Voltage detection of utility service disturbances
First Claim
1. A method of switching a main electrical AC power supply to a standby electrical AC power supply, the method comprising the steps of:
- a) sampling an instantaneous voltage magnitude of a main power supply waveform for a plurality of sampling periods at a preselected sampling rate;
b) squaring each instantaneous voltage magnitude in real time to create respective instantaneous squared voltage values;
c) generating a running voltage value by accumulating the instantaneous squared voltage values for an accumulation window of time, wherein the running voltage value is adjusted in real time by subtracting the instantaneous square voltage value for the sampling period immediately prior to the start of the accumulation window from the running voltage value and adding the instantaneous square voltage value for the most recent sampling period to the running voltage value;
d) comparing the running voltage value to a preselected under-voltage threshold value; and
e) switching to the standby electrical AC power supply when the running voltage value sags to or below the preselected under-voltage threshold value.
1 Assignment
0 Petitions
Accused Products
Abstract
A digital voltage detector uses a running average to detect utility service disturbances in real time. An isolation transformer taps the main electrical AC power supply line and provides an analog voltage waveform to a system controller. The analog waveform is sampled digitally in real time, and the samples are squared to create respective instantaneous squared voltage values. A running average is kept of the instantaneous squared voltage values for a preselected period of time, preferably one half-cycle for the main power supply waveform. The running average is compared to a preselected under-voltage threshold value and a preselected over-voltage threshold value, and a disturbance detection signal is generated if the running average violates either threshold value. The disturbance detection signal is preferably used to activate a standby electrical AC power supply, and contemporaneously to disable the main electric AC power supply.
52 Citations
29 Claims
-
1. A method of switching a main electrical AC power supply to a standby electrical AC power supply, the method comprising the steps of:
-
a) sampling an instantaneous voltage magnitude of a main power supply waveform for a plurality of sampling periods at a preselected sampling rate; b) squaring each instantaneous voltage magnitude in real time to create respective instantaneous squared voltage values; c) generating a running voltage value by accumulating the instantaneous squared voltage values for an accumulation window of time, wherein the running voltage value is adjusted in real time by subtracting the instantaneous square voltage value for the sampling period immediately prior to the start of the accumulation window from the running voltage value and adding the instantaneous square voltage value for the most recent sampling period to the running voltage value; d) comparing the running voltage value to a preselected under-voltage threshold value; and e) switching to the standby electrical AC power supply when the running voltage value sags to or below the preselected under-voltage threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. A detector for monitoring voltage disturbances in electrical AC power lines, the detector comprising:
-
an isolation transformer that outputs an isolated voltage signal in response to voltage in the electrical AC power line; a system controller including; a system clock; a sampling element that receives the isolated voltage signal from the isolation transformer and outputs a plurality of digital values at a system sampling rate, each digital value representing an instantaneous voltage magnitude value for the isolated voltage signal at the respective sampling rate; a squaring element that squares each instantaneous voltage magnitude value during the respective sampling to form an instantaneous squared voltage value in real time; an accumulating element that generates a running voltage value by accumulating the instantaneous squared voltage values for an accumulation window of time, wherein the running voltage value is adjusted in real time by subtracting the instantaneous squared voltage values for a sampling period immediately prior to the start of the accumulation window from the running voltage value and adding the instantaneous squared voltage value for the most recent sampling period to the running voltage value; and a first comparing element that compares the running voltage value to an under-voltage threshold value and outputs a disturbance detection signal when the running voltage value sags to or below the under-voltage threshold value. - View Dependent Claims (17, 18, 19, 20, 21)
-
-
22. A detector for monitoring voltage disturbance in electrical AC power lines, the detector comprising:
-
an isolation transformer that outputs an isolated voltage signal in response to voltage in an electrical AC power line; and a system controller having a system clock, a sampling element, a microprocessor, and memory, wherein the sampling element receives the isolated voltage signal from the isolation transformer and outputs a plurality of digital values at a system sampling rate, each digital value representing an instantaneous voltage magnitude value for the isolated voltage signal at each respective sampling period and further wherein the memory contains software that instructs the microprocessor to implement the following steps; squaring each instantaneous voltage magnitude in real time to create respective instantaneous squared voltage values; generating a running voltage value by accumulating the instantaneous squared voltage values for an accumulation window of time, wherein the running voltage value is adjusted in real time by subtracting the instantaneous squared voltage values for the sampling period immediately prior to the start of the accumulation window from the running voltage value and adding the instantaneous squared voltage value for the most recent sampling period to the running voltage value; comparing the running voltage value to a preselected under-voltage threshold value; and outputting a disturbance detection signal when the running voltage value sags to or below the under-voltage threshold value. - View Dependent Claims (23, 24)
-
-
25. A switching mechanism for an uninterruptable power supply comprising:
-
a main electrical AC power supply line; a static switch in the main power supply line; a standby electrical AC power supply; an isolation transformer that outputs an isolated voltage signal in response to voltage in the electrical AC power line; means for sampling the isolated voltage signal at a system sampling rate and generating a digital value representing the instantaneous voltage magnitude for each respective sampling period; a microprocessor; memory containing software that instructs the microprocessor to implement the following steps; squaring each instantaneous voltage magnitude in real time to create respective instantaneous squared voltage values; generating a running voltage value by accumulating the instantaneous squared voltage values for an accumulation window of time, wherein the running voltage value is adjusted in real time by subtracting the instantaneous squared voltage values for the sampling period immediately prior to the start of the accumulation window from the running voltage value and adding the instantaneous squared voltage values for the most recent sampling period to the running voltage value; comparing the running voltage value to a preselected under-voltage threshold value; and transmitting a disturbance detection signal when the running voltage value sags to or below the under-voltage threshold value to the standby power supply to activate the standby power supply and contemporaneously to the static switch to disable the main electrical AC power line. - View Dependent Claims (26)
-
-
27. A method of detecting a power disturbance in a main electrical AC power supply, the method comprising the steps of:
-
a) sampling the instantaneous voltage magnitude of a main power supply waveform for a plurality of sampling periods at a preselected sampling rate; b) squaring each instantaneous voltage magnitude in real time to create respective instantaneous squared voltage values; c) generating an average RMS voltage value by summing the instantaneous squared voltage values for a preselected number of sampling periods and dividing the sum of the instantaneous squared voltage values by the number of sampling periods; d) comparing the average RMS voltage value to a preselected under-voltage threshold value defined by multiplying the number of sampling periods used to determine the average RMS voltage value by the square of a normalized voltage tolerance for a critical load receiving power from the main electrical AC power supply; and e) outputting a disturbance detection signal when the average RMS voltage value sags to or below the under-voltage threshold value. - View Dependent Claims (28, 29)
-
Specification