The uniform and precise time source is an important basis for analyzing all kinds of device actions in power grid accidents. Therefore, the power clock system plays a very important role in smart substations. Based on the application of substation clock system, this paper analyzes and recommends the commonly used power clock, and further illustrates its characteristics and selection considerations.

The power clock provides accurate clock signals for each workstation of the power plant. The specific applications include distributed control system, DCS system, MIS production management system, power plant dispatching automation system and so on.

The recommended products of electric clock system are SYN2136, SYN4505 and SYN4505A. The latter two products are produced according to the requirements of the power plant time synchronization system and equipment specification, and can be used as the master slave clock in the power system clock project.

The SYN2136 type time server, as a power clock, is usually a temporary increase in a power plant which is not particularly important. It only needs NTP network to give time. It can be designed to receive GPS and Beidou dual-mode satellite signals, dual power supply, output 2 or 4 NTP network ports, and choose constant temperature crystal oscillator to keep time.

When a power plant needs to replace the old equipment and redesign the power clock system, it is suggested that the SYN4505 and SYN4505A type power clock should be used directly, and input and output various signal formats, which can meet the timing of all the common equipment in the substation, such as IRIG-B code AC and DC, PTP, pulse air contact, NTP and serial port.

The design of master clock and extended clock is usually adopted. SYN4505 is used as the main power clock device to receive GPS, Beidou and GLONASS satellite signals. When the satellite is out of lock, it can rely on the internal high precision constant temperature crystal oscillator for punctuality. At the same time, it receives external reference IRIG-B code signal, outputs commonly used NTP network and RS485 level B code (DC), B code (AC), PPM, PPS, serial port, second pulse and relay alarm.

The SYN4505A can be used as an expansion clock or B code expansion device in the power clock system. The device is an electric clock upgraded on the basis of SYN4505. In contrast, the outstanding feature is the addition of IRIG-B code optical fiber input and output and PTP input and output signal format. As an extension clock, it only needs to receive the external reference signal, and does not receive the satellite signal through the network, ordinary twisted pair or optical fiber.

When choosing the power system, please sort out the functions and technical requirements in advance, which equipment needs time service, whether there is one place, which kind of time service mode to support, and how much time precision requirement is required.

One NTP network port can provide tens of thousands of devices to the local area network, and computers, servers, cameras and other commonly used network devices support NTP time service. We need to connect to the core switch through the network cable to complete the time service.

IRIG-B code is divided into AC and DC. The 485 level B (DC) is commonly used. Generally speaking, for the sake of stability and accuracy, the 1 output corresponds to a device's timing. If the equipment is too large, it can also be carried out by 1 channels with 5 devices. When the budget is loose, it is recommended that the output of multiple B codes is enough. The output of dozens of roads is enough, and the B (DC) interface is green screw terminals.

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