As a result of increasing law regulations, energy subscribers will be provided more freedom to choose between tariffs and utilities, optimizing their energy costs. However, with an increase in renewable energy generation, local utilities require a more efficient way to monitor the energy consumed on a subscriber level, to adjust the conventional electrical energy generation. The utility’s business – pre-paid vs. after-paid – will mainly be driven by local consumption and payment habits. Consequently, future electricity meters will require reliable bidirectional communication paths to address these needs. The solutions that will be chosen will depend on local circumstances and will be either wired or wireless. Although the solution presented addresses a 1-Ph shunt E-Meter, the same principles of operation are applicable to current transformer and Rogowski-coil based sensing approaches with the intrinsic isolation provided by the inductive.

System Benefits:

  • As an alternative to the suggested intelligent analog front-end, the RL78/I1C microcontroller (MCU), the final solution may use the cost-effective RL78/I1B MCU, a design variant of the I1C without hardware encryption; both devices integrate a 24-bit Sigma–Delta (ΣΔ) ADC.
  • The calculated energy parameters will be digitized and transferred via UART to the application's controller through an optical isolator. Depending on the number of lines, the serial interface is based on “n” number of isolators that may be needed.
  • The selected applications controller is an Arm® Cortex®-M4 device with 512kB flash and 256kB RAM.
  • The suggested LED/IrDA and RS-485 interfaces address the capability of bidirectional serial connectivity in production and/or out in the field.
  • For remote rural deployments with poor grid quality, 2G or 5G wireless connectivity is a must.
  • The suggested mechanical switch is a common approach to detect tamper approaches, triggering a register flag upon case opening.
  • For urban deployments, either Sub-1-GHz communication via a data logger or wired connectivity via power line communication (PLC) is a must; while the RAA604S00 supports a proprietary frequency-shift keying (FSK) or the Wi-SUN protocol, the R9A06G037 as well as the following line driver support both the 3G-PLC and PRIME specification.
  • The PS2561FL optical isolator is a good choice for a device that complies with the G3 requirement of zero-crossing detection, which is required for both non-isolated and isolated coupling designs.
  • The wireless module’s nominal voltage is specified at 3.8V (min 3.3V). The supply will have to be supplied separately through its own DC/DC buck; yet, whether this system will have to be galvanically isolated from the rest of the system is a matter of discussion and cost.
  • The rest of the system (except metrology) can be supplied through a similar, separate DC/DC buck, as the other component’s nominal supply voltages are typically at 3.3V.
  • To guarantee galvanic isolation through the complete signal path, the metrology’s power will have to be supplied through a separate LDO; alternatively, an additional LDO could be used to power the RS-485 modem.



Winning Combinations Interactive Diagram

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4:3 ratio Sheet.1 Sheet.2 Sheet.3 Sheet.4 EU018 EU018 EU018 Resistor - Fixed AC/DC AC/DC AC/DC LDO LDO LDO Buck Regulator 1 Buck Regulator Buck Regulator Buck Regulator 2 Buck Regulator Buck Regulator LED Module LED Module LED Module MODBUS MODBUS MODBUS Photocoupler 2 Photocoupler Photocoupler GRPS + LTE - M GRPS + LTE - M GRPS + LTE - M Real-Time Clock Real-Time Clock Real-Time Clock Mech. Switch Mech. Switch Mech. Switch LCD LCD LCD Line Driver Line Driver Line Driver Filtering Protection Filtering Protection Filtering Protection PLC Modem PLC Modem PLC Modem Transceiver Transceiver Transceiver Sub-1 GHz Sub-1 GHz Sub-1 GHz Antenna Sheet.41 Sheet.42 Sheet.43 Sheet.44 Sheet.45 Inductor Iron Core Line.841 Inductor Air Core.212 Sheet.49 Sheet.50 Sheet.51 Sheet.52 Sheet.53 Sheet.54 Sheet.55 Sheet.56 Sheet.57 Line.29 Inductor Coreless (Air conductor) Sheet.60 Sheet.61 Sheet.62 Sheet.63 Sheet.64 Sheet.65 Sheet.66 Sheet.67 Sheet.68 Sheet.7 Sheet.8 Diode.316 Sheet.10 Sheet.11 Sheet.12 Sheet.14 Sheet.15 Resistor - Fixed.70 Sheet.71 Sheet.72 Sheet.73 Sheet.74 Sheet.75 Sheet.76 Resistor - Fixed.77 Resistor - Fixed.78 Sheet.79 Sheet.80 Sheet.81 Sheet.82 Sheet.83 Sheet.84 Sheet.85 Sheet.86 Sheet.87 Sheet.88 Sheet.89 Sheet.90 Sheet.91 Sheet.92 Sheet.93 Sheet.94 Sheet.95 Sheet.96 Sheet.97 Sheet.98 Sheet.99 Sheet.100 Sheet.101 Sheet.102 Sheet.103 Sheet.104 Sheet.105 Sheet.106 Sheet.107 Sheet.108 Sheet.109 O-Crossing O-Crossing O-Crossing Photocoupler 1 Photocoupler Photocoupler Sheet.111 Sheet.112 Sheet.113 Sheet.114 Sheet.115 Sheet.116 Sheet.117 Sheet.118 Sheet.119 Sheet.120 Sheet.121 Sheet.122 Sheet.123 Sheet.124 Sheet.125 Sheet.126 Sheet.132 Sheet.133 Sheet.134 Sheet.135 Sheet.136 Sheet.137 Sheet.138 Sheet.139 Sheet.140 Sheet.142 Phase Phase Phase Neutral Neutral Neutral Shunt Shunt Shunt Load Load Load 3.3V, 8.5mA 3.3V, 8.5mA 3.3V, 8.5mA 3.8V, 110mA/10dBm 3.8V, 110mA/10dBm 3.8V, 110mA/10dBm 3.3V, 136mA (max) 3.3V, 136mA (max) 3.3V, 136mA (max) Phase Phase Phase Neutral Neutral Neutral Connector 1.160 Connector 1.160.153 Connector 1.160.154 Connector 1.160.155 Connector 1.160.156 Connector 1.160.157 Connector 1.160.158 Connector 1.160.159 Connector 1.160.160 Connector 1.160.161 Connector 1.160.163 Connector 1.160.164 Connector 1.160.165 Connector 1.160.166 Connector 1.160.169 Sheet.171 MCU 1 MCU MCU Σ∆ Σ∆ Σ∆ UART UART UART Sheet.172 MCU 2 MCU MCU IrDA IrDA IrDA UART UART UART
Exiting Interactive Block Diagram