Testing times: will the power come on when it counts?

Emergency backup systems need to be ‘kept in shape’ so they work when called on

Testing and maintenance can mean the difference between well-functioning or failing emergency power applications. Faced with economic pressures, are mission critical organisations giving testing and maintenance the investment it deserves?

In the worst-case scenario, inadvertent power supply failure can be a matter of life or death. In hospitals, for example, outages may mean the loss of respiratory devices and other critical equipment for patients in intensive care, neonatal or cardiac units; or the loss of life-support systems and monitoring equipment during high-risk surgical procedures.

Healthcare providers were recently reminded of the importance of ensuring the reliability of their emergency power systems when the Royal Victoria Hospital in Belfast experienced a 10-minute delay in one of its backup generators starting up during power cuts. The investigation into how this happened and whether it had any impact on patient care is currently ongoing (source: BBC, 28 February 2017).

Data centres are another industry example where there is a need for reliable emergency power and where the financial costs associated with downtime can be extremely high. However, suppliers of control systems for decentralised power production often meet customers who do not follow industry recommendations on how to test and maintain their emergency power plants.

“Perhaps it is a consequence of the economic crisis, but we often talk to companies that simply skip testing and maintenance of their emergency power plant, yet this is crucial,” comments Henrik Rødtnes, from Deif UK.

Emergency power systems need to be ready to take over power at all times, and when the power returns the emergency power system must transfer the load back to the grid without interruptions and remain on standby for the next grid failure.

In principle this is as simple as it sounds – but only when it works. The problem is that emergency power systems require regular maintenance and test runs to ensure they work properly.

“During the past six to eight years, faced with economic pressures, many companies have seen severe cutbacks which have also affected their financial ability to maintain emergency power systems. ‘As long as it runs, why do more?’ is the attitude of some. But a failing emergency power plant can result in a massive loss.

“For smaller companies, the loss could well be devastating. At hospitals it can be fatal – so investing in the insurance (which is what an emergency power plant really is) makes good sense,” says Rødtnes.

In addition to supplying emergency power, generator plants are also used for grid support in geographies around the world. In addition, with prices fluctuating during the day, it has become feasible to use diesel generators when prices are peaking,” says Deif’s Rene Kristensen.

In the UK, demand side response (DSR) technologies help National Grid to manage peaks and troughs in electricity supply and demand – for example, when a power station fails – and in the process help to reduce UK carbon emissions and provide a more robust grid.

With the new government incentive scheme recently launched for DSR, awareness campaigns have been suggested for businesses to take part in DSR schemes that can provide significant revenue and cost saving opportunities.

There are several factors at work – older, generation power stations are closing down and National Grid has committed to 30-50% of grid balancing requirements being met through DSR by 2020.

KiWi Power (a UK DSR aggregator) and Deif UK have successfully completed the frequency injection test required by National Grid at a major London financial institution. This test demonstrates their site’s ability to respond automatically, within seconds, to balance the grid. Successfully completing this test now enables the company to take part in a fast response DSR programme managed by KiWi Power on behalf of National Grid.

Keep your plants in shape 

Emergency power systems can be designed in many ways but, in general, they include a UPS (battery or rotating), which supplies power to the servers, machine plant operating systems and operating rooms in hospitals. The UPS is often supplemented by a diesel generator, which provides energy partly to the UPS, and partly to the operation of production facilities.

The challenge is that the plants are idle most of their life and therefore need to be ‘kept in shape’. But what does it take to ensure that the emergency backup system works when it is needed?

“All mechanical components containing moving parts must be used regularly in order to make sure they do not become inoperative and faulty,” Rødtnes says.

“Therefore, it is essential that all contactors and breakers are tested and lubricated at least every third year. The lubricating agent becomes harder over time and, worst case scenario, the breakers cannot be closed quickly enough, thus risking getting out of phase and short circuits.”

The start batteries of the generator plant constitute another area to be checked to ensure correct startup of the plant: “A measurement of the battery voltage during startup can reveal if problems are on the way – such functionality can be integrated in some controllers available on the market today, including Deif’s,” Kristensen adds.

“Our AGC Automatic Genset Controller, for instance, has a standard battery test feature capable of detecting ‘bad’ batteries. The controller simply turns the genset starter for example 20 seconds without activating the fuel pump. Using predefined ‘Bat. Voltage OK’ limit values and time delays, the controller measures battery voltage and triggers an alarm if the settings are exceeded.”

Three kinds of testing

In Denmark, it is also possible to use the grid as the load for test runs and it is therefore a good idea to run the generator at 75-80 % of max for an hour or so once a month.

Kristensen says: “We recommend performing three tests: 1) cut off the external power supply without synchronisation to simulate a real grid blackout ; 2) test a controlled island operation where you start a generator and synchronise with the grid, deload the mains breaker and go into island operation with your generator without blackout or power interruptions. Then you synchronise with the external supply and shut down the generator;  3) a parallel test stressing the generators with 75 to 80% of their maximum capacity without shutting off the external power supply.”

Rødtnes adds: “We often talk to customers who are afraid of testing their emergency power systems, which is a concern. One of our customers, a large data centre, cuts off the grid power once a month letting its own emergency power system take over the supply. But this is rarely seen. On the contrary, we often encounter companies who are reluctant to test just a part of their emergency power systems.”

Remote testing 

Deif recommends regular testing of the different sequences that are part of an emergency situation: “When we deliver emergency power solutions, we always train our customers in handling the situations that will put the system into operation. Customers need to become familiar with pushing all buttons. Examples include cutting off the grid power completely, or running the system in parallel operation for a period of time,” says Kristensen.

“Today, the test can be performed remotely. This is helpful if clients have a large number of emergency power systems placed at different locations, because they can monitor, manage and test functionality from one central location. Via an integrated timer function in our AGC genset controller, we can perform automatic tests – for instance once a week – and log the results within the controller. Particularly interesting for telecom sites and other sites in remote locations, starting the test sequence can also be done from a remote location, typically using either a VPN connection or a GSM modem.

“In many countries the uptime on the national grid is very high, making some ‘neglect’ the importance of their backup power. But as most know, a chain is only as strong as the weakest link – if you make that link your emergency power system, it may prove costly.

“We recommend creating solid testing procedures and intervals to ensure a fully operational system at all times,” Rødtnes concludes.


Maintaining and testing of emergency power and generator sets


• Preheating: every day

• Oil, cooling water, fuel: once a month

• Start battery (fluid level): every six months


• Contactors/circuit breakers: at least every third year

Replacement of

• Engine oil, oil filter, fuel filter, air filter: annually

• Start batteries: every five years (or as needed – measure battery voltage during startup)

• UPS batteries: depending on the make and type of each third to fifth year

• Measuring relays on contactors/switches: every 10 years

• The genset control system: every 10 years

• UPS systems, electronics: every 10, 15 or 20 years depending on the manufacturer and type

Test runs

• Load test – generators loaded up to 80% of capacity, without interruption of the external power supply; power from the generator is exported to the grid: once every month

• Partial test, synchronised switching on and off the generators: once a week for 10 minutes

• Full test, interruption of grid supply without synchronisation: once a month (one hour test)



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