What are they?
What is the definition of a Power Sag?
Voltage sags – or dips which are the same thing – are brief reductions in voltage, typically lasting from a cycle to a second or so, or tens of milliseconds to hundreds of milliseconds.
National Power Outage Map: PowerOutage.US
Voltage Sags
Voltage sags are caused by abrupt increases in loads such as short circuits or faults, motors starting, or electric heaters turning on, or they are caused by abrupt increases in source impedance, typically caused by a loose connection.
Voltage sags can arrive from the utility; however, in most cases, the majority of sags are generated inside a building. For example, in residential wiring, the most common cause of voltage sags is the starting current drawn by refrigerator and air conditioning motors.
Sags do not generally disturb incandescent or fluorescent lighting. motors, or heaters. However, some electronic equipment lacks sufficient internal energy storage and, therefore, cannot ride through sags in the supply voltage. Equipment may be able to ride through very brief, deep sags, or it may be able to ride through longer but shallower sags.
Voltage Swells
Voltage swells are almost always caused by an abrupt reduction in load on a circuit with a poor or damaged voltage regulator, although they can also be caused by a damaged or loose neutral connection. Voltage swells are brief increases in voltage over the same time range. Longer periods of low or high voltage are referred to as “undervoltage” or “overvoltage.”
| 10% +/- sag/surge: | Continuous wear on PLC’s, boards, line equipment, motors, lasers, process equipment |
| 20% – drop in voltage: | Considerable spike in amperage due to the low voltage, may see long term or immediate damage to equipment |
| 50% – drop in voltage: | Will appear to be outage, flicker or drop of lights. Considerable amperage spike to all loads, damaging. |
| 80% drop in voltage: | Power loss occurs, may be gradual sag if on one phase. Damaging to all Electronic Equipment. |
The following is what an AVC (Active Voltage Correction) System can provide for sag activity.
Voltage Correction Chart (95%+ Sags occur in a single phase of power)
| 10% +/- sag/surge | 10% +/- sag/surge regulation AVC corrects to nominal power voltage |
| 20% – drop in voltage (Sag to 80%nv) | AVC corrects to 100%, 3 phase for 3+ minutes, 1 phase Continuous |
| 50% – drop in voltage (Sag to 50%nv) | AVC corrects to 90% 3 phase for 1 minute, 1 phase 100% continuous |
| 80% drop in voltage (Sag to 20% nv) | AVC corrects 1 Phase 100% continuous |
3 phase Sag more than 70% is considered outage. Unit will still correct but not in acceptable voltage output window.
Have an ICP site survey done to survey your facility and install a power metering device.
When you install equipment that will correct power and hold voltage within your facility, you will be providing your facility with protection against all outside influences of power. Halting wear and tear on other equipment in the facility by having stable voltage and power factor is the goal. The long term positives are lowered operations and maintenance costs by limiting voltage and amperage anomalies inside the facility. It is common to vet these issues by installing a monitoring device at the service entrance of the facility utility power. This is a low-cost method to really understand these issues and to make a proper diagnosis.
We are available to review electrical one-lines, Power Reports, Demand Usage, and any other data on your facility power.
Call your ICP Technical Representative today to discuss options to increase efficiency in your facility and correct our facility power issues!