Precision Time Protocol (Ptp) - GE T1000 Technical Manual

Chapter 4 – Functions
12

Precision Time Protocol (PTP)

12.1 Timing Requirements for Power System Applications
104
The Precision Time Protocol is available in T1000 and S2024G models.
Precision Time Protocol (PTP) was standardized by IEEE 1588 document, which
defines precision clock synchronization protocol for networked measurement and
control systems. It was developed to fulfil the requirement of a microsecond and sub-
microsecond network protocol to be used as synchronization protocol in
measurement and control applications, as the existing NTP protocol relies at the
millisecond accuracy.
For power system applications, NTP had a good performance until the requirement
of sub-microsecond precision for merging units, PMU and other applications. IEC
61850 standards had also lead modern substation communication to be performed
in a same shared network. Thus, synchronization should be performed directly at
Ethernet network, sharing physical medium with analogue values (packet at Sampled
Values frames), digital values (packet at GOOSE frames) and control messages
(packet at MMS messages).
This chapter contains the following sections:

Timing requirements for power system applications basics;

Precision Time Protocol (PTP) function;

PTP function in Reason Switches.
Precise timing to be used by IED in a substation has grown its importance over the
years. Legacy equipment does not allow the operators and analysers to have as
much information as nowadays, as they are not allowed to perform high automation
levels and their main application was as stand-alone equipment. After the usage of
digital protection schemes and digital power system automation, time stamping
events allowed the companies to study the outages in a system point of view,
increasing system reliability and making energy market more competitive.
Besides, modern substations with IEC 61850 capabilities cannot operate without
precise time synchronization of the equipment. Sampled Values data must be time-
stamped when leaving merging units, IED must consider time information for
sequence-of-events registers and digital fault recorders must output their
oscillography data time-stamped to allow many substations can perform a system
analysis of a disturbance event, to point some examples. The Phasor Measurement
Units (PMU) must time-stamp its data, as Wide Area Monitoring Systems (WAMS) can
only work properly if there is time synchronization of PMU equipment at the hole
system.
There are several ways to distribute time information to IED at a given power system
installation. IEC 61850-90-4 Technical Report recommends:
GE Reason Switches
REASON SWITCHES-TM-EN-3