Proof of Concept: See How Rapid Shutdown (RSD) Works

Testing with Huawei equipment, which already has the RSD standardized from the factory, complies with all the safety requirements indicated by the standards

4 min 14 sec read

With the growth in the number of photovoltaic power plant installations in recent years, there has also been an increase in concerns about human safety, especially those related to fire control in this type of installation. Photovoltaic modules are characterized by the conversion of sunlight radiation into electrical energy, i.e., while under the effect of sunlight, the module will convert energy uninterruptedly.

Taking into that the current operating range of direct current (DC) voltage of photovoltaic strings commonly operates in a voltage range between 600 and 1000V, this type of installation represents a danger to human life in cases of fire or flooding, for example.

between modules and water can conduct electrical energy, which puts everyone nearby at risk, especially in cases of roof fires – the high voltage of the DC circuit limits the firefighters' ability to fight the fire, which can lead to the total loss of the installation. Therefore, the Rapid Shutdown (RSD) function is a solution for eliminating high voltages in the DC circuit, in order to increase the safety of people near the installation.

What is RSD

As the name suggests, RSD is a rapid shutdown system intended to reduce the voltage of the set to a safe level. Currently, the safety regulation NEC690.12 has requirements for RSD of photovoltaic inverters. In Brazil, ABNT NBR 17193:2025 is approved as the responsible standard for the safety premises that cover the rapid shutdown of a photovoltaic system, in other words the RSD function.

As indicated in the ABNT NBR 17193: 2025 The circuits that must have their voltage controlled by the RSD are the DC circuits of the photovoltaic system and the alternating current (AC) output circuits that are within the array limit (defined as 300mm from the array in all directions).

Also as indicated by the standard, the DC circuits of the photovoltaic system that are outside the array limit must reduce their voltage to up to 60Vdc within 30 seconds after the RSD is initialized. While the DC circuits that are within the array limit must reduce their voltage to up to 120Vdc 30 seconds after the RSD is initialized.

Real Case – Proof of Concept

In order to synthesize the RSD concept and test its functionality, performance and application tests of the RSD were carried out in a real installation. The test installation is located in the city of Recife in the state of Pernambuco and has the following characteristics:

Table 1 – Project Details

Installation Type	Roof
DC Power	28,86kWp
AC power	25kW
Inverter Model	HUAWEI SUN2000-25KTL-M5
Module Models	570Wp N-type 545Wp N-type
Number of Modules	48 units
String Division	PV1: 14 Modules PV2: 14 Modules PV4: 20 Modules
Optimizer Model	HUAWEI SUN2000-600W-P

During the tests, only the PV4 string is connected to the Huawei SUN2000-600W-P optimizer which, among other features, has the RSD function.

The test consists of measuring the open circuit voltage of all strings in the photovoltaic system and comparing the open circuit voltage between strings that do not have the RSD function with those that do, using the Huawei SUN2000-600W-P optimizer. The test routine was performed as follows:

One of the strings that do not have optimizers connected was disconnected, which in this case was PV1;
The voltage between the positive and negative poles of the PV1 string was measured with a multimeter;
Recording of the value obtained;
The PV4 string, which has the Huawei SUN2000-600W-P optimizer with the RSD function enabled, has been disconnected;
The voltage between the positive and negative poles of the PV4 string was measured with a multimeter;
Recording of the value obtained.

Following the testing routine, the following results were obtained:

Table 2 – Test results

Disconnected String	Measured Voltage
PV1	589,2Vdc
PV4	0V

Figure 2a – Open circuit voltage recording of string PV1

Figure 2b - Open circuit voltage record of PV4 string. and (b) Open circuit voltage record of PV4 string — Figure 2b – Open circuit voltage recording of the PV4 string

Conclusion of the essay

As observed in the tests, the RSD function complied with the safety requirements indicated by the standard for eliminating high voltage from the DC circuit when disconnected. This can be used to help mitigate risks related to human and plant safety during maintenance, or in cases of extreme danger, such as during fires in rooftop photovoltaic plants.

The opinions and information expressed are the sole responsibility of the author and do not necessarily represent the official position of the author. Canal Solar.

Primary Cabin Course Huawei rapid shutdown

HDT Brasil

HDT is a hub of high-value solutions for the green technology, photovoltaic energy and critical energy markets. Recognized and awarded for its results in the region, it is the exclusive Huawei representative in Brazil in the solar segment and the main regional representative of the Chinese company in the Americas. HDT Brazil operates in the B2B segment by supplying high-performance, safe and productive generation products and services from the largest manufacturers in the world - Huawei. Its mission is to enable projects in order to exponentially increase the return on investment of its business partners. The company is a division of HDT Group Limited, present in China, Hong Kong, Brazil, Chile and Panama.