Abstract
Pilot projects of digital substations under current development are based on the application of the IEC61850 standard. Typically, such projects use a separate station and process buses. Therefore, instantaneous current and voltage measurements are transmitted in the SV protocol with the response time of 25 ms, and the same network is used for synchronization of measuring devices with PTP protocol. In this case the process bus is characterized by high load and, to implement it, the capacity of 100 megabit Ethernet commutator switch is not high enough, so in some cases, Gigabit Ethernet technology must be used, which increases the cost of the project significantly. Due to its high load, the process bus can’t be used to transfer the control commands, which are transferred by means of GOOSE protocol, that is why a separate network referred to as the station is used for it. This makes the substation communication network very complicated, which is inconvenient from the point of view of operation and maintenance. The paper is concerned with an alternative variant of transmission of current and voltage measurements by means of С37.118 protocol. Unlike Sampled values protocol, this one makes it possible to transmit vector measurements calculated on the basis of measurements for one basic frequency period. At present, this protocol is used in the wide-area measurement system (WAMS) with the update rate of vector data every 20 ms. However, the update rate is an adjustable parameter and if one can provide transmission of 4 vectors for one basic frequency period, it is possible to provide the required protection response time of the digital substation of 25 ms. The paper describes the main approaches to testing and implementation of a measuring digital substation o the basis of an operating WAMS system.
Keywords
Digital substation, protection functions, vector measurements.
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