Power system

A power system comprising:

• a central unit;
• a zone unit capable of communicating with the central unit;
• and
• a downstream electric wire configured to electrically connect a predetermined downstream unit to the zone unit,
• wherein the zone unit comprises
• one or more zone processors,
• one or more zone memories coupled to the one or more zone processors,
• a zone storage device that is electrically writable nonvolatile,
• a semiconductor switch capable of electrically connecting the downstream electric wire, which is coupled to the downstream unit, to a power supply, and
• a current sensor configured to detect a current flowing to the downstream electric wire through the semiconductor switch,
• wherein the central unit comprises
• one or more central processors,
• one or more central memories coupled to the one or more central processors, and
• a central storage device in which electric wire characteristic data indicating a characteristic of the downstream electric wire is stored in advance,
• wherein the one or more central processors execute processing including transmitting the electric wire characteristic data stored in the central storage device to the zone unit at a predetermined timing, and
• wherein the zone processor executes processing including
• writing the electric wire characteristic data transmitted from the central unit into the zone storage device in response to reception of the electric wire characteristic data transmitted from the central unit, and
• calculating a temperature estimation value that is an estimation value of a temperature of the downstream electric wire, based on the electric wire characteristic data written into the zone storage device and the current detected by the current sensor,
• turning the semiconductor switch to an OFF state when the temperature estimation value exceeds a predetermined temperature threshold, and
• turning the semiconductor switch to the OFF state, even when the temperature estimation value is equal to or lower than the predetermined temperature threshold, if a downstream OFF command, which is a command for interrupting the electric power to the downstream unit corresponding to the semiconductor switch, is received from the central unit.