Hikvision’s ultraviolet corona discharge monitor allows continuous, 24-7 monitoring of temperature and corona discharges at electrical substations. This note takes a closer look, based on product tests conducted by a&s China.
Hikvision’s ultraviolet corona discharge monitor allows continuous, 24-7 monitoring of temperature and corona discharges at electrical substations, using a tri-spectral technology combining visible light, thermal and UV. This note takes a closer look, based on product tests conducted by a&s China.
With the rise of “smart grids,” China has gradually introduced a variety of mobile solutions such as industrial drones and inspection robots to monitor power lines and other power system components. Various technologies including visible light, thermal imaging, and ultrasonic are used in the process, thus eliminating hidden dangers.
However, in the process of electric power operation, a phenomenon called corona discharge may occur – caused by the ionization of a fluid such as air surrounding a conductor carrying a high voltage. If the corona discharge situation is left unattended for a long time, it will lead to transmission power loss and, more severely, transmission line corrosion.
In order to detect corona discharges as they occur, Hikvision has launched their UV corona discharge monitor, which integrates three types of imaging technologies – UV, thermal and visible light – to enhance the monitoring of power systems. At the same time, the device can detect and count the occurrence of corona discharges in real time. Once the set threshold is crossed, the backend platform will automatically issue an alarm. This, then, will further guarantee the safe and efficient operation of power systems.
Safety and reliability
Compared with traditional monitoring cameras, the UV corona discharge monitor has a unique design. The main body has three camera units integrated into it: IR imaging, visible light and UV imaging, which are put together side by side. The unique parallel structure makes the camera stand out among competing pan/tilt cameras.
As a PTZ camera made of aluminum alloy material, the monitor has a weight of only 17 kg, which is much lower than that of competing cameras. Aside from weight reduction, the solid aluminum alloy shell can also provide protection for the internal electronic components, making possible the device’s IP67 protection rating.
The monitor is divided into two parts. The upper part is the main camera body, which is primarily used for video capturing and detection. The lower part is the pan-tilt part, which is mainly responsible for fixing and rotating the camera left and right.
On the main part of the camera, the top is designed with a protective cover, which can effectively avoid direct sunlight and rain interference, further ensuring output of high-quality and clear images. The interior is equipped with three camera units for infrared imaging, visible light, and ultraviolet imaging. Among them, the visible light camera unit is equipped with a wiper, which can wipe away dirt/soil on the visible light lens. Below the lens, there are four infrared fill lights and warm lights, which are mainly used for night-time monitoring.
At the same time, the camera also has a built-in SD card slot that can support 256GB of memory. When the network fails for a short time, the camera image data can be saved locally to ensure data stability without loss.
The pan/tilt below can assist the camera to achieve continuous rotation of 360° in the horizontal direction and +40° to -90° in the vertical range. The speed is 0.1°-120°/s for horizontal rotation and 0.1°-50°/s for vertical.
At the bottom of the camera, there are power line, alarm, network and other I/O interfaces. Compared with previous interface designs, the monitor adopts unified standard interfaces which can effectively save installation time.
It is worth noting that the monitor has passed the EMC4 level certification and can be directly applied in electrical substation environments, as the device is protected against power radiation and other interferences.
Superb imaging performance with tri-spectral technology
The monitor is consisted of several camera units so as to meet various environmental requirements in substation scenarios.
Among them, the thermal imaging unit uses a 25mm fixed-focus lens with a maximum resolution of 640 x 512. It can monitor heat generated by excessive power load in real time. a&s test results show that, when detecting in a -20-150°C range or 0-550°C range, the margin of error is ±2°C.
The visible light unit uses a 1/1.8" progressive scan CMOS sensor, which can generate good color video even in 0.0005 Lux conditions. The camera will enter black-and-white mode below 0.0005 Lux, and turn on the fill lights when the Lux reaches 0, with a maximum fill light distance of 150 meters.
The visible light camera is also equipped with a 6-240mm zoom lens, whose 40x zoom can meet various user needs for large scene and partial scene coverage. In addition, the visible light camera also supports ultra-wide dynamic range, backlight compensation, strong light suppression, 3D noise reduction, anti-shake and other functions, capable of 24-7 monitoring in various indoor, outdoor and ultra-low illumination environments.
The ultraviolet imaging unit is the core of the camera. It uses a 50mm fixed-focus lens with a maximum resolution of 720 x 576, which can extract ultraviolet light in the 240nm-280nm band. It is worth noting that, as the largest radiator, the sun can emit light of different wavelengths, but in the presence of the ozone layer, most of the radiation below 280nm is absorbed by the ozone. This then allows the monitor to effectively avoid the influence of solar radiation.
It is found that ultraviolet light is easily perceived by the UV corona discharge monitor. a&s test results show that that even at a distance of 100 meters, the monitor can still capture UV light and display it on the backend platform. To display the position of the ultraviolet light more intuitively, the device automatically marks the corresponding position in the visible light image, thereby making things easier for maintenance workers.
It is worth noting that with each corona discharge, the amount of electrons increases as the insulator deteriorates. For this reason, the monitor will automatically count the photon value. Once the set threshold is reached, it will automatically issue an alarm to the relevant platform. The maintenance personnel can then recognize the equipment that needs to be repaired. Their work thus becomes much more efficient.
In addition, to be compatible with various platforms, the monitor supports many application interface protocols (APIs) and can integrate with different systems through protocols such as ISAPI, SDK, ISUP (5.0) and GB28181.
1. 4 MP visible light camera and 40-time zoom lens meet the need for large scene and local scene coverage;
2. Four white fill lights ensure accurate color reproduction and clear images;
3. UV camera unit has maximum resolution of 720 x 576 and can display the number of ultraviolet photons in real time;
4. The maximum resolution of infrared thermal imaging is 640 x 512, with detection margin of error of only ±2°C;
5. The ultraviolet imaging unit can co-work with the visible light unit, helping the user more easily pinpoint the problematic spot;
6. The PTZ design enables the device to cover a large scene;
7. IP67 protection and Level-4 power protection ensure the applicability of the product.
Power generation and delivery is a fundamental part of the society, supporting the rapid development of the national economy. To better ensure the safety of electrical substations, China has formulated relevant industry standards and requirements in recent years. Among them, the digitization of substations as proposed by the State Grid Corp. of China has elevated the concept of ultraviolet diagnosis to a new height, with State Grid clearly stating that in the future, ultraviolet diagnosis will become a supplement to visible light and thermal imaging, realizing true multi-spectral monitoring.
In this regard, the Hikvision UV corona discharge monitor can play a critical role. Aside from UV, the device is also equipped with a thermal imaging and a visible light camera unit. Through this tri-spectral fusion, it can monitor substations continuously and detect problems such as excessive heat and corona discharges. At the same time, based on the characteristics of a corona discharge, the device can count the number of photons in real time, ensuring the safety of substations and meeting user needs for operational and maintenance efficiency.