PLC-I technology.

1. Introduction 

      PLC-I technology is designed to form remote data collection networks and manage microprocessor electricity meters of Mercury -200, 201, 202, Mercury -230 types.
      The technology uses distributive networks of AC 0.4kV 50 Hz mains as physical environment for translation.
      The sizes of PLC-I networks are limited by one 0.4kV 50Hz distributive transformer coverage. One data collection and management network can cover up to a few hundred user electricity meters.

2. Component description of PLC-I system

The number of main system components is reduced to minimum. They are:

      1. Electricity Meters: Electricity meters: mono-phase - Mercury 200, Mercury 201, three-phase - Mercury 230 with built-in data transfer modem via power mains (PLC-modem). Meters provide: energy consumption accumulation and storage by accruing total; operation in multi-tariff mode; reactive energy registration; remote switching on/off or consumption limitation; measurement and display of instant values of power, current voltage, cos F.

      2. Mercury 225.1 hub ( one-channel digital data receiver via power mains and power consumption data storage). The hub performs data transmission and reception synchronization from electricity meters by one phase and data transfer through selected data channel to the central control office. It is available to transfer the stored data to a portable inspector’s PC directly at Mercury -225 hub installation site through consecutive ports RS485 or USB. A pack of three Mercury 225 hubs interfaced via RS-485 is used in three-phase network.

The hub ensures:

      3. Mercury -223 technological modem (ТМ).
TM is used to program network addresses of user PLC-modems in the structure of Mercury meters.

      4. Communication equipment
1. GSM шлюз «Mercury 228» GSM gateway is designed to ensure remote access to the device or a group of devices equipped with RS-485 serial interfaces. For this purpose it is used to transmit data from territorially distributed Mercury 225.1 hubs to energy registration control office.

2. Siemens MC35 or another GSM modem. It is connected to registration operator’s PC to ensure a two-way communication with remote devices through GSM channel.

      5. Программные средства

   - The "ТМсомм.exe" programm
is used together with technological modem Mercury 223 to assign individual meter network address.

   - The "BМonitor.exe" programm
is designed to set configuration parameters of Mercury 225 hub and review received packages with user meter data on energy consumption in the network segment serviced by this hub.

   - The "BQuark.exe" programm
Can be used as registration operator’s workstation. By means of this program data are remotely read from territorially distributed Mercury 225 hubs. Also, there is a possibility to transfer any admissible group and individual commands to manage a single registration point to hubs.

 3. Technical features of PLC-I networks

      230V 50Hz electric grid is used as data transfer environment for data exchange between hubs and electricity meters. In order to support a high noise stability there are used OFDM-modulation (Orthogonal Frequency Division Modulation) algorithms which forms resultant signal by summing up a few broadband signals ranged within 20-95kHz.
      The network segment serviced by one hub can include up to 1024 registration points per each phase. This capacity is enough for one hub to cover all users connected to this phase. It means, within one TS it is enough to have not over three mono-phase hubs provided that all meters are located within visibility range, i.e. they are in a stable relation with the hub. Otherwise, repeaters would be needed at the confident reception boundaries. The same hubs are used as such repeaters. At the majority of objects that we know communication is provided at the distance of 400-800m in new networks with self-carrying wire up to 1000m. Application of repeaters increases the confident reception distance as much as 1,5-1,8 times. Communication range is highly affected by bad contacts in places of aerial wire joining, sub-branches, i.e. high transitive resistances in which PLC signal power is essentially lost. Each registration unit is identified by means of the assigned unique network address of meter modem.
      Since the basic purpose of this kind instruments is to construct inexpensive AMM for household consumers by means of PLC-I equipment it is available to receive only data on current value of active electric energy registered by each electricity meter under each tariff. If a wider data set is required, PLC-II networks shall be applied.

 4. Data transfer between hub and slaves (meters)

      Data collection system functions as follows. The hub periodically (once per some seconds) radiates sync signal of 2.5s duration which is received by all system slaves that interpret the received sync signal as the command to transmit one data bit in the form of broadband noise-like flash. Thus node №1 transmits its bit immediately upon sync signal termination, node №2 with a 10-msec delay, node №3 with a 20-msec delay and so on.
      Data transfer is realized by all nodes in the intersection area of zero level with basic supply voltage as this area of network half-cycle is the most noiseless made by electric energy consumers. Complete data package contains 64 bits and its transmission duration depends on such parameter as «network capacity». For 16 meters it shall take 3 minutes, for 1000 maters - 20 minutes. It means that data update rate in hub memory shall take about 5-30 minutes depending on how many registration nodes are installed.
      Meter modems shall perform transmission only if sync signal from hub is available at this network point. Sync signal presence and level in registration node installation point inspection are provided in meters by means of specific mnemogram LCD display, which essentially facilitates starting-up and adjustment operations.
      Hubs receive bit-by-bit data from meters, decrypt and store them in own non-volatile memory whence they can be readout at any time through one of their serial interfaces (RS-485, USB). Apart from current values hub non-volatile memory stores data on registered electric energy for each meter by terminal dates for 6 last months. The request for the stored by hubs data transmission is initiated by registration operator or executed in automatic mode by means of relevant software.
      If no data arrive from any meter, it means that either registration node is faulty or user has somehow manipulated with meter connection. The fact of such intervention is easy to identify by using the system, as it is an open system. Data transfer protocols are provided, thus our equipment may be used as downstream in energy resources registration systems of a wider profile.

 5. Mounting and adjustment

           System deployment in a very simple version is reduced to individual meter installation with users, house meters servicing lifts and lighting, balancing meters at building’s or TS’s switchboards and some equipment setting (see the "Mercury software. Quick start" file and other documentation).
     Thus, irrespective of the automation object nature, whether it is a block of flats or cottage settlement, topological circuit of equipment arrangement will not change (see Figure below).

If during maintenance some meters need replacing or number of registration points is to be increased, another meter shall be installed without interference in hub operation which is non-serviceable device like meters.
      However before installing at an automation object one should accomplish easy setting of meters and hubs. Meter setting is reduced to assigning network address to each meter from the range of admissible addresses by means of Mercury 223 technological modem. Hub setting is reduced to setting accurate time, the network capacity parameter which means quantity of the installed meters and operation mode (master or slave if hub is supposed to use for data relaying).
       Hubs are equipped with digital RS-485 interface via which they are united in uniform local area network with each other and extra devices of data transmission to control office remote PC, e.g. Mercury 228 GSM gate. If needed, Mercury meters with this interface (e.g. balance meter at TS) may be connected to this network. In this case remote management of all feasible parameters recorded by meter shall be available. The stored data may be transferred to a portable inspector's PC directly at the hub installation site via USB port.

Mercury software system distinguishes from existing analogues by:

• Reliable enough data transmission via power mains due to application of own construction modems, which unlike other existing ones are featured by very low working signal/noise ratio in reception point (up to minus 20dB) and at attenuation – about 60dB. Such features ensure a reliable data reception even when noise exceeds signal by over 10 times (by amplitude) and at the distance up to 1000m* at any time.

  • Low cost of the equipment ensured with a high technical performance.

  • Low implementation cost reduced to meter installation with pre-set network address and hub.

  • No necessity in any extra wires of digital communication interface which ensures an absolute anti-tempering feature. The number of users is increased by means of another meter installation without re-setting the data collection and transmission unit and software.

  • 1024 is a maximum meter quantity scanned by one hub.

  • Data update rate in hub memory takes 4-30 minutes (from the most remote meter delays up to a few hours are possible, thus upper-level software scanning period is not recommended more often than once per day).

  • The system is universal and has uniform topology facilitating to use it in private, municipal and industrial sectors.

  
  

6. Additional information

Other reference manuals and documentation may be checked at the Documentation page >>>.

You are welcome to ask us any question you may have >>>