HDO signal 16.03.2020 15:52 16.03.2020 15:52

This chapter describes the characteristics and requirements of the ripple control, and the basic ways how to control the installation and the connection to the Foxtrot system. This chapter was written in cooperation with Pražská energetika, a. s.

Ripple control (mass remote control) is a load management system used by the power generation industry, which allows to transfer information via the grid, making it possible to remotely control electricity tariffs and blocked appliances directly at the supply point (SP). The current tariff structure works with two high tariffs (T1 in the electricity meter) and a low tariff (T2); occasionally you can come across up to four experimental tariffs, i.e. T3 and T4. Although controlling tariffs and blocked appliances is technically independent, the two-tariff supply follows the principle that the low tariff is only applicable when at least one blocked appliance is in operation.

The ripple control can be implemented in the electricity meter distribution cabinet as a stand-alone device that controls one or several supply points; it can also be designed as a built-in module in the electricity meter, or as the so-called smart meter (still in the experimentation stage), which does not utilize the ripple technology, but develops the idea of remote control improved by assigning AP addresses to each specific supply point and integrating a two-way communication. Finally, the distribution cabinet can contain a combination of a smart meter and a ripple control (this is typical for supply points with a photovoltaic power plant). However, it is a sole decision of the power company which specific equipment (a switching element) will be used, and the customer has no say in it, unless it is related to a contractual product that requires a specific solution.

The supply point equipped with appliances that are included in the load management system of the power company (water heating, storage heating, direct electric heating, mixed heating, a heat pump) and that are appropriately sized to comply with the characteristics of the supply point, requires more tariff measurements, and its electrical installation must be ready for individual control of the blocked appliances in a one-circuit or two-circuit connection. Separate circuits are required because the blockage of various appliances within 24-hour periods differs: heating water is blocked for 8 h, while mixed heating 16 h, direct electrical heating for 20 h and the heat pump for 22 hrs. The duration of blockage does not need to be continuous. There are also differences among the distribution companies, so e.g. ČEZ Distribution and E.ON Distribution control heat pumps by three point switching and require a separately controlled circuit for bivalent direct electrical heating. Detailed specifications including the number of circuits (the number of switching element commands) are listed in the technical terms of each of the power distribution companies, which are available on their websites.

The electricity meter cabinet is fitted with a switching element, which indicates individual commands by one to three control neutral wires, i.e. usually the status of individual appliances (such as heating water, accumulation heating, direct electrical heating, heat pump, etc.). A standard recommended cable is 3C CYKY 1.5, and if additional circuits are needed, the phase or the protective wire should be marked in light blue. When an appliance is unblocked, the switching element relay connects the neutral wire to PEN (N if a change of the network from TN-C to TN-C-S has been implemented already in the meter control panel, or in the TT network). On the side of the house distribution panel in a standard connection this results in energizing the contactor, which is connected to the phase via a protection element.

In terms of the Foxtrot system applications there are several options, which depend on the specific needs.

If you only want to detect the low tariff, it is sufficient to sense the blocked circuit; in multi-command switching elements the circuit for accumulation heating, direct electrical heating and the heat pump (the others are only a low tariff subset of time.

If you also want to control the blocked appliances with Foxtrot, you should sense all circuits in the multiple command switching element. Technically the circuit can be scanned by a direct connection of the switching element to the 230V Foxtrot inputs, by parallel connection of the 230V CP input to the contactor coil (this only makes sense when detecting the low tariff); otherwise, auxiliary relays can be used, whose coils are connected as the contactors, but the contacts are controlled by Foxtrot inputs. It is also possible to select an appropriate combination of these methods.

 

Notes:

  1. The development in the power sector of EU countries is heading towards the use of smart meters. It can therefore be expected that within the AMM (Automated Meter Management) standard, the communication with the supply points will be replaced by the bus. Therefore it is advisable, especially in new supply points, where the investors plan installing an intelligent home control system, to install simultaneously 3C CYKY 1.5 and a shielded twisted pair, ideally the STP cat5e, from the supply point (the utility room with the control system) to the electricity control panel.

  2. The Foxtrot system is already prepared for several options of a direct connection of the electricity meter, both with wired and wireless buses (Wmbus, etc.). These technologies are still being developed and are expanding.

  3. Distribution companies have not reacted so far by changing their technical conditions to adapt to the requirements of the smart home systems, and still assume that the contactor coil is connected to the neutral wire in the supply point. When a worker of the power distribution company inspects the connection and does not detect the presence of the phase, e.g. due to the fact that the neutral wire is terminated directly on the ripple control of the Foxtrot input, a dispute may arise, in which the decisive factor is the mentioned technical condition of the connection. Direct control by the contactor also de facto means, that the power engineering does not allow for the situation that control could be shared by an algorithm in the Foxtrot system, and theoretically in marginal cases a dispute may also arise.

  4. N.B.: There are still supply points, which are connected according to invalid standards, where the switching element commands are executed by L, and not by N.

  5. Another option how to learn about the validity of a tariff and how to control appliances in PRE Distribuce territory would be to download data from the web PRE. A library is being prepared in the Mosaic development environment, which will take advantage of the communication with the PRE Distribuce interface and provide the users with the table listing the times for the specified command groups. The advantage is that the user program knows the future times and respond proactively.

 

 

The following articles primarily illustrate the method of capturing the switching elements commands. The number of commands and the method is already an individual matter, which should be evaluated by the designer.

 

If the ripple control output switches several devices, they must be supplied from the same phase, otherwise there is a risk that if the output is switched off (the zero wire N is switched off), on some device can appear (almost) the 400 V phase-to-phase voltage and destroy it.