Precision Time Protocol

About: Precision Time Protocol is a research topic. Over the lifetime, 604 publications have been published within this topic receiving 6006 citations. The topic is also known as: PTP & IEEE 1588.

Evaluation of Precision Time synchronisation methods for substation applications

Abstract: Many substation applications require accurate time-stamping. The performance of systems such as Network Time Protocol (NTP), IRIG-B and one pulse per second (1-PPS) have been sufficient to date. However, new applications, including IEC 61850-9-2 process bus and phasor measurement, require accuracy of one microsecond or better. Furthermore, process bus applications are taking time synchronisation out into high voltage switchyards where cable lengths may have an impact on timing accuracy. IEEE Std 1588, Precision Time Protocol (PTP), is the means preferred by the smart grid standardisation roadmaps (from both the IEC and US National Institute of Standards and Technology) of achieving this higher level of performance, and integrates well into Ethernet based substation automation systems. Significant benefits of PTP include automatic path length compensation, support for redundant time sources and the cabling efficiency of a shared network. This paper benchmarks the performance of established IRIG-B and 1-PPS synchronisation methods over a range of path lengths representative of a transmission substation. The performance of PTP using the same distribution system is then evaluated and compared to the existing methods to determine if the performance justifies the additional complexity. Experimental results show that a PTP timing system maintains the synchronising performance of 1-PPS and IRIG-B timing systems, when using the same fibre optic cables, and further meets the needs of process buses in large substations.

Research of time synchronization in digital substation based on IEEE 1588

Abstract: IEEE1588 defines a precision time protocol (PTP) for networked measurement and control systems, which supports system-wide synchronization accuracy in the sub-microsecond range This paper introduces the principle of high precision clock synchronization and the PTP clock models defined in IEEE1588 standard According to topological structure of substation communication network conforming to IEC61850 standard, application schemes of IEEE1588 in digital substation are proposed, and their advantages and disadvantages are also discussed Then the redundancy configuration method of clock unit and its function implement are given Clock synchronization error of IEEE1588 standard is theoretically analyzed At last, concrete system wide application strategies of IEEE1588 standard in area power network are researched

Method and devices for compensating for path asymmetry

Abstract: This invention relates to methods and devices for compensating for path asymmetry, particularly with reference to time and frequency synchronization. The invention has particular application where time and frequency synchronization over packet networks using, for example, the IEEE 1588 Precision Time Protocol (PTP) is being carried out. Typically communication path delays between a time server (master) and a client (slave) are estimated using the assumption that the forward delay on the path is the same as the reverse delay. As a result, differences between these delays (delay asymmetries) can cause errors in the estimation of the offset of the slave clock from that of the master. Embodiments of the invention provide techniques and devices for compensating for path delay asymmetries that arise when timing protocol messages experience dissimilar queuing delays in the forward and reverse paths.

Transparent Clocks vs. Enterprise Ethernet switches

Abstract: Precision Time Protocol (PTP) is a high-precision time synchronization protocol designed to operate over a local area network. PTP, typically referred to as 1588, is defined by the IEEE Standard 1588™-2008 and provides clock synchronization at the nanosecond level. Even though devices with support for 1588 are widely available, there have been few performance studies of such devices. This paper investigates the impact of latency and high bandwidth background traffic on 1588 clock synchronization in a network consisting of both 1588 and non-1588 aware switches. As expected, we found that 1588-aware switches provide higher precision time synchronization in smaller-scale networks. In larger networks with congestion, 1588-aware switches were unable to maintain high accuracy clock synchronization due to the lack of traffic prioritization. Our results also show that having cut-through Enterprise Ethernet switches with prioritization enabled is adequate for maintaining sub-microsecond synchronization.

Time synchronization method and system for synchronous messages of IEEE1588 (Precision Time Protocol) master-slave clocks of intelligent transformer substation

Abstract: The invention discloses a time synchronization method and a time synchronization system for synchronous messages of IEEE1588 master-slave clocks of an intelligent transformer substation. The method comprises the following steps of: establishing a master clock synchronous message, and sending the timestamp t1 of the sending moment of the message to the clock in a broadcasting manner; recording a receiving moment t2 of the master clock synchronous message; recording an absolute receiving moment TT2 when the master clock synchronous message is received by a slave clock; establishing a slave clock responding message, sending the slave clock responding message to the master clock in a peer-to-peer manner, and recording the timestamp t3 of the sending moment of the message; recording an absolute sending moment TT3 when the slave clock sends the clock responding message; recording an acquiring moment t4 when the master clock acquires the message; calculating a time deviation, and calculating asymmetry errors according to the timestamp t1, the absolute receiving moment TT2, the absolute sending moment TT3 and the acquiring moment t4; and carrying out time correction on the slave clock by the time deviation and the asymmetry errors. According to the time synchronization method and the time synchronization system for synchronous messages of IEEE1588 master-slave clocks of the intelligent transformer substation, the influences of the asymmetry errors can be eliminated, and the time synchronization precision of the master-slave clocks is improved.