[generatorguy]

Electrical Engineers would determine the settings for the electrical protection of a generator. Mechanical Engineers would determine the settings for mechanical protection of a motor. To operate the equipment beyond thresholds would result in reduced lifespan or immediate and permanent damage to the equipment. If this is what the customer requires they have to specify that to the Engineer so that when the equipment blows up the Engineer is not liable.

Diesel generators for hospitals and water pumps for fire suppression systems are generally set up with very loose settings as it is clearly worse for a patient to die or a building to burn down than to destroy a machine, and this requirement is in the specifications.

[brudgers]

Diesel generators for hospitals and water pumps for fire suppression systems

Those systems also require regular testing by qualified personnel. NFPA 25 requires monthly testing of fire pumps and annual flow testing. For low rise buildings with inadequate municipal water pressure, a water tower might be cheaper and easier. NFPA 99 - Standard for health care facilities, requires emergency generators to be tested 12 times per year.

[generatorguy]

The testing would consist of running the diesel generators under load but not operating in abnormal conditions.

[bluGill]

True, but the easiest test is to pull the main power to the hospital and watch the system automatically take over. If anything fails you know what is wrong. This is scheduled so that those in surgery (or other worrisome situations) have extra help and can signal get back to mains power now.

[generatorguy]

ideally the hospital’s generator control system or transfer switch is able to start and synchronize the generators and turn up the throttle until no power is being imported from the utility prior to opening the utility feed, thereby transferring the load from the utility to the generators. This test is only performed when there are no surgeries scheduled and it is cancelled if there are any emergencies coming in all of the sudden. If the test is already in progress incoming ambulances with patients requiring surgery are diverted to another hospital. To finish the test the hospital is synchronized to the utility, the throttle on the generators turned down until no power is flowing through the generator breaker which is then opened.

I’ve built and programmed control systems that do all this with multiple generators, multiple utility feeds, and multiple tiers of loads of different priorities.

[jimmygrapes]

That is a good way to test the generator without interruption, but at some point you still need to test the ATS under real world circumstances: unstable or suddenly missing utility power. Throwing the main covers one of those, and the other requires a little more planning and resources.

[generatorguy]

Honestly I am struggling to remember an instance where we purposefully plunged an operating hospital in to darkness.

You can test the system’s ability to detect loss of power or poor quality power by lifting sensing wires or injecting out of frequency or voltage range power with a test set, and load pickup and load testing we used a load bank. The actual hospital load is fed through bypass breakers during these tests so if the utility went out we would have to manually operate breakers to disconnect the load bank and swing the vital loads over to the generators.

If I am setting up electrical protection on a generator I don’t put a short circuit on the generator, I show the protection relay what it would see by injecting current and voltage with a relay test set and make sure the relay gives the signal to open the breaker when it should.

Greenfield hospital generation sites are straightforward to open the utility feeds since the vital loads are still fed through the old power system.