Voltage optimisation – Call centre installation
For this job we were faced with a classic Catch 22. The site was a critical call centre, where the power could not be turned off; however, to complete our works we had to turn the power off.
So how could we turn off mains voltage whilst keeping the call centre powered up and operational?
To compound the problem, the site had three sections of main switchgear (used to isolate electrical equipment), supplied from 2no transformers – and all of this equipment was on the sixth floor of the building.
First we had to check the operation of the switchgear. The automatic controls between an old onsite generator and the mains supply had been modified when the generator had been removed and replaced with a rotary UPS.
But with no drawings and no accurate records, no one was sure how the switchgear now operated.
We arranged for the manufacturers of the main protective devices to attend site whilst we checked the operation of the switchgear. As the call centre had to remain operational, we worked with the Regional Network operator to use existing switchgear bus-couplers to parallel supplies temporally, whilst opening main incoming devices one at a time.
This process was repeated for all the main switches on the switchgear, allowing us to carry out a much-needed service to the switches at the same time. We also removed the automatic controls, which should have been taken out long ago when the switchgear was modified.
Next, we created a detailed ‘switching schedule’ showing how we would carry out the work; by following this we could ensure that the works were correctly planned and executed.
A few weeks later we returned to carry out the work. Temporary generators were connected into spare outgoing ways of the switchgear to parallel with the mains supply. This ‘syncing’ of the generator with the mains supply was carried out by Golden Triangle Generators and allowed us to turn off the mains whilst the generator supported the site.
The mains supply was turned off – and the call centre never even knew about it.
We carried out our work safely, then returned the following day with the site still supported by the temporary generators.
We powered all our work including the new Voltage optimisation units back to the switchgear. However the generators now needed to be paralleled back with mains so that we didn’t turn off the power to the call centre. Using a ‘back syncing’ method, the Golden Triangle Generators were able to slow or speed up the generator until it matched the mains exactly.
The main switch was closed and then the generator switch opened to return the site back to the mains. Again, the call centre was able to continue operating smoothly with no knowledge of the work.
Another success story from AES!
The cable which needed to be connected with the mains power isolated
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