Load bank testing benefits those with critical power needs
Load Banks are devices designed to provide electrical loads for testing power sources such as generators and UPS’s. They provide a stable, continuous and variable load, which imitates real loads in real-time.
Generators are installed as emergency standby systems in the event of mains failures, while UPS systems run from the mains supply with a battery to provide power when the mains supply fails Image the disuption that would occur if this equipment did not function correctly when there was a power failure.
Routine testing of generators and UPS’s gives peace of mind in the equipment's ability to perform. It is a vital task to ensure that a generator and UPS remain in full working order. Full resistive Load Bank testing plays a critical part of any scheduled service and maintenance routine.
Businesses that have critical power needs such as hospitals, financial institutions, computer data centres, and manufacturing plants, inparticular, would benefit greatly from Load Bank Testing.
Fully loading the Standby Power Systems (SPS) stresses all its components. It is, therefore, preferable to identify any potential weakness under controlled conditions than to wait until the system is supporting a critical load. It is also cost effective to take advantage of the expertise and experience of specialist service providers such as Merlin Power Management
Testing methods
There are a number of ways of testing SPS systems, including some that use the electrical load connected at the time of the test. The advantage of this is that the device is tested in operation performing as it would in an emergency. However, there are some circumstances whereby loads are only connected to a generator or UPS after the mains supply has failed. In such circumstances, additional loads may be imposed on the devices, which may cause problems that are not apparent under ‘normal’ operating conditions, e.g. the air conditioning and the UPS battery.
An alternative, and more accurate method, is to test the system to its design specification. Modern load bank systems are now available that use the latest technology and collect the test results and analyse the data against the standards, giving simple reports showing the pass or fail criteria.
Diesel generator
When a diesel generator is operated at below its design load, carbon deposits build up on the pistons and exhaust system and the cylinders become ‘glazed’. The results of this build-up are a reduction in output power, an increase in fuel consumption and possible overheating and auto-shutdown. One way of removing the deposits and reducing the cylinder glazing at the same time is to test the generator by running it at full load in a controlled situation for a set period. In the case of a diesel generator this may be up to 3 hours at 100% load with a further overload test at 110% for a short period.
The alternator and control systems are checked and the voltage and frequency monitored and recorded to confirm the output is within specification. This type of testing will also identify any weaknesses in the systems and allow repairs or modifications to be carried out before the system fails under emergency conditions.
Testing should be undertaken approximately every 12 to 18 months, depending on individual site conditions and customer operational practices. It should consist of a site survey and positioning of the Load Bank as well as site logistics including road closures, craneage, etc., as necessary.
Following testing the Load Bank should be disconnected and removed and the mains reconnected to the normal load. A detailed report would then be issued giving full information on all load acceptance and rejection tests.
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