How reliable is the Dutch power supply? This is something that most organizations never consider. And if they do, their answer is probably ‘stable enough’. The Dutch electricity network is known for its high reliability! Even so, there are occasional fluctuations. And as the Jeroen Bosch Hospital in Den Bosch discovered, small deviations can have large impacts. Entire systems could and did shut down. How was that possible? More importantly, how could a repeat of that situation be prevented? Our assessment (a first!) provided answers.
Rest assured, by and large the Dutch power supply truly is stable. Even so, small fluctuations in the high and medium voltage range occur more frequently than most people think. For the average business this is of no consequence and they can keep conducting business as usual. But a hospital is different. The Jeroen Bosch Hospital in Den Bosch recognized this, took precautions, and connected its critical medical equipment to an emergency power supply. Minor disruptions and deviations in the power supply could still shut down other systems, though, and the effects would ripple out. In one instance, the air treatment and other control systems had to be restarted. The result: a down time of several hours and cases of postponed medical treatment.
Overzealous transfer switches
The electrical 10 kV power supply employed at the hospital consisted two main distributors: one for critical equipment and one for all other systems. The voltage was constantly measured by transfer switches that were connected to the central PLC. And although the transfer switches were operating within specs, they were unable to differentiate minor issues and genuine hazards, based on the duration and magnitude of a surge or sag. As a result, the switch would occasionally cut off grid power due to sags that should have been within a tolerance envelope. We added some logic to the transfer switch so that it could properly classify ensuing issues. Our solution was to use a universal 10% setting (within the parameters of all connected equipment) in combination with a time delay. That is, don’t disconnect for very brief voltage sags (under 1 second) that are under 10%. Otherwise switch to backup power. Ben van der Linden, Technical Service Coordinator at the Jeroen Bosch Hospital, is pleased with the results of the power assessment and, more importantly, with the improvements that became possible: “Power sags were giving us problems several times per year. Together with Energy Solutions Center and Schneider Electric we finally found out why. We’re very happy with the advice they provided, as we could finally fix the problem. And it hasn’t occurred since.”
Energy Solutions Center