Commuter Railroad YardTHE SITUATION

UPS power-backup systems installed to protect transportation control centers and other critical facilities are set to respond to even modest over-voltage conditions. In most industrialized regions, this is not a problem, as over-voltage conditions are rare. However, in very dense urban regions, such as New York City, over-voltage is an all-too-common condition in the summer months.

Urban utilities “stiffen the grid” in the summer to accommodate wide swings in hourly power usage. However, when the power demand drops rapidly, like when air conditioning units are simultaneously switched off at the end of the workday, utilities often cannot respond rapidly enough to prevent voltage from drifting upward.

UPS power-backup systems read these periods of over-voltage not as minor and transitory events, but as potential system failures. They are designed to compensate by immediately cutting power from the source and switching to battery backup until generators can kick in. The system works. However, it can be quite costly, as this “overreaction” to high voltage has a negative impact on the life of expensive UPS batteries.

Subway MapThis was the situation at a very busy control center for a major regional U.S. passenger rail system. During the summer months, the UPS was triggering frequently as utility power drifted out of the system’s set safe range.


Attracted by a recently published white paper about employing electronic voltage regulators (EVRs) as standard components of UPS power-backup systems, rail system executives approached UST seeking a solution. We demonstrated how our standard SureVolt™, a fully automatic and virtually maintenance-free EVR, could easily be installed as a retrofit without any interruption in service or protection.

In just a few short months, the carrier had a custom solution in place

The client’s UPS system will now be called upon only to manage deep sags and blackouts, not to regulate voltage. Next summer, when utility power drifts out of spec, the SureVolt will compensate. The UPS will sit in safe standby mode, fully charged and ready to respond … if it is ever needed.


By reducing the stress on its UPS system batteries, the rail service can expect a quick ROI simply through longer battery life.


Throughout the United States and across the industrialized world, the combination of an aging grid and increasing reliance on wind, solar and other highly variable energy resources are increasing the frequency of voltage irregularities. Over-voltage conditions are becoming far more common.

UST provides the industrial-grade power conditioning and voltage regulation solutions that help managers at data centers and other critical facilities keep costs down, keep risks low and keep things rolling.