Thermostat device with line under frequency detection and load shedding capability
First Claim
1. A method of responding to an under frequency event in an electrical delivery system that provides power to an electrical appliance, the method comprising the steps of:
- measuring a time period of each power line cycle of a power source;
comparing the measured time period to a trigger period,if a cycle time period is greater than or equal to the trigger period, an under frequency counter is incremented,if the cycle time period is less than the trigger period, the under frequency counter is decremented;
detecting an under frequency condition and initializing the line under frequency (LUF) response when the counter is incremented to a counter trigger level; and
initializing a restore response after the frequency rises above a restore valve that triggers the under frequency counter to count down until it reaches zero, thereafter indicating that the under frequency event has ceased.
5 Assignments
0 Petitions
Accused Products
Abstract
A method for detecting line under frequency (LUF) events and initializing load shedding of loads located near the electrical disturbance without customer and utility intervention is disclosed. In one example embodiment, the LUF detection system measures the time period of each power line cycle and then compares the measured time period to a utility-configurable trigger period. If the cycle length is greater than or equal to the trigger period, a counter is incremented. If the cycle is less than the trigger period, the counter is decremented. If the counter is incremented to a counter trigger, an under-frequency condition is detected and the LUF response either controls the load or temporarily disconnects it. A restore response is initialized after the frequency rises above a restore value and an under-frequency counter counts down to zero.
-
Citations
11 Claims
-
1. A method of responding to an under frequency event in an electrical delivery system that provides power to an electrical appliance, the method comprising the steps of:
-
measuring a time period of each power line cycle of a power source; comparing the measured time period to a trigger period, if a cycle time period is greater than or equal to the trigger period, an under frequency counter is incremented, if the cycle time period is less than the trigger period, the under frequency counter is decremented; detecting an under frequency condition and initializing the line under frequency (LUF) response when the counter is incremented to a counter trigger level; and initializing a restore response after the frequency rises above a restore valve that triggers the under frequency counter to count down until it reaches zero, thereafter indicating that the under frequency event has ceased. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
-
8. A system for responding to an under frequency event in an electrical delivery system that provides power to an electrical appliance, the system comprising:
-
means for measuring a time period of each power line cycle of a power source; means for comparing the measured time period to a trigger period, if a cycle time period is greater than or equal to the trigger period, an under frequency counter is incremented, if the cycle time period is less than the trigger period, the under frequency counter is decremented; means for detecting an under frequency condition and initializing the line under frequency (LUF) response when the counter is incremented to a counter trigger level; and means for initializing a restore response after the frequency rises above a restore value that triggers the under frequency counter to count down until it reaches zero, thereafter indicating that the under frequency event has ceased. - View Dependent Claims (9, 10, 11)
-
Specification