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Associate

Join Date: Jun 2015
Posts: 37

Siemens Bus Bar Protection 7SS5..

04/15/2017 9:25 AM

I am trying to simulate a bus zone fault on a distributed Siemens bus bar protection system with central unit type 7SS522..The bay units are Siprotec 3 devices.

I connected only one line bay to the bus bar; that is after closing the Bus bar dis-connector and the Circuit breaker.

I then injected single phase current into the bay unit assigned to the line connected to the bus bar. (This bus has a total of 5 bays including a bus section). The central unit accurately measures a differential current equal to the injected current; but then, blocks tripping with a message 'Error with Block'. The current supervision alarm comes up as well. It appears the bus bar system 'knows' the 'fault' is not real!

- Could it be some logic blocking the trip?

- Could it be that because it is only one bay connected to this bus, he system is blocking the trip command?

- Or could it be the bus bar protection is not functioning?

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Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 19416
Good Answers: 1139
#1

Re: Siemens Bus Bar Protection 7SS5..

04/15/2017 1:43 PM

Go back and double check your wiring location....something may not be wired correctly....or something may be loose...something may be connected improperly....

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Power-User

Join Date: Jul 2016
Posts: 374
Good Answers: 20
#2

Re: Siemens Bus Bar Protection 7SS5..

04/18/2017 11:00 AM

The block is likely protection for a failure of current monitoring circuits, to protect against tripping power off for a relay measurement failure.

It monitors all of the current transformer circuits; connecting your laptop to it should give you a better explanation than Current Supervision Alarm.

I'd think your test set up should have worked. Maybe it doesn't like that the residual current and the phase current are the same angle and magnitude, unlikely to happen in real 3 phase world...?

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