Understand the differences between clock controllers and time relays in one article

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Clock controllers and time relays are both switching electrical devices in control circuits. The so-called control loop refers to the loop that carries out logical measurement and control, electrical parameter acquisition, signal amplification and transmission, as well as information management. Clock controllers are used for accurate measurement and control over long periods of time, whereas time controllers are used for control over short periods. Time relays have limited precision in measuring and controlling time, but they require good repeatability as well as a variety of contact types. The difference between a clock controller and a time relay: yunrun.com.cn/tech/2159.html. The following diagram shows the timing diagrams for relays with delay upon power-on and delay upon power-off: http://yunrun.com.cn/upload/201808/23/201808232349327155.png. The time values t in these diagrams are quite short, ranging from 10 milliseconds to 10 seconds. It can be seen that there is a significant difference between a clock controller and a time relay. In use, timing synchronization by the clock controller is crucial. Typical clock controllers use an internal high-frequency oscillation, convert this oscillation into 0/1 pulses, and determine how many pulses correspond to one second, thereby achieving basic timing. This method introduces measurement errors; it is normal to see deviations of several seconds or even minutes every 24 hours. Therefore, the clock controller needs to be synchronized with the reference time. Time relays do not require such operation. In actual measurement and control, the PLC is a most typical component. It can meet the requirements of clock controllers as well as perform the functions of time relays, and the number of clock controllers and time relays is more than sufficient to satisfy actual needs. The following image shows schematic diagrams of medium-voltage distribution systems and low-voltage distribution systems: http://yunrun.com.cn/upload/201808/24/201808240003350144.png For implementing power monitoring on the systems shown in the above image, the most commonly used device is a PLC. We use PLCs to carry out logical control tasks on-site, to collect electrical parameters, and to manage communications. The image below shows ABB’s most basic PLC; the TON is a relay module for timed delays, used to eliminate jitter in digital signals: http://yunrun.com.cn/upload/201808/24/201808240018084148.png Note: The PLC used here is too basic and has been discontinued; it has been replaced by more advanced PLCs. When using a PLC as the clock controller, it is necessary to synchronize the time. When designing the measurement and control system for substations, engineers install GPS time synchronization devices (using Beijing time) within the station, enabling the PLC to synchronize with GPS several times a day in order to calibrate its internal timing reference clock. The image below shows a GPS time synchronization device used for measurement and control in substations: http://yunrun.com.cn/upload/201808/24/201808240024015148.png This GPS time synchronization device has an outdoor antenna, which is not shown in the image. The image below depicts a typical GPS device used in car navigation, illustrating the difference between GPS devices used for timing and those used for navigation: http://yunrun.com.cn/upload/201808/24/201808240032040450.png The image below is a real-life view of power monitoring in a substation. Here, the so-called time controller function is a piece of cake. http://yunrun.com.cn/upload/201808/24/201808240030248928.png The diagram below shows the program structure of the clock controller, which is used for parameter variation recording in SOE. The time accuracy for measuring and recording the state changes of digital switches is 1 millisecond, and the continuous recording period is 1 year: http://yunrun.com.cn/upload/201808/24/201808240036271166.png With this program, it is possible to record information on the state changes of hundreds of digital switches, with time recordings precise to year, month, day, hour, minute, second, and 0.1 second.