Load shed system
A load shed module configured to be connected in series between a power supply and a load is disclosed. A separate load shed module is connected in series between each load and the power supply. The load shed module determines the frequency of the voltage supplied from the power supply. Based on the frequency, the load shed module determines if utility power is connected or if a generator is connected. If the generator is connected and the frequency of the voltage goes outside of a desired operating range for a preset time, the load shed module disconnects the load from the power supply. Each load shed module includes a priority setting and reconnects its corresponding load after a predetermined time corresponding to the priority setting.
1. A load shed system configured to be connected in series between an output of a transfer switch and a plurality of loads, wherein the transfer switch selectively connects one of a utility power source and an alternate power source to the output of the transfer switch, the load shed system comprising:
a plurality of load shed modules, each load shed module electrically connected between the output of the transfer switch and one of the plurality of loads, wherein each load shed module includes:
a housing configured to be mounted independently of each of the other load shed modules;
an input configured to receive a first electrical connection from the transfer switch;
an output configured to provide a second electrical connection for the corresponding load;
a switch operatively connected in series between the input and the output, wherein the switch receives a control signal to selectively open and close the switch;
a sensor configured to generate a feedback signal corresponding to an alternating current (AC) voltage present at the input;
a priority selector operable to generate a priority signal for the load shed module; and
a controller connected to the sensor to receive the feedback signal,
connected to the priority selector to receive the priority signal, and connected to the switch to supply the control signal;
wherein:
the controller is operable to determine whether the power source is the utility power source or the alternate power source as a function of the feedback signal and to generate the control signal to close the switch when the power source is the alternate power source and when an initial predetermined time has passed;
the initial predetermined time is selected as a function of the priority signal; and
each of the plurality of load shed modules has no communication with the other of the plurality of load shed modules.
2. The load shed system of claim 1 wherein the controller is further operable to compare the feedback signal to a threshold when the power source is the alternate power source and to generate the control signal to open the switch when the feedback signal exceeds the threshold for a running mode predetermined time.
3. The load shed system of claim 2 wherein the controller is further operable to:
determine a frequency of the AC voltage present at the input, and
determine whether the power source is the utility power source or the alternate power source as a function of the frequency of the AC voltage.
4. A load shed system configured to be connected in series between an output of a transfer switch and a plurality of loads, wherein the transfer switch selectively connects one of a utility power source and an alternate power source to the output of the transfer switch, the load shed system comprising:
a plurality of load shed modules, each load shed module electrically connected between the output of the transfer switch and one of the plurality of loads, wherein each load shed module incudes:
a housing configured to be mounted independently of each of the other load shed modules;
an input configured to receive a first electrical connection from the transfer switch;
an output configured to provide a second electrical connection for the corresponding load;
a switch operatively connected in series between the input and the output, wherein the switch receives a control signal to selectively open and close the switch;
a sensor configured to generate a feedback signal corresponding to an alternating current (AC) voltage present at the input;
a priority selector operable to generate a priority signal for the load shed module; and
a controller connected to the sensor to receive the feedback signal connected to the priority selector to receive the priority signal, and connected to the switch to supply the control signal;
wherein:
the controller is operable to determine whether the power source is the utility power source or the alternate power source as a function of the feedback signal and to generate the control signal to close the switch when the power source is the alternate power source and when an initial predetermined time has passed;
the initial predetermined time is selected as a function of the priority signal;
each of the plurality of load shed modules has no communication with the other of the plurality of load shed modules;
the controller is further operable to:
compare the feedback signal to a threshold when the power source is the alternate power source and to generate the control signal to open the switch when the feedback signal exceeds the threshold for a running mode predetermined time;
determine a frequency of the AC voltage present at the input, and
determine whether the power source is the utility power source or the alternate power source as a function of the frequency of the frequency of the AC voltage; and
each load shed module further includes a memory device and the controller is further operable to:
store a minimum frequency of the AC voltage in the memory device;
store a maximum frequency of the AC voltage in the memory device;
determine a difference between the minimum frequency and the maximum frequency, wherein the threshold is a maximum difference between the minimum frequency and the maximum frequency; and
generate the control signal to open the switch when the difference exceeds the maximum difference for the running mode predetermined time.
5. A load shed system configured to be connected in a series between an output of a transfer switch and a plurality of loads, wherein the transfer switch selectively connects one of a utility power source and an alternate power source to the output of the transfer switch, the load shed system comprising;
a plurality of load shed modules, each load shed module electrically connected between the output of the transfer switch and one of the plurality of loads, wherein each load shed module includes:
a housing configured to be mounted independently of each of the other load shed modules;
an input configured to receive a first electrical connection from the transfer switch;
an output configured to provide a second electrical connection for the corresponding load;
a switch operatively connected in series between the input and the output, wherein the switch receives a control signal to selectively open and close the switch;
a sensor configured to generate a feedback signal corresponding to an alternating current (AC) voltage present at the input;
a priority selector operable to generate a priority signal for the load shed module; and
a controller connected to the sensor to receive the feedback signal, connected to the priority selector to receive the priority signal, and connected to the switch to supply the control signal;
wherein:
the controller is operable to determine whether the power source is the utility power source or the alternate power source as a function of the feedback signal and to generate the control signal to close the switch when the power source is the alternate power source and when an initial predetermined time has passed;
the initial predetermined time is selected as a function of the priority signal;
each of the plurality of load shed modules has no communication with the other of the plurality of load shed modules;
the controller is further operable to;
compare the feedback signal to a threshold when the power source is the alternate power source and to generate the control signal to open the switch when the feedback signal exceeds the threshold for a running mode predetermined time;
determine a frequency of the AC voltage present at the input, and
determine whether the power source is the utility power source or the alternate power source as a function of the frequency of the AC voltage;
determine a difference between the frequency of the AC voltage present at the input and an expected frequency of the AC voltage present at the input, wherein the threshold is a maximum difference between the frequency of the AC voltage present at the input and an expected frequency of the AC voltage present at the input, and
generate the control signal to open the switch when the difference exceeds the maximum difference for the running mode predetermined time.
6. A load shed system configured to be connected in series between an output of a transfer switch and a plurality of loads, wherein the transfer switch selectively connects one of a utility power source and an alternate power source to the output of the transfer switch, the load shed system comprising;
a plurality of load shed modules, each load shed module electrically connected between the output of the transfer switch and one of the plurality of loads, wherein each load shed module includes;
a housing configured to be mounted independently of each of the other load shed modules;
an input configured to receive a first electrical connection from the transfer switch;
an output configured to provide a second electrical connection for the corresponding load;
a switch operatively connected in series between the input and the output,
wherein the switch receives a control signal to selectively open and close the switch;
a sensor configured to generate a feedback signal corresponding to an alternating current (AC) voltage present at the input;
a priority selector operable to generate a priority signal for the load shed module; and
a controller connected to the sensor to receive the feedback signal, connected to the priority selector to receive the priority signal, and connected to the switch to supply the control signal;
wherein
the controller is operable to determine whether the power source is the utility power source or the alternate power source as a function of the feedback signal and to generate the control signal to close the switch when the power source is the alternate power source and when initial predetermined time has passed;
the initial predetermined time is selected as a function of the priority signal;
each of the plurality of load shed modules has no communication with the other of the plurality of load shed modules;
the controller is configured to operate in a first operating mode and in a second operating mode;
during the first operating mode, the controller generates the control signal to open the switch when the feedback signal exceeds the threshold for a running mode predetermined time;
during the second operating mode, the controller generates the control signal to open the switch when the feedback signal exceeds the threshold for a transitional mode predetermined time; and
the transitional mode predetermined time is less than the running mode predetermined time.
7. The load shed system of claim 6 wherein during the second operating mode, the controller is further operable to enter a lock out operating mode when the feedback signal exceeds the threshold for the transitional mode predetermined time.
8. The load shed system of claim 1 wherein the load shed module is configured to he mounted either proximate to the transfer switch or proximate to the corresponding load.