Adopting advanced microelectronics, LSIC, digital processing technology and SMT technics, our newly developed DDS1661DIN rail mounted three phase KWH meter utterly conform to the relative technic requirement of grade 1 single phase KWH meter of IEC 62053-21. It can precisely calculate the active energy loss of RP 50Hz or 60Hz three phase AC network. Reliable, small size, light, gorgeous and easy installation, It is widely-used and convenient collaborating.