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ISO 8528: Generator Set Performance and Tender Realities
10 July 2025
When it comes to backup and standby power systems, ISO 8528 is the definitive international standard that governs the design, performance, and testing of generator sets. In Singapore, where reliability and compliance are paramount, it is frequently referenced in tenders and project specifications—yet it is also one of the most misunderstood standards among consultants and specifiers.
What is ISO 8528?
ISO 8528 is a comprehensive, multi-part international standard that governs the design, performance, and testing of reciprocating internal combustion engine-driven generator sets. It ensures generator sets are reliable, efficient, and safe for use in commercial, industrial, and critical infrastructure applications. Here’s a breakdown of the main parts and what each covers.
ISO 8528-1:2018 – Application, ratings and performance
Defines classifications for application, rating, and performance of generating sets, including RIC engines, a.c. generators, and associated equipment. Sets the basis for supplementary requirements in special applications (e.g. hospitals, high-rise buildings).
ISO 8528-2:2018 – Engines
Specifies requirements and tests for reciprocating internal combustion engines used in generator sets.
ISO 8528-3:2020 – Alternating current generators
Covers requirements and tests for a.c. generators used in generating sets.
ISO 8528-4:2005 – Controlgear and switchgear
Details requirements for the controlgear and switchgear associated with generator sets.
ISO 8528-5:2025 – Generating sets
Specifies test methods for determining the performance of complete generating sets, including step load testing and transient response.
ISO 8528-6:2023 – Test methods
Outlines general test methods for generator sets, ensuring consistent performance evaluation.
ISO 8528-7:2017 – Technical declarations for specification and design
Provides guidance for the technical declarations needed when specifying and designing generator sets.
ISO 8528-8:2016 – Requirements for generating sets driven by reciprocating internal combustion engines for emergency power supply to safety services
Focuses on requirements for emergency power supply generator sets.
ISO 8528-9:2017 – Measurement and evaluation of mechanical vibrations
Specifies methods for measuring and evaluating mechanical vibrations of generator sets.
ISO 8528-10:2022 – Determination of sound power levels
Details procedures for determining the sound power levels of generating sets.
ISO 8528-12:2022 – Emergency power supply to safety services
Specifies requirements for generator sets providing emergency power to safety services.
ISO 8528-13:2016 – Safety
Addresses safety requirements for generator sets and their components.
This structured approach ensures that every aspect of generator set design, installation, and operation is covered, giving consultants and specifiers in Singapore the clarity and confidence needed to deliver compliant, reliable power solutions.
Debunking Common Myths
A persistent myth in the industry is the requirement for a “0–100% load test” during generator commissioning. Many tenders still call for this, but ISO 8528-5 actually specifies step load testing—not an instantaneous jump from zero to full load. In fact, the standard focuses on a generator’s ability to handle sudden load increases in defined steps, measuring transient response and recovery times, rather than demanding unrealistic and potentially damaging test conditions.
What’s Really Needed for Compliance?
To meet ISO 8528 requirements in Singapore:
- Step Load Testing: Generators must demonstrate their ability to accept load in increments (e.g., 25%, 50%, 75%, 100%), with performance measurement at each stage.
- Performance Documentation: Detailed test results, including transient response and voltage/frequency recovery times, must be recorded and submitted as part of the compliance package.
- Third-Party Verification: For critical projects, independent audits or factory acceptance tests (FAT) may be required to validate compliance.
By understanding the true requirements and specifying them correctly, consultants can avoid unnecessary costs, prevent equipment damage, and ensure smooth project approvals. At Power Partners Group, our deep expertise in generator system design and testing helps clients navigate these complexities and deliver fully compliant, audit-ready solutions.
Tender Myths vs Reality
Tender specifications for power systems in Singapore often cite international standards, but misunderstandings about what these standards actually require can lead to confusion, unnecessary costs, and even project delays. Therefore, it is crucial for consultants and specifiers to distinguish between common myths and the real, enforceable requirements—especially when it comes to generator set testing and compliance.
Common Myths
0–100% Load Test is Mandatory
Many tenders still call for generators to be tested by jumping instantly from zero to full load. In reality, ISO 8528-5 specifies step load testing, where loads are applied in increments (such as 25%, 50%, 75%, and 100%), not all at once. Instantaneous full-load jumps can be unrealistic and may risk damaging equipment.
Any Test Method is Acceptable
Some believe that as long as a generator is tested, the method doesn’t matter. ISO 8528 outlines specific procedures for performance, transient response, and recovery—requiring detailed documentation and adherence to standardised protocols.
All Generators Are Automatically Compliant
Not all generator sets on the market meet ISO 8528 requirements. Compliance must be demonstrated through certified testing, proper documentation, and, where necessary, third-party verification.
The Reality
Step Load Testing is the Standard
ISO 8528-5 mandates that generator sets are subjected to stepwise increases in load, with performance measured at each step. This approach ensures the generator’s ability to handle real-world operational demands while protecting system integrity.
Detailed Documentation is Essential
Compliance isn’t just about passing a test—it’s about maintaining accurate records of test results, performance data, and any corrective actions taken. These records are often reviewed during audits and can be decisive for project approval.
Specify What’s Achievable and Compliant
Consultants need to ensure that tender documents reflect the true requirements of ISO 8528, avoiding over-specification or unrealistic demands that can inflate costs or delay delivery.
By separating myth from reality and aligning specifications with the actual standards, consultants and specifiers can streamline project delivery, avoid disputes, and ensure that power systems are both compliant and reliable from day one.
How PPG Supports Your Compliance Journey
At Power Partners Group (PPG), we understand that achieving and demonstrating compliance in Singapore’s demanding regulatory environment is a complex, high-stakes challenge. That’s why our approach goes beyond simply supplying equipment—we partner with consultants, specifiers, and end-users at every stage of the project lifecycle to ensure seamless, audit-ready compliance.
Ready to Ensure Compliance? Let’s Talk.
Navigating Singapore’s complex landscape of power system standards doesn’t have to be overwhelming. Whether you’re a consultant, specifier, or project manager, Power Partners Group (PPG) is here to support your compliance journey from design to commissioning.
Stay ahead of the curve. Partner with PPG for compliant, future-ready power solutions.
P.S. Stay tuned for our downloadable guide on power compliance, which comprehensively touches on ISO 8528, 22301, TIA-942 & more.