MONITORING DEVICE USED FOR MONITORING HARMONICS AND HARMONIC MONITORING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a monitoring device which is suitable for preventing a trouble due to a harmonic current and to provide a monitoring system which inspects its data in a concentrated manner and which can specify the generation source of harmonics. SOLUTION: The monitoring system is composed of local monitoring devices 4 (4a to 4d) which obtain current signals and voltage signals by current transformers 2 (2a to 2d) and VT's (transformers) installed at electric circuits 1 (1a to 1d) and of a central monitoring device 25 which transmits and receives signals from a plurality of local monitoring devices 4 via a transmission line 5. In every local monitoring device 4, a harmonic current signal is sampled, digitized and frequency-analyzed, and a monitoring value and a warning time limit are set so as to be output to a warning contact when they are exceeded. The central monitoring device 25 judges the direction of a harmonic power flow and specifies the generation source of harmonics on the basis of received data.