ABB RELION 670 Series Technical Manual page 1253

Generator protection

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1MRK 502 066-UUS B

Operation principle

General concepts

Time definitions

The error of a clock is the difference between the actual time of the clock, and the time the clock is

intended to have. Clock accuracy indicates the increase in error, that is, the time gained or lost by

the clock. A disciplined clock knows its own faults and tries to compensate for them.

Design of the time system (clock synchronization)

The time system is based on software and hardware clocks that run independently from each

other. See figure

Synchronization

IEC08000287 V2 EN-US

Figure 629: Design of the time system (clock synchronization)

All time tagging is performed by the software clock. When, for example, a status signal is changed

in the protection system of a function based on the free running hardware clock, the event is time

tagged by the software clock when it reaches the event recorder. The hardware clock can thus run

independently.

The echo mode of differential protection is based on the hardware clock. Thus, there is no need to

synchronize the hardware clock and the software clock.

Technical manual

(fast or slow)

Time tagging and general synchronisation

Connected when GPS-time is

used for differential protection

Synchronization for differential protection

(ECHO-mode or GPS)

Basic IED functions

M11346-77 v1

M11346-80 v3

GUID-E2B9E81C-5733-4521-B27F-BF33E05CCFB0 v6

*IEC 61850-9-2

IEC08000287-2-en.vsd

IP12360-1 v4

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