PROBLEM: A manufacturer of computer flooring using 36 independent single phase welders was causing unacceptable voltage flicker on the serving utility's circuits.
A 6 MVAR-rated TSC, designed to reduce 13.2 kV voltage flicker from an uncorrected Pst of 5.5 to a correct-ed Pst of <2.8 at the factory fence. Using a dedicated feeder results in a utility Pst of <1 at the point of common coupling (PCC)
- The Modular TSC design provided a system designed to reliably meet the operating requirements. (A more expensive option, with Pst < 1.1 was also offered).
- In service since 2007, this system has demonstrated over 99.95% availability, having experienced a total of 3 component failures over the years.
- Customer preferred this solution over obtaining a transmission level connection with the utility at a cost over $2 million. Unit is deemed “must run.” Customer cannot operate more than 1 shift without it.
- When a newly-enhanced control system became available, customer elected to upgrade the controls in the field.
- T-Star performs ongoing remote monitoring and assistance as requested.
On-screen display showing 10 seconds of Operation on standard controller screen.
The welding patterns do not repeat and each phase operates independently of the other 2
The chart at left is derived and shows how each of the 3 phases react differently in order to maintain a stable 3-phase voltage.
Based on this information it's not surprising that the unit operates constantly, on each of the three phases.
That requires both a rapid,accurate controller and an system that is able to operate constantly without operating wear and tear.
An excerpt from a standard control system screen is shown at let. Note that Valve C4 (Phase C) shows approximately 106 million operations - for 14 months of operation.
Lifetime valve operations are over 2,000,000,000 operations per valve. Properly maintained solid state devices don't experience wear and tear from daily operations.
Operational success is defined here as meeting agreed-upon performance standards in reliable operation. Some of these standards include:
- IEEE 1493—Flicker standard, largely adopted from the IEC flicker standard. Deals with the measurement and remediation of periodic voltage fluctuations. Measures include: Voltage perturbations, Pst (short-term) and Plt (long term). The GE Flicker curve is also cross-referenced for specific flicker patterns..
- IEEE 519– Power Quality standard, primarily about harmonics, secondarily voltage fluctuations. Metric includes the GE Flicker curve.