隨著變電站自動化技術的發展，對變電站內時間的精確和統一提出了更高的要求。本文提出了一種采用IRIG-B時間碼來對時的方案。在這種對時方案中，每個變電站只安裝一個GPS接收裝置，利用RS422/485總線傳輸IRIG-B碼，保護裝置對IRIG-B碼解碼器后，來設置自己的時間。本文還詳細介紹了IRIG-B碼的概念和原理以及用CPLD實現IRIG-B碼解碼器的設計思想和實現方法。IRIG-B碼對時方式簡化了回路設計，并且能夠可靠地提供精確的時間信息，必將在電力系統中得到廣泛的應用。

　　Abstract:

　　With the progress of automatic technology in transformer substations， requirements for unified and accurate time in a substation are put forward. An economic and accurate scheme to synchronize time by using IRIG-B code is presented in the paper. In this scheme， only one GPS receiver is used in every substation， and the IRIG-B code is transmitted by RS422/485. After decoding the IRIG-B code， the protection device can set its own time. The concept and principle of IRIG-B code are explained， and the particular method of decode IRIG-B code by using CPLD is stated in detail. The way to synchronize time with IRIG-B code can simplify the circuit design，and provide accurate the information of time，which will be widely used in power system.

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