27 February 2020

When an obsolete Unitrol M Excitation Control System failed in service at Nottingham based, low carbon focussed district heating suppliers Enviroenergy, Quartzelec, the independent engineering service provider that’s globally recognised as an expert in rotating electrical machines, was quickly appointed to deliver a full solution that has supported a 20% increase in efficiency improvements.

Following the system failure, an urgent repair / replacement was required with Quartzelec being awarded the contract to upgrade the Excitation Control System on a 12635 kVA, 11kV, 4-pole generator.  Instigating an immediate temporary solution was critical with Quartzelec installing a DECS250 module into the existing scheme, replacing the Unitrol M modules and ultimately restoring generation.

A subsequent failure occurred when the existing Synchrotact synchroniser also failed on a return to service following a trip. The solution was to replace this module with Deif auto and check synchronisers.  These replacements however left vulnerabilities within the system, as other obsolete and ageing components were still in use. Quartzelec responded by designing a bespoke replacement solution to meet the clients’ exacting requirement.

“It was important that we delivered immediate support to ensure Enviroenergy remained operational, but our focus quickly turned to developing a bespoke replacement system that was compliant with today’s safety standards and would be robust enough to deliver reliable operations moving forward,” stated Pete Stuchbury, Quartzelec’s Sales Manager responsible for AVR/Excitation System Upgrades.  “Whilst our 'repairs' were successful in enabling the customer to continue operations, a considerable amount of obsolete and ageing equipment remained in use and needed replacing to ensure full availability, moving forwards, could be guaranteed.”

A full upgrade was performed delivering a dual channel DECS 250 also incorporating; full PLC control with HMI for metering, status alarms, trending and control.  Due to Control Room layout and access, the existing cubicle chassis had to be re-used; stripped out with back and side plates replaced, and a new door provided.  A complete new set of documentation was also provided including general arrangement drawings, electrical diagrams, terminal arrangement, bill of material and technical manual.

“We are delighted with the entire AVR project from start to finish,” confirmed Alan Fletcher from Enviroenergy. “The guys in the control room have also been extremely complementary about the install and the finished article. The upgrade, along with a number of other improvements carried out in parallel, has resulted in an efficiency improvement at the site of more than 20%."

Enviroenergy is one of the first district heating suppliers in the UK, managing low carbon energy production, supply and billing for domestic and commercial customers across the UK.

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