S&C PureWave DSTATCOM, UPS and AVC: spares, repair and upgrades

If you run an S&C PureWave DSTATCOM, a PureWave UPS or a PureWave AVC, you own a good piece of equipment with a problem attached. The company that built it stopped making the line in 2018, and the number on the door no longer leads to a factory. Renewable Energy & Drives (RE&D) owns the PureWave technology today, and we support the installed units: spares, board repair, control upgrades, on-site rebuilds and service contracts.

This page is for the people who own or look after those units: utilities, wind farm operators, facility managers at factories and data centres, and the contractors they call when something trips. It explains what happened to the product line, what tends to fail on units of this age, and what can be done about it without buying a new system.

What happened to the PureWave line

S&C Electric Company built the PureWave family through the 2000s and 2010s: the DSTATCOM for grid voltage support, the UPS and UPS XT for whole-facility backup power, the AVC for factories with fast-changing loads, and the SMS storage management system for battery projects. In early 2018 S&C announced it would stop manufacturing the whole PureWave range and concentrate on integrating hardware built by others. The UPS and storage products now sit on S&C's discontinued products page with no successor and no parts path listed.

The equipment did not stop working when the production line did. More than 500 MW of PureWave DSTATCOM capacity was installed on wind farms in the UK and Ireland alone, and PureWave UPS systems went into factories, hospitals, laboratories and data centres around the world. Most of it is still in service and still doing the job it was bought for. What went missing was the support path: drawings, programmed spare boards, firmware, and people who know the product.

That is where we come in. RE&D acquired the PureWave technology and now publishes the instruction sheets, holds the design documentation, and builds and services the line from our facilities in Leicestershire and Wisconsin. If the nameplate says PureWave, it is ours to look after.

The three product families

PureWave DSTATCOM. A distribution static compensator: a container of inverters that pushes reactive power into the grid or pulls it out, within a few thousandths of a second, to hold voltage steady. Wind farms use them to meet the grid code at the connection point; utilities use them to stop voltage sagging on long lines. Each container is rated up to plus or minus 10 MVAR in 1.25 MVAR steps, connects at 480 V through a single step-up transformer to systems up to 35 kV, and can deliver 264 percent of rated output for two seconds when the grid needs a hard shove. Up to four containers can be paralleled. If you are weighing a DSTATCOM against a static VAR compensator for a new site, our STATCOM vs SVC comparison covers the trade.

PureWave UPS and UPS XT. Uninterruptible power supplies that protect a whole facility rather than a single room. The low voltage range runs from 250 kW to 1,000 kW at 208 to 600 V; the medium voltage UPS runs from 2.5 to 20 MVA at 4 to 15 kV; the UPS XT extends that to 25 MVA and 25 kV. They are an offline design. The utility feeds the load straight through a solid-state switch while a disturbance monitor watches the supply, and when the voltage steps outside limits the batteries take over within 1 to 4 milliseconds, under a quarter of a cycle. The batteries carry full load for about a minute, long enough to bridge to a generator, and the controls can start the generator and hand over to it on their own.

PureWave AVC. The adaptive VAR compensator is the smaller, factory-floor member of the family: a distribution-class device that adjusts reactive power cycle by cycle so that lights stop flickering and voltage stops dipping when a large load such as a welder or a crane switches on and off. It joined the PureWave family through an acquisition and has the fewest installed units of the three, which makes its documentation and spares the hardest to find.

What typically fails on units of this age

Most PureWave equipment in service today was built between the early 2000s and the mid 2010s. The steelwork, transformers and bus bars are usually fine at that age. The parts that fail are the same across the fleet, and most of them are wear items rather than design faults.

Batteries. The UPS was designed around sealed, maintenance-free battery strings, and the original literature recommended replacing each string in the sixth year. Many installations are on their second or third set; some are still on their first. A tired string shows up as shorter ride-through, failed equalise charges and battery alarms. Where the original module is no longer made, the replacement has to be qualified against the system rather than bought on voltage alone. Our Kokam battery replacement work describes how that qualification is done.

Capacitors. The AC filter capacitors, DC link capacitors and snubber capacitors in the power conversion modules and the solid-state switch dry out with age and heat. A vented capacitor was the root cause in a recent power conversion module failure we investigated, and it is the first thing we look for when a module trips or a unit derates. They are replaceable at board and module level.

Cooling. Every PureWave enclosure moves a lot of air. Blocked inlet filters, failed blowers and air conditioners past their service life show up as over-temperature warnings on the switch, the transformer compartment or the inverter. The instruction sheets call for quarterly filter checks for a reason; a unit that has missed a few years of them will be running hot.

Control and monitoring electronics. The monitoring computer runs an operating system that has been out of support for years, remote access was designed around a modem, and the gate driver and regulator boards are custom parts that were never sold through distributors. When a board fails, the question is whether anyone can supply, program and commission a replacement. More on that below.

Switching devices and connections. Shorted thyristors in the solid-state switch, worn breakers, and loose connections that arc. One loose breaker connection started the fire that destroyed a DSTATCOM inverter section we later rebuilt on site.

Enclosures. Door seals, corrosion at the base, and water where it should not be. Minor on their own, expensive when they let moisture reach a bus bar.

What we can do

Spares. We hold or source the parts the PureWave line needs, from filter media and blowers to complete power conversion modules, and we remanufacture custom items such as bus bars to the original drawings when no stock exists.

Board-level repair. Gate driver, regulator and control boards are repaired and tested rather than written off, which matters when the board is unique to your site.

Control platform upgrades. Where the control hardware or its operating system is unsupported, we move the site-specific control software onto current industrial computers and recommission the unit against the performance it was originally accepted to. On the STATCOM fleets we support this includes the CCP5 to CCP9 migration. The power hardware stays where it is.

On-site rebuild. When a section is damaged by fire, arc or water, we strip it, clean it, source every part and rebuild it in place rather than pulling healthy equipment out of the way to ship the damaged section to a factory.

Refurbished exchange units. For modules that are quicker to swap than to repair in the field, we can supply a refurbished, tested unit on exchange so the system is back on line while the original is repaired.

Service contracts. Quarterly and annual maintenance to the original schedule, condition data on the batteries and capacitors, and a named engineer who knows the product. It is also the cheapest way to avoid an emergency call.

Diagnosis comes first. A unit that keeps tripping on grid disturbances may be responding correctly to a supply problem rather than failing. When that is unclear we start with power quality root cause analysis before anyone orders parts.

Refurbish, repair, or replace?

The question we are asked most often is whether an old PureWave unit is worth keeping. Three questions settle it:

1. Is the power hardware sound? Transformers, inverter stacks, bus work and steel are built for decades. If condition testing says they are healthy, the unit has a future.
2. What actually failed? Batteries, capacitors, cooling and controls are all replaceable at a fraction of the cost of a new system. A replacement STATCOM or facility-scale UPS is a capital project with civil works and lead times measured in years.
3. Is the site still asking the unit to do the right job? Loads change. If a site has grown past what the unit can carry, expansion or a supplementary unit is the honest answer, and we will say so.

In most cases the answer is repair, and we say that with condition data to back it. Where new equipment genuinely fits better, we quote that too.

Send us the nameplate

You do not need to diagnose the fault before you call. Two things get us started:

1. A photo of the nameplate, usually inside the control bay door or on the enclosure, so we know the model, rating and serial number.
2. A short description of what happened: the alarm on the screen, what the unit did, and when it started.

Email both to sales@renewable-d.com and an engineer will come back to you with the likely cause and a plan.

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Running a PureWave DSTATCOM, UPS or AVC that nobody will support? We own the technology and service it worldwide. Email a nameplate photo and the fault to sales@renewable-d.com, or call +1 414 562 6559 (US) or +44 116 279 6131 (UK).