Medium voltage UPS repair, refurbishment and service: keeping a facility-scale UPS on duty for decades

A medium voltage UPS protects a whole site, not a server room: the factory, the fab, the hospital, the data hall and everything that feeds them. When it fails, the site has no ride-through, and the replacement conversation starts with a lead time of years and a civil works budget. Most of the time that conversation is unnecessary, because what has failed is a battery string, a capacitor, a fan or a control board, and all of those can be put right with the system where it stands.

This page is for the people responsible for large UPS systems: facility and plant managers, data centre and manufacturing operations leads, and the contractors who maintain them. It covers what we repair, refurbish and service on medium voltage and large low voltage UPS systems, from any manufacturer, and how to start.

What we do

Battery string replacement and qualification. A tired string shows up as shorter ride-through, failed equalise charges and battery alarms. We replace strings in lead acid or lithium iron phosphate, and where the original module is no longer made we qualify the replacement against the system rather than buying on voltage alone, as our Kokam battery replacement work describes. Old cells go to recycling; module steelwork is reused where its condition allows.

Power module and capacitor repair. DC link, filter and snubber capacitors dry out with age and heat. A vented capacitor is the first thing we look for when a module trips or a unit derates. Modules are repaired at component level in our workshops or exchanged for a refurbished, tested unit so the system is back on line while the original is repaired.

Control and monitoring upgrades. Many facility-scale UPS systems still run monitoring computers on operating systems that have been out of support for years, with remote access designed around a modem. We move the site-specific control software onto current, supported hardware and recommission the system against its original acceptance performance.

Cooling. Blocked filters, failed blowers and air conditioning past its service life show up as over-temperature alarms on the static switch, the transformer compartment or the inverter. We service or replace, and we check the ventilation was sized for the site it is actually in.

Static switch and connections. Shorted thyristors, worn breakers, loose connections that arc. Remade, retorqued or replaced, with the protection settings rechecked.

Testing, commissioning and maintenance contracts. Factory and site acceptance testing at full load, quarterly and annual maintenance to the original schedule, condition data on batteries and capacitors, and a named engineer who knows the system.

Medium voltage is the part nobody else does

Every UK UPS repair firm we can find works below one megawatt: rack and room UPS for IT loads. A medium voltage UPS is a different machine. It sits on the distribution network at 4 to 25 kV, protects everything downstream at once, and is an offline design: the utility feeds the load through a solid-state switch while a disturbance monitor watches the supply, and when the voltage steps outside limits the batteries take over within one to four milliseconds, under a quarter of a cycle.

We design and build these systems, from 250 kW low voltage units to medium voltage systems of more than 20 MW, and we service the installed base, including fleets whose original manufacturer no longer supports them. For the PureWave range, which we own, see our PureWave DSTATCOM, UPS and AVC support page (not yet live). For the trade-offs between medium and low voltage protection, our comparison article (not yet live) covers the choice; our UPS product page covers the new-build platforms.

What typically fails on a UPS of this age

Some systems we maintain are 25 years old and still carrying critical load. Where the condition supports it, refurbishment reuses the existing structure, recycles what it replaces, and costs a fraction of a new system. Where it does not, we will say so and build you a new one.

How it works

1. Send us the nameplate and the fault. A photo of the nameplate, usually inside the control bay door or on the enclosure, and a line on what happened: the alarm on the screen, what the unit did, when it started. An engineer replies within one working day with what we would check first and whether a site visit is needed.
2. Diagnosis and a written quote. Where the cause is unclear, we start with power quality root cause analysis at the connection point, because a UPS that keeps transferring may be responding correctly to a supply problem. You get an itemised quote before any work starts.
3. The work. Batteries and modules in our Wisconsin or Leicestershire workshops or on site during a planned outage. Refurbished parts are tested and warranted.
4. Testing and handover. Full-load testing against the original acceptance performance, and a maintenance schedule so the next call is planned rather than urgent.

Is your UPS tripping, transferring, or out of support? Send a nameplate photo and a line on the fault to sales@renewable-d.com, or call +1 414 562 6559 (US) or +44 116 279 6131 (UK). An engineer replies within one working day.