Testing of Load Bank through DG Set

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 event of a power outage, supply standby or backup power.
• Also used in load testing to replicate actual power loads for equipment testing (via load banks).

Key ISO 8528 Series – Main Standard for DG Sets

The main international standard that controls diesel generator sets' performance, testing, and categorization is this one:

• ISO 8528-1: General Requirements
  Outlines the broad definitions, categories, and specifications for generator sets.
• ISO 8528-5: Generating Sets – Performance Requirements
  Key standard for dynamic characteristics. Covers frequency and voltage dip, recovery time, load acceptance, overshoot, etc.
  Defines generator set performance classes (G1–G4):
  G1 – Basic requirements; large voltage/ frequency variation allowed
  G2 – Stoddard Use; Moderate Regulation, Acceptable for most Industrial Loads.
  G3 – High Performance; Suitable For sensitive Equipments(e.g. Data centre).
  G4 – Very High Performance; Tightest tolerances, used for critical system.
• ISO 8528-6: Test Methods
  Outlines procedures for evaluating generator sets under diverse operational conditions. Includes methods for testing stability, transient behavior, load stages, etc.
• ISO 8528-13: Special Tests
  Emphasizes special-purpose testing, such as performance in unusual or non-standard circumstances (such as high ambient temperatures or altitudes). Beneficial for load bank testing under harsh circumstances.
• ISO 3046 Series – Reciprocating Internal Combustion Engines.
• ISO 7637 (Particularly for Control Electronics)
  If the DG set has sophisticated electronic controllers, this standard helps evaluate electrical disturbances.
• ISO 9001 (Quality Management) (Indirectly relevant)
  Ensures that manufacturing and testing of DG sets follow quality processes.

Standard Title Use in Load Bank Testing

Standard	Title	Use in Load Bank Testing
ISO 8528-1	General Requirements	Defines basic structure and ratings
ISO 8528-5	Performance Requirements	Defines dynamic behavior under load
ISO 8528-6	Test Methods	Specifies load bank testing procedures
ISO 8528-13	Special Tests	Load testing in extreme/special conditions
ISO 3046-1	Engine Testing	Test engine performance before coupling
ISO 9001	Quality Management	Ensures quality of DG manufacturing and testing.

Testing Load Bank through DG Set

In order to replicate real-world loads and assess the generator's performance under varied circumstances, load bank testing is an essential component of DG set testing. The DG set's load is progressively increased throughout this test, which also keeps an eye on important variables like engine response, voltage stability, and exhaust conditions.

Dynamic Characteristics

• ISO 8528-5 states that transient response, voltage flicker, and frequency deviations under various load circumstances are examples of dynamic characteristics of diesel generator sets (DGs) during load bank testing. The DG's ability to adjust to variations in load, including steady-state variation, frequency dips under abrupt increases in load, and frequency climbs upon load removal, is assessed by this test. Limits for voltage variations and recovery durations following transient events are also specified by the standard.
• The capacity of the DG to stabilize its output voltage and frequency following an abrupt change in load, such as a load bank raising or decreasing load, is known as transient response.
• Voltage Flicker:
  During load bank testing, the variations in voltage output can be detected and examined.
• Frequency Deviations:
  ISO 8528-5 establishes upper and lower bounds for the maximum frequency increase and recovery time following load variations. Additionally, the standard outlines the steady-state frequency variation that must
• Load Bank Testing:
  This technique applies an artificial load to the DG to replicate real-world stress circumstances, enabling the assessment of these dynamic properties.
• Testing Procedures:
  ISO 8528-5 describes precise procedures for testing certain dynamic properties, such as how to monitor frequency and voltage variations and apply and remove load stages.
• Performance Classes:
  According to ISO 8528, DG performance is divided into several classes (such as G1, G2), each of which has distinct specifications for frequency deviations, transient response, and voltage flicker
  Class G1 is applicable to generating set applications (such as general purpose applications, lights, and other simple electrical loads) when the associated loads are such that only the most basic voltage and frequency parameters need to be provided.
  Applications for Class G2 generating sets are those whose voltage characteristics closely resemble those of the commercial public utility electrical power system they are used with. There may be brief but acceptable variations in voltage and frequency as load changes (e.g. Lighting systems, pumps, fans, and hoists).

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

• Voltage Regulation:
  Generators maintain consistent voltage despite load changes, typically within ±1% to ±2.5% of the rated voltage.
• Frequency Regulation:
  Frequency deviation from the nominal value during load changes, until stabilization, is typically ±0.5% to ±2%, depending on the governor type.
• Power Factor Capability:
  Generators accommodate power factors ranging from 0.8 lagging (standard) to 1.0 (unity) at full load.
• Steady-State Voltage and Frequency Deviation:
  Under constant load, acceptable voltage deviation is ±1% to ±2.5%, and frequency deviation is ±0.5% to ±1%.
• Load Sharing (in parallel operation):
  Multiple generators share loads proportionally and stably, assessed via load bank testing during parallel operation.
• Efficiency:
  Efficiency, the ratio of electrical output to fuel input, is evaluated during steady-state testing at various load levels (25%, 50%, 75%, 100%).
• Fuel Consumption:
  Fuel consumption (L/hr or g/kWh) is measured at different load points for cost and emissions analysis.

Difference Between Static and Dynamic Characteristics

Aspects	Static Characteristics	Dynamic Characteristics
Definition	Steady-state performance	Transient performance (sudden load changes)
Load Condition	Constant load	Sudden load change (step load application/removal)
Focus	Stability and regulation during normal operation	Response and recovery from disturbances
Key Parameters	- Voltage regulation - Frequency regulation - Power factor - Efficiency - THD	- Voltage dip/rise - Frequency dip/rise - Recovery time - Load acceptance
Testing Type	Steady load steps (25%, 50%, 75%, 100%)	Sudden load application/removal
Time Domain	Long-term behavior (seconds to minutes post-stabilization)	Short-term behavior (milliseconds to seconds)
Example	Voltage within ±2% at 75% load	Frequency dips 8%, recovers in 4 seconds after a 50% load step