Merging unit which collects information of power system

A merging unit which collects information of at least current or voltage from a power system, comprising:

• a processing unit which processes an analog signal obtained from said power system and outputs digital data indicating a state of the power system;
• and
• a communication unit which communicates with an external device via a communication line, wherein
• said processing unit includes
• a first conversion unit which converts an analog signal of the current or the voltage of said power system to digital data with a first sample rate, and
• a second conversion unit which converts the analog signal of the current or the voltage of said power system to digital data with a second sample rate lower than said first sample rate, and
• said processing unit is configured to store the digital data with said first sample rate converted by said first conversion unit, over a prescribed period which is based on timing at which said merging unit receives a prescribed signal via said communication unit, and to transmit the digital data with said second sample rate converted by said second conversion unit, via said communication unit.