Systems Subject to the Central Plant Controller: What You Need to Know
Guide to Installations Requiring the Central Plant Controller (C.P.C.)
What is the CCI and for which systems is it mandatory?
The CCI is a device that integrates with the production plant in which it is installed, in such a way as to perform the following functions:
> Mandatory services.
> Acquisition and communication to the DSO of the following data (observability)
> Measurement of P, Q and V at the Connection Point (PdC)
Resolution 540/21/R/el defines the field of application of the CCI, indicating the installation obligation for production plants with nominal power greater than, or equal to, 1 MW and connected in MV, which will come into operation from 1 ° December 2022.
For plants, always with a nominal power greater than or equal to 1 MW and connected in MV, but which entered into operation before 30 November 2022, it establishes the obligation to adjust by 31 January 2024.
There are no distinctions of technology (technology neutrality).
The CCI is mandatory for any electricity production plant with a nominal power greater than 1MW and connected in MT.
Plants in total self-consumption: obligation to adjust the CCI.
Resolution 540/21/R/el establishes, on page 14, that the CCI is also mandatory for systems connected in MV to SDC (Closed Distribution Systems), with nominal power greater than or equal to 1MW.
"Inasmuch as these systems are to all intents and purposes distribution systems for which the technical conditions for connection in force for public networks with third party connection obligations apply."
How are plants subject to upgrading considered for the purposes of CCI adjustment?
In the case of an existing production plant with a power of less than 1 MW, which was subject to revamping after 31 March 2023 and which brought the plant's power beyond one MW, the plant is considered NEW.
It follows the following functions, where the CEI 0-16 2022-03 divides the functions of the CCI into 3 groups:
> PF1: mandatory features.
> PF2 monitoring: optional features (from the point of view of the DSO).
> PF3 Regulation and Control: optional features (from the manufacturer's point of view) - Participation in Flexibility and Plant Optimization Markets
Optional features may be requested at the discretion of the DSO.
The timing according to which even the currently optional and/or optional functions will become mandatory will be established later by ARERA with appropriate resolutions.
P and Q controls, NPT sync and O attachment.
P and Q regulation is one of the PF2 optional functions, and the distributor will request it, if he deems it appropriate. (We expect this functionality to be requested in the connection estimate or in the Operating Regulations, for new plants).
For existing plants, it will be requested in the RdE that the Distributor will have to send updated, by 30 September 2022, to the producers subject to the adjustment.
Annex T of CEI 0-16 2022-03, paragraph T.3.3.4.5, clarifies that Annex O, in section O.13.1.5, indicates that the time synchronization function can be performed by an integrated GPS receiver in the CCI, or it can be provided via a communication network service.
Subsequently, the same paragraph indicates the secure NTS version of NTP as the protocol to be used.
Connectivity of distributors (DSO) and internet connection of the CCI
Resolution 540/21/R/el assigns distributors (DSO) the responsibility for building and maintaining the communication infrastructure, including the management of encryption keys, necessary to connect the CCIs with their monitoring and control systems.
On the other hand, it assigns manufacturers the responsibility for installing and maintaining the CCI in the plant.
When we talk about the CCI's internet connection, a PKI (Public Key Infrastructure) must be used for the management of security certificates (See CEI 0-16 T.3.3.4.9).
According to Annex T there are 3 ways to do this:
> Manual Management (temporary solution only): Installations, updates, revocations, replacements of the DSO certificates and any BSPs must be done manually on each plant. Challenging and error-prone if there are many CCIs to manage.
> Local PKI in the plant and OCSP protocol: Installing and managing a local PKI is very expensive and difficult. It is neither convenient nor safe.
> External PKI in the CLOUD: The CCI uses an external PKI in the #cloud, through the internet connection. Secure, centralized and automatic certificate lifecycle management.
Furthermore, a CCI connected to the internet is easier to update, to reach and consult and to replace in case of failure, automatic backup of configurations and data.
What data does the CCI collect?
The CEI 0-16 2022-03 standard requires the following data to be collected:
> Delivery Point: measurement of P, Q, V and optionally I.
> DG and DI status of individual generators: P and DDG status The CEI standard requires measurements of individual generators only if they have a rated power greater than: 170kW for static converters (e.g. photovoltaic inverters) 250kW for traditional generators 50kW for storage In addition, the Article 2 of Resolution Arera 540/21 indicates that the measurements of the individual generators are required only for new plants.
For measurements, the precision required is that indicated in tables 5 and 6 of Attachment A.6
> Terna: maximum measurement error less than or equal to 2.2%. For only the single existing generators, the maximum error rises to 10%.
How is P,Q & V measured?
According to CEI 0-16 2022-03 it requires that the measurements are taken at the delivery point, in MV, by means of a measurement converter (Power Analyzer) of class 0.2, or better, and CT and VT measurement of class 0.5, or better, with 5 VA or 10 VA performance. The CTs and VTs can be used in sharing with other systems, with the exception of the custody transfer unit, and without creating interference.
Measurement systems with different characteristics are also acceptable, provided they comply with the accuracy required by Annex A.6 of Terna's Grid Code table 5: maximum error on the measurement of P, Q and V less than 2.2%.
SPI for each transformer substation: how does the CCI control the plant?
As indicated in paragraph O.14 and in figures O.1 and O.7 of CEI-016 2022-03, monitoring of the status of the DG and of all DIs is required, via direct acquisition (dry contact) or by communicating with other system elements (e.g. SPI).
While, the control functions of the CCI are based on closed-loop regulators, which read the measurements at the delivery point, compare them with the set points, received (slave mode) or calculated (autonomous mode), calculate the set points from send to the generators/converters and they send them.
Consequently, the CCI must be able to communicate reliably and quickly with the generators/converters, which must implement a standard communication interface and protocol which provides for the possibility of receiving commands in P and Q (or equivalent, for example PF or PHI ).
If the communication is based on serial protocols, such as RS485 or CANBUS, and not Ethernet, it is more difficult to respect the prescribed response times, and it is necessary to evaluate the feasibility case by case.
How to get a CCI
Once all the tests have been carried out and the certifications described in chapter O.15 of CEI 0-16 2022-03 have been carried out, CCI manufacturers will be able to issue a self-declaration of conformity to the standard, annexes O and T.
The technical file thus obtained must be kept for at least 10 years starting from the last date of manufacture of the product and must be kept at the disposal of the control authorities.
A third party, accredited for these attachments to the standard, can certify the conformity of the product, as an enhancement to the self-declaration.
In conclusion, the CCI is mandatory for plants with power exceeding 1 MW.
New systems must have it by 1 December 2022, while existing ones by 31 January 2024.
Even self-consumption plants with a power of at least 1 MW must have the CCI, and there are mandatory and optional functions, and the DSO can request others.
