9 Fault elimination
47
BA5789879-01 EN
This chapter describes how to eliminate simple operating faults.
9.1 Testing the tripping circuit and reason for tripping
If the signal pin is in the
operation
position, the pressure relief device has not
tripped. If a micro-switch has, nevertheless, issued a signal, the error can lie
in the tripping circuit.
► In this case, check whether the signals in the tripping circuit are being reli-
ably transmitted.
If the signal pin is in the
alarm
position, the pressure relief device has
tripped. In this case, clarify the following questions and, if necessary, contact
the transformer / on-load tap-changer manufacturer in order that further
measures can be introduced.
▪ Has oil escaped from the pressure relief device?
▪ Was the transformer subjected to a mechanical load?
▪ How large was the load on the transformer at the instant of tripping?
▪ Was the on-load tap-changer moved immediately before or during trip-
ping?
▪ Did any other protective devices respond at the instant of tripping?
▪ Were switching operations being carried out in the grid at the instant of
tripping?
▪ Were overvoltages registered at the instant of tripping?
▪ How high is the static pressure on the pressure relief device (height differ-
ence between the oil level in the expansion tank and in the pressure relief
device)?
► Once all potential errors have been remedied, push the signal pin back
into the device, otherwise any further tripping of the valve cannot be dis-
played.
Summary of Contents for MESSKO MPREC
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