Is DPS mandatory in the entry standard with photovoltaic system?

Article published in the 14st edition of the Magazine Canal Solar

Os surge protection devices, known by its acronym DPS, are used to protect equipment and installations of transient voltage surges arising, mainly, from atmospheric discharges and maneuvers in the electrical network.

This equipment is frequently used in circuit distribution boards in residential, commercial and industrial installations. They are also used in photovoltaic plant installations, both on the direct current (DC) and alternating current (AC) side.

However, there are many doubts whether, in UCs (Consumer Units) that have a photovoltaic plant installed, the DPS is required in the input standard, that is, if there is a need to install them inside the measurement box and/or protect the standard. .

To answer this question, we will use the regulations in force in the country and the technical standards of electricity distributors.

First, by consulting the Prodist module 3, which deals with the connection to the electrical energy distribution system, we found that the use of overvoltage protection is a minimum requirement provided for at the plant's connection point, but it does not detail whether this equipment must be installed in the input standard.

Therefore, there is no obligation to install these devices inside standards with connected photovoltaic systems. One question that remains is: in general entry standards, even those that do not have photovoltaic systems connected, is the installation of this device mandatory?

And the most important question: can the concessionaire require the installation of the DPS in the input pattern to approve the connection of the photovoltaic generator?

To answer this question, we analyzed the ABNT NBR 5410 standard and can see how it addresses the issue of DPS location.

But first, it is essential that we have two well-defined concepts, which will be essential in understanding this text. We must know the difference between entry point and delivery point.

A NBR 5410 defines the entry point as “the point at which the external line penetrates the building”, as shown in the 5410 definition in Figure 1, that is, we can consider this point as the place where the network enters the building, right after passing through the input pattern.

The delivery point is the point where the concessionaire's network connects to the customer's input branch, normally located at the borders of the input standard, according to this section of NBR 5410.

To clarify the differences between these two terms, Figure 2 presents an illustration where the region circled in red defines the delivery point, where the concessionaire's branch connects to the customer's input branch, and the area circled in blue presents the point entry point into the customer's building, which is the point where the network enters the building.

With the concepts defined, we now analyze what guides ABNT NBR 5410 regarding the location of the DPS.

In item 6.3.5.2.1 a), as shown in Figure 3, the installation of the DPS must be next to the entry point or in the main distribution board when the objective is to protect against overvoltages from atmospheric discharges transmitted by the external power line and also switching overvoltages.

The illustration in Figure 4 explains what was said in the previous paragraph. In it we can see that the wall through which the network enters the building can be considered the entry point. It is there or nearby that the DPS must be installed.

There is also the alternative of installing the DPS in the main panel located as close as possible to this entry point, as instructed in item 6.3.5.2.1 a) of 5410. Generally, we call this main panel QGBT (General Low Voltage Panel ).

In cases where it is desired to protect the system against direct atmospheric discharges, the DPS must be installed at the entry point, as indicated in item 6.3.5.2.1 b), of Figure 3.

Figure 5 illustrates this second situation and shows that in these cases of direct discharge, the device must be installed at the point of entry of the network into the building.

If you wish to place this DPS within the QGBT, it must be located at the point where the network enters the building.

The ABNT NBR 5419 standard, which deals with protection against atmospheric discharges, advises that a risk analysis be carried out to find out whether there is a need to use an SPDA (Atmospheric Discharge Protection System).

If there is such a need, the standard indicates the use of DPS at the entrance to the structure line, on the border that divides the external and internal part of the building, as shown in Figure 6.

If the QGBT is on this border, the DPS can be allocated within it, otherwise, as shown in Figure 5, the DPS must be allocated in an appropriate box on this border.

If there is no need to use SPDA, the use of DPS will follow the criteria established in 5410, which have already been mentioned in previous paragraphs.

The use or not of the SPDA will be defined after following the steps indicated in ABNT NBR 5419-2, when carrying out the risk analysis of the building. Figure 7 presents the excerpt taken from NBR 5410-3, which confirms what was reported in this paragraph.

Until now, the need to use DPS in the input standard has not been clarified and our question remains unanswered.

So, let's move on to analyzing the distributors' standards, because as input standards are inspected and connected to the distribution system by these companies, the analysis of whether or not this use is necessary will be guided by their standards.

Is this use mandatory or not?

The final answer depends on the distributor. Some distributors have updated their distribution standards and started to require the use of DPS in all new standards that are built and connected to their network.

Most of them do not have in their regulations the mandatory installation of this device and this is what we observed when we analyzed the vast majority of entry standards.