What is DG (Diesel Generator) Set?

A power generation system that generates electricity by using a diesel engine to power an alternator.

Purpose:

• In the case of a power failure, provide standby or backup power.
• Used in load testing to simulate real power loads (via load banks) for testing equipment.

Key ISO 8528 Series – Main Standard for DG Sets

The main international standard controlling diesel generator sets' performance, testing, and categorization:

• ISO 8528-1: General Requirements
  Outlines broad definitions, categories, and specifications for generator sets.
• ISO 8528-5: Generating Sets – Performance Requirements
  Key standard for dynamic characteristics. Defines generator set performance classes (G1–G4):
  • G1 – Basic requirements; large voltage/frequency variation allowed.
  • G2 – Standard Use; Moderate Regulation, Acceptable for most Industrial Loads.
  • G3 – High Performance; Suitable for sensitive equipment (e.g., Data centers).
  • G4 – Very High Performance; Tightest tolerances, used for critical systems.
• ISO 8528-6: Test Methods
  Outlines procedures for evaluating generator sets under diverse operational conditions including stability, transient behavior, load stages.
• ISO 8528-13: Special Tests
  Focuses on special-purpose testing in non-standard conditions (high ambient temperature, altitude), useful for challenging load bank tests.
• ISO 3046 Series – Reciprocating Internal Combustion Engines.
• ISO 7637 (for Control Electronics)
  Evaluates electrical disturbances in DG sets with sophisticated electronic controllers.
• ISO 9001 (Quality Management) (Indirectly relevant)
  Ensures manufacturing and testing of DG sets follow quality processes.

Standard Title Use in Load Bank Testing

Testing Load Bank through DG Set

Load bank testing is essential for replicating real-world loads and assessing the generator's performance under various conditions. The load is progressively increased while monitoring variables such as engine response, voltage stability, and exhaust conditions.

Dynamic Characteristics

• Transient Response: The DG’s ability to stabilize output voltage and frequency after sudden load changes (step increases or decreases).
• Voltage Flicker: Voltage variations monitored during load bank testing to identify flicker issues.
• Frequency Deviations: ISO 8528-5 sets limits on max frequency increase and recovery times after load changes. Also defines steady-state frequency variation requirements.
• Load Bank Testing: Artificial loads simulate real stress, enabling assessment of dynamic properties.
• Testing Procedures: ISO 8528-5 details how to apply/remove load stages and monitor voltage/frequency variations.
• Performance Classes: DG sets are classified (G1, G2, etc.) by their dynamic behavior tolerances.

Key Static Characteristics of a DG Set (per ISO 8528)

• Voltage Regulation: Maintains voltage within ±1% to ±2.5% despite load changes.
• Frequency Regulation: Frequency deviation typically ±0.5% to ±2%, depending on governor type.
• Power Factor Capability: Handles power factors from 0.8 lagging (standard) to unity (1.0) at max load.
• Steady-State Voltage and Frequency Deviation: Voltage ±1% to ±2.5%, frequency ±0.5% to ±1% under constant load.
• Load Sharing (parallel operation): Multiple generators distribute loads proportionally and stably, verified during simultaneous load bank testing.
• Efficiency: Ratio of electrical output to fuel input, measured at 25%, 50%, 75%, and 100% loads.
• Fuel Consumption: Measured in L/hr or g/kWh at different loads for cost and emissions analysis.

Difference Between Static and Dynamic Characteristics: