Functionality
58 USER MANUAL FPC 200 - 3/2017
Buchholz relay protection – ANSI code 63
2.5.6.1 Description
Buchholz relay protection is external protection that
mechanically controls oil level and oil flow in certain
power transformers. Protection consists of two
instances one dedicated to Leak and pressure switch
and second to Float switch. Float switch indicates slow
air build up in Buchholz cylinder, usually indicating
minor discharge fault in transformer. While Leak and
pressure switch detects forceful oil flow usually
indicating major short-circuit related fault in
transformer.
Float switch
Leak and
preassure switch
Figure 2.35 Schematic of Buchholz relay operation.
It is recommended that pressure switch
immediately trips CB while float switch
indicates fault that needs to be treated as
soon as possible to prevent further damage
to transformer.
2.5.6.1.1 Setting parameters
Enabling protection function.
Enabling protection function separately for each group level.
Time stabilization of fault detection. As a filter of short disturbances on
measuring circuits. Time before protection starts.
Time stabilization of pickup signal. Time when the monitored value is
outside the operating range, but the protection does not stop yet.
None
Variable 1
Variable 2
Variable 3
Variable 4
Source of blocking signal.
Table 48 Buchholz function parameters.
2.5.6.1.2 Associated digital inputs
External trigger of Buchholz relay 1 protection.
External trigger of Buchholz relay 2 protection.
Table 49 Digital inputs associated with the protection.
2.5.6.1.3 Counters
Total consecutive number of pickup signals.
Consecutive number of trip signals.
Table 50: Counters presented in buchholz protection.
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