Electrical panelboard with integrated arc fault protection
Aspects of this disclosure concern the integration of AFCI protection into the electrical panel itself. An electrical panelboard includes a main terminal that receives a supply of electricity, multiple terminals to supply electricity to branch circuits, and a bus structure that distributes the electricity from the main terminal to the branch circuit terminals. The branch circuit terminals may be conductive stabs, to which traditional overcurrent circuit breakers are attached. The AFCI protection is integrated, either fully or partially, onto the panelboard, rather than implemented as separate stand-alone devices. The integrated AFCI protection includes current sensors, switching devices and a processing system. The current sensors sense the flow of electricity through the branch circuits and the switching devices can interrupt this flow of electricity. The processing system analyzes the detected currents for arc faults and controls the switching devices accordingly.
1 . An electrical panelboard comprising:
a main terminal configured to receive a supply of electricity;
a plurality of branch circuit terminals configured to supply electricity to branch circuits, wherein the branch circuit terminals are (a) stabs configured for connection to overcurrent circuit breakers for the branch circuits or (b) fuse holders configured for connection to fuses for the branch circuits;
a bus structure configured to distribute the supply of electricity from the main terminal to the branch circuit terminals;
current sensors electrically coupled to conductive paths between the bus structure and the branch circuit terminals, wherein the current sensors are configured to sense a flow of electricity through the branch circuits;
switching devices electrically connected between the bus structure and the branch circuit terminals; wherein the switching devices are configured to interrupt the flow of electricity in the branch circuits; and
a processing system that analyzes current signals from the current sensors, detects arc fault events based on the analysis, and controls the switching devices to interrupt the flow of electricity to the branch circuits in response to detecting arc fault events.
2 . The panelboard of claim 1 wherein a separate current sensor and switching device are used for each branch circuit, the processing system comprises one or more processing devices, and each processing device detects arc fault events for multiple branch circuits.
3 . The panelboard of claim 1 further comprising:
a main switching device configured to interrupt the flow of electricity from the main terminal to the bus structure; wherein if one of the switching devices corresponding to a branch circuit does not interrupt the flow of electricity to the branch circuit in response to control by the processing system, the processing system then controls the main switching device to interrupt the flow of electricity from the main terminal to the bus structure.
4 . The panelboard of claim 1 wherein AFCI protection provided by the processing system is software configurable, including turning AFCI protection on and off for different branch circuits.
5 . The panelboard of claim 1 wherein the detection of arc fault events is adaptive.
6 . The panelboard of claim 5 wherein the detection of arc fault events is adapted based on measurements of the branch circuits that characterize an electrical behavior of the branch circuits.
7 . The panelboard of claim 5 wherein the detection of arc fault events is adapted based on cross-talk between branch circuits.
8 . The panelboard of claim 5 wherein the detection of arc fault events is adapted based on historical data for the branch circuits.
9 . The panelboard of claim 5 wherein the detection of arc fault events is adapted based on what appliances load which branch circuits.
10 . The panelboard of claim 5 wherein the detection of arc fault events is adapted to reduce a rate of false positives.
11 . The panelboard of claim 1 wherein controlling at least one of the switching devices to interrupt the flow of electricity to one branch circuit depends on the analysis of current signals for other branch circuits.
12 . The panelboard of claim 1 wherein, for a detected arc fault event, the processing system determines which branch circuit is a likely location of the arc fault event and controls the corresponding switching device to interrupt the flow of electricity to that branch circuit and does not interrupt the flow of electricity to other branch circuits.
13 . The panelboard of claim 1 wherein the processing system stores a record of detected arc fault events, and the record includes metadata characterizing the detected arc fault event.
14 . The panelboard of claim 1 wherein the processing system further determines electricity usage based on the analysis of current signals from the current sensors.
15 . The panelboard of claim 14 wherein the processing system further controls the switching devices in response to the determined electricity usage.
16 . The panelboard of claim 1 wherein the processing system detects arc fault events for every branch circuit supplied by the panelboard.
17 . The panelboard of claim 1 wherein:
the processing system detects arc fault events based on at least one of: a frequency domain analysis of the current signals, and a time domain analysis of the current signals;
the current sensors comprise at least one of: a current transformer, a Hall effect sensor, a current sensor based on magnetoresistive elements, an inductive pickup coil, a shunt resistor, an impedance in series with current flow, and a fluxgate current sensor; and
the switching devices comprise at least one of: a semiconductor switch, a relay, a motor-driven switch, a shunt trip circuit breaker, and an electrically triggered spring-driven contact system.
18 . A system comprising:
an electrical panelboard comprising:
a plurality of branch circuit terminals configured to supply electricity to branch circuits, wherein the branch circuit terminals are (a) stabs configured for connection to overcurrent circuit breakers for the branch circuits or (b) fuse holders configured for connection to fuses for the branch circuits;
a bus structure that provides a supply of electricity to the branch circuit terminals;
current sensors that sense a flow of electricity through the branch circuits; and
switching devices that control the flow of electricity through the branch circuits, wherein the current sensors and switching devices are electrically coupled to conductive paths between the bus structure and the branch circuit terminals; and
a processing system that analyzes current signals from the current sensors, detects arc fault events based on the analysis, and controls the switching devices to interrupt the flow of electricity in response to the detection of arc fault events.
19 . The system of claim 18 wherein:
the processing system includes an in-panel processing device contained in the electrical panelboard and an off-panel compute resource external to the electrical panelboard; and
the electrical panelboard further comprises:
a power supply that receives power from the electricity supplied to the panelboard, and provides power to the switching devices and to the in-panel processing device; and
a wireless terminal that provides communication between the in-panel processing device and the off-panel compute resource.