Device, system and method for monitoring electrical load by measuring magnetic field

The invention provides a method, device and system for monitoring an electrical load. According to the invention, the magnetic field data of the primary side of a transformer is measured and the magnetic field data of the primary side is compared with the magnetic field data of a second side, so that electrical load monitoring is achieved. Compared with the prior art that a current transformer measures currents, the current transformer generally is connected onto an electric transmission line in a sleeveing manner, a power line needs to be disconnected and power is off during installation, the electrical load monitoring method, device and system have the advantages that the installation can be performed without powering off the power line, and magnetic flux is not easily saturated.