale solar plants. The meters meet Class 0.2S accuracy with GPS time synchronisation and real-time communication to grid operators. For solar IPPs, the ABT meter is essential infrastructure for grid scheduling, settlement, and billing.