Load bank for DG set Testing

It depends on what you are testing.

If you wish to test simply for endurance with a purely resistive load. Then No.

If you wish to test the Gensets ability to support the load under varying Power Factors, a reactive loadbank is what you require.

Regards,
Sapper

Thanks for your reply.

What is the necessity to check the capability of DG set under varing load?

Is there any operational difference for resistive load & reactive load?

Power output from engine will be same irrespective of type of the load.

A load bank is required primarily to test the engine not the generator because no-load test is detrimental to the engine in the wet end. As a result useful life of the engine will be reduced.

You could go for readily available dry-resistor load bank or indigenous electrolitic brine load bank.

Yes and No....While I agree with your comment in regards to looking after the Primemover "Wet End" that is not the only reason for a Loadbank on a Genset.

All Generator behave differently under different load conditions and a loadbank which can generate leading and lagging power factor load profiles will provide a more conclusive test of the generator ability to cater to the standing load.

Regards,
Sapper

No building load is purely resistive. Motor loads and electronic loads vary the power quality and must be tested during gen-set and UPS commissioning and validation. I hope the following helps you understand the requirements.

From Wikpedia:

Reactive load bank

A "reactive" load includes inductive (lagging power factor) and/or capacitive (leading power factor) loads.

Inductive loads, the more common type, consist of iron-core reactive elements which, when used in conjunction with a resistive load bank, create a lagging power factor load. Typically, the inductive load will be rated at a numeric value 75% that of the corresponding resistive load such that when applied together a resultant 0.8 power factor load is provided. That is to say, for each 100 kW of resistive load, 75 KVAR of inductive load is provided. Other ratios are possible to obtain other power factor ratings. Inductive loads are used to simulate real-life mixed commercial loads consisting of lighting, heating, motors, transformers, etc. With a resistive/inductive load bank, full power system testing is possible, given the impact of reactive currents on generator/voltage regulator performance as well as effects on conductors and switchgear.

Capacitive load bank

A capacitive load bank is similar to a reactive load bank in rating and purpose, except leading power factor loads are created. These loads simulate certain electronic or non-linear loads typical of telecommunications, computer or UPS industries.

I think we are having this conversation backwards.

Testing should be the result of finding out that the equipment provided is in good working order to perform its duty when called for. If you are wondering why there were certain tests being performed on a schedule, and you want to eliminate it due to costs or some other influence. Then you need to ask yourself, what is the operation parameters of this generator? Then, what kind of testing do I need to do to it in order to insure its functionality?

No matter how you look at it it always goes back to the function of the equipment itself.

We as outsiders can't answer that question due to the lack of information at hand. If your firm does not have engineers or technicians that can answer your questions. It would be a good idea to hire outside sources to completely research your question before you make a decision to eleminate testing. Otherwise you are setting the equipment up for failure when you need it to perform.

Hi Lajendra,

Load banks are applied to DG to correct the effect of WET STACKING on DG. The Wet stacking is normally caused by prolong running of DG under partial loading, ie <40% of its capacity.

When DGs operate below 40% capacity, the engine temperature do not rise to a level that will burn all fuel injected to the combustion chambers. This will result also in higher diesel consumption by the DGs, evidence of this can be seen by the accumulation of black ooze round the exhaust pipe. As such, the resistive load bank will serve your purpose.

However, you should be careful on the size of the load bank in order not to impair your engine.

Technical Note - Load Bank Testing - DG SETS

Load bank testing during the commissioning process ensures that standby power systems operate as designed.

Emergency and legally required electrical systems and critical installations require load bank testing of standby power systems during the commissioning process to ensure that the complete systems will operate as designed in the installed location. These test requirements are typically spelled out in electrical engineering specifications for optional loads and can be a requirement of local authorities having jurisdiction for standby power systems that provide power to code-required life safety and legally required standby loads.

Generator exercising can be programmed into the automatic transfer switch (ATS) to automatically start and run the standby system at predetermined times. If the loads to be served cannot endure a brief outage during transfer and retransfer between sources, a load bank can be used to isolate the generator from the electrical distribution system during testing. Fixed systems can be configured to switch stepped amounts of resistive loads to simulate varying levels of real system load. Extended no-load testing not only can damage the generator's engine, but also result in wet stacking and carboning. It is important to have a long-term generator testing plan in place at the turn over of a project.

Some electrical engineers provide specifications to provide both a resistive and a reactive load bank test in the field. In many systems, I think this form of testing is not necessary; it's overkill. This is especially true when the manufacturer provides a reactive and resistive load bank test in the factory before shipping the generator to the site. It is important for the engineer or commissioning agent to review the factory test prior to witnessing the field testing.

Resistive load bank is the most common form of load bank testing of generator systems. These load bank systems will provide a test of the rated KW. Testing the generator at the rated kW will test the engine cooling system, the fuel system and the exhaust system.

Most specifications contain text similar to the following:

Although the typical generator will be tested in the factory before shipping to the site, actual load bank testing of the generator is critical to ensure that it will properly operate at the installed location. The generator system can be significantly affected by the altitude and ambient temperature. These parameters can be adequately tested with a resistive load bank test only.

You can't see the advantage of a field reactive load bank test in addition to a factory reactive load bank test

Load bank testing is an important criterion for ensuring proper operation of critical generators. It is typically recommended to exercise the engine monthly with a minimum load of 30% of the standby power rating or loaded to recommended exhaust stack temperatures. Generators tested at no-load or loads less than 30% of standby rating for long periods of time can develop wet stacking or carboning caused by incomplete combustion and incomplete burning of fuel. This potentially leads to generator malfunction and failure.

What does it say in the Operation and Maintenance Manual? It can't be seen from here. If it isn't to hand, then contact the original equipment manufacturer and obtain a replacement. Telephone?