Solenoid Series Reactors (SSRx)
Patented fault current reduction and voltage stabilization technology can reduce the risk of wide area power outages and wildfires caused by faulted power lines.
When combined with our wildfire risk assessment tool or other risk assessment services, Prescient’s patented Solenoid Series Reactors (SSRx) can prevent wide area power outages and reduce the risk of wildfires caused by faulted power lines.
How Do SSRx Work?
When the electric power grid is operating as normal, power generated is equal to power consumed. However, after a short circuit occurs, power demand is significantly greater than power generated. This phenomenon, illustrated in Figure 1, is called the post-short circuit power recovery transient. It is due to motors requiring extra power to reaccelerate to optimal performance after the short circuit.
Prescient’s patented SSRx will minimize the transient post-short circuit power recovery bubble shown in Figure 1 to the preferred transient post-short circuit bubble shown in Figure 2.
Once installed in a substation, SSRx will actuate in 8 milliseconds, thereby significantly increasing fault impedance and restoring grid voltage. SSRx activate before motors slow down or stall, and then, when the short circuit is cleared, the post-short circuit power recovery transient is nonexistent.
With so little time between the initial short circuit and voltage recovery, air conditioning units, fans, and other motors throughout the system will not experience a momentary power loss during the short circuit, and therefore will not draw extra power to reaccelerate after the short circuit is cleared. In addition, if a fault would occur within a mile of the substation, SSRx will reduce the risk of a wildfire from a sparking fault by reducing high fault current levels.
Figure 1: Without Prescient's patented SSRx technology, the transient post-short circuit power consumption bubble is large and likely to lead to a wide area power outage.
Figure 2: The transient post-short circuit power consumption bubble with patented SSRx technology is normal. No power outage will occur.
SSRx and Power Outages
Today, the power system is configured in such a way that if a three-phase short circuit with stuck circuit breaker were to occur in July or August on any transmission line 345 KV or above, the result would be a multi-state, wide area power outage.
This has been proven by events such as that detailed in the Washington, D.C., Area Low-Voltage Disturbance Event of April 7, 2015 report issued by NERC; this report shows how the power grid was challenged by a three-phase short circuit with stuck circuit breaker on a 230 KV transmission line in Maryland.
This event would have led to a wide area power outage in July or August when load is much higher than in April. With SSRx technology, this risk is eliminated because the duration of voltage dips is only 8 milliseconds, which essentially eliminates this precursor to wide area power outages.
To understand this scenario more fully, it’s important to recognize that the electric power grid is perpetually in a quasi-steady state condition, operating at 3600 RPM with continuous changes in load and power generation. Pumps and water recirculating motors operate at 3500 RPM. Fans, blowers, room air conditioners, and heat pumps operate at 1150 RPM. Newer room air conditioners and outdoor heat pumps operate at 850 RPM.
During any given day, load can ramp up at the rate of 10% per hour in the morning and ramp down at 10% per hour in the evening. When short circuits occur, the load ramp down rate can be 25% in 100 milliseconds and recovery can persist for 20 seconds.
When short circuits occur, the electric power grid changes from a quasi-steady state of motion to a dynamic state. Motors slow down during the short circuit and reaccelerate as soon as the short circuit is cleared. Factors that determine whether the power grid will recover after the short circuit is cleared include available generation, motor speed, mechanical load, and short circuit clearing time.
When a stuck circuit breaker occurs, short circuits can persist for 200 milliseconds, the equivalent of 12 revolutions of a 3500 RPM motor, 4 revolutions of a 1150 RPM motor, or 3 revolutions of an 850 RPM motor. Currently, the hope is that mechanical inertia will carry the motor through the voltage dip caused by a short circuit; when this doesn’t happen, a wide area power outage is likely. SSRx will assure that voltage recovers so quickly that motors do not slow down, and recovery occurs in less than one second.
SSRx and Wildfire Risk Reduction
In addition, SSRx will reduce the risk of wildfires caused by sparking distribution lines when current during very high current short circuits, such as 20,000 amps, is reduced to lower values, such as 6,000 amps before circuit breakers open to clear the short circuit.
Energy released during short circuits is a function of I R - current (I) and arc resistance (R). When short circuit current is reduced from 20,000 amps to 6,000 amps, energy release and energy deposited on nearby vegetation are reduced by a factor of 10. This reduces the possibility of power distribution lines initiating wildfires when short circuits occur within the first mile out of a substation.
For more information about Prescient's wildfire risk assessment tool or blackout risk assessment service, contact us.
Get in touch with us to schedule a presentation with more in-depth information.