Dirceu Ferreira

ANEELwhich deals with agents that operate in energy compensation mode, a new classification of consumers into micro and mini generation emerged. This classification is well defined as: Microgeneration: installed generation capacity of up to 75 kW; Minigeneration: installed capacity above 75 kW and up to 5 MW. And within this context, energy distributors in Brazil accept several configuration concepts for connecting a customer to the medium voltage system, called A4. Going through the different concessionaire standards, it is observed that there is no consensus on the use of a common configuration, even though the characteristics of each region of the country are preserved. But we can highlight at least two aspects: They allow the use of fuse switches in medium voltage and; They require the use of a circuit breaker in medium voltage. Another important issue concerns the billing measurement system for A4 customers. According to NBR 14039, measurement can be at low voltage if the installed capacity is up to 300 kVA. Above this value, the measurement must be at medium voltage. Therefore, the location of the measurement sector is another important factor in the configuration of a primary cabin. Here we will address the protection aspects using the typical concepts of 2 concessionaires for minigeneration - Celesc and CPFL - in accordance with their technical standards: CELESC: I-432.0004 - Requirements for connecting micro or mini power generators to the Celesc Distribuição electrical system CPFL: GED 15303 - Connection of micro and mini distributed generation under an electrical energy compensation system Reference Diagrams To address the 2 typical configurations, the schemes adopted by CELESC and CPFL are presented, shown in Figures 1 and 2. Figure 1: Primary cabin configuration according to Celesc Figure 2: Primary cabin configuration according to CPFL Comparisons Observing the diagrams, it is noted that the companies already present differences in relation to the classification method. While Celesc uses apparent power, CPFL uses active power. The Celesc standard makes no mention in the text regarding the use of a fuse switch on the medium voltage side, but the configuration adopted indicates the use of a fuse switch (Figure 1). On the other hand, CPFL does not allow the use of a fuse switch between the connection point and the generation, based on technical standard GED 33 (Connection of Self-Producers in Parallel with the CPFL Distribution System), item 6.1: “...It should be noted that the use of fuses or single-pole disconnectors is not permitted between the input switch and the generator or generators.” This requirement is ratified in the configuration shown in Figure 2. The same restriction is also required by Prodist Module 3, section 3.3: “5.4.8 Single-pole fuses or disconnectors must not be used between the input circuit breaker and the generators.” However, this item is not highlighted in section 3.7, which deals with micro and mini-generation procedures. Specifically regarding protection functions, particularly regarding photovoltaic generation, the diagrams shown in Figures 1 and 2 indicate that they must act on the respective circuit breakers, although some protections can be performed by the inverters. Table 1 presents the protections required by Module 3 and that can be enabled in the relay and/or inverters. Table: Protection functions of relays or inverters Protection Function Description Enable Relay Inverter Conventional 50/51 Phase overcurrent X 50N/51N Neutral overcurrent X Complementary 59N or Neutral overvoltage X 67N Neutral directional overcurrent X 32 Power directional XX 25 Synchronization X 27 Undervoltage XX 59 Neutral overvoltage XX 46 Current unbalance X 47 Voltage unbalance X 51V Voltage-restrained overcurrent X 67 Phase directional overcurrent X 78 Phase angle measurement X 81 O/U Over and under frequency XX s/n Anti-islanding X When protections are performed by relays, it is necessary to install current transformers (CTs) and potential transformers (PTs) properly installed to detect signals on the medium voltage side. For example, the 59N function requires the use of three VTs on the medium voltage side, and the overcurrent functions require 3 CTs. These needs imply the existence of a suitable environment, that is, a medium voltage cabin. In general, Table 2 presents the main characteristics between the configurations of the two dealerships. Table 2: Characteristics of the primary cabin configurations for two concessionaires Celesc CPFL device P ≤ 300 kVA P > 300 kVA P > 75 kW Fuse switch in MV Yes Yes No Circuit breaker in MV No Yes Yes Actuations of LV Protections MV MV It can be seen that CPFL, for any minigeneration, requires the use of an MV circuit breaker. Comments This article dealt with configurations adopted by two dealerships and the two lines of configurations still suffer variations in some dealerships. It can be said that the configuration adopted by CPFL is similar to that of Elektro and Roraima Energia. The configuration adopted by Celesc, with some variations, is followed by Copel and Cemig. At Copel and Cemig there are variations in relation to the use of inverters and depending on the power and type of substations. In any case, these variants affect the cabin specification, reflecting the cost of implementing the plant. In the case of photovoltaic generation, it would be appropriate for there to be a single procedure among the concessionaires and some optimizations could be evaluated: Use of fuse switches in the MV, with simultaneous opening between phases; In situations where there is no space for construction or installation of a primary cabin, evaluate the possibility of using reclosers on a pole and time measurement; Teleprotection between the distributor's protections and the plant's protections (relay and/or inverters). Bibliography NBR 14039 – Medium voltage electrical installations Prodist Module 3 Resolution 482/2012 –ANEEL GED 33 - Connection of Self-Producers in Parallel with the CPFL Distribution System GED 15303 - Connection of Micro and Mini Distributed Generation under the Electric Energy Compensation System – CPFL I-432.0004 - Requirements for the Connection of Micro or Mini Power Generators to the Celesc Distribuição Electric System – CELESC DT - DTE 01/NT 001 Access of Micro and Mini Distributed Generation to the Roraima Energia Distribution Network NTC 905200 - Access of Micro and Mini Distributed Generation to the Copel System (with energy compensation) ND 5.31 - Requirements for Connection of Accessing Electric Energy Producers to the Cemig Distribution System D – Medium Voltage

Dirceu Ferreira

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