The power of insurance
Peter Duncan, a director of Cressall Resistors discusses the importance of frequent testing of generating sets using load banks
When I came to write this article, it occurred to me that if power outages were more common, the value of a standby generator would be more clearly understood in both the built environment and industry. The black-outs in New York and London several years ago were clear reminders to us all, but my perception is that since then the profile of this corner of our industry has dipped. Not so. A Google search reveals seven separate incidents in the seven days before the time of writing – and these are on the first page of search results alone. However, only two of these mention standby power. It seems that while we may not have forgotten the consequences of losing power, we may have forgotten the power of insurance.
For many years it has been routine for all newly-installed generating sets to have a load test during the commissioning process in order to prove the performance of the set and all its ancillaries – the cooling system, exhaust system, switchgear and protection scheme. However, the very infrequency of power outages in most developed countries, and thus the rarity with which standby sets are called on to run ‘for real’, makes regular proving essential if sets are to operate reliably when needed.
When using mobile equipment, these tests have traditionally been performed by contractors who visit the site, bringing with them a portable load bank. However, we have recently seen instances of very high profile financial and telecoms firms investing in their own portable load banks and in many cases still using the same contractors to test. Added to those instances of fixed loadbanks for routine testing we have always seen, it is clear that most high profile companies now put their trust in regular testing of standby power. A big step forward from the days when testing would only be performed on installation.
Indeed, for any standby generating set, routine testing can have maintenance savings that outweigh the cost of the test itself. Smoky exhausts, carbon build-up, fuel system problems and lubricating oil deterioration, all of which decrease reliability and add to running costs, can be avoided by regularly running the device at 40% of its maximum load. In some cases there is a further benefit because the load bank can act as a ballast load during normal operation.
Cressall Resistors’ load banks for fixed installations are designed as a bolt-on addition to the set, requiring a space of only 400 – 800 mm between the radiator and the acoustic splitters. The resistor elements themselves are type HPR stainless steel grids. These have a large surface area, with a typical power density of only 1-2W/cm2 and a very low pressure loss: about 10-20 Pa (1-2 mm water gauge) in the radiator airflow. The grids are assembled in banks with ceramic insulation rated for 1kV operation. Because the load bank makes use of the radiator airflow for cooling, the basic design is simple, low-cost and adaptable to almost any engine. Most standard generating sets in the 50-1000kW range, have radiators with a free pressure loss of at least 125Pa, so a load bank can be added without the need for modifications to the basic design or an increase in the rating or cost of the acoustic splitters.
Where power ratings of more than 50% of a set’s capacity are required, or where a single load bank is installed to serve multiple generating sets, other cooling arrangements can be used. Cressall has even arranged for cooling systems to use the existing plant room fans.
Cressall’s latest stand alone load bank, the AC100, is designed for testing three phase generating sets of up to 100kW rating. It uses metal sheathed wire elements manufactured from high-grade nickel/chrome resistance wire in magnesium oxide insulated stainless steel tubes and 600V primary insulation. It is fan cooled with a single 450mm fan powered from the test load itself or an external supply. The fan is mounted in the base of the load bank and blows vertically through mesh bird screens at the top and bottom.
One Cressall customer using the AC100 is Jersey based Computer Protek Systems (CPS), a contractor servicing the island’s huge financial industry. According to CPS’ Martin Cruickshank, one of the biggest benefits of the AC100 is the unit’s rugged construction. “Aside from the fact that the AC100 is completely plug and play, and thus very simple to use, we benefit from the fact that its looks totally suit the requirements. Half of a client’s initial confidence is inspired by appearance, it’s only later when they come to trust you that it’s your reliability and skill they believe in,” he explained.
I began this article by comparing frequent testing to insurance. However, there are some subtle differences. Insurance is generally recognised to mean the process of making a regular payment to a trusted third party so that that third party will in turn cover any significantly higher payments should an unexpected problem arise. However, regularly running a genset using a loadbank is subtly different. While it can incur a regular cost, if you opt to hire a contractor to do it for you, there is no third party that will compensate you should the unexpected happen. Instead you are mitigating for that unexpected event – in the instance of a power outage your business, your data and your customer’s data will be safe. If I could get insurance like that in my day to day life, I wouldn’t think twice.