650nm analog fiber transceiver, switch cabinet arc detection expert

Photocoupler

As an electrical switchgear apparatus, the power generation function is performed in the power system, the process of transmission, distribution and conversion of electrical energy, the electrical device acts on the opening and closing, control and protection.

As a common fault in the switchgear , arc short circuit will radiate huge energy such as sound, light, electricity and heat. If it is not timely, it will cause damage to the power system and electrical equipment, and even personal injury. Therefore, effective measures must be taken to quickly extinguish the arc to ensure the normal operation of the switchgear. The basic idea of ​​arc fault protection is to detect the arc or current and voltage signals of the fault arc in real time. When the signal amplitude exceeds a predetermined threshold, the control system is started to make the circuit breaker work. Compared with the traditional current and voltage detection methods, the light detection method not only can generate extremely fast response, but also has ultra-low transmission delay, which can greatly reduce the response time of the detection system. In addition, the light is complicated in the operation of the detector. Extremely stable in EMI environments. Therefore, light detection has become the best way of arc detection.

For the light detection of arcs in switchgear , Shiqiang supplier Avago has introduced a 650nm high-reliability analog fiber transceiver unit (AFBR-S10TR001Z) that can operate from -40°C to +85°C. At the same time, the system designer can use the device to design an arc sensor on a 1 mm plastic optical fiber (POF). Its shape and internal structure are shown in Figure 1.

Figure 1: Outline and internal structure of AFBR-S10TR001Z

The AFBR-S10TR001Z is mainly composed of a transmitter and a receiver. The transmitter contains an LED with a center emission wavelength of 650 nm. The receiver contains an ASIC that integrates a photocell (PD) and a transimpedance amplifier (TIA). This ASIC provides an analog voltage output to the pull-arc monitoring unit.

Figure 2: Relative spectral sensitivity curves of photocells in a transceiver

2 is a relative spectral sensitivity curve of a photocell in a transceiver, the black line indicating that the relative spectral sensitivity of the photocell of the ASIC integrated in the transceiver is related to the wavelength of the light of the input light. The blue line depicts a typical arc spectrum. The photocell response completely covers the spectral range of the arc, ensuring complete detection of arc events. The typical application circuit of the AFBR-S10TR001Z is shown in Figure 3.

Figure 3: Typical application circuit for AFBR-S10TR001Z